35:null 36:["$","title",null,{"children":"Investigating Montana Snow Depth Using Raster Data | Sarah Bethea | Observable"}] 3c:Tef1,{ const container = document.createElement("div"); container.style.cssText = ` font-family: system-ui, sans-serif; color: #222; max-width: 1100px; `; const dateLabel = new Date(`2000-${selectedDateFinal}T12:00:00Z`) .toLocaleDateString("en-US", { month: "long", day: "numeric", timeZone: "UTC" }); const heading = document.createElement("h2"); heading.textContent = "Montana mountain snowpack"; heading.style.margin = "0 0 4px"; const subtitle = document.createElement("p"); subtitle.textContent = `${dateLabel} · Estimated snow depth`; subtitle.style.cssText = "margin: 0 0 18px; color: #555;"; container.append(heading, subtitle); // Two maps with a shared color scale. const maps = document.createElement("div"); maps.style.cssText = ` display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 16px; `; for (const [index, year] of [leftYearFinal, rightYearFinal].entries()) { const panel = document.createElement("div"); const label = document.createElement("h3"); label.textContent = String(year); label.style.cssText = "margin: 0 0 8px; font-size: 20px;"; panel.append(label, drawSnow(selectedSnowFinal[index])); maps.append(panel); } container.append(maps); // Shared continuous legend. const legend = document.createElement("div"); legend.style.cssText = ` margin: 14px 0 0; width: 260px; max-width: 100%; `; const legendTitle = document.createElement("div"); legendTitle.textContent = "Snow depth (meters)"; legendTitle.style.cssText = ` font-size: 13px; font-weight: 600; margin-bottom: 8px; `; const gradient = document.createElement("div"); const stops = d3.range(21).map(i => `${d3.interpolateBlues(i / 20)} ${i * 5}%` ); gradient.style.cssText = ` height: 14px; border: 1px solid #bbb; background: linear-gradient(to right, ${stops.join(", ")}); `; const ticks = document.createElement("div"); ticks.style.cssText = ` position: relative; height: 24px; font-size: 12px; margin-top: 4px; `; for (const value of [0, 1, 2, 3]) { const tick = document.createElement("span"); tick.textContent = value === 3 ? "3+" : String(value); tick.style.position = "absolute"; if (value === 0) { tick.style.left = "0"; } else if (value === 3) { tick.style.right = "0"; } else { tick.style.left = `${value / 3 * 100}%`; tick.style.transform = "translateX(-50%)"; } ticks.append(tick); } // Separate swatches for zero snow and missing data. const categories = document.createElement("div"); categories.style.cssText = ` display: flex; gap: 20px; font-size: 12px; margin-top: 4px; `; for (const [label, fill] of [ ["No snow (0)", "#eeeeee"], ["Missing data", "#ffffff"] ]) { const item = document.createElement("div"); item.style.cssText = "display: flex; align-items: center; gap: 6px;"; const swatch = document.createElement("span"); swatch.style.cssText = ` display: inline-block; width: 14px; height: 14px; background: ${fill}; border: 1px solid #aaa; `; item.append(swatch, document.createTextNode(label)); categories.append(item); } legend.append(legendTitle, gradient, ticks, categories); container.append(legend); const note = document.createElement("p"); note.style.cssText = ` margin-top: 18px; font-size: 12px; line-height: 1.5; color: #666; `; note.textContent = "Source: NOAA SNODAS, distributed by NSIDC. " + "Both maps use the same color scale; depths above 3 meters " + "share the darkest blue. Historical repair mask not yet applied."; container.append(note); return container; }3d:Tf58,{ const root = document.createElement("div"); root.style.cssText = ` font-family: system-ui, sans-serif; color: #222; `; const title = document.createElement("h2"); title.textContent = "Snowpack across all years, 2005–2025"; title.style.margin = "0 0 6px"; // Derive the displayed date from the loaded data. const loadedDate = allYearsDataFinal.find(d => d.grid)?.grid.date; const monthDay = loadedDate?.slice(5) ?? allYearsMonthFinal; const dateLabel = new Date(`2000-${monthDay}T12:00:00Z`) .toLocaleDateString("en-US", { month: "long", day: "numeric", timeZone: "UTC" }); const subtitle = document.createElement("p"); subtitle.textContent = `${dateLabel} in each year · Single-date snapshots, not monthly averages`; subtitle.style.cssText = ` margin: 0 0 18px; color: #555; font-size: 14px; `; root.append(title, subtitle); const grid = document.createElement("div"); grid.style.cssText = ` display: grid; grid-template-columns: repeat(auto-fit, minmax(140px, 1fr)); gap: 14px 10px; `; for (const entry of allYearsDataFinal) { const tile = document.createElement("figure"); tile.style.cssText = "margin: 0; min-width: 0;"; if (entry.grid) { const map = drawSnow(entry.grid); map.title = `${dateLabel}, ${entry.year}`; tile.append(map); } else { const placeholder = document.createElement("div"); const aspect = (8 * Math.cos(46.85 * Math.PI / 180)) / 5.3; placeholder.style.cssText = ` aspect-ratio: ${aspect}; display: grid; place-items: center; background: #fafafa; border: 1px solid #ddd; color: #777; font-size: 12px; `; placeholder.textContent = "Data unavailable"; tile.append(placeholder); } const caption = document.createElement("figcaption"); caption.textContent = String(entry.year); caption.style.cssText = ` margin-top: 6px; text-align: center; font-size: 14px; font-weight: 600; `; tile.append(caption); grid.append(tile); } root.append(grid); const legend = document.createElement("div"); legend.style.cssText = ` width: 260px; max-width: 100%; margin-top: 20px; `; const stops = d3.range(21).map(i => `${d3.interpolateBlues(i / 20)} ${i * 5}%` ).join(", "); legend.innerHTML = `

Snow depth (meters)

0123+

No snow Missing data

Snow depth (meters)

0 1 2 3+

No snow: basemap visible
Missing data: gray overlay

`; const note = document.createElement("p"); note.style.cssText = ` font-size:12px; line-height:1.5; color:#666; `; note.textContent = "Snow: NOAA SNODAS / NSIDC. Snow colors are 80% opaque. " + "Historical repair mask not yet applied. " + "Use +/− to zoom; drag either map to pan."; root.append(legend, note); // Fit the raster extent when the maps become visible. // Prevent zooming out beyond that extent. let fitted = false; const observer = new ResizeObserver(() => { if (!root.isConnected || !row.clientWidth) return; synchronizing = true; try { maps.forEach(map => { map.invalidateSize({ pan: false }); // "inside: true" ensures the viewport stays within the raster, // including minor differences caused by pixel rounding. const fitZoom = map.getBoundsZoom(initialBounds, true); map.setMinZoom(fitZoom); }); if (!fitted) { fitted = true; const zoom = Math.max( ...maps.map(map => map.getMinZoom()) ); maps.forEach(map => { map.setView(initialBounds.getCenter(), zoom, { animate: false }); }); } else { const zoom = Math.max( maps[0].getZoom(), ...maps.map(map => map.getMinZoom()) ); const center = maps[0].getCenter(); maps.forEach(map => { map.setView(center, zoom, { animate: false }); map.panInsideBounds(initialBounds, { animate: false }); }); } } finally { synchronizing = false; } }); observer.observe(row); invalidation.then(() => { observer.disconnect(); maps.forEach(map => map.remove()); }); return { root, maps, titles, layers, dateLabel }; }4a:T123a,{ const root = document.createElement("div"); root.style.cssText = ` font-family: system-ui, sans-serif; color: #222; `; const title = document.createElement("h2"); title.textContent = "Spring snowpack across two decades"; title.style.margin = "0 0 6px"; const subtitle = document.createElement("p"); subtitle.textContent = "Compare across each row for differences between years, " + "and down each column for seasonal snow retreat."; subtitle.style.cssText = ` margin: 0 0 18px; color: #555; font-size: 14px; `; root.append(title, subtitle); // Allow horizontal scrolling on narrow screens, // rather than shrinking the maps until they are unreadable. const scroll = document.createElement("div"); scroll.style.overflowX = "auto"; const matrix = document.createElement("div"); matrix.style.cssText = ` display: grid; grid-template-columns: 72px repeat(${smallMapYears.length}, minmax(160px, 1fr)); gap: 12px; align-items: start; min-width: ${72 + smallMapYears.length * 172}px; `; // Empty top-left corner, followed by year headings. matrix.append(document.createElement("div")); for (const year of smallMapYears) { const header = document.createElement("div"); header.textContent = String(year); header.style.cssText = ` text-align: center; font-size: 17px; font-weight: 650; `; matrix.append(header); } // One row per date. for (const { monthDay, label } of smallMapDates) { const rowLabel = document.createElement("div"); rowLabel.textContent = label; rowLabel.style.cssText = ` align-self: center; font-size: 13px; font-weight: 600; `; matrix.append(rowLabel); for (const year of smallMapYears) { const entry = smallMapData.find(d => d.year === year && d.monthDay === monthDay ); const panel = document.createElement("div"); panel.style.minWidth = "0"; panel.title = `${label}, ${year}`; if (entry?.grid) { panel.append(drawSnow(entry.grid)); } else { const placeholder = document.createElement("div"); // Match the approximate aspect ratio used by drawSnow. const aspect = (8 * Math.cos(46.85 * Math.PI / 180)) / 5.3; placeholder.style.cssText = ` aspect-ratio: ${aspect}; display: grid; place-items: center; border: 1px solid #ddd; background: #fafafa; color: #777; font-size: 12px; text-align: center; `; placeholder.textContent = "Data unavailable"; panel.append(placeholder); } matrix.append(panel); } } scroll.append(matrix); root.append(scroll); // Shared legend matches drawSnow's opaque color scale. const legend = document.createElement("div"); legend.style.cssText = ` width: 260px; max-width: 100%; margin-top: 18px; `; const stops = d3.range(21).map(i => `${d3.interpolateBlues(i / 20)} ${i * 5}%` ).join(", "); legend.innerHTML = `

Snow depth (meters)

0 1 2 3+

No snow Missing data

`; root.append(legend); const note = document.createElement("p"); note.style.cssText = ` font-size:12px; color:#666; line-height:1.5; margin-top:16px; `; note.textContent = "Source: NOAA SNODAS / NSIDC. All maps use the same extent " + "and snow-depth scale. Years are shown at five-year intervals. " + "These snapshots show snow-depth differences, not snow-disappearance " + "dates directly. Historical repair mask not yet applied."; root.append(note); return root; }4b:Tf49,{ const root = document.createElement("div"); root.style.cssText = ` font-family: system-ui, sans-serif; color: #222; `; const title = document.createElement("h2"); title.textContent = "Snowpack across all years, 2005–2025"; title.style.margin = "0 0 6px"; // Derive the displayed date from the loaded data. const loadedDate = allYearsData.find(d => d.grid)?.grid.date; const monthDay = loadedDate?.slice(5) ?? allYearsMonth; const dateLabel = new Date(`2000-${monthDay}T12:00:00Z`) .toLocaleDateString("en-US", { month: "long", day: "numeric", timeZone: "UTC" }); const subtitle = document.createElement("p"); subtitle.textContent = `${dateLabel} in each year · Single-date snapshots, not monthly averages`; subtitle.style.cssText = ` margin: 0 0 18px; color: #555; font-size: 14px; `; root.append(title, subtitle); const grid = document.createElement("div"); grid.style.cssText = ` display: grid; grid-template-columns: repeat(auto-fit, minmax(140px, 1fr)); gap: 14px 10px; `; for (const entry of allYearsData) { const tile = document.createElement("figure"); tile.style.cssText = "margin: 0; min-width: 0;"; if (entry.grid) { const map = drawSnow(entry.grid); map.title = `${dateLabel}, ${entry.year}`; tile.append(map); } else { const placeholder = document.createElement("div"); const aspect = (8 * Math.cos(46.85 * Math.PI / 180)) / 5.3; placeholder.style.cssText = ` aspect-ratio: ${aspect}; display: grid; place-items: center; background: #fafafa; border: 1px solid #ddd; color: #777; font-size: 12px; `; placeholder.textContent = "Data unavailable"; tile.append(placeholder); } const caption = document.createElement("figcaption"); caption.textContent = String(entry.year); caption.style.cssText = ` margin-top: 6px; text-align: center; font-size: 14px; font-weight: 600; `; tile.append(caption); grid.append(tile); } root.append(grid); const legend = document.createElement("div"); legend.style.cssText = ` width: 260px; max-width: 100%; margin-top: 20px; `; const stops = d3.range(21).map(i => `${d3.interpolateBlues(i / 20)} ${i * 5}%` ).join(", "); legend.innerHTML = `

Snow depth (meters)

0123+

No snow Missing data

`; root.append(legend); const note = document.createElement("p"); note.style.cssText = ` margin-top:16px; font-size:12px; color:#666; line-height:1.5; `; note.textContent = "Source: NOAA SNODAS / NSIDC. All maps share the same extent " + "and color scale. Missing dates are not replaced with other dates. " + "Historical repair mask not yet applied."; root.append(note); return root; }4c:T4d6,allYearsData = { const years = d3.range(2005, 2026); const results = []; let cancelled = false; invalidation.then(() => { cancelled = true; }); async function loadYear(year) { const record = snowManifest2.find(d => d.year === year && d.monthDay === allYearsMonth && d.status === "ready" ); if (!record) { return { year, grid: null }; } const archive = await getAllYearsArchive(year); const file = archive.file(record.file); if (!file) { throw new Error(`File missing from ZIP: ${record.file}`); } const tiff = await GeoTIFF.fromArrayBuffer( await file.async("arraybuffer") ); const image = await tiff.getImage(); return { year, grid: { date: record.date, width: image.getWidth(), height: image.getHeight(), bounds: image.getBoundingBox(), noData: image.getGDALNoData(), values: await image.readRasters({ samples: [0], interleave: true }) } }; } for (let i = 0; i < years.length; i += 3) { if (cancelled) return []; results.push( ...await Promise.all(years.slice(i, i + 3).map(loadYear)) ); } return results; }4d:T5bc,SnowPlot.plot({ title: "How does seasonal snow retreat vary between years?", subtitle: "Montana within the mapped extent · Snow-covered = modeled depth ≥ 1 cm", width: 950, height: 450, marginLeft: 65, marginBottom: 45, x: { type: "utc", label: null, domain: [ new Date("2001-03-01T00:00:00Z"), new Date("2001-09-30T00:00:00Z") ], ticks: d3.utcMonth.every(1), tickFormat: d3.utcFormat("%b") }, y: { label: "Snow-covered area (%)", domain: [0, 100], grid: true }, color: { type: "linear", domain: [2005, 2025], scheme: "plasma", legend: true, label: "Year", ticks: 5, tickFormat: year => String(year) }, marks: [ SnowPlot.ruleY([0]), SnowPlot.lineY(meltSeasonData, { x: "seasonDate", y: "snowCoverPercent", z: "year", stroke: "year", strokeWidth: 1.5, strokeOpacity: 0.75 }), SnowPlot.dot(meltSeasonData, { x: "seasonDate", y: "snowCoverPercent", stroke: "year", r: 2, tip: true, title: d => `${d.year} · ${d3.utcFormat("%B %-d")(d.seasonDate)}\n` + `${d.snowCoverPercent.toFixed(1)}% snow-covered` }) ], caption: "Source: NOAA SNODAS / NSIDC. Percentages use a fixed set of " + "cells valid throughout the available series. Gaps indicate missing " + "observations. Provisional: official historical repair mask not applied." })4e:T70b,{ const points = retreatResults.filter(d => d.status === "Estimated"); const formatDay = day => d3.utcFormat("%b %-d")( new Date(Date.UTC(2001, 0, 1) + (day - 1) * 86400000) ); return SnowPlot.plot({ title: `When does snow cover fall below ${retreatThreshold}%?`, subtitle: "Remains below the threshold through the final August observation", width: 900, height: 420, marginLeft: 75, marginBottom: 45, x: { label: "Year", domain: [2005, 2025], ticks: d3.range(2005, 2026, 2), tickFormat: year => String(year) }, y: { label: "Snow-retreat date", domain: [60, 243], ticks: [60, 91, 121, 152, 182, 213, 243], tickFormat: formatDay, grid: true }, marks: [ SnowPlot.ruleX(points, { x: "year", y1: "lowerDay", y2: "upperDay", stroke: "#769bad", strokeWidth: 2 }), ...(retreatTrend.valid ? [ SnowPlot.lineY(retreatTrend.line, { x: "year", y: "retreatDay", stroke: "#d97732", strokeWidth: 2.5 }) ] : []), SnowPlot.dot(points, { x: "year", y: "retreatDay", fill: "#2878a5", stroke: "white", r: 4.5, tip: true, title: d => `${d.year}\n` + `Estimated date: ${formatDay(d.retreatDay)}\n` + `Crossing interval: ${formatDay(d.lowerDay)}–` + `${formatDay(d.upperDay)}` }) ], caption: "Dots: midpoint estimates. Bars: observation intervals. " + "Orange line: fitted linear trend. Years with incomplete seasonal " + "data or no identifiable crossing are omitted. " + "SNODAS estimates; historical repair mask not yet applied." }); }4f:T7eb,retreatResults = { const dayMs = 86400000; const referenceStart = Date.UTC(2001, 0, 1); const dayOfYear = monthDay => (Date.parse(`2001-${monthDay}T00:00:00Z`) - referenceStart) / dayMs + 1; const seasonDates = [...new Set( snowCoverData .filter(d => d.monthDay >= "03-01" && d.monthDay <= "08-31") .map(d => d.monthDay) )].sort(); return d3.range(2005, 2026).map(year => { const byDate = new Map( snowCoverData .filter(d => d.year === year) .map(d => [d.monthDay, d]) ); const observations = seasonDates.map(date => byDate.get(date)); if (observations.some(d => !d || !Number.isFinite(d.snowCoverPercent) )) { return { year, status: "Excluded: missing March–August observations" }; } const spring = observations.filter(d => d.monthDay <= "05-31"); const peak = d3.greatest(spring, d => d.snowCoverPercent); if (!peak || peak.snowCoverPercent < retreatThreshold) { return { year, status: "Already below threshold throughout March–May" }; } const afterPeak = observations.filter(d => d.monthDay >= peak.monthDay ); // Find the final observation at or above the threshold. let lastAbove = -1; for (let i = 0; i < afterPeak.length; i++) { if (afterPeak[i].snowCoverPercent >= retreatThreshold) { lastAbove = i; } } if (lastAbove === afterPeak.length - 1) { return { year, status: "Not persistently below threshold by late August" }; } const lower = afterPeak[lastAbove]; const upper = afterPeak[lastAbove + 1]; const lowerDay = dayOfYear(lower.monthDay); const upperDay = dayOfYear(upper.monthDay); return { year, status: "Estimated", lowerDate: lower.monthDay, upperDate: upper.monthDay, lowerDay, upperDay, retreatDay: (lowerDay + upperDay) / 2, intervalDays: upperDay - lowerDay }; }); }50:T59b,retreatTrend = { const points = retreatResults.filter(d => d.status === "Estimated"); function fit(data) { const meanX = d3.mean(data, d => d.year); const meanY = d3.mean(data, d => d.retreatDay); const denominator = d3.sum(data, d => (d.year - meanX) ** 2); if (!denominator) return null; const slope = d3.sum( data, d => (d.year - meanX) * (d.retreatDay - meanY) ) / denominator; return { slope, predict: year => meanY + slope * (year - meanX) }; } if (points.length < 8) { return { valid: false, n: points.length, message: "Too few eligible years for this trend summary." }; } const model = fit(points); let seed = 42; const random = () => { seed = (1664525 * seed + 1013904223) >>> 0; return seed / 4294967296; }; const slopes = []; for (let b = 0; b < 5000; b++) { const sample = Array.from( { length: points.length }, () => points[Math.floor(random() * points.length)] ); const result = fit(sample); if (result) slopes.push(result.slope * 10); } slopes.sort((a, b) => a - b); return { valid: true, n: points.length, daysPerDecade: model.slope * 10, lower: d3.quantileSorted(slopes, 0.025), upper: d3.quantileSorted(slopes, 0.975), line: d3.extent(points, d => d.year).map(year => ({ year, retreatDay: model.predict(year) })) }; }51:T5ae,let smallMapYears = [2005, 2010, 2015, 2020, 2025] let smallMapDates = [ { monthDay: "04-05", label: "April 5" }, { monthDay: "05-03", label: "May 3" }, { monthDay: "06-07", label: "June 7" } ] let smallMapArchives = new Map(await Promise.all( smallMapYears.map(async year => [ year, await JSZip.loadAsync( await snowZipFiles2.get(year).arrayBuffer() ) ]) )) let smallMapData = await Promise.all( smallMapDates.flatMap(({ monthDay, label }) => smallMapYears.map(async year => { const record = snowManifest2.find(d => d.year === year && d.monthDay === monthDay && d.status === "ready" ); if (!record) { return { year, monthDay, label, grid: null }; } const file = smallMapArchives.get(year).file(record.file); if (!file) { throw new Error(`File missing from ZIP: ${record.file}`); } const tiff = await GeoTIFF.fromArrayBuffer( await file.async("arraybuffer") ); const image = await tiff.getImage(); return { year, monthDay, label, grid: { date: record.date, width: image.getWidth(), height: image.getHeight(), bounds: image.getBoundingBox(), noData: image.getGDALNoData(), values: await image.readRasters({ samples: [0], interleave: true }) } }; }) ) 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3a:{"id":"c32cc65b851c2ac1","slug":"investigating-montana-snow-depth-using-raster-data","title":"Investigating Montana Snow Depth Using Raster Data","thumbnail":"59bc66f8eacdfe8794c213ec77b4cee3a68e1f9cd8e18c998eef37e521e973d8","access_level":"public","create_time":"$D2026-10-15T14:29:18.067Z","update_time":"$D2026-10-19T15:14:33.508Z","view_time":null,"first_public_time":"$D2026-10-19T15:17:07.498Z","has_unpublished_edits":null,"fork":false,"stars":0,"starred":false,"owner":{"type":"team","id":"23c5b41fb99349d8","login":"sarah-bethea2","name":"Sarah Bethea","avatar_url":null,"tier":"starter_2024","bio":"","following":false},"version":718,"publish_version":718,"role":null,"authored":false,"authors":[{"type":"individual","id":"8a373c5cb2e04d32","login":"sarah-bethea2","name":"Sarah Bethea","avatar_url":null,"tier":null,"bio":"","following":false}],"members":[{"type":"team","id":"23c5b41fb99349d8","login":"sarah-bethea2","name":"Sarah Bethea","avatar_url":null,"tier":"starter_2024","role":"editor"}],"comments":[],"custom_thumbnail":false,"trashed":false,"lapsed":null,"subscribed":null,"forks":0,"collection":null,"type":"notebook","body":{"titling":"auto","title":"Investigating Montana Snow Depth Using Raster Data","cells":[{"id":1,"value":"# Investigating Montana Snow Depth Using Raster Data","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":62,"value":"Having lived in Montana since 2018, I believe I have noticed changes in our climate in that time. Winters feel warmer and less snowy. However, this is only my personal experience, and I wanted to look at real data to see if the effects of climate change are visible in our snowpack. In particular, I was curious whether spring snow cover has been disappearing earlier over time.\n\n### Hypothesis:\nSpring snow cover in western Montana is retreating earlier in the year over time.\n\n#### Sources:\n[SNODAS Dataset](https://nsidc.org/data/g02158/versions/1)","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":149,"value":"## Comparing snowpack between two years\nChoose two years and move the date slider to compare snow depth at the same point in the season.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":135,"value":"viewof leftYearFinal = Inputs.select(d3.range(2005, 2026), {\n label: \"Left year\",\n value: 2005,\n format: year => String(year)\n})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":136,"value":"viewof rightYearFinal = Inputs.select(d3.range(2005, 2026), {\n label: \"Right year\",\n value: 2025,\n format: year => String(year)\n})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":137,"value":"viewof dateIndexFinal = Inputs.range(\n [0, Math.max(0, comparisonDatesFinal.length - 1)],\n {\n label: \"Date step\",\n step: 1,\n value: 0\n }\n)","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":138,"value":"$3c","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":151,"value":"## Snowpack across the years\n\nChoose a month to compare snow cover across all 21 years. Each map shows a single date near the beginning of that month.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":140,"value":"viewof allYearsMonthFinal = Inputs.select(\n new Map([\n [\"January\", \"01-04\"],\n [\"February\", \"02-01\"],\n [\"March\", \"03-01\"],\n [\"April\", \"04-05\"],\n [\"May\", \"05-03\"],\n [\"June\", \"06-07\"],\n [\"July\", \"07-05\"],\n [\"August\", \"08-02\"],\n [\"September\", \"09-06\"],\n [\"October\", \"10-04\"],\n [\"November\", \"11-01\"],\n [\"December\", \"12-06\"]\n ]),\n {\n label: \"Month\",\n value: \"05-03\"\n }\n)","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":141,"value":"$3d","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":144,"value":"viewof retreatThresholdFinal = Inputs.select(\n new Map([\n [\"5% of study area\", 5],\n [\"10% of study area\", 10],\n [\"20% of study area\", 20]\n ]),\n {\n label: \"Snow-cover threshold\",\n value: 10\n }\n)","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":152,"value":"## Is spring snow retreat happening earlier?\n\nChoose a snow cover threshold to explore when coverage falls below that level and stays below it through the last August observation.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":145,"value":"$3e","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":153,"value":"## Conclusions\nThe regression lines for the 5% and 10% snow-cover thresholds slope slightly downward, suggesting that these levels are being reached earlier in the year. However, the 20% threshold shows a slight trend in the opposite direction, so the result depends on how we define it. The raster maps also show considerable variation between years: snow appears to melt relatively early in 2005–2007, followed by more persistent June snow cover during much of 2008–2014, before shifting back toward earlier melting in later years. This variation makes it difficult to determine long term patterns. Overall, support for my hypothesis among the findings is limited. There may not be enough years available in this dataset to identify a clear trend.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":147,"value":"$3f","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":146,"value":"$40","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":142,"value":"$41","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":130,"value":"comparisonDatesFinal = {\n const available = year => new Set(\n snowManifest2\n .filter(d => d.year === Number(year) && d.status === \"ready\")\n .map(d => d.monthDay)\n );\n\n const left = available(leftYear3);\n const right = available(rightYear3);\n\n return [...left].filter(date => right.has(date)).sort();\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":131,"value":"selectedDateFinal = comparisonDatesFinal[\n Math.min(dateIndexFinal, comparisonDatesFinal.length - 1)\n]","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":132,"value":"selectedArchivesFinal= new Map(await Promise.all(\n [...new Set([Number(leftYearFinal), Number(rightYearFinal)])]\n .map(async year => [\n year,\n await JSZip.loadAsync(\n await snowZipFiles2.get(year).arrayBuffer()\n )\n ])\n))","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":133,"value":"loadSnowFinal = async (year, monthDay) => {\n const record = snowManifest2.find(d =>\n d.year === Number(year) &&\n d.monthDay === monthDay &&\n d.status === \"ready\"\n );\n\n if (!record) {\n throw new Error(`No available raster for ${year}-${monthDay}`);\n }\n\n const file = selectedArchivesFinal.get(Number(year))?.file(record.file);\n\n if (!file) {\n throw new Error(`File missing from ZIP: ${record.file}`);\n }\n\n const tiff = await GeoTIFF.fromArrayBuffer(\n await file.async(\"arraybuffer\")\n );\n\n const image = await tiff.getImage();\n\n return {\n date: record.date,\n width: image.getWidth(),\n height: image.getHeight(),\n bounds: image.getBoundingBox(),\n noData: image.getGDALNoData(),\n values: await image.readRasters({\n samples: [0],\n interleave: true\n })\n };\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":134,"value":"selectedSnowFinal = await Promise.all([\n loadSnowFinal(leftYearFinal, selectedDateFinal),\n loadSnowFinal(rightYearFinal, selectedDateFinal)\n])","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":19,"value":"# Revision History\n\nI started by downloading one day of raster data from 2025 as a proof of concept. I cropped it to western Montana, converted it to GeoTIFF, and loaded it into Observable. Once the raster was displaying correctly, I added state boundaries to provide geographic context.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":5,"value":"snowImage = await snowTiff.getImage()","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":7,"value":"snowDepth = await snowImage.readRasters({\n samples: [0],\n interleave: true\n})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":10,"value":"snowGrid = ({\n width: snowImage.getWidth(),\n height: snowImage.getHeight(),\n bounds: snowImage.getBoundingBox(),\n values: snowDepth,\n noData: snowImage.getGDALNoData()\n})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":8,"value":"({\n columns: snowGrid.width,\n rows: snowGrid.height,\n bounds: snowGrid.bounds,\n totalValues: snowGrid.values.length,\n expectedValues: snowGrid.width * snowGrid.height,\n first20Values: Array.from(snowGrid.values.slice(0, 20))\n})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":13,"value":"{\n const { width, height, values, noData } = snowGrid;\n\n const canvas = document.createElement(\"canvas\");\n canvas.width = width;\n canvas.height = height;\n\n const context = canvas.getContext(\"2d\");\n const pixels = context.createImageData(width, height);\n\n // Values are stored in millimeters.\n const color = d3.scaleSequential(d3.interpolateBlues)\n .domain([0, 3000])\n .clamp(true);\n\n for (let i = 0; i < values.length; i++) {\n const depth = values[i];\n const offset = i * 4;\n\n if (depth === noData || depth < 0 || !Number.isFinite(depth)) {\n pixels.data[offset + 3] = 0;\n continue;\n }\n\n const c = d3.rgb(depth === 0 ? \"#eeeeee\" : color(depth));\n\n pixels.data[offset] = c.r;\n pixels.data[offset + 1] = c.g;\n pixels.data[offset + 2] = c.b;\n pixels.data[offset + 3] = 255;\n }\n\n context.putImageData(pixels, 0, 0);\n\n canvas.style.maxWidth = \"100%\";\n canvas.style.height = \"auto\";\n\n return canvas;\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":15,"value":"topojson = await import(\n \"https://cdn.jsdelivr.net/npm/topojson-client@3/+esm\"\n)","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":16,"value":"usStates = await d3.json(\n \"https://cdn.jsdelivr.net/npm/us-atlas@3/states-10m.json\"\n)","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":17,"value":"stateFeatures = topojson.feature(usStates, usStates.objects.states).features","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":18,"value":"$42","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":20,"value":"#### Critique\nThe raster appears to be rendering correctly, but the map is cropped too tightly. Montana’s northern border sits right against the edge of the frame, which makes the frame crowded.\n\n## Revision: Wider Crop\nI adjusted my Python script to expand the crop, then converted and uploaded the updated file.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":22,"value":"$43","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":66,"value":"#### Critique\nThe wider crop gives the map more context and includes the mountain ranges I wanted to show. The surrounding areas help orient the viewer, and the rectangular frame feels more balanced than the original square layout.\n\n## Revision: Load multiple years of data and create interactive visualization\nWith the framing improved, I loaded weekly data from March through September for 2005, 2015, and 2025. I started with just three years to make sure the loading and visualization code worked before expanding the dataset.\n\nI added two dropdown menus so users could choose years to compare side by side, along with a shared date slider to move both maps through the season together. This makes it possible to compare snow conditions on the same date in different years.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":30,"value":"JSZip = (await import(\n \"https://cdn.jsdelivr.net/npm/jszip@3.10.1/+esm\"\n)).default","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":32,"value":"snowArchives = new Map(await Promise.all([\n [2005, FileAttachment(\"snow_2005.zip\")],\n [2015, FileAttachment(\"snow_2015.zip\")],\n [2025, FileAttachment(\"snow_2025.zip\")]\n].map(async ([year, attachment]) => [\n year,\n await JSZip.loadAsync(await attachment.arrayBuffer())\n])))","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":33,"value":"loadSnow = async (year, monthDay) => {\n const record = snowManifest.find(d =>\n d.year === Number(year) &&\n d.monthDay === monthDay &&\n d.status === \"ready\"\n );\n\n if (!record) {\n throw new Error(`No available raster for ${year}-${monthDay}`);\n }\n\n const archive = snowArchives.get(Number(year));\n const file = archive?.file(record.file);\n\n if (!file) {\n throw new Error(`File missing from ZIP: ${record.file}`);\n }\n\n const buffer = await file.async(\"arraybuffer\");\n const tiff = await GeoTIFF.fromArrayBuffer(buffer);\n const image = await tiff.getImage();\n\n return {\n date: record.date,\n width: image.getWidth(),\n height: image.getHeight(),\n bounds: image.getBoundingBox(),\n noData: image.getGDALNoData(),\n values: await image.readRasters({\n samples: [0],\n interleave: true\n })\n };\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":26,"value":"snowManifest = await FileAttachment(\"manifest.json\").json()","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":27,"value":"comparisonDates = {\n const years = [2005, 2015, 2025];\n\n const dates = [...new Set(snowManifest.map(d => d.monthDay))].sort();\n\n return dates.filter(monthDay =>\n years.every(year =>\n snowManifest.some(d =>\n d.year === year &&\n d.monthDay === monthDay &&\n d.status === \"ready\"\n )\n )\n );\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":35,"value":"testSnow = await loadSnow(2025, \"03-01\")","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":36,"value":"({\n date: testSnow.date,\n columns: testSnow.width,\n rows: testSnow.height,\n bounds: testSnow.bounds,\n totalValues: testSnow.values.length\n})","pinned":false,"hidden":false,"mode":"ts","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":41,"value":"selectedDate = comparisonDates[dateIndex]","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":42,"value":"selectedSnow = await Promise.all([\n loadSnow(leftYear, selectedDate),\n loadSnow(rightYear, selectedDate)\n])","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":43,"value":"$44","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":37,"value":"viewof leftYear = Inputs.select([2005, 2015, 2025], {\n label: \"Left year\",\n value: 2005\n})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":39,"value":"viewof rightYear = Inputs.select([2005, 2015, 2025], {\n label: \"Right year\",\n value: 2025\n})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":40,"value":"viewof dateIndex = Inputs.range([0, comparisonDates.length - 1], {\n label: \"Date step\",\n step: 1,\n value: 0\n})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":44,"value":"$45","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":69,"value":"#### Critique\nOverall, I am very happy with how this visualization is coming together. There are several changes to be made: the number formatting in the dropdown selectors must be adjusted to not use a comma, a legend should be added, and the background tile map could have improved labeling. However, I first want to expand the dataset so it is more complete. Downloading and processing the initial files was relatively quick, so including weekly data for every year from 2005 through 2025 is manageable. Comparing only a few selected years could give a misleading impression if those years had unusually high or low snowpack. Including all years will make it easier to see the broader pattern and the variation between years.\n\n## Revision: Load all years between 2005-2025\nI expanded the dataset to include weekly observations throughout the calendar year for every year from 2005 through 2025. I also adjusted the dropdown formatting and added a legend.\n","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":48,"value":"viewof leftYear2 = Inputs.select([2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020, 2021, 2022, 2023, 2024, 2025], {\n label: \"Left year\",\n value: 2005\n})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":49,"value":"viewof rightYear2 = Inputs.select([2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020, 2021, 2022, 2023, 2024, 2025], {\n label: \"Right year\",\n value: 2025\n})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":50,"value":"viewof dateIndex2 = Inputs.range(\n [0, Math.max(0, comparisonDates2.length - 1)],\n {\n label: \"Date step\",\n step: 1,\n value: 0\n }\n)","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":60,"value":"$46","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":173,"value":"selectedSnow2 = await Promise.all([\n loadSnow2(leftYear2, selectedDate2),\n loadSnow2(rightYear2, selectedDate2)\n])","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":172,"value":"loadSnow2 = async (year, monthDay) => {\n const record = snowManifest2.find(d =>\n d.year === Number(year) &&\n d.monthDay === monthDay &&\n d.status === \"ready\"\n );\n\n if (!record) {\n throw new Error(`No available raster for ${year}-${monthDay}`);\n }\n\n const file = selectedArchives2.get(Number(year))?.file(record.file);\n\n if (!file) {\n throw new Error(`File missing from ZIP: ${record.file}`);\n }\n\n const tiff = await GeoTIFF.fromArrayBuffer(\n await file.async(\"arraybuffer\")\n );\n\n const image = await tiff.getImage();\n\n return {\n date: record.date,\n width: image.getWidth(),\n height: image.getHeight(),\n bounds: image.getBoundingBox(),\n noData: image.getGDALNoData(),\n values: await image.readRasters({\n samples: [0],\n interleave: true\n })\n };\n}\n","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":57,"value":"selectedDate2 = comparisonDates2[\n Math.min(dateIndex2, comparisonDates2.length - 1)\n]","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":55,"value":"comparisonDates2 = {\n const available = year => new Set(\n snowManifest2\n .filter(d => d.year === Number(year) && d.status === \"ready\")\n .map(d => d.monthDay)\n );\n\n const left = available(leftYear2);\n const right = available(rightYear2);\n\n return [...left].filter(date => right.has(date)).sort();\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":54,"value":"selectedArchives2 = new Map(await Promise.all(\n [...new Set([Number(leftYear2), Number(rightYear2)])]\n .map(async year => [\n year,\n await JSZip.loadAsync(\n await snowZipFiles2.get(year).arrayBuffer()\n )\n ])\n))","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":53,"value":"snowZipFiles2 = new Map([\n [2005, FileAttachment(\"snow_2005.zip\")],\n [2006, FileAttachment(\"snow_2006.zip\")],\n [2007, FileAttachment(\"snow_2007.zip\")],\n [2008, FileAttachment(\"snow_2008.zip\")],\n [2009, FileAttachment(\"snow_2009.zip\")],\n [2010, FileAttachment(\"snow_2010.zip\")],\n [2011, FileAttachment(\"snow_2011.zip\")],\n [2012, FileAttachment(\"snow_2012.zip\")],\n [2013, FileAttachment(\"snow_2013.zip\")],\n [2014, FileAttachment(\"snow_2014.zip\")],\n [2015, FileAttachment(\"snow_2015.zip\")],\n [2016, FileAttachment(\"snow_2016.zip\")],\n [2017, FileAttachment(\"snow_2017.zip\")],\n [2018, FileAttachment(\"snow_2018.zip\")],\n [2019, FileAttachment(\"snow_2019.zip\")],\n [2020, FileAttachment(\"snow_2020.zip\")],\n [2021, FileAttachment(\"snow_2021.zip\")],\n [2022, FileAttachment(\"snow_2022.zip\")],\n [2023, FileAttachment(\"snow_2023.zip\")],\n [2024, FileAttachment(\"snow_2024.zip\")],\n [2025, FileAttachment(\"snow_2025.zip\")]\n])","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":52,"value":"snowManifest2 = await FileAttachment(\"manifest2.json\").json()","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":3,"value":"GeoTIFF = await import(\"https://cdn.jsdelivr.net/npm/geotiff@2/+esm\")","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":4,"value":"snowTiff = await GeoTIFF.fromArrayBuffer(\n await FileAttachment(\"western_montana_snow_depth_20250501.tif\").arrayBuffer()\n)","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":73,"value":"## Revision: Add legend, adjust number formatting.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":74,"value":"viewof leftYear3 = Inputs.select(d3.range(2005, 2026), {\n label: \"Left year\",\n value: 2005,\n format: year => String(year)\n})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":75,"value":"viewof rightYear3 = Inputs.select(d3.range(2005, 2026), {\n label: \"Right year\",\n value: 2025,\n format: year => String(year)\n})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":77,"value":"viewof dateIndex3 = Inputs.range(\n [0, Math.max(0, comparisonDates3.length - 1)],\n {\n label: \"Date step\",\n step: 1,\n value: 0\n }\n)","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":81,"value":"$47","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":76,"value":"comparisonDates3 = {\n const available = year => new Set(\n snowManifest2\n .filter(d => d.year === Number(year) && d.status === \"ready\")\n .map(d => d.monthDay)\n );\n\n const left = available(leftYear3);\n const right = available(rightYear3);\n\n return [...left].filter(date => right.has(date)).sort();\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":78,"value":"selectedDate3 = comparisonDates3[\n Math.min(dateIndex3, comparisonDates3.length - 1)\n]","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":79,"value":"selectedArchives3 = new Map(await Promise.all(\n [...new Set([Number(leftYear3), Number(rightYear3)])]\n .map(async year => [\n year,\n await JSZip.loadAsync(\n await snowZipFiles2.get(year).arrayBuffer()\n )\n ])\n))","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":80,"value":"loadSnow3 = async (year, monthDay) => {\n const record = snowManifest2.find(d =>\n d.year === Number(year) &&\n d.monthDay === monthDay &&\n d.status === \"ready\"\n );\n\n if (!record) {\n throw new Error(`No available raster for ${year}-${monthDay}`);\n }\n\n const file = selectedArchives3.get(Number(year))?.file(record.file);\n\n if (!file) {\n throw new Error(`File missing from ZIP: ${record.file}`);\n }\n\n const tiff = await GeoTIFF.fromArrayBuffer(\n await file.async(\"arraybuffer\")\n );\n\n const image = await tiff.getImage();\n\n return {\n date: record.date,\n width: image.getWidth(),\n height: image.getHeight(),\n bounds: image.getBoundingBox(),\n noData: image.getGDALNoData(),\n values: await image.readRasters({\n samples: [0],\n interleave: true\n })\n };\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":82,"value":"selectedSnow3 = await Promise.all([\n loadSnow3(leftYear3, selectedDate3),\n loadSnow3(rightYear3, selectedDate3)\n])","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":85,"value":"#### Critique\nThe visualization now does what I intended: users can compare snow conditions across years and follow accumulation and retreat through the seasons. I’d still like to experiment with a labeled basemap and zoom controls to see whether they make the geography easier to explore.\n\n## Revision: Interactive tile map\nI added an interactive tiled basemap with geographic labels, zooming, and panning. I also made the basemap grayscale.\n","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":86,"value":"L4 = {\n const href = \"https://cdn.jsdelivr.net/npm/leaflet@1.9.4/dist/leaflet.css\";\n\n if (!document.querySelector('link[data-snow-leaflet]')) {\n await new Promise((resolve, reject) => {\n const link = document.createElement(\"link\");\n link.rel = \"stylesheet\";\n link.href = href;\n link.dataset.snowLeaflet = \"true\";\n link.onload = resolve;\n link.onerror = () => {\n link.remove();\n reject(new Error(\"Could not load Leaflet stylesheet\"));\n };\n document.head.append(link);\n });\n }\n\n const module = await import(\n \"https://cdn.jsdelivr.net/npm/leaflet@1.9.4/+esm\"\n );\n\n return module.default ?? module;\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":87,"value":"$48","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":88,"value":"$49","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":89,"value":"mapView4.root","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":90,"value":"{\n const grids = selectedSnow3;\n const rendered = grids.map(snowImage4);\n\n rendered.forEach((image, index) => {\n const existing = mapView4.layers[index];\n\n if (existing) {\n existing.setBounds(image.bounds);\n existing.setUrl(image.url);\n } else {\n mapView4.layers[index] = L4.imageOverlay(\n image.url,\n image.bounds,\n {\n opacity: 0.8,\n interactive: false,\n zIndex: 300\n }\n ).addTo(mapView4.maps[index]);\n }\n\n // Derive titles from the loaded rasters so labels match the data.\n mapView4.titles[index].textContent = grids[index].date.slice(0, 4);\n });\n\n mapView4.dateLabel.textContent = new Date(\n `${grids[0].date}T12:00:00Z`\n ).toLocaleDateString(\"en-US\", {\n month: \"long\",\n day: \"numeric\",\n timeZone: \"UTC\"\n });\n\n return \"Map layers updated\";\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":95,"value":"#### Critique\nThe raster data is opaque where data exists, and so to use a map with labels, you must reduce the opacity of the raster data layer, which makes the data less visible. Overall, I feel that this interactive map does not add a lot of value. It is messier and harder to parse visually. Therefore, I decided to stick with my earlier map for the final version.\n\nThe side-by-side maps are useful for exploring individual years, but comparing many years requires repeatedly changing the dropdowns. I wanted another view that would make those comparisons easier.\n\n## Revision: Grid layout\nI arranged selected years in columns and dates in rows, showing snowpack in early April, May, and June. This allows viewers to compare years across each row and follow seasonal snow retreat down each column.\n","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":101,"value":"$4a","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":102,"value":"#### Critique\nThis layout makes comparisons easier, but it still relies on a handful of selected years that might be outliers. I’d rather show every year, label each map with its year, and let users select the month.\n\n## Revision: Grid layout with all years\nI created a grid showing all 21 years, with a year label beneath each map and a dropdown for selecting the month. Each map displays the same weekly snapshot near the beginning of that month, using a shared extent and color scale. This gives viewers a broader picture of year-to-year snowpack trends without having to switch between individual years.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":104,"value":"viewof allYearsMonth = Inputs.select(\n new Map([\n [\"January\", \"01-04\"],\n [\"February\", \"02-01\"],\n [\"March\", \"03-01\"],\n [\"April\", \"04-05\"],\n [\"May\", \"05-03\"],\n [\"June\", \"06-07\"],\n [\"July\", \"07-05\"],\n [\"August\", \"08-02\"],\n [\"September\", \"09-06\"],\n [\"October\", \"10-04\"],\n [\"November\", \"11-01\"],\n [\"December\", \"12-06\"]\n ]),\n {\n label: \"Month\",\n value: \"05-03\"\n }\n)","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":107,"value":"$4b","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":106,"value":"$4c","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":105,"value":"getAllYearsArchive = {\n const cache = new Map();\n\n return year => {\n if (!cache.has(year)) {\n const promise = (async () => {\n const attachment = snowZipFiles2.get(year);\n\n if (!attachment) {\n throw new Error(`No ZIP attachment for ${year}`);\n }\n\n return JSZip.loadAsync(await attachment.arrayBuffer());\n })();\n\n cache.set(year, promise);\n promise.catch(() => cache.delete(year));\n }\n\n return cache.get(year);\n };\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":109,"value":"#### Critique\nThe user must scroll a bit to see every tile, but making them any smaller would make the snow pack patterns hard to see. I think the overview is useful enough to keep, as it lets viewers compare all years at once and spot unusually snowy or low-snow years.\n\nWhile raster maps provide a useful geographic view, I also want to include a chart that summarizes how snow cover changes over time and helps answer the hypothesis more directly.\n\n## Revision: Line chart of snow-covered area through the melt season\nI used a Python script to calculate the percentage of the study area covered by at least 1 cm of snow on each sampled date, accounting for differences in cell area. I exported the results as a CSV and created a line chart with one line per year to show how snow coverage changes through the melt season.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":112,"value":"snowCoverCSV = await FileAttachment(\"snow_cover_summary.csv\").csv()","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":113,"value":"snowCoverData = snowCoverCSV.map(d => ({\n year: Number(d.year),\n date: d.date,\n monthDay: d.monthDay,\n seasonDate: new Date(`2001-${d.monthDay}T00:00:00Z`),\n snowCoverPercent:\n d.snowCoverPercent === \"\" ? NaN : Number(d.snowCoverPercent)\n}))","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":114,"value":"SnowPlot = await import(\n \"https://cdn.jsdelivr.net/npm/@observablehq/plot@0.6.17/+esm\"\n)","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":115,"value":"meltSeasonData = snowCoverData.filter(d =>\n d.monthDay >= \"03-01\" && d.monthDay <= \"09-30\"\n)","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":116,"value":"$4d","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":122,"value":"#### Critique\nWith 21 overlapping lines, the chart is too busy and difficult to interpret. It shows substantial year-to-year variation, but it’s hard to tell whether snow is consistently retreating earlier.\n\n## Revision: Snow-retreat threshold date\nI calculated when snow covered area falls below a selected threshold - either 5%, 10%, or 20% of the study area - and remains below it through the summer. Because the data are sampled weekly, I estimated each crossing date as the midpoint between the observations on either side of the threshold.\n\nUsers can change the threshold to see how the result depends on the definition of snow retreat. This addresses the timing question more directly than comparing snow coverage on individual dates.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":123,"value":"viewof retreatThreshold = Inputs.select(\n new Map([\n [\"5% of study area\", 5],\n [\"10% of study area\", 10],\n [\"20% of study area\", 20]\n ]),\n {\n label: \"Snow-cover threshold\",\n value: 10\n }\n)","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":127,"value":"$4e","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":124,"value":"$4f","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":126,"value":"$50","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":128,"value":"{\n const result = document.createElement(\"p\");\n\n if (!retreatTrend.valid) {\n result.textContent = retreatTrend.message;\n return result;\n }\n\n const { daysPerDecade, lower, upper, n } = retreatTrend;\n const direction = daysPerDecade < 0 ? \"earlier\" : \"later\";\n\n const interpretation =\n upper < 0\n ? \"The interval supports earlier retreat under this definition.\"\n : lower > 0\n ? \"The interval supports later retreat under this definition.\"\n : \"The interval includes zero, so the direction is inconclusive.\";\n\n result.textContent =\n `Estimated change: ${Math.abs(daysPerDecade).toFixed(1)} days ` +\n `${direction} per decade. ` +\n `95% bootstrap interval: ${lower.toFixed(1)} to ${upper.toFixed(1)} ` +\n `days per decade (negative = earlier). ` +\n `Based on ${n} eligible years. ${interpretation}`;\n\n return result;\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":165,"value":"$51","pinned":false,"hidden":false,"mode":"ts","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"}],"files":"$W52","stdlib":"2"}} 3b:"$3a:body"