refactor(LST_download): 优化LST数据处理流程, 封装复用函数.
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@ -2,7 +2,7 @@
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* 地表温度 (LST) 数据下载 —— 以年平均温度处理下载为例
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*
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* @author CVEO Team
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* @date 2026-01-15
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* @date 2026-01-16
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*
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* 1. 加载并合并 Landsat-8, 9 30m LST 数据
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* 2. 加载 MODIS MOD11A2 1km LST 数据
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@ -11,14 +11,16 @@
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*/
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// 加载研究区域和影像
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var region_name = "应城市";
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var region_name_en = "Yingcheng";
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var region = Yingcheng;
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var crs = "EPSG:4526";
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// var region_name = "保康县";
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// var region_name_en = "Baokang";
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// var region = Baokang;
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// var crs = "EPSG:4525";
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// var region_name = "应城市";
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// var region_name_en = "Yingcheng";
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// var region = Yingcheng;
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// var crs = "EPSG:4526";
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var region_name = "保康县";
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var region_name_en = "Baokang";
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var region = Baokang;
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var crs = "EPSG:4525";
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var target_res = 30;
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var orign_res = 1000;
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var start_year = 2021;
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var end_year = 2025;
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var start_date = start_year + "-01-01";
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@ -27,9 +29,9 @@ var cloud_threshold = 90; // 最大云量阈值
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var LansatBands = ["ST_B10"];
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var MODISBands = ["LST_Day_1km"];
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var commonBands = ["LST"];
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// 设置研究区域的缓冲区, 确保粗分辨率数据能够完整覆盖研究区域
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var region_geo = region.geometry();
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var bounds = region_geo.bounds();
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var bounds = ee.Feature(region_geo.bounds()).buffer(orign_res * 3).geometry();
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var common_filter = ee.Filter.and(
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ee.Filter.bounds(bounds),
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ee.Filter.date(start_date, end_date)
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@ -81,9 +83,11 @@ function maskLandsatclouds(image) {
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// Bits 3 and 4 are cloud and cloud shadow, respectively.
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var cloudBitMask = 1 << 3;
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var shadowBitMask = 1 << 4;
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var snowBitMask = 1 << 5;
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// Both flags should be set to zero, indicating clear conditions.
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var mask = qa.bitwiseAnd(cloudBitMask).eq(0)
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.and(qa.bitwiseAnd(shadowBitMask).eq(0))
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.and(qa.bitwiseAnd(snowBitMask).eq(0))
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.and(qa_radsat.eq(0));
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image = image.updateMask(mask);
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return image
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@ -91,6 +95,34 @@ function maskLandsatclouds(image) {
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.copyProperties(image, ["system:time_start", "system:index", "system:id"]);
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}
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/**
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* 合成年度平均数据
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* @param {ee.ImageCollection} imageCollection 数据集合
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* @param {number} start_year 开始年份
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* @param {number} end_year 结束年份
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* @returns {ee.ImageCollection} 合成年度平均数据集合
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*/
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function compositeYearly(imageCollection, start_year, end_year) {
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var years = ee.List.sequence(start_year, end_year);
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var months = ee.List.sequence(1, 12);
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var yearlyImgCol = ee.ImageCollection.fromImages(
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years.map(function (y) {
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return ee.ImageCollection.fromImages(
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months.map(function (m) {
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return imageCollection
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.filter(ee.Filter.calendarRange(y, y, "year"))
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.filter(ee.Filter.calendarRange(m, m, "month"))
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.mean()
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.clip(bounds)
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.set("month", m)
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.set("year", y);
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})
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).mean().set("year", y);
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})
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);
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return yearlyImgCol;
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}
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// 加载 Landsat-8, Landsat-9 SR 数据
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var L8dataset = ee.ImageCollection("LANDSAT/LC08/C02/T1_L2")
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.filter(common_filter)
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@ -101,6 +133,27 @@ var L9dataset = ee.ImageCollection("LANDSAT/LC09/C02/T1_L2")
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.filter(ee.Filter.lt("CLOUD_COVER", cloud_threshold));
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print(start_date + " - " + end_date + " Landsat-9 SR dataset", L9dataset);
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// 加载 Landsat-8, Landsat-9 T2_L2 数据 (Tier 2)
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var L8T2dataset = ee.ImageCollection("LANDSAT/LC08/C02/T2_L2")
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.filter(common_filter)
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.filter(ee.Filter.lt("CLOUD_COVER", cloud_threshold));
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print(start_date + " - " + end_date + " Landsat-8 T2_L2 SR dataset", L8T2dataset);
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var L9T2dataset = ee.ImageCollection("LANDSAT/LC09/C02/T2_L2")
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.filter(common_filter)
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.filter(ee.Filter.lt("CLOUD_COVER", cloud_threshold));
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print(start_date + " - " + end_date + " Landsat-9 T2_L2 SR dataset", L9T2dataset);
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// 合并 Landsat-8, Landsat-9 LST 数据 (包括 T1_L2 和 T2_L2)
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var LSTdataset = L8dataset.merge(L9dataset)
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.merge(L8T2dataset)
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.merge(L9T2dataset)
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.filter(ee.Filter.eq("PROCESSING_LEVEL", "L2SP"))
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.map(applyScaleFactors)
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.map(maskLandsatclouds)
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.select(LansatBands, commonBands)
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.map(kelvinToCelsius);
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print(start_date + " - " + end_date + " Landsat-8,9 T1_L2 & T2_L2 LST dataset", LSTdataset);
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// 加载 MODIS LST 数据
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var MODISLSTdataset = ee.ImageCollection('MODIS/061/MOD11A2')
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.filter(common_filter)
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@ -109,32 +162,8 @@ var MODISLSTdataset = ee.ImageCollection('MODIS/061/MOD11A2')
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.map(kelvinToCelsius);
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print(start_date + " - " + end_date + " MODIS LST dataset", MODISLSTdataset);
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// 合并 Landsat-8, Landsat-9 LST 数据
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var LSTdataset = L8dataset.merge(L9dataset)
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.map(applyScaleFactors)
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.map(maskLandsatclouds)
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.select(LansatBands, commonBands)
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.map(kelvinToCelsius);
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print(start_date + " - " + end_date + " Landsat-8,9 LST dataset", LSTdataset);
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// 合成年度平均 Landsat LST 数据
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var years = ee.List.sequence(start_year, end_year);
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var months = ee.List.sequence(1, 12);
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var yearlyLST = ee.ImageCollection.fromImages(
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years.map(function (y) {
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return ee.ImageCollection.fromImages(
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months.map(function (m) {
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return LSTdataset
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.filter(ee.Filter.calendarRange(y, y, "year"))
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.filter(ee.Filter.calendarRange(m, m, "month"))
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.mean()
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.clip(bounds)
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.set("month", m)
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.set("year", y);
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})
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).mean().set("year", y);
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})
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);
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var yearlyLST = compositeYearly(LSTdataset, start_year, end_year);
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if (start_year == end_year) {
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var year_str = start_year;
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} else {
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@ -143,35 +172,29 @@ if (start_year == end_year) {
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print(year_str + " Annual Mean Landsat LST dataset", yearlyLST);
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// 合成年度平均 MODIS LST 数据
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var yearlyMODISLST = ee.ImageCollection.fromImages(
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years.map(function (y) {
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return ee.ImageCollection.fromImages(
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months.map(function (m) {
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return MODISLSTdataset
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.filter(ee.Filter.calendarRange(y, y, "year"))
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.filter(ee.Filter.calendarRange(m, m, "month"))
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.mean()
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.clip(bounds)
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.set("month", m)
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.set("year", y);
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})
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).mean().set("year", y);
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})
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);
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var yearlyMODISLST = compositeYearly(MODISLSTdataset, start_year, end_year);
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print(year_str + " Annual Mean MODIS LST dataset", yearlyMODISLST);
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var total_mean_LST = LSTdataset.select("LST").mean();
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// 合成处理后会丢失投影信息, 需要重新设置投影
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var lst_proj = LSTdataset.first().select(0).projection();
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var modis_proj = MODISLSTdataset.first().select(0).projection();
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var total_mean_LST = LSTdataset.select("LST").mean().setDefaultProjection(lst_proj);
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print(year_str + " Total Year Mean Landsat LST Histogram", ui.Chart.image.histogram(total_mean_LST, region, 100, 258));
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var annual_mean_LST = yearlyLST.select("LST").mean();
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var annual_mean_LST = yearlyLST.select("LST").mean().setDefaultProjection(lst_proj);
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print(year_str + " Annual Mean Landsat LST Histogram", ui.Chart.image.histogram(annual_mean_LST, region, 100, 258));
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var total_mean_MODIS_LST = MODISLSTdataset.select("LST").mean();
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var total_mean_MODIS_LST = MODISLSTdataset.select("LST").mean().setDefaultProjection(modis_proj);
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print(year_str + " Total Year Mean MODIS LST Histogram", ui.Chart.image.histogram(total_mean_MODIS_LST, region, 1000, 258));
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var annual_mean_MODIS_LST = yearlyMODISLST.select("LST").mean();
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var annual_mean_MODIS_LST = yearlyMODISLST.select("LST").mean().setDefaultProjection(modis_proj);
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print(year_str + " Annual Mean MODIS LST Histogram", ui.Chart.image.histogram(annual_mean_MODIS_LST, region, 1000, 258));
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var annual_mean_MODIS_LST_30m = annual_mean_MODIS_LST.resample("bicubic").reproject({
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crs: "EPSG:4326",
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scale: target_res,
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});
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var lst_vis = {
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min: 5,
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max: 35,
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@ -190,23 +213,26 @@ var styling = {
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};
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Map.centerObject(region, 10);
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Map.addLayer(total_mean_LST, lst_vis, year_str + " Landsat Total Year Mean LST");
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Map.addLayer(annual_mean_LST, lst_vis, year_str + " Landsat Annual Mean LST");
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Map.addLayer(total_mean_MODIS_LST, lst_vis, year_str + " MODIS Total Year Mean LST");
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Map.addLayer(annual_mean_MODIS_LST, lst_vis, year_str + " MODIS Annual Mean LST");
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Map.addLayer(annual_mean_MODIS_LST_30m, lst_vis, year_str + " MODIS Annual Mean LST 30m");
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Map.addLayer(total_mean_LST, lst_vis, year_str + " Landsat Total Year Mean LST");
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Map.addLayer(annual_mean_LST, lst_vis, year_str + " Landsat Annual Mean LST");
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Map.addLayer(region.style(styling), {}, region_name);
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// 导出合并后的影像
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// 明确设置数据类型为Float32, 否则默认类型为Float64, 会占用更多内存
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// 并对缺失值进行填充, 否则默认为nan不便于后续本地处理
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var processed_img = annual_mean_LST.toFloat().unmask(-9999.0);
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print("Start exporting " + year_str + "Yearly Mean LST image (" + crs + ")", processed_img);
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Export.image.toDrive({
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image: processed_img,
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description: region_name_en + "_Landsat_LST_" + year_str + "_30m",
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folder: "LST",
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function exportCOG(image, description, folder, region, scale, crs) {
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image = image.toFloat().unmask(-9999.0);
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// 默认为 EPSG:4326 投影
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crs = crs || "EPSG:4326";
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Export.image.toDrive({
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image: image,
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description: description,
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folder: folder,
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region: region, // 添加后会自动裁剪
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scale: 30,
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scale: scale,
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crs: crs,
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maxPixels: 1e13, // GEE 最多支持 1e8 像素, 当超过时会自动分块
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fileFormat: "GeoTIFF",
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@ -215,22 +241,11 @@ Export.image.toDrive({
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cloudOptimized: true,
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noData: -9999.0,
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},
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});
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});
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}
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// 导出 MODIS 合并后的影像
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var processed_modis_img = annual_mean_MODIS_LST.toFloat().unmask(-9999.0);
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print("Start exporting " + year_str + " MODIS Yearly Mean LST image (" + crs + ")", processed_modis_img);
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Export.image.toDrive({
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image: processed_modis_img,
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description: region_name_en + "_MODIS_LST_" + year_str + "_1km",
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folder: "LST",
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region: region,
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scale: 1000,
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crs: crs,
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maxPixels: 1e13,
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fileFormat: "GeoTIFF",
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formatOptions: {
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cloudOptimized: true,
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noData: -9999.0,
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},
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});
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print("Start exporting " + year_str + "Yearly Mean LST image (" + crs + ")", annual_mean_LST);
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exportCOG(annual_mean_LST, region_name_en + "_Landsat_LST_" + year_str + "_30m", "LST", region, 30, crs);
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print("Start exporting " + year_str + " MODIS Yearly Mean LST image (" + crs + ")", annual_mean_MODIS_LST);
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exportCOG(annual_mean_MODIS_LST, region_name_en + "_MODIS_LST_" + year_str + "_1km", "LST", region, 1000, crs);
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