GEE提取 MODIS 地表温度

用 Google Earth Engine 提取 MODIS 地表温度，只需指定区域与时间，就能快速得到：

✅ 白天地表温度
🌙 夜间地表温度
🌡️ 昼夜平均温度

🌈 支持可视化（红蓝渐变色带）
📂 一键导出 GeoTIFF 到 Google Drive
📊 可用于城市热岛研究、干旱监测、生态评估。

// -------------------- 1️⃣ 设置研究区 --------------------var roi = ee.FeatureCollection("projects/land-111/assets/ankang");
// var roi = geometry;  // 如果你手绘了 ROI，用这行替换上面
Map.centerObject(roi, 8);
Map.addLayer(roi, {color: 'red'}, 'ROI');
// -------------------- 2️⃣ 设置时间范围 --------------------
var startDate = '2023-07-01';
var endDate   = '2023-07-31';
// -------------------- 3️⃣ 读取 MODIS LST 数据 --------------------
var modis = ee.ImageCollection("MODIS/061/MOD11A2").filterDate(startDate, endDate).filterBounds(roi);
// 白天与夜间波段
var lst_day = modis.select('LST_Day_1km').mean().multiply(0.02).subtract(273.15).rename('LST_Day_C');
var lst_night = modis.select('LST_Night_1km').mean().multiply(0.02).subtract(273.15).rename('LST_Night_C');
// 昼夜平均温度
var lst_mean = lst_day.add(lst_night).divide(2).rename('LST_Mean_C');
// -------------------- 4️⃣ 可视化设置 --------------------
var viz_day   = {min: 15, max: 55, palette: ['#001aff','#00bfff','#7fff00','#ffff00','#ff7f00','#ff0000']};
var viz_night = {min: 5, max: 35, palette: ['#001a66','#0073e6','#66ccff','#ffff99','#ff9933','#cc0000']};
var viz_mean  = {min: 10, max: 45, palette: ['#003366','#0099cc','#66ff66','#ffff66','#ff9900','#ff0000']};
// -------------------- 5️⃣ 显示在地图上 --------------------
Map.addLayer(lst_day.clip(roi), viz_day, 'LST Daytime (°C)', true);
Map.addLayer(lst_night.clip(roi), viz_night, 'LST Nighttime (°C)', false);
Map.addLayer(lst_mean.clip(roi), viz_mean, 'LST Mean (°C)', false);
// -------------------- 6️⃣ 导出到 Google Drive --------------------
// 白天
Export.image.toDrive({image: lst_day.clip(roi),description: 'LST_Day_' + startDate + '_to_' + endDate,folder: 'GEE_LST',fileNamePrefix: 'LST_Day_' + startDate + '_' + endDate,region: roi,scale: 1000,maxPixels: 1e13,crs: 'EPSG:4326'
});
// 夜间
Export.image.toDrive({image: lst_night.clip(roi),description: 'LST_Night_' + startDate + '_to_' + endDate,folder: 'GEE_LST',fileNamePrefix: 'LST_Night_' + startDate + '_' + endDate,region: roi,scale: 1000,maxPixels: 1e13,crs: 'EPSG:4326'
});
// 平均
Export.image.toDrive({image: lst_mean.clip(roi),description: 'LST_Mean_' + startDate + '_to_' + endDate,folder: 'GEE_LST',fileNamePrefix: 'LST_Mean_' + startDate + '_' + endDate,region: roi,scale: 1000,maxPixels: 1e13,crs: 'EPSG:4326'
});