前言：这次主要介绍MODIS/006/MOD11A1下的地表温度的数据分析。

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1 MODIS/006/MOD11A1介绍

MOD11A1 V6产品提供1200 x 1200公里网格中的每日地表温度（LST）和发射率值。温度值由MOD11_ L2线束乘积导出。在30度纬度以上，某些像素可能具有多个观测值，满足晴空标准。发生这种情况时，像素值是所有合格观测值的平均值。与白天和夜间地表温度带及其质量指示层一起提供的是MODIS波段31和32以及六个观测层。
分辨率：1000ｍ
波段：白天和夜晚的LST都有

2 遥感影像获取

代码如下（以鹿邑县为例）：

var geometry = ee.FeatureCollection('users/www1573979951/luyixian')
Map.centerObject(geometry,7)
 
// Get  temperature data for 1 year.
var modis = ee.ImageCollection('MODIS/006/MOD11A1');
var modisLST = modis.filterBounds(geometry).filterDate('2021-01-01', '2021-12-31').select('LST_Day_1km');

// Convert temperature to Celsius.
modisLST = modisLST.map(function(img){
  var date = img.get('system:time_start');
  return img.multiply(0.02).subtract(273.15).set('system:time_start', date);
});
print(modisLST)
Map.addLayer(modisLST.mean().clip(geometry), {min: 10, max: 30, palette: ['green','yellow', 'red']},'LST');
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遥感图像截图

影像数据截图（364个）

3 每日遥感数据获取

第一种代码如下（以鹿邑县为例）

var geometry = ee.FeatureCollection('users/www1573979951/luyixian')

// Get  temperature data for 1 year.
var modis = ee.ImageCollection('MODIS/006/MOD11A1');
var modisLST = modis.filterBounds(geometry).filterDate('2021-01-01', '2021-12-31').select('LST_Day_1km');

// Convert temperature to Celsius.
modisLST = modisLST.map(function(img){
  var date = img.get('system:time_start');
  return img.multiply(0.02).subtract(273.15).set('system:time_start', date);
});

print(modisLST)
print(ui.Chart.image.series(modisLST, geometry, ee.Reducer.mean(), 1000));//打印成折线图

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CSV数据截图：

第二种代码如下（以鹿邑县为例）

var geometry = ee.FeatureCollection('users/www1573979951/luyixian')

// Get  temperature data for 1 year.
var modis = ee.ImageCollection('MODIS/006/MOD11A1');
var modisLST = modis.filterBounds(geometry).filterDate('2021-01-01', '2021-12-31').select('LST_Day_1km');

// Convert temperature to Celsius.
modisLST = modisLST.map(function(img){
  var date = img.get('system:time_start');
  return img.multiply(0.02).subtract(273.15).set('system:time_start', date);
});


var createTS = function(img){
  var date = img.get('system:time_start');
  var value = img.reduceRegion(ee.Reducer.mean(), geometry).get('LST_Day_1km');
  var ft = ee.Feature(null, {'system:time_start': date,'date': ee.Date(date).format('Y/M/d'),'value': value});
  return ft;
};
 
// Apply the function to each image in modisLST.
var TS = modisLST.map(createTS);
print('TS', TS);

print(ui.Chart.image.series(modisLST, geometry, ee.Reducer.mean(), 1000));//打印成折线图
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4 每月遥感数据获取

代码如下（以鹿邑县为例）

var geometry = ee.FeatureCollection('users/www1573979951/luyixian')

// Get  temperature data for 1 year.
var modis = ee.ImageCollection('MODIS/006/MOD11A1');
var modisLST = modis.filterBounds(geometry).filterDate('2021-01-01', '2021-12-31').select('LST_Day_1km');

// Convert temperature to Celsius.
modisLST = modisLST.map(function(img){
  var date = img.get('system:time_start');
  return img.multiply(0.02).subtract(273.15).set('system:time_start', date);
});


var MODISproj = ee.Image(modisLST.first()).projection();
var monthList = ee.List.sequence({start:1,end:12,step:1});
 
//** Function that takes the images for a specified month, calculates the
//   mean over that month, then over a geometry, and returns a value
//   alongside the first date as that month as a time stamp property
var createMonthTS = function(month){
  //--- Define start and end of current month search window (end is exclusive)
  var start = ee.Date.fromYMD(2021, month, 1);
  var end = start.advance(1, 'month');
  //--- Filter by start and end dates
  var monthColl = modisLST.filterDate(start, end);
  //--- First reduce collection with mean reducer, then extract value from geometry
  var monthMean = monthColl.mean();
  var meanVal = monthMean.reduceRegion({
    reducer: ee.Reducer.mean(),
    geometry: geometry,
    crs: MODISproj});
 
  //--- Create feature with desired data/properties and empty geometry
  var ft = ee.Feature(null, {
    'system:time_start': ee.Image(monthColl.first()).get('system:time_start'),
    'date': start.format('Y/M/d'),
    'value': meanVal.get('LST_Day_1km')
  });
  return ft;
};
 
//** Map funciton over month list; recast as feature colleciton
var monthTS = ee.FeatureCollection(monthList.map(createMonthTS));
print('monthTS:', monthTS);
 
//** Create new graph for monthly temperatures
var monthGraph = ui.Chart.feature.byFeature({
  features:monthTS,
  xProperty:'system:time_start',
  yProperties: 'value'});
 
//** Print graph to console
print(monthGraph.setChartType("ColumnChart").setOptions({vAxis: {title: 'LST [deg. C]'},hAxis: {title: 'Date'}}));
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