问题描述
我正在查看降水数据(GPM 和CHIRPS) 使用 Google 地球引擎针对印度尼西亚的不同省份.GPM 为次日(每 30 分钟一次),CHIRPS 为每日一次.我只对获得每月的价值感兴趣.不像这里和这里 我对获得多年每月值,但只是每个月的平均值并制作时间序列.
I am looking at precipitation data (both GPM and CHIRPS) for different provinces in Indonesia using Google Earth Engine. GPM is sub-daily (every 30 minutes) and CHIRPS is daily. I am only interested in getting the monthly values. Unlike here and here I am not interested in getting the multi-annual monthly values, but simply the average of each month and make a time series.
这里 我找到了一种方法来创建包含每个月平均值的值列表.
Here I found a way to create a list of values containing the mean of each month.
感谢 Nicholas Clinton 的 answer 我设法让它工作:
Thanks to Nicholas Clinton's answer I managed to get it to work:
var fc = ee.FeatureCollection('ft:1J2EbxO3zzCLggEYc57Q4mzItFFaaPCAHqe1CBA4u') // Containing multiple polygons
.filter(ee.Filter.eq('name', 'bangka')); // Here I select my ROI
Map.addLayer(fc, {}, 'area');
Map.centerObject(fc, 7);
var aggregate_array = fc.aggregate_array('name');
print('Name of area: ', aggregate_array, 'Selected data in FeatureCollection:', fc);
var month_mean = ee.List.sequence(0, 16*12).map(function(n) { // .sequence: number of years from starting year to present
var start = ee.Date('2002-01-01').advance(n, 'month'); // Starting date
var end = start.advance(1, 'month'); // Step by each iteration
return ee.ImageCollection("UCSB-CHG/CHIRPS/DAILY")
.filterDate(start, end)
.mean()
.set('system:time_start', start.millis());
});
print(month_mean);
var collection = ee.ImageCollection(month_mean);
print(collection);
// Plotting
var area_name = fc.aggregate_array('name').getInfo();
var title = 'CHIRPS [mm/hr] for ' + area_name;
var TimeSeries = ui.Chart.image.seriesByRegion({
imageCollection: collection,
regions: fc,
reducer: ee.Reducer.mean(),
scale: 5000,
xProperty: 'system:time_start',
seriesProperty: 'label'
}).setChartType('ScatterChart')
.setOptions({
title: title,
vAxis: {title: '[mm/hr]'},
lineWidth: 1,
pointSize: 1,
});
print('TimeSeries of selected area:', TimeSeries);
推荐答案
尚未测试,但应该是这样的(或设置一些其他date
属性):
Have not tested, but should be something like this (or set some other date
property):
return ee.ImageCollection("UCSB-CHG/CHIRPS/DAILY")
.filterDate(start, end)
.sum()
.set('system:time_start', start.millis());
这篇关于使用 Google Earth Engine 将每日数据减少到每月的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!