I am trying to get a monthly time series of MODIS evaporation for a point with the script below, however the problem is that it gives me the weekly values for every month. How can I modify this script to have only the average value of each month?


var geometry = /* color: #d63000 */ee.Geometry.Point([0, 0]);

var modisPET= ee.ImageCollection("MODIS/006/MOD16A2");
var collection05=ee.ImageCollection(modisPET.filterDate('2006-01-01', '2018-12-31'));
var clipped05=collection05.mean().clip(geometry)
var TS5=Chart.image.seriesByRegion(collection05,geometry,ee.Reducer.mean


1 Answer 1


Based on this answer: How to create and use a list of unique dates of images in an ImageCollection GEE you can build a list with all unique months and then create a new monthly image collection:

var monthlyMean = uniqueDatesSimple.map(function(date){
  var monthStart = ee.Date(date)
  var monthEnd = ee.Date(date).advance(1, 'month').advance(-1,'day')
  var subset = collection05.filterDate(monthStart,monthEnd);
  return ee.Image(subset.mean()).copyProperties(subset.first());


  • Thank you, indeed it works
    – Bouram
    Mar 25, 2022 at 10:28

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