Google Earth Engine – How to Download Entire Image Collection of a Specific Month from 1990-2020

google-earth-enginegoogle-earth-engine-javascript-apijavascriptrastertime series

I am trying to download ERA-5 daily minimum temperature data of 10 years (2010-2020) for a particular month (at present for November) and a study area (an imported shapefile as WH). I have extracted the daily minimum temperature for the study area but couldn't download the images for each day.

var era5_2mt = ee.ImageCollection('ECMWF/ERA5/DAILY')
                   .select('minimum_2m_air_temperature')
                   .filter(ee.Filter.calendarRange(1990,2020,'year'))
                   .filter(ee.Filter.calendarRange(11,11,'month'));

var era5_2mt_list = era5_2mt.toList(era5_2mt.size());

print(era5_2mt_list);

var study_area = era5_2mt_list.map(function(img){
  
  var date = ee.Date(ee.Image(img).get('system:time_start')).format().slice(0, 10);
  img = ee.Image(img).subtract(273.15);
  
  // Reducing region and getting value
  var value_temp = ee.Image(img)
    .reduceRegion(ee.Reducer.mean(), table)
    .get('minimum_2m_air_temperature');
  
  return [date, value_temp];
  
});

var vis2mt = {
  min: -20,
  max: -10,
  palette: [
    '#000080', '#0000D9', '#4000FF', '#8000FF', '#0080FF', '#00FFFF', '#00FF80',
    '#80FF00', '#DAFF00', '#FFFF00', '#FFF500', '#FFDA00', '#FFB000', '#FFA400',
    '#FF4F00', '#FF2500', '#FF0A00', '#FF00FF'
  ]
};

var image = ee.Image(era5_2mt_list.get(0))
  .subtract(273.15)
  .clip(table);

print(image);

Map.centerObject(image);
Map.addLayer(image, vis2mt);

print(study_area);

I am getting a mean value for the entire area but I want to download each single daily data i.e.,900 elements which is listed in the task section in .tiff format.

the GEE link of my code is below:-GEE CODE

Best Answer

You can try converting the image collection to bands in a single image. I just tried the following code and it took around 10 minutes to export to Google Drive.

var era5_2mt = ee.ImageCollection('ECMWF/ERA5/DAILY')
                   .select('minimum_2m_air_temperature')
                   .filter(ee.Filter.calendarRange(1990,2020,'year'))
                   .filter(ee.Filter.calendarRange(11,11,'month'))
                   // clip to your study area
                   .map(function(image) {return image.clip(table)});


// if you actually need to subtract 273.15, you can map over the image collection, rather than a list of images
// uncomment the following block

// var study_area = era5_2mt.map(function(img){
//   var s_ts = img.get('system:time_start')    // get the 'system:time start' property from the image
//   img = ee.Image(img).subtract(273.15)
//                      .set({'system:time_start': s_ts});   // set the 'system:time_start' property from the output image
//   return(img);
  
// });


// flatten collection to a single image
var merged = era5_2mt.toBands();
// var merged = study_area.toBands();  // use this if you need the calculated images


// export image to Google Drive
Export.image.toDrive({
  image: merged,
  description: 'era5_2mt',
  scale: 20000,
  region: table
});
Related Question