Google Earth Engine CHIRPS Data – Solving Visualization Issues

google-earth-enginegoogle-earth-engine-javascript-api

I want to load Precipitaion Data for my region. But when I ran the code, just the global South beneath Germany appears. Can you help?

https://code.earthengine.google.com/?accept_repo=users/laraemsinghoff/Start

var styling2 = {color: 'red', fillColor: '00000000'};
Map.addLayer (Westfalen.style(styling2));
Map.centerObject (Westfalen)

var dataset = ee.ImageCollection('UCSB-CHG/CHIRPS/DAILY')
                  .filter(ee.Filter.date('2018-03-01', '2021-10-01'))
                  .filterBounds (Westfalen);
var precipitation = dataset.select('precipitation');
var precipitationVis = {
  min: 1.0,
  max: 17.0,
  palette: ['001137', '0aab1e', 'e7eb05', 'ff4a2d', 'e90000'],
};

Map.addLayer(precipitation, precipitationVis, 'Precipitation');

Best Answer

According to the reference that appears in the citations tab of the CHIRPS dataset (https://www.nature.com/articles/sdata201566), the data is "quasi-global (50°S-50°N)", so that is the reason why there is no data north of 50°N.

Related Solutions

Raster – How to Extract Daily Rainfall Data from CHIRPS Database for Polygons Using Google Earth Engine

Not sure if this is what you are after:

var totalOutput = ee.ImageCollection(img_col).map(function(image){
  //deriving the date of the image
  var date= image.get('system:index')
  
  var test = coc.map(function(feature){ 
    var rain = image.reduceRegion({
      reducer: ee.Reducer.mean(),
      geometry: feature.geometry(),
      scale: 5500, //the CHIRPS dataset has 0.05 degree resolution
      maxPixels: 5e12
    });
    
   return ee.Feature(feature.set('MeanRain', rain.get('precipitation'))
                            .set ("Date", date))
  })
  
  return ee.FeatureCollection(test);
}).flatten()

print(totalOutput.limit(50))

https://code.earthengine.google.com/c7371aced206da99d9cd6e1a169d943f?asset=users%2Fasifishti%2FCoC_subdis

A quick look gave me a lot of 0 values for rainfall so maybe double check!

Google Earth Engine – Grouping Weather Data by Region

It's a bit fiddly to do this. Here's one approach:

var days = endDate.difference(startDate, "days") // Number of days in date range
var dailyTempByCounty = ee.FeatureCollection(ee.List.sequence(0, days.subtract(1))
  .map(function(dayOffset) { // Calculate mean per day
    var date = startDate.advance(ee.Number(dayOffset), 'days')
    var dailyMean = tmpCollection
      .filterDate(date, date.advance(1, 'days'))
      .mean()
    return counties.map(function (county) {
       // Calculate mean for every county separately, 
       // so the date can be included
      var mean = dailyMean.reduceRegion({
        reducer: ee.Reducer.mean(), 
        geometry: county.geometry(), 
        scale: 4000
      })
      return county
        .set(mean)
        .set('date', date.format('yyyy-MM-dd'))
    })
  })
).flatten() // Flattens the collection of collection of features into a collection of features

https://code.earthengine.google.com/64937228d07d5c2d05cec1d5400aa914

It takes quite a lot of processing to do this. The linked script uses only data for a couple of days, and just two counties, to give a fast result that can be printed in the console.

Note that the end date is exclusive. Just like the date filter in collections - many people seem to get that wrong, and miss the last day of the year, just like in your question.

Best Answer

Related Solutions

Raster – How to Extract Daily Rainfall Data from CHIRPS Database for Polygons Using Google Earth Engine

Google Earth Engine – Grouping Weather Data by Region

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