Downloading daily precipitation and temperature data from ERA5 using Google Earth Engine JavaScript API

Question

I tried using the code below to download the data. I have doubts about the correctness of the code.

Can you help me correct it?

I encountered errors, which may be due to the large size of the dataset. Additionally, I'm plotting the data, which might cause further issues.

ar roi = geometry;

// Define the time range
var startDate = '2021-01-01';
var endDate = '2021-05-31';

// Create a date range
var dateRange = ee.DateRange(startDate, endDate);

// Load ERA5-Land temperature data
var era5Land = ee.ImageCollection('ECMWF/ERA5_LAND/DAILY_AGGR')
  .filterBounds(roi)
  .filterDate(dateRange)
  .select(['temperature_2m']);

// Aggregate the data to daily scale by calculating the mean
var dailyEra5Land = era5Land.mean();

// Print the first image in the collection
print('First image in the collection:', dailyEra5Land);

// Create a time series chart for temperature
var tempChart = ui.Chart.image.seriesByRegion({
  imageCollection: era5Land,
  regions: roi,
  reducer: ee.Reducer.mean(),
  scale: 10000,
  xProperty: 'system:time_start'
}).setOptions({
  title: 'Temperature Time Series',
  hAxis: {title: 'Date'},
  vAxis: {title: 'Temperature (°C)'},
});

Answer 1

You're using era5Land (the original image collection) instead of dailyEra5Land (the aggregated daily mean) when creating the time series chart.

var admin2 = ee.FeatureCollection("FAO/GAUL_SIMPLIFIED_500m/2015/level2");
 
var bangalore = admin2.filter(ee.Filter.eq('ADM2_NAME', 'Bangalore Urban'))
var roi = bangalore.geometry()

// Define the time range
var startDate = '2021-01-01';
var endDate = '2021-05-31';

// Create a date range
var dateRange = ee.DateRange(startDate, endDate);

// Load ERA5-Land temperature data
var era5Land = ee.ImageCollection('ECMWF/ERA5_LAND/DAILY_AGGR')
  .filterBounds(roi)
  .filterDate(dateRange)
  .select(['temperature_2m']);

// Aggregate the data to daily scale by calculating the mean
var dailyEra5Land = era5Land.mean();

// Print the first image in the collection
print('First image in the collection:', dailyEra5Land);

// Create a time series chart for temperature
var tempChart = ui.Chart.image.seriesByRegion({
  imageCollection: era5Land,
  regions: roi,
  reducer: ee.Reducer.mean(),
  scale: 10000,
  xProperty: 'system:time_start'
}).setOptions({
  title: 'Temperature Time Series',
  hAxis: { title: 'Date' },
  vAxis: { title: 'Temperature (°C)' },
});

// Print the chart
print(tempChart);