ERA5-Land monthly averaged data from 1950 to present

Datasets and Usage
1

Hi, Kevin!
There is a problem with interpreting monthly precipitation data for Ukraine for the period 2006-2020 -Total precipitation. The value of monthly precipitation in “m” is very small and when converted to “mm” by multiplying by 1000. For Ukraine, the standard value is 80-120 mm per month. We get from 0.4 to 1.2. Maybe I interpret this data incorrectly? Can you help me? Thank you very much. My API request code:
import cdsapi

dataset = “reanalysis-era5-land-monthly-means”
request = {
“product_type”: [“monthly_averaged_reanalysis”],
“variable”: [
“2m_temperature”,
“skin_temperature”,
“soil_temperature_level_1”,
“soil_temperature_level_2”,
“soil_temperature_level_3”,
“soil_temperature_level_4”,
“snow_depth”,
“volumetric_soil_water_layer_1”,
“volumetric_soil_water_layer_2”,
“volumetric_soil_water_layer_3”,
“volumetric_soil_water_layer_4”,
“surface_solar_radiation_downwards”,
“total evaporation”,
“total precipitation”,
“leaf_area_index_high_vegetation”,
“leaf_area_index_low_vegetation”
],
“year”: [“2019”],
“month”: [
“04”, “05”, “06”,
“07”, “08”, “09”,
“10”
],
“time”: [
“00:00”, “06:00”, “12:00”,
“18:00”
],
“data_format”: “netcdf”,
“download_format”: “zip”,
“area”: [51.8, 26, 50.2, 31.04]
}

client = cdsapi.Client()
client.retrieve(dataset, request).download()

2

Hi Tatiana!
I checked and I think it’s just related to the units the data are stored in; from the ERA5-Land: data documentation - Copernicus Knowledge Base - ECMWF Confluence Wiki

'The accumulations in monthly means of daily means (stream=moda) have units that include “per day”. So for accumulations in this stream:

  • The hydrological parameters are in units of “m of water equivalent per day” and so they should be multiplied by 1000 to convert to kgm-2day-1 or mmday-1. ’

So to get the total precipitation for a given month, you need to also multiply by the number of days in the month e.g. for your value 0.4 mm* 31 = 12.4 mm.

Hope that helps!

3

Hi Kevin! Thanks for the explanation. This is useful information! Although 0.4x31=12.4. But, this is not so important. The main thing is the correct interpretation of the output data - the sum of monthly precipitation.
All the best, Tatiana

4

Hi Tatiana, apologies, I have corrected my mistake with the numeric value from the calculation,
Kevin