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Product description
Versions
| Version | Change description |
|---|---|
v2.0 |
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v1.1
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v1.0
| Initial release of AgERA5 |
Introduction
Climate forcing data is used in analysis and agro-environmental modelling to study aspects of productivity and externalities of agriculture (e.g. Toreti et al, 2019; Glotter et al., 2016; De Wit et al., 2010). In this service we start from the hourly ECMWF ERA5 model data and convert the data into meaningful input for these analyses and modelling. It involves a large amount of data that needs to be processed. Acquisition and pre-processing of ERA5 data, both archive and near real-time (NRT) data, is a large and specialized job. It requires a heavy investment for users like technical policymakers, information agencies, NGOs, commodity traders, agri-businesses, insurance providers etcetera. The complex task and required effort may even be a barrier to start using the data.
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Table 3.1: List of variables in the AgERA5 data set
Short name | Long name | Unit | Aggregation | AGROVOC URI | In V2 |
Cloud_Cover_Mean | Total cloud cover (00-00LT) | (0 - 1) | Mean | N | |
Dew_Point_Temperature_2m_Mean | 2 meter dewpoint temperature (00-00LT) | K | Mean | N | |
Preciptation_Flux | Total precipitation (00-00LT) | mm d-1 | Sum | N | |
Preciptation_Rain_Duration_Fraction | Precipitation type duration - rain (00-00LT) | - | Count | N | |
Preciptation_Solid_Duration_Fraction | Precipitation type duration - solid fraction (no hail) composed of: precipitation types freezing rain (3), snow (5), wet snow (6), mixture of | - | Count | N | |
Relative_Humidity_2m_06h | Relative humidity at 06LT | % | - | N | |
Relative_Humidity_2m_09h | Relative humidity at 09LT | % | - | N | |
Relative_Humidity_2m_12h | Relative humidity at 12LT | % | - | N | |
Relative_Humidity_2m_15h | Relative humidity at 15LT | % | - | N | |
Relative_Humidity_2m_18h | Relative humidity at 18LT | % | - | N | |
Snow_Thickness_LWE_Mean | Snow liquid water equivalent (00-00LT) | cm of liquid water equivalent | Mean | N | |
Snow_Thickness_Mean | Snow depth (00-00LT) | cm snow | Mean | N | |
Solar_Radiation_Flux | Surface solar radiation downwards (00-00LT) | J m-2d-1 | Sum | N | |
Temperature_Air_2m_Max_24h | Maximum air temperature at 2 meter (00-00LT) | K | Maximum | N | |
Temperature_Air_2m_Max_Day_Time | Maximum air temperature at 2 meter (06-18LT) | K | Maximum | N | |
Temperature_Air_2m_Mean_24h | 2 meter air temperature (00-00LT) | K | Mean | N | |
Temperature_Air_2m_Mean_Day_Time |
| K | Mean | N | |
Temperature_Air_2m_Mean_Night_Ti me |
| K | Mean | N | |
Temperature_Air_2m_Min_24h | Minimum air temperature at 2 meter (00-00LT) | K | Minimum | N | |
Temperature_Air_2m_Min_Night_Time | Minimum air temperature at 2 meter (18-06LT) | K | Minimum | N | |
Vapour_Pressure_Mean | Vapour pressure (00-00LT) | hPa | Mean | N | |
Wind_Speed_10m_Mean | 10 meter wind component (00-00LT) | m s-1 | Mean | N | |
ReferenceET_PenmanMonteith_FAO56 | Penman-Monteith reference evapotranspiration according to the FAO56 approach | mm d-1 | - | Y | |
Derived_Relative_Humidity_2m_Min* | Minimum Relative Humidity: derived from AgERA5 24h-maximum temperature and mean vapor pressure (00-00LT) as a post-processing step. | % | - | Y | |
Derived_Relative_Humidity_2m_Max* | Maximum Relative Humidity: derived from AgERA5 24h-minimum temperature and mean vapor pressure (00-00LT) as a post-processing step. | % | - | Y | |
Vapour_Pressure_Deficit_at_Maximum_Temperature | Vapour pressure deficit derived from saturated vapour pressure for maximum temperature and 24h mean vapour pressure | hPa | - | Y | |
Precipitation_Duration_Fraction | Precipitation duration fraction composed of: hours with precipitation amount >= 0.1 mm / h divided by 24. (00-00LT) | - | Count | Y |
*The term “derived” was added to indicate the difference with the relative humidity layers at specific time intervals. The latter are derived from the original ERA5 input fields: the temperature (t2m) and dewpoint (d2m) fields while the “derived” variables are computed from the AgERA5 layers as a post-processing step. See the ATBD in the AgERA5 documentation for details. The advantage of the "derived" relative humidity layers is that they avoid the "striping" effect in the relative humidity layers at specific time intervals. See the relevant section inthe "known issues v1.1"
Product target requirements
DATA DESCRIPTION | |
Horizontal coverage | Global (on a regular latitude-longitude grid) |
Temporal Coverage | 3 January 1979 to present |
Temporal resolution | Daily |
File format | NetCDF 4, Climate and Forecast (CF) Metadata Convention v1.7 |
Data type | Grid |
Horizontal resolution | 0.1° x 0.1° |
Some remarks related to the quality of the AgERA5 data set:
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Several users have reported erroneous temperature values in the Tmin-24h variable where the value for selected grid cells could reach unrealistic values of around 220 K (-50 C) in locations with otherwise high temperatures. Analysis of the spatial distribution demonstrated that the cells with erroneous values can often be found in Western Australia but are not limited to that region and can be found in other parts of the World as well (Figure 1).
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Figure 1: Maps of AgERA5 Tmin-24h with rogue values (black cells) for several regions in the World
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Table 1: Values for vapour pressure and humidith at local time for the selected points.
Blue dot | Red dot | |||||
latitude | 1.14 | latitude | 1.14 | |||
longitude | 22.4 | longitude | 22.5 | |||
Vapour pressure | 21.54 | hPa | Vapour pressure | 21.45 | hPa | |
06h | 88.05 | % | 06h | 89.1 | % | |
09h | 61.3 | % | 09h | 87.3 | % | |
12h | 43.8 | % | 12h | 60.3 | % | |
15h | 56.9 | % | 15h | 43.1 | % | |
18h | 69.7 | % | 18h | 54.7 | % | |
Figure 5: Relative humidity values throughout the day for the two points on opposite sides of the discontinuity.
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