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table1
table1
Table 1: WFDE5 variables summary

Variable name

Description

Units

Time coverage (v1.0, v1.1)

Time coverage (v2.0)

Wind

Near-surface wind speed

m s-1

1979-01-01 00:00:00 to

2018-12-31 23:00:00

1979-01-01 00:00:00 to

2019-12-31 23:00:00

Tair

Near-surface air temperature

K

1979-01-01 00:00:00 to

2018-12-31 23:00:00

1979-01-01 00:00:00 to

2019-12-31 23:00:00

PSurf

Surface air pressure

Pa

1979-01-01 00:00:00 to

2018-12-31 23:00:00

1979-01-01 00:00:00 to

2019-12-31 23:00:00

Qair

Near-surface specific humidity

kg kg-1

1979-01-01 00:00:00 to

2018-12-31 23:00:00

1979-01-01 00:00:00 to

2019-12-31 23:00:00

LWdown

Surface downwelling longwave radiation

W m-2

1979-01-01 07:00:00 to

2018-12-31 23:00:00

1979-01-01 07:00:00 to

2019-12-31 23:00:00

SW down

Surface downwelling shortwave radiation

W m-2

1979-01-01 07:00:00 to

2018-12-31 23:00:00

1979-01-01 07:00:00 to

2019-12-31 23:00:00

Rainf (CRU)

Rainfall flux (corrected using CRU TS dataset)

kg m-2 s-1

1979-01-01 07:00:00 to

2018-12-31 23:00:00

1979-01-01 07:00:00 to

2019-12-31 23:00:00

Snowf (CRU)

Snowfall flux (corrected using CRU TS dataset)

kg m-2 s-1

1979-01-01 07:00:00 to

2018-12-31 23:00:00

1979-01-01 07:00:00 to

2019-12-31 23:00:00

Rainf (CRU+GPCC)

Rainfall flux (corrected using CRU TS and GPCC datasets)

kg m-2 s-1

1979-01-01 07:00:00 to

2016-12-31 23:00:00

1979-01-01 07:00:00 to

2019-12-31 23:00:00

Snowf (CRU+GPCC)

Snowfall flux (corrected using CRU TS and GPCC datasets)

kg m-2 s-1

1979-01-01 07:00:00 to

2016-12-31 23:00:00

1979-01-01 07:00:00 to

2019-12-31 23:00:00

ASurf

Gird-point altitude

m

-

-

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table2
table2
Table 2: WFDE5 versions history

Version

Observational datasets used

Changes from previous version

v1.0

·  CRU TS 4.03 (all variables)

·  GPCCv2018 (Rainf and Snowf)

-

v1.1

·  CRU TS 4.03 (all variables)

·  GPCCv2018 (Rainf and Snowf)

·  Fix SWdown values, affected in v1.0 by a bug compromising correct computation

v2.0

·  CRU TS 4.04 (all variables)

·  GPCCv2020 (Rainf and Snowf)

·  Use latest versions of the observational datasets

·  Extend time coverage to 2019

·  Update diurnal temperature range correction algorithm

v2.1

·  CRU TS 4.04 (all variables)

·  GPCCv2020 (Rainf and Snowf)

·  Fix issue affecting Qair and LWdown values (see "Known issues" section) 

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table3
table3
Table 3: Input datasets

Dataset

Summary

Variables used

ERA5

ECMWF reanalysis product

·  10 m u-component of wind

·  10 m v-component of wind

·  2 m temperature

·  Surface pressure

·  2 m dewpoint temperature

·  Surface thermal radiation downwards

·  Surface solar radiation downwards

·  Cloud cover

·  Total precipitation

·  Snowfall

·  Land-sea mask

·  Lake cover mask

·  Orography

CRU TS 4.03,

CRU TS 4.04

Climate Research Unit gridded station observations (multiple variables)

·  Temperature

·  Diurnal temperature range

·  Cloud cover

·  Wet days

·  Precipitation

·  Grid-points altitude

GPCCv2018, GPCCv2020

Global Precipitation Climatology Centre gridded station precipitation observations

·  Precipitation

Other

-

·  Rainfall and snowfall gauge corrections 1

·  Aerosol loading corrections to shortwave downward radiation 2


Info
iconfalse

1Provided by Jennifer Adam (jcadam@wsu.edu), following the methodology described in [8]

2Provided by Nicolas Bellouin (n.bellouin@reading.ac.uk), following the methodology described in [1] with updates on input datasets described in [7].

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table4
table4
Table 4: WFDE5 dataset general attributes

Dataset attribute

Details

Horizontal coverage

Global

Horizontal resolution

0.5° x 0.5°

Vertical coverage

Surface

Temporal coverage

Depends on variable (see Table 3)

Temporal resolution

Hourly

File format

netCDF

Data type

Grid

Versions

v1.0, v1.1, v2.0, v2.1

Aggregation to the half-degree grid is applied on sea-level adjusted values of the different ERA5 variables, which are obtained as part of the elevation-correction procedure.

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As an example, possible file names are:

  • Tair_WFDE5_CRU_201801_v1.0.nc
  • Rainf_WFDE5_CRU_201801_v1.0.nc
  • Rain_WFDE5_CRU+GPCC_201801_v1.0.nc

File content

Actual file content and dimensions size varies from month to month and depending on the variable, but the general file structure is constant and analogous to the following example:

...

If publishing using this dataset please cite [7], where a more detailed description of the dataset can be found.

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appendixa
appendixa

Appendix A – WFDE5v2.0: DTR-based correction algorithm update

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  1. For each month, interpolated ERA5 hourly near-surface air temperatures are used to compute the ERA5 interpolated monthly average diurnal temperature range (DTRE5,mm);

  2. DTR correction factors A and R are computed in the following way: 

    Mathdisplay
    A = DTR_{CRU} - DTR_{E5,mm}


    Mathdisplay
    R = \frac{DTR_{CRU}}{DRT_{E5,mm}}


  3. ERA5 interpolated diurnal temperature range values are corrected (DTRE5,corr), depending on the value of R at each grid-point, in the following way: 


    Mathdisplay
    DTR_{E5,corr} = 
\begin{cases}
DTR_{E5} * R & R \le 1 \\
DTR_{E5} + A & R < 1 \\
\end{cases}


  4. A multiplicative correction factor F is computed as: 

    Mathdisplay
    F = \frac{DTR_{E5,corr}}{DTR_{E5}}


  5. After applying the correction for monthly mean biases, deviations of corrected hourly ERA5 near-surface air temperature values (TairE5,corr) from their respective daily means (TairE5,corr,dm) are multiplied by F , and results are added to ERA5 near-surface air temperature daily means (TairE5,dm) to obtain final corrected hourly WFDE5 near-surface air temperature values (TairW5): 

    Mathdisplay
    Tair_{W5} = Tair_{E5,corr,dm} + (Tair_{E5,corr} - Tair_{E5,corr,dm}) \ast F


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appendixb
appendixb

Appendix B – WFDE5v2.1: Qair derivation algorithm update

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references1
references1
[1]    G. P. Weedon, S. Gomes, P. Viterbo, H. Österle, J. C. Adam, N. Bellouin, O. Boucher and M. Best, "The WATCH Forcing Data 1958-2001: A meteorological forcing dataset for land surface- and hydrological-models", WATCH Technical Report 22, https://publications.pik-potsdam.de/rest/items/item_16400_1/component/file_16401/content, 2010.

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references2
references2
[2]    G. P. Weedon, S. Gomes, P. Viterbo, W. J. Shuttleworth, E. Blyth, H. Österle, J. C. Adam, N. Bellouin, O. Boucher and M. Best, "Creation of the WATCH Forcing Data and Its Use to Assess Global and Regional Reference Crop Evapouration over Land during the Twentieth Century", Journal of Hydrometeorology, vol. 12, pp. 823-848, doi: 10.1175/2011JHM1369.1, 2011.

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references9
references9
[9]    A. L. Buck, "New equations for computing vapour pressure and enhancement factor", Journal of Applied Meteorology and Climatology, doi: 10.1175/1520-0450(1981)020<1527:NEFCVP>2.0.CO;2, 1981

Info
iconfalse

This document has been produced in the context of the Copernicus Climate Change Service (C3S).

The activities leading to these results have been contracted by the European Centre for Medium-Range Weather Forecasts, operator of C3S on behalf of the European Union (Delegation

agreement

Agreement signed on 11/11/2014 and Contribution Agreement signed on 22/07/2021). All information in this document is provided "as is" and no guarantee or warranty is given that the information is fit for any particular purpose.

The users thereof use the information at their sole risk and liability. For the avoidance of all doubt , the European Commission and the European Centre for Medium - Range Weather Forecasts have no liability in respect of this document, which is merely representing the author's view.

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