The precipitation and temperature data are derived from the CRU TS 3.21 dataset produced by the Climate Research Unit at the University of East Anglia. This is a global gridded dataset of monthly observations over the period 1901-2012. The spatial resolution of the dataset is 0.5°.
University of East Anglia Climatic Research Unit; Jones, P.D.; Harris, I. (2013): CRU TS3.21: Climatic Research Unit (CRU) Time-Series (TS) Version 3.21 of High Resolution Gridded Data of Month-by-month Variation in Climate (Jan. 1901- Dec. 2012). NCAS British Atmospheric Data Centre, 24th September 2013. doi:10.5285/D0E1585D-3417-485F-87AE-4FCECF10A992. http://dx.doi.org/10.5285/D0E1585D-3417-485F-87AE-4FCECF10A992
The reliability of the dataset depends on the number of stations used in the interpolation, which is spatially and temporally variable. For a station to be included in the interpolation, its record must be >75% complete over the period 1961-1990. Station data, showing the number of station observations in each grid cell at each time-step (i.e. month), have been averaged over the period 1950-2010 and are shown on the maps below. Station data can influence the gridded value in a given cell if it lies within a predefined Correlation Decay Distance. This is 450 km for precipitation and 1200 km for mean temperature. For Africa, approximately 75% of the grid cells contain station data, or have station data within the correlation decay distance, with valid values over the period 1901-2000. The number of stations used to calculate the interpolated data value at each grid cell has been averaged over all time-steps between 1950 and 2010 and is shown on the maps below.
The climate zones are taken from the updated Köppen-Geiger climate classification presented by Peel et al. This is a widely used classification scheme that has been updated using long-term station records of monthly precipitation and temperature from the Global Historical Climatology Network (GHCN) version 2.0 dataset. As for the gridded precipitation and temperature data, the reliability of this dataset is dependent on the density of input data. Detailed information on the data and methodology can be found in the following paper:
Peel MC, Finlayson BL and McMahon TA. 2007. Updated world map of the Köppen-Geiger climate classification. Hydrol. Earth Syst. Sci., 11, 1633-1644.
|Af||Tropical Rainforest||Am||Tropical Monsoon||Aw||Tropical Savannah|
|BSh||Arid Steppe (hot)||BSk||Arid Steppe (cold)|
|BWh||Arid Desert (hot)||BWk||Arid Desert (cold)|
|Cfa||Temperate without dry season (hot summer)||Cfb||Temperate without dry season (warm summer)|
|Csa||Temperate with dry summer (hot summer)||Csb||Temperate with dry summer (warm summer)|
|Cwa||Temperate with dry winter (hot summer)||Cwb||Temperate with dry winter (warm summer)|
Links to External Data
The CRU TS3.21 dataset is freely available through the Centre for Environmental Data Archival (CEDA). Users must register with CEDA to access the dataset.
Further information on the development of the preceding dataset (CRU TS3.10) can be found in:
Harris, I., Jones, P.D., Osborn, T.J., and Lister, D.H. 2013. Updated high-resolution grids of monthly climatic observations – the CRU TS3.10 Dataset. International Journal of Climatology 34(3): 623-642 (DOI: 10.1002/joc.3711)
The Köppen-Geiger climate map is freely available in the supplementary material to the paper presented by Peel et al.