The POWER project was initiated in 2003 as an outgrowth of the Surface meteorology and Solar Energy (SSE) project, which has as its focus the development of parameters related to the solar based energy industry. The current POWER project encompasses the SSE project with the objective to improve subsequent releases of SSE, and to create new datasets with applicability to the architectural (e.g. Sustainable Buildings) and agricultural (e.g. Agroclimatology) industries. In general, the underlying data behind the parameters used by each of these industries is the same – global solar radiation, or insolation, and meteorology, including surface and air temperatures, moisture, and winds.
The Agroclimatology Methodology document describes the underlying data and parameters derived from these data and their estimated accuracies. The intent is to provide information that will enable new and/or long time users to make decisions concerning the suitability of the Agroclimatology data for their project in a particular region of the globe.
This section provides a summary overview of estimates for the uncertainties associated with the solar and meteorological parameters in the POWER/Agroclimatology data archive. These estimates were derived through comparisons with ground based observations. A more detailed discussion of the analysis and comparisons with the observational data is available in the PDF version of the agroclimatology methodology document which can be downloaded using the link at the bottom of this page.
The solar and meteorological parameters in the Agroclimatology Archive have been developed from various data sources as follows:
- For the time period July 1, 1983 – December 31, 2007 solar parameters are taken from release 3 of the NASA/GEWEX Surface Radiation Budget (GEWEX SRB 3.0 - http://eosweb.larc.nasa.gov/PRODOCS/srb/table_srb.html) project;
- For the time period from January 1, 2008 to within a week of real time solar parameters are taken from NASA’s Fast Longwave And SHortwave Radiative Fluxes (FLASHFlux - http://flashflux.larc.nasa.gov/ & https://eosweb.larc.nasa.gov/project/ceres/flashflux-tisa_table ) project;
- Meteorological parameters (i.e. daily temperatures, relative humidity, and dew point) are from NASA’s Global Model and Assimilation Office (GMAO - http://gmao.gsfc.nasa.gov/ ), Goddard Earth Observing System model version 4 (GEOS-4) for the time period from January 1, 1983–December 31, 2007; and from GEOS–5.2 for the time period from January 1, 2008 to within several days of real time.
- Daily precipitation values were obtained from the Global Precipitation Climate Project (GPCP - http://precip.gsfc.nasa.gov/ ) from January 1, 1997 – August 31, 2009.
- Daily mean wind speeds over the time period January 1, 1983 –December 31, 2007 are from the NASA/GMAO GEOS version 4 (GEOS-4) assimilation model and over the time period January 1, 2008 to within several days of current time are from the GEOS-5.2 model.
Estimates of Parameter Accuracies:
Solar: The uncertainties associated with the GEWEX/SRB and FLASHFlux solar insolation are based upon comparisons to ground based observations from the Baseline Surface Radiation Network (BSRN).
Temperatures: The uncertainties associated with the GEOS-4 and GEOS-5.2 temperatures parameters are based upon comparisons to ground based observations available from the National Climate Data Center (NCDC) global summary of the day (GSOD) files .
Winds Speed: The uncertainties associated with the wind speed data are based upon comparisons with observations reported in the NCDC GSOD files for the GEOS-4 and GEOS-5.2 winds.
Precipitation: The uncertaities associated with the GPCP precipitation values are based upon comparisons with ground observations reported in the NCDC GSOD files.