RS MINERVE currently offers the possibility to calculate the Potential Evapotranspiration (ETP) values from different methods when no ETP data is available.
The 4 implemented ETP methods are :
- Turc: calculation of ETP depending on the global radiation Rg (based only on latitude and longitude) and temperature
- McGuinness: method depending on Rg (based only on latitude and longitude) and temperature
- Oudin: a french method depending on the extra-terrestrial radiation Re (based only on latitude) and T
- A uniform ETP
The value of global radiation Rg is a monthly averaged value which depends on the latitude and longitude of the hydrological model. These Rg data were obtained from the Surface meteorological and Solar Energy (SSE) web portal, sponsored by the NASA’s Applied Science Program (http://eosweb.larc.nasa.gov/sse).
Rg data takes into account 22 year monthly average (July 1983 – June 2005). The latitude and the longitude values indicate the lower left corner of a 1×1 degree region. Negative values are south and west; positive values are north and east. Boundaries of the -90/-180 region are -90 to -89 (south) and -180 to -179 (west). The last region, 89/180, is bounded by 89 to 90 (north) and 179 to 180 (east). The mid-point of the region is +0.5 added to the latitude/longitude value. These data are regional averages, not point data.
The value of extra-terrestrial radiation Re is directly computed based on the latitude of the hydrological model and parameters such as sun-earth distance and solar declination.
For more information, please refer to the RS MINERVE Technical Manual.