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The GPCC drought index provides SPEI datasets at a 1.0° spatial resolution for limited timescales (1, 3, 6, 9, 12, 24, and 48 months). [5] Inputs to SPEI datasets can include high-resolution potential evapotranspiration (PET) from the Global Land Evaporation Amsterdam Model (GLEAM) and hourly Potential Evapotranspiration (hPET). GLEAM is a set ...
Other equations for estimating evapotranspiration from meteorological data include the Makkink equation, which is simple but must be calibrated to a specific location, and the Hargreaves equations. To convert the reference evapotranspiration to the actual crop evapotranspiration, a crop coefficient and a stress coefficient must be used.
The Palmer drought index, sometimes called the Palmer drought severity index (PDSI), is a regional drought index commonly used for monitoring drought events and studying areal extent and severity of drought episodes. [1] The index uses precipitation and temperature data to study moisture supply and demand using a simple water balance model.
Given the limited data input to the equation, the calculated evapotranspiration should be regarded as only broadly accurate. Rather than a precise measure of evapotranspiration, the output of the equation is better thought of as providing an order of magnitude. [2] The inaccuracy of the equation is exacerbated by extreme variants of weather.
This equation uses the principles of conservation of mass in a closed system, whereby any water entering a system (via precipitation), must be transferred into either evaporation, transpiration, surface runoff (eventually reaching the channel and leaving in the form of river discharge), or stored in the ground. This equation requires the system ...
Monthly estimated potential evapotranspiration and measured pan evaporation for two locations in Hawaii, Hilo and Pahala. Potential evapotranspiration is usually measured indirectly, from other climatic factors, but also depends on the surface type, such as free water (for lakes and oceans), the soil type for bare soil, and also the density and diversity of vegetation.
The hydrological cycle is a system whereby the evaporation of moisture in one place leads to precipitation (rain or snow) in another place. For example, evaporation always exceeds precipitation over the oceans. This allows moisture to be transported by the atmosphere from the oceans onto land where precipitation exceeds evapotranspiration.
The Keetch–Byram drought index (known as KBDI), created by John Keetch and George Byram in 1968 for the United States Department of Agriculture's Forest Service, is a measure of drought conditions. It is commonly used for the purpose of predicting the likelihood and severity of wildfire .