Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA2) is a 30+ year global climate reanalysis dataset. MERRA2 uses modern satellite databases to provide climate variables such as temperature and precipitation.
Min Temperature: Minimum air temperature at 2m height
Max Temperature: Maximum air temperature at 2m height
Precipitation: Daily total precipitation (depth)
ASCE Grass Reference Evapotranspiration (ETo): Penman-Monteith reference ET based on a grass reference crop defined by American Society of Civil Engineers (Allen et al., 2005)
ASCE Alfalfa Reference Evapotranspiration (ETr): Penman Monteith reference ET based on a alfalfa reference crop defined by American Society of Civil Engineers (Allen et al., 2005)
Evap. Demand Drought Index (EDDI): A multi-timescale drought index based on evaporative demand of the atmosphere (Hobbins et al., 2016; McEvoy et al., 2016)
Standard Precipitation Index (SPI): A multi-timescale drought drought index based on precipitation (McKee 1993)
Standard Precipitation Evaporation Index (SPEI): A multi-timescale drought index based on precipitation minus ASCE grass reference evapotranspiration (ETo) (Vicente-Serrano 2010)
Period of Record
Allen, T. G., I. A. Walter, R. Elliot, and T. A. Howell (2005), ASCE-EWRI Standardization of Reference Evapotranspiration, Am. Soc. Civ. Eng. Water Int.
Hobbins, M. T., Wood, A., McEvoy, D. J., Huntington, J. L., Morton, C., Anderson, M., & Hain, C. (2016). The evaporative demand drought index. Part I: Linking drought evolution to variations in evaporative demand. Journal of Hydrometeorology, 17(6), 1745-1761.
McKee, T. B., N. J. Doesken, and J. Kliest, 1993: The relationship of drought frequency and duration to time scales. In Proceedings of the 8th Conference of Applied Climatology, 17-22 January, Anaheim, CA. American Meteorological Society, Boston, MA. 179-184.
McEvoy, D.J., J.L. Huntington, M. Hobbins, A. Wood, and C. Morton, James Verdin, Martha Anderson, and Christopher Hain, 2016: The Evaporative Demand Drought Index: Part II – CONUS-wide Assessment Against Common Drought Indicators. Journal of Hydrometeorology. 17, 1763-1779, doi: 10.1175/JHM-D-15-0122.1.
MERRA-2 Overview: The Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA-2), Ronald Gelaro, et al., 2017, J. Clim., doi: 10.1175/JCLI-D-16-0758.1
Vicente-Serrano S.M., Santiago Beguería, Juan I. López-Moreno, (2010) A Multi-scalar drought index sensitive to global warming: The Standardized Precipitation Evapotranspiration Index – SPEI. Journal of Climate 23: 1696-1718.
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