Historical estimates of spatial reference evapotranspiration for the Central Valley of California
Abstract
In this study we present spatial reference evapotranspiration (ETo) estimates for the Central Valley from 1921 to 2008 derived from NCDC/NOAA daily climate data and PRISM monthly climate data grids (PRISM group; Oregon State University, Corvallis, USA; http://www.prism.oregonstate.edu). Data from the California Irrigation Management Information System (CIMIS) weather station were also used. 2009 is currently the third year of drought in California and better tools for irrigation and water resource management are needed to provide a secure water supply in the future. Temperature and Precipitation are driving variables in the estimation of ET occurring on the landscape scale. Consequently, modeling evaluations of a growing number of hydrological issues are increasingly requiring reliable area coverage of meteorological datasets. The availability of these datasets with adequate spatial and temporal resolution is particularly critical for decision support models for better management of water resources, such as the SIMETAW-II project supported with this study. Daily maximum-minimum temperature and precipitation spatial datasets were calculated by combining daily NCDC climate station data and monthly PRISM climate data grids. This study relies on the input PRISM grids to reproduce spatial climate patterns as well as anchor the daily climate values to the monthly averages given in the PRISM dataset such as total monthly precipitation and average daily temperatures. The historic daily climate data available for the period from 1921 to present consists of data for minimum temperature, maximum temperature and precipitation. Due to this restricted historical data set we cannot directly compute Penman-Monteith Reference Evapotranspiration (ETo) as adopted by the Environmental Water Resources Institute - American Society of Civil Engineers (ASCE-EWRI, 2004). Instead this study uses the Hargreaves-Samani equation for estimating Reference Evapotranspiration (ETh). For the final ETo estimates, we developed a correction factor based on CIMIS station ETo data and ETh data calculated from NCDC/NOAA COOP station data. Results from our study were validated against spatial ETo estimates by the CIMIS-GOES project from 2005 to present.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFM.H51B0771F
- Keywords:
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- 0438 BIOGEOSCIENCES / Diel;
- seasonal;
- and annual cycles;
- 1818 HYDROLOGY / Evapotranspiration;
- 1842 HYDROLOGY / Irrigation;
- 1843 HYDROLOGY / Land/atmosphere interactions