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United States Department of Agriculture (USDA) 2009

THE NATURE OF WET AND DRY CYCLES IN THE GREAT BASIN, AND CONNECTIONS TO EVAPOTRANSPIRATION

Wet Dry Evapotranspiration

United States Department of Agriculture (USDA) Research, Education & Economics Information System (REEIS)

Titre : THE NATURE OF WET AND DRY CYCLES IN THE GREAT BASIN, AND CONNECTIONS TO EVAPOTRANSPIRATION

Identification : UTA00327

Pays : Etats Unis

Durée : Jul 1, 2009 à Jun 30, 2014

Domaine : precipitation ; great basin ; atmosphere ; drought ; evaporation ; oceanic factors

Partenaire : UTAH STATE UNIVERSITY LOGAN,UT 84322

Objectifs
There are two general goals for the project. First, study the wet and dry cycles of the intermountain region, and the large-scale features of the atmosphere and ocean that are associated with them. Second, since evapotranspiration (ET) of land surfaces is a critical part of the water balance and is connected to climate, this process will be further studied using both measurements and models. Specific objectives for the first general goal include : quantify the cyclical behavior of the wet and dry cycles with large-scale atmosphere and ocean features using various time series analyses ; and quantify the importance of various cycles of drought over longer time scales approaching 1000 years from time series analyses of the tree ring data. The second main goal includes these specific objectives : make eddy covariance measurements of ET for several surfaces including irrigated turfgrass, a mountain meadow and irrigated fields ; combine the measurements with ET models to determine the surface and atmospheric processes that control ET and its response to climate.

Descriptif
Data will be acquired and compiled for climate of the Great Basin, and upper atmosphere and ocean properties in the western US and Pacific Ocean in the modern record spanning about 50 years. Daily temperature and precipitation data will be gathered for stations in the region, which generally go back at most 100 to 130 years. Finally, long-term, 1000 years, archived estimates of annual temperature and precipitation derived from tree rings will be obtained for available locations. The time series behavior of temperature and precipitation will be conducted for locations in the Great Basin for all data sets. Various approaches including power spectra and wavelet analyses will be employed to reveal the peaks in frequencies of dry and wet periods. In the modern record, the relationships between these cycles and large-scale atmospheric and ocean features will be quantified using cross spectra and coherence analyses. Of particular interest will be any consistent time lags between these features and precipitation, which might imply predictability. The long-term record of precipitation and temperature from tree ring data will also be used to identify droughts and their characteristics. The probability distributions of occurrence, duration and severity of drought will be determined. The ET studies will be largely based on eddy covariance measurements of sensible heat and water vapor fluxes as well as energy balance. These will be conducted over an irrigated turf grass site near USU and a mountain meadow in the nearby Bear River Range. The mountain site is a multidisciplinary observatory with observations including soil water, vegetation properties, snow depth and water equivalent, weather data and other variables. In addition, the eddy covariance measurements of ET and energy balance will also be made for irrigated crops. In all of these ecosystems, the ET measurements will be used to validate simple models, document the key plant and atmospheric processes that control ET, and examine the feasibility of developing new models. The relationship of surface water balance to climate in each of these ecosystems will be determined.

Présentation : USDA

Page publiée le 29 novembre 2015, mise à jour le 7 novembre 2017