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Indiana University (2014)

Quantifying the influence of irrigated agriculture on atmospheric heat content and boundary layer dynamics

Wright, Timothy E

Titre : Quantifying the influence of irrigated agriculture on atmospheric heat content and boundary layer dynamics

Auteur : Wright, Timothy E

Université de soutenance : Indiana University

Grade : Master of Science (MS) 2014

Résumé
Irrigation delivers about 2,600 km3 of water to the global land surface each year ( 2% of annual over-land precipitation) (Sacks et al. 2009). This research examines the scales of resulting changes to local and regional climates using in situ and remote sensing measurements. The effects of irrigated agriculture on the overlying atmosphere are compared with adjacent non-irrigated locations using equivalent potential temperature (θ e ) and potential evapotranspiration (ETo ). These are better metrics for quantifying total atmospheric heat content near the surface than temperature alone because of the effect of latent heat exchange (LE) which separates temperature from total heat content. Satellite-derived surface albedo and emissivity are used to quantify the differences in net radiation at the surface between adjacent irrigated and non-irrigated landscapes. These data are used with θ e and ETo in a spectrum of climates across the United States to quantify impacts of irrigation in each regime. The results indicate the effects depend on both the climate and surrounding land cover. For arid regions, net radiation and θe are higher over irrigation because of lower albedo ; however, higher emissivity offsets much of the warming. Increased LE due to higher water availability results in lower temperatures over irrigation, to a degree that is a function of regional humidity. As one moves from drier to more humid environments, the effects of irrigation transition from large positive forcing on net radiation and LE to near zero. However, the differences in θ e and ET o sometimes far exceed what net radiation and the heat budget suggest and thus clearly indicate a regional response to irrigation and as documented herein that the enhancement of θe scales with fetch over irrigation. The effects on the boundary layer dynamics due to the change in net radiation and heat fluxes typically are characterized by suppression of convection over irrigation and enhancement over adjacent non-irrigated areas.

Mots clés : Agriculture, Atmospheric sciences, Climate Change, Water Resource Management, Meteorology, Biological sciences , Earth sciences

Accès au document : Proquest Dissertations & Theses

Page publiée le 2 février 2015, mise à jour le 29 décembre 2017