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Accueil du site → Doctorat → États-Unis → 2007 → THE SPATIAL AND TEMPORAL ROLE OF IRRIGATION ON DAILY WARM SEASON PRECIPITATION IN THE GREAT PLAINS 1950 - 2005

Kent State University (2007)

THE SPATIAL AND TEMPORAL ROLE OF IRRIGATION ON DAILY WARM SEASON PRECIPITATION IN THE GREAT PLAINS 1950 - 2005

Senkbeil, Jason C

Titre : THE SPATIAL AND TEMPORAL ROLE OF IRRIGATION ON DAILY WARM SEASON PRECIPITATION IN THE GREAT PLAINS 1950 - 2005

Auteur : Senkbeil, Jason C

Université de soutenance : Kent State University

Grade : Doctor of Philosophy (PhD) 2007

Résumé
Irrigation use has been steadily increasing in much of the Great Plains since the end of World War II. The impacts of irrigation have resulted in a significant decrease in daily maximum growing season temperature over irrigated areas. While the irrigation impacts on temperature have been studied extensively, there have been relatively few studies detailing the possible relationship between irrigation and precipitation. Previous studies that have explored irrigation/precipitation relationships have resulted in contrary findings using a variety of statistical interpolation and modeling techniques. This research approaches the problem from an observed data perspective using precipitation values from Cooperative stations throughout the Great Plains. The specific research question is : Does irrigation create a precipitation feedback when the amount and density of irrigation exceeds some critical threshold ? This question is answered spatially and temporally using a combination of statistical analyses and classification systems for surface and atmospheric variables at five irrigated regions. The procedure involves the use of the Palmer Drought Severity Index (PDSI) as a proxy for irrigation use, the Spatial Synoptic Classification (SSC) as a means of classifying surface air mass type, and the use of five atmospheric flow types characterizing the synoptic flow pattern. Scenarios, at each irrigated region, involving PDSI level and either air mass type or flow type were tested using both parametric and nonparametric procedures. This novel approach yields precipitation results according to flow type and air mass type at times when irrigation was likely or not likely to be used. Case studies on significant irrigation results at each region involved the use of surface based dynamics. In the absence of considerable dynamic influence upon precipitation, irrigation is assumed to be a probable cause for slightly higher precipitation at stations within or downwind of heavily irrigated regions. Although many spatial results are significant, irrigation is only a minor contributor to precipitation. The most significant irrigation impacts are found on days when the synoptic pattern supports uplift and irrigation is a further agent of destabilization. Temporal results mirror the spatial results. More precipitation was observed at each region during years when irrigation use was higher.

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