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University of Arizona (2022)

Investigating Water Stress in Drylands

Javadian, Mostafa

Titre : Investigating Water Stress in Drylands

Auteur : Javadian, Mostafa

Université de soutenance : University of Arizona

Grade : Doctor of Philosophy (PhD) 2022

Résumé partiel
Drylands are defined as tropical and temperate areas with a ratio of precipitation to potential evapotranspiration of less than 0.65. They cover 40% of the Earth’s surface and they are home to one-third of the world’s population. Water Stress is by definition characteristic of dryland systems and only 8% of global renewable water supply is in dryland regions while 2 billion people live there. This dissertation consists of four studies that address water stress in these complex areas. All span multiple components of the water stress in drylands on site, regional, and global scales.In the first study, we studied water stress impacts on dust storms severity and predictability in drylands utilizing the relation between drought events in Iraq and dust storms in Southwest Iran (SWI) between 2003 and 2018. Dust storms are common meteorological events in arid and semi-arid regions, particularly in SWI. The Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model showed central and southern Iraq are the main dust sources for SWI. Mean annual aerosol optical depth (AOD) analysis demonstrated 2008 and 2009 were the dustiest years since 2003 and there is an increased frequency of summertime extreme dust events in the years 2008 and 2009. The Standardized Precipitation Evapotranspiration Index (SPEI) revealed drought in Iraq significantly affects dust storms in Iran. Similarly, dramatic desiccation of Iraq wetlands has contributed to increasing fall dust events in SWI. AOD in SWI was highly correlated (−0.76) with previous-month vapor pressure deficit (VPD) over Iraq, demonstrating the potential of VPD for dust event forecasting. In the second study, we focused on global evapotranspiration products as an index of water stress. Evapotranspiration (ET) is one of the main components of water and energy balance. In this study, we compared two ET products, suitable for regional analysis at high spatial resolution : The recent WaPOR product developed by the Food and Agriculture Organization and METRIC algorithm. WaPOR is based on ETLook, which is a two-source model and relies on microwave images. WaPOR is unique as it has no limitation under cloudy days, but METRIC is limited by clouds. METRIC and WaPOR are more sensitive to land surface temperature and soil moisture, respectively. We showed that in most regions, ET from METRIC is higher than WaPOR and the deference has an ascending trend with the elevation

Mots clés : Canopy Temperature Cropland Dust Storm Ecohydrology Evapotranspiration Vegetation Dynamics


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