Study region: The state of Oklahoma located in the Southern Plains region of the United States. Study focus: The standardized precipitation evapotranspiration index (SPEI) is a widely used meteorological drought index that incorporates potential evapotranspiration (PET) into a precipitation-based index. However. the understanding of the appropriate PET method for SPEI across different... https://excellentphoto.shop/product-category/film-development/