Climate adaptation in the southwest US: The SWPar4.5 parameter set for stochastic weather generators

Authors: FULLHART, ANDREW - University Of Arizona; GAO, SHANG - University Of Arizona; WANG, WENTING - Northeast Agricultural University, China; Elias, Emile; Armendariz, Gerardo; Goodrich, David

Submitted to: Scientific Data
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/1/2025
Publication Date: 11/19/2025
Citation: Fullhart, A.T., Gao, S., Wang, W., Elias, E.H., Armendariz, G.A., Goodrich, D.C. 2025. Climate adaptation in the southwest US: The SWPar4.5 parameter set for stochastic weather generators. Scientific Data. 11:Article1825.

Interpretive Summary: Climate impact studies for rangeland sites in the Southwestern United States are challenged by the presence of widely varying climates types that transition rapidly across space. This challenge also makes it difficult to gather localized climate data for environmental site assessments. Climate datasets can improve the accuracy of how localized dynamics are represented by increasing the resolution of the dataset (analogous to what happens when the resolution of a blurry image is increased). However, doing so results in creation of a larger volume of data, making the dataset burdensome to use. A developed climate dataset called Southwest Parameter Set 4.5 (SWPar4.5) uses an approach for creating probabilistic climate timeseries for historical and future time windows at high resolution without increasing the volume of data that is produced. The SWPar4.5 dataset represents model simulations from a global standard climate projection that is referred colloquially as the “middle-ground” emission scenario. The dataset derives information from two pre-existing datasets representing this same climate scenario in order to produce time series for a variety of weather variables. The dataset can be readily integrated with USDA field-scale and hill-slope scale agricultural and conservation models, such as the Water Erosion Prediction Project model and the Rangeland Hydrology and Erosion Model. In addition to rising temperatures, the time series reveal increases in precipitation intensity and important localized changes that occur over the course of the century. This has implications for land management and allows best practices to be followed as outlined in several technical guides.

Technical Abstract: Climate assessment in the southwestern US is complicated by extreme spatial gradients and short, intense rainfall events. In this region, gridded climate data, including commonly applied ~4'km daily datasets, often obscure spatial gradients and short-term precipitation dynamics. Contrasting, point-scale data (as measured by ground instruments like rain gauges) better reflects important precipitation factors and is preferred input for certain site-specific environmental models, including models classified by their domain as point-, plot-, field-, and hillslope-scale models. Facilitating targeted climate assessment, Southwest Parameter Set 4.5 (SWPar4.5) enables a framework for creating probable historical and future point-scale climate time series at ~800'm resolution. SWPar4.5 provides monthly climate benchmarks to parameterize a stochastic weather generator estimated using a data fusion of two existing gridded climate projections with differing spatiotemporal resolutions based on the middle ground representative concentration pathway scenario (RCP4.5). Resulting daily time series contain basic weather variables and include sub-daily precipitation patterns. Increases in precipitation intensity at local scale were found, with implications for soil erosion, runoff, and other environmental indicators.