The University of Arizona

Evaluating Existing and Developing New Drought Indices Using Modeled Soil Moisture Time Series | CLIMAS

Evaluating Existing and Developing New Drought Indices Using Modeled Soil Moisture Time Series

Evaluating Existing and Developing New Drought Indices Using Modeled Soil Moisture Time Series

CLIMAS Lead:  

Stakeholders across the Southwest have struggled to utilize existing drought indices because of their failure to capture the unique seasonality and complex hydroclimate of the region. Soil moisture is a key drought indicator that is not well represented in existing drought indices, and deficits in soil moisture are difficult to measure directly, as there are few existing monitoring sites and even fewer historical time series to analyze. To understand the relative roles of changing precipitation and temperature regimes on soil moisture, we will model historical time series of soil moisture at numerous stations across Arizona and New Mexico using a soil water model (HYDRUS 1-D). These time series will be integrated into an analysis of the role of hydroclimatic variability and temperature in controlling drought intensity and frequency in the semi-arid climate of the Southwest, and  compared with traditional drought monitoring indices to identify strengths and weaknesses for capturing soil moisture, and to establish drought monitoring best practices.

Central Question: What are the relative roles of changing precipitation regimes and temperatures in the historical variability of soil moisture in Arizona and New Mexico and what drought indices best capture this variability?

This project aims to develop long-term (>50 years), daily resolution soil water profile climatologies for several locations across the Southwest. We will assess how seasonality and precipitation timing and frequency relate to monthly precipitation-based drought indices. Cross correlations and time series analyses will be used to assess when and where traditional drought indices align with modeled soil moisture stress. We will use this modeling approach to assess the performance of temperature-based indices and further explore the role of increasing temperatures in driving drought stress across the region. Our initial project study area focuses on the Las Cienegas National Conservation Area, a multi-use, Bureau of Land Management area in Southeast Arizona. We are working in partnership with The Nature Conservancy to develop modeled long-term soil moisture estimates to examine with long-term vegetation monitoring data. Together we will assess the impacts of precipitation variability and temperature changes on vegetation production and mortality and identify optimal drought monitoring metrics.