As concerns rise over increasing droughts related to climate change, an atmospheric scientist at the University of Houston is leading a federally-backed study to gain a better understanding of what causes these periods of exceptionally dry weather in hopes of better predicting when they might occur.
Honghai Zhang, assistant professor of tropical climate dynamics and global hydrological cycle in the Department of Earth and Atmospheric Sciences at the College of Natural Sciences and Mathematics, received a three-year, $498,599 grant from the National Oceanic and Atmospheric Administration (NOAA) to support his study of moisture anomalies as monitors and predictors of droughts in the southwestern United States, including Houston.
Zhang will analyze variations in precipitation and moisture in the region, looking closely at the potential for moisture from the tropical Pacific as a possible predictor. He is focused on developing a model that can monitor and predict drought conditions.
“In this project, we’re looking at how moisture variations in the tropical Pacific contributed to droughts in the southwest,” Zhang said. “We want to be able to predict droughts one to two seasons ahead.”
Role of moisture pathways in summer droughts
Zhang wants to dig deeper into models that are part of the North American Multi-Model Ensemble (NMME) system. He is working to find how moisture pathways could contribute to the prediction of summer droughts. Moisture pathways, the atmospheric routes through which water vapor is transported, play a crucial role in the global water cycle and can influence weather patterns and precipitation.
Using the NMME’s Geophysical Fluid Dynamics Laboratory Forecast-oriented Low Ocean Resolution (FLOR) model, Zhang found a correlation between tropical Pacific Ocean activity and atmospheric moisture and precipitation in the southwest.
“The FLOR model was used to show how moisture variations in the summer can be more important than atmospheric circulation anomalies,” Zhang said. “The model supported the theory that tropical Pacific activity can influence summer precipitation fluctuations in the southwest through moisture pathways.”
A new model within the NMME system, the Seamless System for Prediction and Earth System (SPEAR), has replaced FLOR. Zhang is comparing regional simulations from both models to see if the results are identical.
“We want to see if the SPEAR model can also simulate the same moisture pathway in the same region,” Zhang said.
Land-based and satellite data collection
For his project, Zhang is collecting and analyzing data from land-based monitors and satellites. Sensors on land, such as rain gauges and soil moisture probes, provide essential real-time information while satellite data offers a broader perspective by capturing spatial distribution of moisture levels while also collecting data in remote areas.
“We are using satellite data of moisture activity from the oceans as a predictor of drought conditions,” Zhang said. “It is a key ingredient in the model under development.”
Zhang is contributing to the development of NOAA’s National Integrated Drought Information System Drought Early Warning System in the southwest. His work will increase the probability of expanding U.S. Drought Monitor System indicators based on land and soil and creating drought predictors based on atmospheric moisture data collected from satellites.
