Texas ranks first in the United States in the variety and frequency of most natural disasters, such as flooding, wildfires, hurricanes, winter storms, and droughts. In February 2021, the winter storm named Uri caused an abnormal decline in the air temperature in the southcentral United States, notably in Texas. Right before Uri, most of Texas was going through a drought spell. Thus, this study analyzed how Uri influenced the drought severity, soil profile moisture content, and vegetation cover (Normalized Difference Vegetation Index, NDVI) across Texas. Data used in this analysis was obtained from the web-based geospatial applications gridMET and Crop-CASMA. The collected datasets include the Palmer Drought Severity Index (PDSI), Snow Water Equivalent (SWE), soil moisture, and NDVI at different spatial resolutions. These datasets were aggregated to the county scale using the zonal statistics analysis. The strength of the correlation between SWE and soil moisture was quantified based on the Pearson correlation coefficient. The percentage change in live vegetation cover due to the impact of the frigid temperature and snow coverage across the state was quantified by analyzing the average weekly NDVI before and after the winter storm. There was a reasonably strong correlation between the SWE contribution of Uri and the increase of the rootzone soil moisture (Pearson's r = 0.42). Similarly, the SWE showed a higher correlation with daily rootzone soil moisture with a Pearson's correlation coefficient of 0.49 on March 1. Furthermore, our results revealed a reduction in the NDVI values to less than 0.60 across Texas during the third week of February. Overall, Texas NDVI values seriously decreased due to Uri. Despite its disruptive effects on the state infrastructures and the economy, Uri snow lessened the drought conditions relatively for a short time.
Keywords: NDVI; PDSI; Snow Water Equivalent; Winter storm Uri.
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