The Evolution and Impact of Contrasting Flash Droughts Captured by Multivariate Land Data Assimilation
Abstract
Droughts form one end of the hydrologic extremes that usually evolve over months to years to reach their peak intensity. However, another category of events, termed as flash droughts, evolve and intensify very rapidly under the influence of weather anomalies. Such events can have multiple triggering factors, including those driven by precipitation deficits or extreme heat, often leading to distinct mechanisms of progression. It is imperative to effectively characterize the driving mechanism of flash droughts and their subsequent impacts on the ecology. The northern Great Plains recently experienced two such flash droughts in 2016 and 2017. In 2016, an early heat wave during March caused warmer-than-normal conditions, leading to increased evaporative demands and drawdown of soil moisture. The 2017 drought experienced a contrasting trigger where near-record-low precipitation anomalies caused rapid depletion of soil moisture. Resulting dry soil conditions persisted and led to increased vegetation stress, severely impacting the crop production and yield. Using NASA Land Information System (LIS) frameworks, we demonstrate that data assimilation (DA) of various land and remote sensing observations is essential in capturing the mechanism and progression of the two contrasting flash droughts. Results suggest that during the 2016 drought characterized by intense heat wave, assimilation of MODIS-derived leaf area index (LAI) within Noah-MP helped the model to resolve the elevated evaporative demands in late spring that rapidly drove the region into drought conditions. However, for the precipitation-deficit-driven drought of 2017, assimilating SMAP soil moisture helped capture the large negative soil moisture anomalies at the onset that led to a cascade of disturbances impacting vegetation and sparking massive wildfires. The value in assimilating different variables in the two cases can be attributed to the distinct impacts that the precipitation deficit and heat wave had on the vegetation. The experiments across the two case studies highlight the overarching need for incorporating remote sensing observations to comprehensively capture the different processes involved in flash droughts of different origins.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFMGC21B..06A