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A probabilistic characterization of the interaction between large-scale atmosphere, land surface and fire to enable improvement of drought early warnings over the Great Plains and California

We propose to characterize and understand the integral effect of the coupling between
atmosphere, land surface and fire generated aerosols on drought triggers and persistence for a
seasonal scale, and its interannual and decadal variability over the United States (US) Great
Plains (GP) and California. These two regions consist the first and second largest economy in
the US, but are prone to extreme droughts. Yet, we cannot predict such droughts over a seasonal
or longer time scale, including the recent extreme droughts in both regions. Statistical models
based on observed persistence of the past droughts appear to provide better skill for seasonal
predictions than the dynamic models in both regions. Yet, we do not fully understand the cause
behind these apparent skills and whether they represent real predictability. We have investigated 
the effect of multi-scale coupling between land surface, shallow and deep convection and large-
scale circulation on the onset and persistence of summer droughts over the US GP, in
collaboration with the Texas Water Development Board (TWDB). In addition, we have started
research on California droughts and experimental seasonal prediction for winter rainfall in
collaboration with the California Department of Water Resources (CDWR). As a logical next
step, we propose to investigate the coupling between atmosphere, land surface/vegetation and
fires, and its impact on drought onset and persistence over the US GP and California with
emphasis on non-local land surface feedbacks and the effects of biomass burning aerosol on
clouds, rainfall and thermodynamic stability of the atmospheric boundary layer, focusing on the
following science questions:
• What large-scale anomalous circulation patterns are responsible for triggering seasonal
drought memory and influence its climate variability?
• How does the coupling between drought and heatwaves influence drought onsets and
intensity regionally?
• Can fires intensify droughts?

We will jointly use machine learning tools, such as Self-Organizing Map (SOM), to provide
a probabilistic observational characterization of the circulation patterns and associated land
surface and fire conditions that contribute to droughts, and detailed process studies to understand
the interplay between droughts and warm surface temperature anomalies in triggering and
amplifying drought through their impacts on heat low, the low-level jets, vegetation response and
aerosols impacts on clouds and precipitation. We will use a suite of interdisciplinary datasets,
including in situ and satellite observations and global and regional reanalysis products, including
those provided by NOAA, the Climate Forecast System Reanalysis Version 2 (CFSRv2), the
North American Regional Reanalysis (NARR) and the North American Land Data Assimilation
System (NLDAS) products. The anticipated results will enable us to provide better seasonal
predictions of rainfall anomalies for TWDB and CDWR. In doing so, we will provide improved
information to support drought early warning for two major stakeholders of the National
Integrated Drought Information System (NIDIS) Southern GP and California/Nevada regions.


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