FLASH cover slide

What is a Flash Drought?

Flash droughts are characterized by rapid intensification of drought to severe levels over large areas, triggered by anomalously high temperatures (heatwave flash drought) or lack of precipitation (precipitation-deficit flash droughts), or both. These fast-evolving droughts cause large-scale agricultural losses, expansive wildfires, and challenges for seasonal and sub-seasonal climate predictions. For more detail on flash droughts, please refer to National Integrated Drought Information System.

What is Flash Drought Stress Index, or, FDSI?

FDSI is an index for flash drought monitoring by leveraging the footprint-scale thresholds of soil hydrologic regimes (energy-limited wet phase, moisture limited transitional, and dry phase) and land-atmospheric coupling strength derived from NASA’s SMAP satellite. We define two complementary indices based on SMAP soil moisture for measuring the severity and the rate of intensification of drought, namely, Soil Moisture Stress (SMS) and Relative Rate of Drydown (RRD), respectively. SMS and RRD are non-linearly combined to provide FDSI (Flash Drought Stress Index) ─ a composite indicator used for global flash drought monitoring.

FDSI can be formulated with a relatively short observational record of soil moisture (as opposed to climatology length observations) and is sensitive to changing land-surface heterogeneity, land-atmospheric interactions, and evolving meteorological anomalies. FDSI is extensively validated globally across multiple timescales (daily, weekly, and monthly) using a suite of vegetation and meteorological drought indices.


NASA Logo Transparent BackgroundWe acknowledge funding support from NASA through the following projects:
SMAP Science using Data Fusion: Forecasting Flash Drought to Flash Flood
Root Zone Soil Hydraulic Property Estimation by SMAP


i)  Sehgal, V.Gaur, N., & Mohanty, B. P. (2021). Global Flash Drought Monitoring using Surface Soil MoistureWater Resources Research57, e2021WR029901.(Link)
ii)  Sehgal, V., Gaur, N. and Mohanty, B.P., 2021. Global Surface Soil Moisture Drydown Patterns. Water Resources Research, 57(1), p.e2020WR027588. (Link)

External links:
National Integrated Drought Information System  |  Global drought monitoring  |  U.S. drought monitor  |  SPEI Global drought monitor  |  India Drought Monitor | QuickDRI | Evaporative Demand Drought Index (EDDI)



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