2017 Drought - Havoc from the Heat
Propagation and Impacts of Great Plains Drought captured by NASA Models and Datasets
The 2017 spring and summer drought over the northern Great Plains has been judged to be the most devastating in the recent times.
Northern Great Plains (Montana, North Dakota and South Dakota)
Considering the importance of agriculture for the region, a better understanding of how they evolve is critical for drought early warning.
Drought Mechanism
An unexpected drought
There was no indication of an upcoming drought until around mid-May (US Drought Monitor).
During Jun-Jul, moderate to exceptional drought conditions swiftly overspread the Northern Great Plains, with the most rapid drought intensification occurring over northeastern Montana and western North Dakota during June.
What Triggered the 2017 Drought?
The 2017 drought was unique in its rapid arrival during the rainy season of May-July which experienced unusually low precipitation over the Great Plains.
GPM sensor captures the low anomalies in precipitation as seen below.
Standardized anomalies for precipitation highlighting an abnormally dry May-Jul season over Great Plains, 2017
Missed by Forecasts
The official NOAA forecast even called for above-average precipitation for May-July 2017 in Montana and equal chances of below- or above-average precipitation elsewhere over the Northern Great Plains
Three-month precipitation forecast from NOAA that clear missed the low anomalies during May-Jul 2017
Evolution of Drought
Abnormally Dry Soils
The significantly below average precipitation during May-July of 2017 led to rapid depletion of soil moisture.
Depletion of root zone soil moisture during 2017 drought
Impact on Vegetation
The resulting dry soils cause increased vegetation stress impacting the leaf area index (LAI) and reduced ET demand.
Rapid deterioration of soil moisture with record high temperatures during June and July led to an exceptional precipitation-deficit-driven flash drought.
Deterioration of LAI over the Great Plains caused by depleted soil moisture
Comparison with 2016
The contrasting beginning in 2016 led to a contrasting flash drought impacting the northern Great Plains in unique ways.
A Contrasting Trigger
In contrast, 2016 drought was mainly a consequence of extreme heat-wave that started in early March and caused the region to go into a sudden flash drought.
Standardized anomalies for temperature highlighting an early March heat-wave that triggered the 2016 drought in Great Plains
Heat wave caused higher ET demands
Abnormally high temperatures led to increased evaporative demand at the onset of drought.
Vegetation transpiration under increased stress in April at the onset of 2016 drought
Vegetation stress precedes soil moisture depletion
Increased ET demands caused the vegetation stress to rapidly rise.
Reduced soil moisture was thus a result of increased vegetation stress, unlike in the precipitation-deficit-driven 2017 drought.
Aftermath of Drought
The aftermath of 2017 drought sparked wildfires and compromised water resources, which led to reduced agricultural production and the destruction of property amounting to billions of dollars.
Left: Pre-fire (July 13); Right: Active wildfire (July 23) MODIS Corrected Reflectance (Terra, bands 7-2-1)
Lodgepole Complex Fire (MO)
The massive wildfire erupted on Jul 19, 2017 and spread over an area over an area of 270,000 acres
Location of Lodgepole Complex Fire
Sensing Fire using MODIS
The MODIS fire product MCD64A1 captures the extent of wildfire
Damaged Crops
2017 drought also caused extensive impacts to agriculture. Field crops including wheat were severely damaged.
Data from USDA reveals 30% lower production of wheat in 2017 compared to a five year average.
Conclusions
- Simultaneous use of datasets from GPM, MODIS, AMSR, and THySM is necessary to capture propagation of droughts.
- Assimilating datasets from different sensors captures the different drought mechanisms
- Open science improves discoverability of NASA datasets and provides actionable information for water and agriculture community.
