During the 2019 growing season, Dr. Eric Hunt of Atmospheric and Environmental Research, Inc. will be providing weekly updates of the soil moisture index (SMI) from the Noah-MP land surface model in the NASA LIS framework for the eastern 3/4 of the U.S. where row-crop agriculture is more common. The Evaporative Stress Index (ESI) is now included in our analysis. The analysis is intended to provide the larger agricultural and meteorological communities insight as to areas where soil moisture is excessive or deficient compared to average for that location and what that may mean for impacts. It is my goal that these maps can be an early warning signal for flash drought development or where flash flooding could be likely in the coming week if heavy precipitation materializes. Please be advised that the SMI should be viewed as complementary, not a substitute, to the U.S. Drought Monitor (USDM) and that declarations of drought for a particular location should never be based on the SMI alone.
This blog post was partially supported by NASA grant NNH16CT05C.
Figure 1. The Soil Moisture Index (SMI) for the 7-day period ending 8 June 2019. Results are based on output from the 0-1 m (surface to 3.23 feet) layers in the Noah-Multiparameterization (Noah-MP) land surface model. Noah-MP is run in the NASA Land Information System (LIS) framework with the North American Land Data Assimilation Version 2 (NLDAS-2) forcing dataset. The SMI calculation is based on the soil moisture index created in Hunt et al. (2009) such that ‘5’(dark green) is the wettest and ‘-5’ (dark red) the driest for the period of record. The period of record used calculate the SMI for the current map is 1979-present.
Figure 2. Same as Figure 1, except Noah-MP is run with a dynamic vegetation option, instead of a climatologically driven leaf area index (LAI).
Figure 3. Comparison of this week’s SMI map the last three week’s SMI maps.
The SMI maps show that soils over most of the Southern/Central Plains and Corn Belt are still abnormally moist but not as wet as in recent weeks. Given the somewhat drier conditions across the region this week, I expect next week’s map to have less total area with SMI’s over 3.0. Over the southeastern U.S., there was some improvement toward the end of the week as the slow moving upper level system last weekend dumped considerable rainfall over much of Georgia and the Carolinas. However, much of that precipitation fell after the NLDAS data cutoff for this map, so expect to see much more substantial changes on next week’s map to places that received multiple inches of rain.
I am also happy to show an ESI map for the first time this season. It is quite reflective of the recent drought over the Carolinas with strong negative anomalies over that area and is also reflective of the drier conditions in North Dakota and northwest Minnesota that I have been showing all spring with the SMI maps. Areas near the Mississippi River in Missouri and Illinois that show strong negative anomalies are most likely the result of flooded vegetation and fields from the flooding that has occurred along the Mississippi in recent weeks.
The latest U.S. Drought Monitor did show some improvement over the southeast, particularly in north Georgia, and is in agreement with moderate drought conditions occurring along the Canadian border in North Dakota.
If you’re interested in how the season-to-date weather has affected the outlook for corn yields in the Corn Belt, please check back next week for our June Corn Forecast Update.