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 12 October 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.
Much of the eastern U.S. continued to have high negative anomalies of soil moisture and this in good agreement with the areas considered in severe to extreme drought on the current U.S. Drought Monitor. There is some good news though in this region. The amount of area with highly negative SMI values has decreased some since the last Ag Blog two weeks ago, with notable improvements in Tennessee and Kentucky. Also, much of the eastern U.S. finally received some significant precipitation since the cutoff for this map, so expect to see improvement on the next map.
Meanwhile the north central U.S. remains wet, which is further shown by the ESI in Figure 4. Parts of the northwestern Corn Belt and northern High Plains received several inches of snow late last week, further compounding an already precarious situation for many producers. Much of the western Corn Belt also experienced a freeze for the first time this fall (Fig. 5). The good news is much of Illinois and Indiana were spared a freeze, so late planted crops should get a bit longer to finish up. Also, much of the Corn Belt has experienced the first decent stretch of dry weather in weeks, which should help expedite dry-down and harvest. Cooler weather does seem to be a decent bet heading into later next week and would fully expect much of the Corn Belt to have had their first freeze by Halloween.
Figure 5. Date of first 28°F freeze across the U.S. Map courtesy of the Midwest Regional Climate Center.