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 24 August 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.
Recent rainfall and the lack of temperatures over 90 have led to some improvements in parts of the Corn Belt that experienced a mild flash drought this summer. Further west into Nebraska, the northeast part of the state remains on the dry side and it remains in the Abnormally dry category on the latest Drought Monitor. Much of the state continues to be abnormally moist, particularly the central section, which received significant precipitation again later last week. This level of abnormal moisture arcs southeast into eastern Kansas, which is having one of its wettest years on record.
Across southwestern Kansas into central/western OK and Texas, the heat and dry weather continued for the first half of the week. However, many of the places that have experienced flash drought did receive significant precipitation later last week. This likely will be reflected as additional improvement on next week’s map. As has been the case the past several weeks, the dynamic vegetation simulation is much more aggressive on the flash drought in the southern Plains. The ESI continues to show normal conditions over much of Oklahoma and stressed conditions across west Texas. The 110-degree heat earlier this week there won’t help matters.
Along the Gulf Coast and southeast, persistence has been the name of the game for most of the region, though parts of southern GA and northern FL did have decent improvements from last week to this week. The New England States also saw some improvement, though the ESI still shows more stress than normal.
I’ll close today by addressing a topic that has been dominating headlines in recent weeks, which is “Will enough of the 2019 corn crop make it to maturity before the first freeze”? Figure 5 shows the percent of corn at the dent stage, which for those unfamiliar is the stage where corn kernels began to dent and is the last stage before physiological maturity. So for corn that is already in dent stage, reaching maturity before the end of September is a pretty safe bet.
In this figure, I am showing the national percentage, the ‘I’ state average, Minnesota, and Nebraska for this week in the season going back to 1981. A couple of things stand out. First, we are definitely behind the long-term median across the board (nationally it’s 41 percent; currently we’re at 27 percent). Second, we aren’t historically low nationally or in any of the major corn producing states. Clearly some of the late-planted corn has an increased risk of not making it to maturity before the first killing freeze. But overall, I am cautiously optimistic that the overwhelming majority of corn in these states will make it to maturity. Furthermore, the recent mild weather has probably helped improve yield on the earlier planted corn.
Figure 5. Percent of corn dented at week 34 going back to 1981.