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 26 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.
Figure 4. 1-month Evaporative Stress Index (ESI) from 28 October 2019. For additional information on the ESI, please refer to Anderson et al. (2012) and Otkin et al. (2013).
Narrative:
Most of the eastern U.S. has seen significant improvement over the last month (Fig. 3) and the most recent SMI map is in good agreement with the 1-month change map from the U.S. Drought Monitor (Fig. 5). As always the map is reflective of conditions as of last Saturday and does not reflect precipitation that has fallen since. With precipitation occurring over much of the eastern U.S. today and cooler weather to follow, expect some improvement in places that haven’t shown as much (e.g., the immediate D.C. area).
The north central U.S. remains moist, too moist in many locations. This has slowed down harvest. It should be noted that while corn harvest is well below the 1981-2018 median (41 percent vs. 66 percent), it is ahead of 2008, 1992, and well ahead of 2009 and not far behind 2014 and 1996 (Fig. 6). While conditions today in much of the Corn Belt are not conducive for harvest, drier (albeit continued cool) weather is expected in the next few weeks. So hopefully we will avoid a repeat of 2009.
Some places have seen degradation over the past several weeks, most notably in the High Plains region of Colorado, western Kansas, and southwestern Nebraska. This is particularly evident in the Evaporative Stress Index (Fig. 4) and this region should be watched carefully as we head into the winter.
This is the final regular Ag Blog for the season, though I will still plan to publish occasional updates between now and next April. Thanks to all of you who have followed the Ag Blog this season. I look forward to continuing this and improving it in 2020. Happy Halloween!
Figure 5. U.S. Drought Monitor class change courtesy of the National Drought Mitigation Center.
Figure 6. Percent harvested at Week 43 (late October) from 1981-2019. Data courtesy of USDA NASS.