The punishing derecho storm that struck the Midwest in early August had an immediate impact on Iowa's farm fields. But it took weeks for the long term damage to appear in satellite imagery. Landsat 8 passed over central Iowa just one day after 100 mile per hour winds pummeled fields of corn and soybeans leaving thousands without power. The lighter shades of green in the natural color August 11th image signal flattened crops still green with life. Sixteen days later the lighter areas from August 11th appear brown and tan, suggesting more permanent crop damage.
Landsat data can also be used to calculate a Normalized Difference Vegetation Index, or NDVI, which is an indicator of plant health. In the NDVI images, darker greens show healthier vegetation. A closer look at the fields north of Ames, Iowa shows a significant drop-off in NDVI between August 11th and August 27th.
Iowa's State Climatologist estimated that the storm damaged 3.6 million acres of corn, and 2.5 million acres of soybeans in the state.