Too Little, Too Much
An extreme lack of rainfall over much of the United States in 1988 caused greater crop losses than any disaster in U.S. history, killed livestock and led to massive fires in Yellowstone National Park. Five years later, excessive rainfall in the summer of 1993 left rivers swollen, farm fields flooded and towns from the Dakotas to Missouri underwater. Like they did with wind patterns over the United States in these same two devastating years (see previous story, "Recreating The Wind"), NASA scientists used a comprehensive dataset called MERRA to compare the extreme precipitation differences in 1988 and 1993. In 1988, a region of high pressure sat over the middle of the country for much of the summer and blocked the usual arrival of moisture from the Gulf of Mexico. In contrast, the typical transport of moisture to the U.S. from the Gulf of Mexico intensified greatly five years later, among other factors. Some cities in 1988 did not see rain for close to two months. Others in 1993 remained flooded for five months or more. In these visualizations of total rainfall from each year, watch as drastic differences between the two seasons unfold from May 1 to July 31 in each year.
Two disastrous summers in U.S. history were caused by a simple lack and excess of rain.
1988: The MERRA rainfall data comes from a combination of modeling plus ground-based and satellite weather measurements.
1993: The heaviest rain is seen in reds and yellows. Rainfall reached 350 percent over normal levels in some states.
A lack of rain over the U.S. on June, 10 1988: Compare this with the moisture-blocking winds on the same day in the "Recreating The Wind" story.
This deluge over parts of the U.S. matches the June 10, 1993 circulation pattern seen in "Recreating The Wind."
The Missouri and Mississippi rivers appear at somewhat normal levels in this Landsat 5 image from Sept. 1988.
This image from Aug. 19, 1993 came a few weeks after the Mississippi crested at 49.6 feet in St. Louis, breaking a 20-year-old record by six feet.
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Please give credit for this item to:
NASA's Goddard Space Flight Center