Climatic Aspects of the 1993 Upper Mississippi River Basin Flood

• Published in: Bulletin of the American Meteorological Society Vol. 75; no. 5; pp. 811 - 822
• Main Authors: Kunkel, Kenneth E., Changnon, Stanley A., Angel, James R.
• Format: Journal Article
• Language: English
• Published: Boston, MA American Meteorological Society 01.05.1994
• Subjects: Atmosphere; Atmospheric circulation; Climate; Climate models; Climatology; Earth, ocean, space; Exact sciences and technology; External geophysics; Floods; Freshwater; Meteorology; Meteors; Precipitation; Rain; Rainfall; River basins; Rivers; Soil water; Water in the atmosphere (humidity, clouds, evaporation, precipitation); Mississippi River Basin; United States; North America; America; Mississippi River; USA, Mississippi R; Mississippi River Basin, United States; Atmospheric condition; Rain; Hydrometeorology; Flood; Climate element; Summer; Atmospheric precipitation
• ISSN: 0003-0007; 1520-0477
• DOI: 10.1175/1520-0477(1994)075<0811:caotum>2.0.co;2

The 1993 record-breaking summer flood in the Upper Mississippi River Basin resulted from an unprecedentedly persistent heavy rain pattern. Rainfall totals for the Upper Mississippi River Basin were, by a large margin, the largest of this century for the 2-, 3-, 4-, and 12-month periods encompassing the 1993 summer. The totals for these periods are estimated to have a probability of occurrence of less than 0.005 yr−1. In addition, the number of reporting stations receiving weekly totals in excess of 100 mm (events identified in a previous study as being closely correlated with floods) was the largest in at least the last 45 yr. Other conditions contributing to the flood include above-normal soil moisture levels at the beginning of June 1993; large-sized areas of moderate to heavy rains; occurrence of rain areas oriented along the main stems of major rivers; a large number of localized extreme daily rainfall totals (greater than 150 mm); and below-normal evaporation. The large-scale atmospheric circulation patterns during the summer of 1993 were similar to the patterns associated with past heavy rain events, although much more persistent than past events.