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Evidence of an Agricultural Heat Island in the Lower Mississippi River Floodplain

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The Mississippi River floodplain in the states of Arkansas, Tennessee, Mississippi, and Louisiana presents a readily discernible feature in weather satellite images. This floodplain appears in the spring and early summer as a daytime warm anomaly at infrared (IR) wavelengths and as a bright reflective area at visible wavelengths. Remnants of this feature can occasionally be identified at nighttime in the IR satellite images. During June the normalized difference vegetation index identifies major contrasts between this intense agricultural region and the surrounding mixed-forest region. This distinction and the homogeneity of the floodplain, with its alluvial soil, contrast with the encircling region, creating an agricultural region containing heat island features. Thirty years of climatological surface station data for the month of June reveal that the surface air temperatures in the floodplain experience less diurnal variation than those in the surrounding regions. This is primarily because nighttime minimums are warmer in the Mississippi River floodplain.

*Cooperative Institute for Meteorological Satellite Studies, University of Wisconsin, Madison, Wisconsin.

+National Severe Storms Laboratory, Norman, Oklahoma.

**National Environmental Satellite Data and Information Service (NOAA), Madison, Wisconsin.

Corresponding author address: William H. Raymond, Cooperative Institute for Meteorological Satellite Studies, University of Wisconsin, Madison, WI 53706.

The Mississippi River floodplain in the states of Arkansas, Tennessee, Mississippi, and Louisiana presents a readily discernible feature in weather satellite images. This floodplain appears in the spring and early summer as a daytime warm anomaly at infrared (IR) wavelengths and as a bright reflective area at visible wavelengths. Remnants of this feature can occasionally be identified at nighttime in the IR satellite images. During June the normalized difference vegetation index identifies major contrasts between this intense agricultural region and the surrounding mixed-forest region. This distinction and the homogeneity of the floodplain, with its alluvial soil, contrast with the encircling region, creating an agricultural region containing heat island features. Thirty years of climatological surface station data for the month of June reveal that the surface air temperatures in the floodplain experience less diurnal variation than those in the surrounding regions. This is primarily because nighttime minimums are warmer in the Mississippi River floodplain.

*Cooperative Institute for Meteorological Satellite Studies, University of Wisconsin, Madison, Wisconsin.

+National Severe Storms Laboratory, Norman, Oklahoma.

**National Environmental Satellite Data and Information Service (NOAA), Madison, Wisconsin.

Corresponding author address: William H. Raymond, Cooperative Institute for Meteorological Satellite Studies, University of Wisconsin, Madison, WI 53706.
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