S157 Comparison of Land–Sea Temperature Gradients and Sea-Breeze Intensity in Coastal Alabama

Sunday, 12 January 2020
Margaret Eldredge, Univ. of South Alabama, Mobile, AL

A seabreeze (SB) is a naturally occurring weather phenomenon which happens during the warm season on the shores of large water bodies such as the Gulf of Mexico and Mobile Bay. A difference in temperature between land and water is the driving force of sea breezes, with a warmer temperature over land (positive Temperature difference). The hypothesis is that larger temperature differences lead to stronger sea breezes. Sea breeze strength is often measured by wind speed at a weather station after the sea breeze front (leading edge) passes. Radar data for the years 2016 and 2017 warm seasons (May-October) were analyzed to determine the occurrence of a SB between the hours of 1400 - 2300 Z (0800 – 1700 CST). Data from a buoy in the Gulf of Mexico south of Baldwin County were used in conjunction with the South Alabama Mesonet station at Grand Bay to obtain land and sea temperatures differences (T-diff) on the days a SB occurred. The number of SB days per month increased throughout the warm season with May having 11 SB days (combined in 2016 and 2017) and September 21 (also combined over the 2 years). It is hard to determine if the increasing trend continues through October, since there were 53 days over the 2 year period missing. On average a positive T-diff occurred between 0800 and 1500 CST. The average maximum T-diff for SB days is 4.14°C and it occurred on average at 1210 CST. The average maximum wind speed on SB days is 3.41 m s-1 and occurred on average at 1400 CST. On average, the positive T-diff on the non-SB days occurred between 8 CST and 16 CST. The average maximum T-diff for non-SB days (including days with widespread convection) is 5.25℃ and it occurred around 12 CST. The average minimum for non-SB days is 1.13 and also occurred around 12 CST. Correlations between wind speed and maximum T-diff will be calculated to see if a relationship exists between T-diff magnitude and SB intensity. The non-SB days will be compared to the values for SB days for the same parameters.
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