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Midweek Increase in U.S. Summer Rain and Storm Heights, Suggests Air Pollution Invigorates RainstormsTropical Rainfall Measuring Mission (TRMM) satellite data show a significant midweek increase in summertime rainfall over the southeast U.S., due to afternoon intensification. TRMM radar data show a significant midweek increase in rain area and in the heights reached by afternoon storms. Weekly variations in model-reanalysis wind patterns over the region and in rain-gauge data are consistent with the satellite data. A midweek decrease of rainfall over the nearby Atlantic is also seen. EPA measurements of particulate concentrations show a midweek peak over much of the U.S. These observations are consistent with the theory that anthropogenic air pollution suppresses cloud-drop coalescence and early rainout during the growth of thunderstorms over land, allowing more water to be carried above the 0 C isotherm, where freezing yields additional latent heat, invigorating the storms--most dramatically evidenced by the shift in the midweek distribution of afternoon-storm heights--and producing large ice hydrometeors. The enhanced convection induces regional convergence, uplifting and an overall increase of rainfall. Compensating downward air motion suppresses convection over the adjacent ocean areas. Pre-TRMM-era data suggest that the weekly cycle only became strong enough to be detectable beginning in the 1980's. Rain-gauge data also suggest that a weekly cycle may have been detectable in the 1940's, but with peak rainfall on Sunday or Monday, possibly explained by the difference in composition of aerosol pollution at that time. This "weekend effect" may thus offer climate researchers an opportunity to study the regional climate-scale impact of aerosols on storm development and monsoon-like circulation.
Document ID
20070022884
Acquisition Source
Goddard Space Flight Center
Document Type
Preprint (Draft being sent to journal)
Authors
Bell, Thomas L. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Rosenfeld, Daniel (Hebrew Univ. Jerusalem, Israel)
Kim, Kyu-Myong (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Yoo, Jung-Moon (Ewha Woman's Univ. Seoul, Korea, Republic of)
Hahnenberger, Maura (Utah Univ. Salt Lake City, UT, United States)
Date Acquired
August 23, 2013
Publication Date
January 1, 2007
Subject Category
Meteorology And Climatology
Distribution Limits
Public
Copyright
Public Use Permitted.

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