Extended Abstract (1.9M)P2.30
Is there a weekly cycle of warm season precipitation?
J. D. Tuttle, NCAR, Boulder, CO; and R. E. Carbone and D. W. Nychka
The recent work of Bell et al. (JGR 2008) documented a midweek increase
in warm season (June-August) rainfall over portions of the United States as
deduced from the Tropical Rainfall Measuring Mission (TRMM) data from 1998
to 2005. It was hypothesized that anthropogenic air pollution is the
principle cause of the observed weekly cycle of a Tuesday/Wednesday maxima
and a Saturday/Sunday minima.
The authors of this study have published several dynamically-based climatologies
of summer rainfall over the United States using a national composited radar
data set from the WSR-88D radar network. Since ground-based radars offer
some advantages to the TRMM data, a study was started to compare and confirm
the results of the satellite-based study. Using a 12-year data set statistics
of radar-derived rainfall are calculated and stratified by day of week. Several
statistical methods are used to determine if significant differences exists
between days. Initial results tended to confirm the findings of Bell et al.,
especially over their most statistically significant area, the east-central
U.S. To further check our results the data were resampled randomly into virtual
"Tuesdays" and "Saturdays". The random resampling produced patterns that are
similar in scale and magnitude to the true Tuesday versus Saturday rainfall
differences. Work will continue to better understand the relationship between
the local PDFs of rainfall amount and the occurrence of large coherent regions
with apparent day-of-week differences.
Poster Session 2, Precipitation and Cloud Microphysics
Monday, 5 October 2009, 1:30 PM-3:30 PM, President's Ballroom
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