Showing papers on "Air-mass thunderstorm published in 1981"

Point-Area-Frequency Conversions for Summer Rainfall in Southeastern Arizona

Abstract: Air -mass thunderstorm rains dominate rainfall -peak discharge relationships on many small watersheds (up to 150 km2) in southeastern and southcentral Arizona, southwestern New Mexico, and northern Sonora, Mexico. Intense rain cells within these storms usually last only minutes and cover relatively small areas. In the Southwest, for watersheds larger than 2 km2, estimates of maximum point rainfall are inadequate for most rainfall -runoff models. To estimate rainfall values within the watershed, frequency of point values should be revised upward to account for the greater likelihood that intense rain would have been recorded within an area, as opposed to a point, and then reduced for average rainfall over the watershed. For larger watersheds, it may also be necessary to position the event and route it through the channel system to obtain the accuracy needed. In this paper, a method is presented to convert air mass thunderstorm rainfall at a point to areal values for use on watersheds up to 150 km2. Limitations are stated, and the reader is referred to other published information if flood routing procedures are needed as well.

Simulation of an Air Mass Thunderstorm Using the Two-Scale Model

Abstract: The two-scale model (Raymond, 1979) is used to simulate a well-documented Colorado thunderstorm. Good agreement is found with the early and middle stages of the storm life cycle. Intense vertical mixing in the early stages is shown to have a crucial effect on both cloud dynamics and microphysics. In particular, precipitation particles formed at high levels in the storm are rapidly mixed down to low levels against the mean updraft even when sedimentation is suppressed. The termination of this mixing not only enables the simulated storm to develop explosively, but also sets the stage for its eventual demise.