Thursday, October 14, 2010

Rainfall Summary For Summer 2010

We have been away on a trip to the east coast and are now back in Tucson. Beautiful Fall weather out there in Rhode Island and a bit of Fall color showing especially on the maple trees.
The following is the rainfall summary for Summer 2010 here at the house - where I'm calling June, July, August, and September "Summer".
June - no measurable rainfall

July - 3.26"

August - 1.44"

September - 0.99"

TOTAL - 5.69" making 2010 the 5th driest summer since I started records here 13 years ago.

Number of days with 0.25" to less than 0.50" 3

Number of days with 0.50" to less than 1.00" 1

Number of days with 1.00" to less than 1.50" 2

Number of days with greater than 1.50" 0

These six days (essentially 5% of the summer) had rainfall of 4.52", or about 80% of the total for the four months.
The three days with the heaviest storms had rainfall of 3.37", or about 60% of the total for the four months. Further, these storms were very heavy and probably produced all of this rain during five hours or less - one event produced 0.77" in 20 minutes. Thus, the bulk of the rain (i.e., the rainfalls determining the character of the entire summer) fell in a time period that accounts for about 0.20% of the summer.
So, what does all this mean? As one might expect, the character of the summer, or a given summer month, for a location in the Sonoran Desert depends primarily upon how many heavy thunderstorms strike that location. Thus, monthly or seasonal averages of meteorological parameters actually provide minimal insight into why a summer (or month) was wet or dry at a given desert location [i.e., low elevation - elevations of around 1350 m (~4500 ft) or less - see above topo map].
The meteorological factors that modulate the character of a summer in the Sonoran Desert occur on only a few days, and are those factors that lead to widespread, heavy storms, i.e., to the organization and propagation of intense thunderstorms on the medium to larger mesoscales.

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