Wednesday, July 18, 2012

NWS Testing Replacement Sonde

The NWS has begun operationally evaluating the Vaisala RS92 sonde as a replacement for the problem-plagued sonde used in the RRS program. Details concerning the Vaisala sonde can be found at:

http://www.wmo.int/pages/prog/www/IMOP/meetings/Upper-Air/Systems-Intercomp/Doc3-4(1)Vaisala.pdf

The RS92 GPS sonde is being tested currently at Caribou, ME; Springfield, MO; and Flagstaff, AZ. It was to be tested at Key West, FL, but I am not sure of the status there. The first flight of the RS92 sonde at Flagstaff was at 00 UTC last evening, and the second was this morning at 12 UTC. These two soundings are shown below, and seem to be well-behaved. I think that the 1-s data are still being processed to produce the soundings, so some degree of noise is unavoidable.



The choice of Flagstaff as a test site is interesting. The upper air site there is at an elevation of 7191 ft MSL. As far as I know, this site is the only one within the NWS (CONUS) that is located in a distinctly montane environment. The unusually high site is an important one for testing the new sonde. However, it rarely experiences cT air masses. It is the cT boundary layer that has proved so difficult to the RRS sonde here in the Southwest. I hope that the new sonde will also be tested at a low elevation site in the Southwest (Tucson, El Paso, or even Midland). Certainly this is good news for all of us who have been concerned about the problems with the RRS sonde.

Finally, we have an unusual situation here in Arizona. On many days upper-air soundings are taken at four sites - Yuma, Phoenix, Flagstaff, and Tucson. It may be that the data in Arizona come from four different makes of sonde - I am not sure however, and would appreciate any information regarding the sondes used at these sites.

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