With his permission, Richard Berler who is Chief Meteorologist of KGNS TV in Laredo, Texas has allowed me to post his quite informative e-mail of October 6 2011 to me. It is reporiduced below.
I e-mailed you several weeks ago concerning “bad” readings from the Laredo, TX AWIS instrumentation administered by the FAA. This has been a topic of interest to me for a number of years. In 2007 in a talk at the 14th Symposium on Meteorological Observation and Instrumentation, I noted (this was not the focus of my presentation) that the AWIS at the Laredo airport consistently read about 2F above the MMTS that I use as a NCDC cooperative observer. This bias was present at all hours of the day, even with a very well mixed atmosphere. I am about 4 miles from the AWIS and about 70 feet lower in elevation. I did note that this would be climatologically significant as it would make the AWIS site warmer than any Texas location by 2F on an annual basis, warmer than Death Valley, and warmer than any Florida station with the exception of the Florida Keys.
Recently (May 2011), the daytime maximum temperatures from the AWIS jumped to well over 4F above my MMTS. The NWS office responsible for our zone forecasts agreed that the readings appeared to be too high. They have a vested interest in this as they forecast to match the AWIS numbers, and verify their forecasts off of those numbers. The AWIS numbers are also what the public is exposed to as those numbers are generated each hour, and are picked up by media outlets such as The Weather Channel. With zero interest and cooperation by the FAA, The NWS came down to Laredo, and on camera, we approached the AWIS instrumentation and made our own temperature measurements and verified that the AWIS was running close to 5F too high during the afternoon hours. The heat of the NWS and a television news story finally prompted the FAA folks to put a replacement unit into operation at the AWIS site. The impact was immediate, and also verified that the earlier day and night 2F bias that I suspected earlier was also correct. Here’s the Tmax (AWIS-MMTS), Tmin (AWIS-MMTS) this year (July not shown as the replacement unit was deployed mid month: Jan 2.2,2.4 Feb 1.9,2.4 Mar 2.2,2.1 Apr 2.3,1.7 May 4.3,1.9 June 4.7, 1.6 Aug 0.6,0.0 Sep 0.5,-0.1.
Remarkably, when the NWS office wanted to go in and eliminate the myriad of record high temperatures that had been generated by the AWIS during the time that it had been commissioned/certified as official in 2009 (and especially the May and June data from 2011), the southern region office in Fort Worth told them to leave it alone, let it stand. I am astounded at this attitude. The experience over the last 7 or more years of lack of cooperation with various governmental agencies (FAA and NWS), and a current lack of interest by the southern region office in correcting verified systematic errors of significance is quite a disappointment. It doesn’t reflect well on the integrity of observational program.
On a different subject, I noted a reference in your recent paper that documented poorly sited thermometers. I do feel as if there should be a distinction made between thermometers used for climate change studies and those used for applied or operational purposes. With model grid boxes becoming smaller, a thermometer located over grass with no man made surfaces within 100 feet may not be representative of a grid box that is urban in nature. Likewise, such an ideal site may not be as useful to energy companies, architectural interests, ect. in an urban setting. I noticed that a poor exposure (a #5 type of site) was associated with temperature errors of >9F. I did see such numbers in the literature from a study conducted in Turkey. My experience has been quite different. I measured a surface temperature on a late June 2009 day with an 86 degree sun angle with an infrared thermometer of 143F on a blacktop parking lot. Three eith’s of an inch above the parking lot surface (3/8″), an UNSHIELDED thermometer in full sun read 105F. My MMTS at the edge of the parking lot was reading 92F (the airport with it’s 2F bias was 94F). I note also that J. Basara found a slight daytime urban COOL island in Oklahoma City…he spoke on this at the 14th Symposium on Meteorological Observation and Instrumentation and at the 2011 AMS Broadcast Meteorology Conference that I co chaired in Oklahoma City. Do you see any evidence supporting a systematic error as large as 9F (day or night) from the many #5 quality stations that you have studied?
Richard “Heatwave” Berler, CBM