Follow-Up Post on IL State Temperature Record Decision by Climatologist
(Monday, January 19, 2009) – I have consulted a couple of independent sources that make the case that the Rochelle, IL low temperature of -37º was dismissed as being in error too quickly. Consider the initial Public Information Statement issued by the Chicago NWS on January 15th:
EARLIER TODAY THE AUTOMATED OBSERVING STATION AT THE ROCHELLE ILLINOIS AIRPORT IN SOUTHEASTERN OGLE COUNTY REGISTERED A TEMPERATURE OF -37 DEGREES FAHRENHEIT. THIS WOULD HAVE BEEN A NEW STATE LOW TEMPERATURE RECORD. HOWEVER…UPON INVESTIGATION…THE ILLINOIS STATE CLIMATOLOGIST FOUND THAT THE AUTOMATED EQUIPMENT HAD
MALFUNCTIONED AND WAS READING 14 DEGREES TOO LOW. THIS HAS BEEN CORRECTED AND THE SITE IS NOW REPORTING A REPRESENTATIVE TEMPERATURE.
Instruments Similar to Those Used in Rochelle, IL
Then it nearly happens again the very next morning! Again, another PNS is issued by the NWS:
…REGARDING ROCHELLE`S LOW TEMPERATURE THIS MORNING…
THE AUTOMATED WEATHER OBSERVING SYSTEM (AWOS) AT THE ROCHELLE
AIRPORT RECORDED A TEMPERATURE OF -36F AT 745 AM THIS MORNING.
WHILE THE THERMOMETER ON THE AWOS WAS RE-CALIBRATED YESTERDAY
AND MAY INDEED BE ACCURATE…AWOS OBSERVATIONS ARE NOT QUALITY
CONTROLLED OR CALIBRATED BY THE NATIONAL WEATHER SERVICE AND
ARE ALSO NOT DESIGNED FOR CLIMATE PURPOSES.
THEREFORE…THE STATE CLIMATOLOGIST DOES NOT CONSIDER THIS
TEMPERATURE AN OFFICIAL MEASUREMENT FOR THE PURPOSE OF
DETERMINING WHETHER OR NOT AN ALL TIME RECORD LOW FOR THE
STATE WAS REACHED. FOR THE PURPOSE OF DETERMINING RECORD
TEMPERATURES FOR THE STATE…ONLY ASOS AND
COOPERATIVE OBSERVER OBSERVATIONS WILL BE USED SINCE BOTH OF
THESE OBSERVATIONS ARE QUALITY CONTROLLED BY THE
NATIONAL WEATHER SERVICE.
This prompted Anthony Watts of http://wattsupwiththat.com take up the issue in this post here. This is an excellent detailed explanation of the situation.
As I noted in the January 15th post, it is my understanding that if there is a bias displayed by a thermometer, it will be a warm bias. It appears there are other methods of quality control and meteorological considerations that should have been made. Especially in light of the fact it happen again after there was a re-calibration. Interesting!
