Misguided thinking: All time low temperature record for Illinois called into question by NWS citing lack of confidence in equipment. “ASOS better than AWOS”

Misguided thinking: All time low temperature record for Illinois called into question by NWS citing lack of confidence in equipment. “ASOS better than AWOS”

From Watts Up with That, January 17, 2009

ASOS (left) AWOS (right) – both at airports click for larger images

People send me stuff. Last night I got an email from reader Andrew Schut that said:

See public information statement below.  I’m perplexed.

ASOS was put in for “aviation purposes” given its tolerances, yet we use it for climate purposes, why should AWOS be any different?

Not to mention the sensor that AWOS uses is a Vaisala sensor and at least a decade ahead in terms of sensor technology compared to the prehistoric 1088 RTD thermistor that the NWS has been using since the mid 80’s.

What Andrew was referring to was this unusual public information statement from the National Weather Service in Chicago, nullifying an apparently new low statewide temperature record from Rochelle Illinois:

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE CHICAGO IL
432 PM CST FRI JAN 16 2009

…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.

See the original here. Personally, I don’t think airports are a suitable place for ANY climate measurements to be made. Here is why.

Airports are dynamic environments, with changes in air traffic, runway upgrades, new runways, new terminals, more tarmac/access roads, and increased infrastructure in general over time. For the NWS in Chicago to say that one ASOS at one airport is somehow better that an AWOS at another, particularly one calibrated the day before, is simply disingenuous. Throw them both out I say. Airports aren’t “quality controlled” for station siting changes. The claim that ASOS is somehow thus better than AWOS is simply ludicrous. There is a basis for this claim.

Let’s look at some examples of ASOS climate stations and the type of quality control that goes on:

First the issue of encroachment by infrastructure, here’s a new fire station going up next to an ASOS station (which is a USHCN climate station) in Lafayette, LA, I believe the station to the lower right is an older AWOS station:

Read the rest here