March 3, 2009
As Meteorologists, we talk a lot about the average high temperature, or record low readings and even normal rainfall. We find this information by daily observations and the McCormick Observatory has been this source of information since 1892
"We take an observation of the maximum and minimum temperatures and the temperature when we take the observation as well as the rainfall for the previous 24 hours and any snow fall and record any unusual events; any hail storms or thunder showers", explained Ricky Patterson, Senior Scientist with the UVa Astronomy Department.
Ricky still records temperature with a mercury and alcohol thermometer, although a digital weather station is there.
"I don't believe that changing from a mercury and alcohol to digital is changing it anymore than the offset between different thermometers that the weather bureau has sent us over time."
However with rainfall...the manual way proves to be better.
"It captures the rain for 24 hours until I come and measure it but the electronic sensors, all the ones I'm aware of have a little thing where they are always reading every hundredth of an inch of rain, and for that second where it's taking the reading it could actually miss a little bit of rain", added Patterson.
Besides the digital weather station at McCormick, there is also an automated weather station at the airport. Differences are seen often due to the location of each station, but Jerry Stenger, who works with the VA state climatology office, prefers McCormick for accurate record keeping.
"The airport takes observations hourly or more frequently and also records parameters such as dew point temperature, winds, and cloud cover. Whereas the McCormick Observatory, focuses on temperature, precipitation, but they also measure snowfall and frozen precipitation."
Although technology is improving everyday, folks at McCormick Observatory will continue to take manual observations for the most accurate information and our climatology reports will continue to come from them.