Q: Rather than measuring rainfall only at Hartsfield-Jackson International Airport, does the National Weather Service believe that averaging rainfall amounts at multiple stations placed around Atlanta would provide greater accuracy?
—Bob Cooksey, Flowery Branch
A: The practice of collecting quality-controlled precipitation observations at set locations dates back to when the National Weather Service was the Weather Bureau, Laura Belanger, meteorologist and interim service hydrologist with the NWS in Peachtree City, told Q&A on the News. Since the 1800s, observations have been collected at "climate sites," locations with volunteer or occupational observers trained and educated in taking quality, official observations.
It is common, she writes, to have one “official” location, which for Atlanta is Hartsfield-Jackson International Airport, although data are kept for many locations, including reports from other area airports and observations from a network of volunteers.
Given the density of other observation sites and the short period of record, NWS Atlanta only officially tracks climate records for the Atlanta, Athens, Columbus and Macon airports, she writes.
“There are many reasons to isolate records for each site, rather than averaging over an area,” she writes.
Monitoring unique sites allows for better understanding of extreme events, and recording “outlier” events helps determine the frequency of things like heavy rainfall amounts. For regional frequency analyses, data from all homogeneous sites are factored, so they essentially act as an average. From the frequency analyses, we get the terms “100-year-event” or “1 percent chance of occurrence,” she writes.
NWS radars provide rainfall estimates (water.weather.gov/precip) to provide a better spatial understanding of the precipitation coverage over a particular time period, she added.
Fast Copy News Service wrote this column. Do you have a question? We’ll try to get the answer. Call 404-222-2002 or email q&a@ajc.com (include name, phone and city).
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