Problems With Using Airport Weather Data To Estimate Heat Stress Risk

There are distinct hazards associated with estimating heat stress by using data obtained from a nearby airport:

(1)                      Time differences. US airports only report weather conditions hourly. The hourly report is made by averaging temperature and humidity readings that were made during the 5-minute period beginning at 15 minutes before the hour and ending at 10 minutes before the hour. These results are sometimes not posted for 15 to 20 minutes after they were made. So, if an athletic trainer is trying to make a practice control decision at 12 noon, the most recent weather information, the 11 am readings, may in fact represent conditions that occurred about 10:45 am. It is possible that conditions may have changed substantially in the intervening 75 minutes.

(2)                      Space differences. The playing field where heat stress is being estimated may be many miles from the airport where temperature and humidity are being measured. In complex urban environments, distances as small as a few hundred yards may produce dramatic differences in heat stress. Not only do cities act as “heat islands”, but even within cities there are multiple microclimates. The ideal method for evaluating heat stress is by making temperature and humidity measurements on the field of play where the practice is being held.

(3)                      Instrumentation differences. US airports employ Automated Surface Observation Systems (ASOS). The ASOS systems do not measure black globe temperature and cannot produce a true WBGT measurement.

Although these obstacles are formidable, the "Airport to WBGT" calculators in Heat Stress Adviser have been optimized to reduce these differences as much as possible. For example, the data used for Heat Stress Adviser’s airport-based calculators was obtained from hundreds of thousands of readings made several feet from a concrete tennis court surface, an environment that should serve as a worst-case example for airport-playing field differences. The airport data were compared with simultaneous tennis court data, and models were based on these comparisons.