Measuring Tornado Dynamics with In-Situ Instrumentation

摘要

Making accurate barometric pressure measurements in tornado cores using an in-situ probe is difficult due to very high wind velocities, heavy rain, and wind driven debris. Special considerations apply to the shape of the probe, as it must remain stationary during tornado passage. In-situ pressure measurements are particularly challenging as wind flow over any object will decrease the local static pressure and cause an erroneous barometric pressure measurement. This is especially important for the wind velocities exceeding 80 meters/second typical inside tornado cores. A specially-designed hardened probe called a “Hardened In-Situ Tornado Pressure Recorder” (HITPR) has been developed by the author at Applied Research Associates Inc.. The HITPR has addressed the abovementioned challenges by using a novel probe geometry that compensates for air flow curvature when measuring pressure, and has a high degree of aerodynamic stability. With this method, accurate measurements of the free-stream static pressure, wind speed, wind direction, temperature, and relative humidity can be made inside tornado cores. The measurement technique will be described in the present paper, as well as actual pressure measurements of tornado cores, including the 100 millibar pressure drop measured for a violent F-4 tornado on June 24th, 2003.