Tuesday, 14 May 2002: 4:15 PM
Climatologies of Upper-Level Turbulence over the Continental U.S. and Oceans
Climatologies of the regional, seasonal, and temporal distributions of aircraft turbulence encounters based on pilot reports (PIREPs) are presented. The PIREP database that is used contains nearly two million entries, and encompasses almost 10 complete years worth of data, going back to February 1992. A procedure was developed to remove air traffic pattern biases from the data, and PIREP consistencies among themselves were evaluated with positive results. Concentration has been on deriving upper level (above 20,000 ft MSL) turbulence statistics. Over the continental U.S., regional maxima are evident in the data over mountainous regions in the West, over the South and Southeast, and over the North Atlantic seaboard. Some limited analyses using lightning flash data and topography statistics are presented to help identify the causes of the turbulence. There does not seem to be any consistent maximum in the altitude of the turbulence encounters, i.e., there are as many encounters above and below the tropopause or jet stream as near that level. The same technique is used to also derive climatologies over oceanic regions. In those regions it is found that the highest percentages of moderate or greater turbulence occur over the North Atlantic.