Climatological aspects of dense fog at Urumqi Diwopu International Airport and its impacts on flight on-time performance

Comprehensive 25-year analysis of dense fog at Urumqi Diwopu International Airport (a major airport in western China) is performed using hourly weather data from January 1985 through December 2009 in an effort to better understand the climatological aspects of the phenomenon. The results show that dense fog is typically a cold-season phenomenon with more than 99 % of dense fog days occur from November through March. Within a day, dense fog peaks during the early morning hours and reaches a minimum in the late afternoon to early night. Most of dense fog events (68.2 %) lasted less than 3 h. Temperatures cooling to the range of −10 to −5 °C, and wind speeds of under 2 m s −1 are optimum for dense fog occurrences. Dense fog occurrences as brief as a couple of hours can disrupt air traffic locally even nationwide and affect flight on-time performance significantly, causing huge losses to both commercial airlines and passengers. There is a critical need for improving air traffic flow management. More importantly, aviation forecasters of airport should provide more timely and accurate information relating to dense fog to accommodate demands of different specific end users. However, the current situation is far from satisfactory. From a practical standpoint, some implications for dense fog forecasting are presented with the hope of improving the forecast of this phenomenon at the site.