Warm Season Cumulus Cloud Base Height Climatology for Hartsfield-Jackson Atlanta International Airport

Hartsfield-‐Jackson Atlanta International Airport (ATL) is the world's busiest airport with aircraft arrival rates (AAR) of 120 arrivals per hour and connecting nearly 100 million passengers annually. Accurate forecasts of wind, precipitation, visibility and cloud heights are essential for improving the safety and efficiency of air traffic at ATL. In order to improve the forecasts of the prevailing cloud height grids in the National Weather Service's Graphical Forecast Editor (GFE) software, a summertime cumulus cloud base height climatology for few and scattered cloud cover categories will be produced for ATL. Even scattered cloud cover at 6000 ft causes a reduction in AAR, so it is important to study more than just cloud ceiling (broken or overcast sky cover) category forecasts. The cloud base climatology will be determined from hourly ASOS observations at ATL from 2003 to 2013 during the warm season (June 1 – August 31). The results will be further stratified by wind direction. The results will be compared with satellite-based convective cloud climatology (Klitch et al. 1985) and with various lifting condensation level forecasts of cloud height based on surface temperature and dewpoint observations at ATL.