Variability of surface air temperature over gently-sloped terrain
David Bodine, Atmospheric Radar Research Center, School of Meteorology, University of Oklahoma, Norman, OK; and P. Klein, S. Arms, E. Fedorovich, and A. M. Shapiro
Several studies have documented large nocturnal temperature variability and a height dependence of temperature over scales of tens of kilometers. However, this study focused on nocturnal temperature variability on a much smaller scale of 100-by-250 meters. Temperature data was collected from January 2005 to October 2006 for 30 stations at the Lake Thunderbird Micronet. This temperature data revealed that cold pools frequently developed in the low-lying region near the lake at night.
Stable conditions promoted the development of strong cold pools (temperature perturbation of at least -2 degrees Celsius). Strong cold pools formed under stable conditions in 11 of the 12 cases analyzed between March and May 2005. However, further analysis revealed that the correlation between stability and cold pool temperature perturbation was weak, and other mechanisms are likely involved in cold pool formation. The relationship between wind speed and cold pool formation was much stronger. The average Norman Mesonet wind speed was 1.84 ms-1 for the strong cold pool cases and 4.95 ms-1 for the non-cold pool cases. Drainage flows were observed for most strong cold pool cases. Based on wind measurements with a sonic anemometer at 1.5-meter above ground, down slope drainage flow was observed on 72.3 percent of the nights for which strong cold pools occurred. Katabatic cases, evident by a change in wind direction between the 1.5-m and a 15-m measurement height, occurred for 60 percent of the strong cold pool cases.
The Micronet temperature data showed that large spatial temperature variability observed at larger scales in previous experiments also occurs at very small scales. The Micronet temperature data showed that temperature differences as large as 8 degrees Celsius can occur with an elevation change as small as 20 meters over a 200-meter distance. The local minimum in elevation in the southeast corner of the Micronet was a favorable area for cold pool formation because drainage flows support transport of cold air into this area.
Poster Session 1, Student Conference General Poster Session
Sunday, 20 January 2008, 5:30 PM-7:00 PM, Exhibit Hall B
Previous paper Next paper
Browse or search entire meeting
AMS Home Page