Testing the Doran summer climate rules in Upper Wright Valley, Antarctica

Abstract

AbstractBased on data from low elevation lake sites, previous studies have suggested three quantitative relationships related to summer (December, January and February) air temperatures in the Dry Valleys of Antarctica: i) decrease with altitude at the dry lapse rate of 9.8°C km-1, ii) increase with distance from the coast at a rate of 0.09°C km-1, and iii) degree-days above freezing during the summer months is logarithmically proportional to the maximum summer air temperature. Here, we tested the first two of these rules at high elevation sites in Upper Wright Valley. Direct measurements confirmed that the summer lapse rate followed the dry lapse rate. For the three furthest stations, Tyrol Valley, Mount Fleming and Horseshoe Crater, the average difference between the measurements and the predicted summer monthly averages are -2.1±1.4°C, -0.5±1.0°C and -0.4±0.9°C, respectively. By contrast, at Linnaeus Terrace (54 km from the coast) the monthly average is warmer than predicted by several degrees: +4.3±1.3°C. The inland temperature gradient at these high elevation sites may result from sunlight effects rather than coastal wind as previously shown for the lower valleys. The warm conditions observedc. 50 km from the coast may reflect a zone affected by both sunlight and coastal wind.