Estimation of Nocturnal Cooling Temperature on a Regional Scale

Abstract

The feasibility of regional estimation of nocturnal cooling between the evening mean temperatures and the next morning's minimum temperatures was estimated using with a nocturnal cooling model. Here, we used the data of the Automated Meteorological Data Acquisition System (AMeDAS) and the aerological observation at Sapporo. In the present analysis, we suppose that the possible temperature drop by nocturnal cooling on each clear night are a constant across a region of about 100km x 150km. The possible temperature drops in the 32 cases were about from 15 degree to 24 degree. The ratio of the actual temperature drops at the AMeDAS monitoring points to the possible temperature drop were from about 0.5 to 0.6 at the higher elevations of the inland areas, 0.4 to 0.5 in the plains and around 0.3 in the coastal areas. There was an interesting similarity between the values and the geographical and topographical futures. A model using these values as parameters was applied for 11-clear days in 1990. Estimated values were found to be less than the observed values, but their errors were within almost 2 degrees.