Statistical Downscaling of Temperature at Kathmandu Airport

Abstract

Kathmandu Airport station is located at Tribhuwan International Airport in Kathmandu, spanning 27.70 degrees of latitude and 85.37 degrees of longitude with the elevation of 1337 meters. It is situated in Kathmandu valley which is surrounded by hills in all sides and is almost circular in shape. Elevation of surrounding hills range from 2000 to 2750m and valley is flat with elevation ranging from 1300 to 1400m .The east to west and north to south axes of valley are about 26km and 37km.kathmandu valley lies between 27°32 to 27°49 E and 85°11 to 85° 32 N .The Kathmandu valley, which has the capital city Kathmandu along with four other municipal towns, Lalitpur, Bhaktapur, Kirtipur and Madhyapur‐Thimi, is the main urban area of Nepal. The valley is located between the Himalayan in the north and the Mahabharata mountains in the south. In order to best describe the expected climate change impacts for the region, climate change scenarios and climate variables must be developed on a regional, or even site‐specific, scale.

To generate the future climate change scenarios in this region statistical downscaling tool was used. For this, daily temperature data from 1968‐1990 A.D. was obtained from Department of Hydrology and Meteorology but for the model to run it has to start from 1960 A.D. so the data from 1961 to 1967 A.D. was coated as ‐999 as missing values for the model to run. This data was used as the basis for developing the initial statistical relationships. Essentially, a predictor‐predictand relationship is defined between global climate model values and the observed values at Kathmandu Airport. Future climate variables (predictors) are then extracted from HADCM3 model experiment. The predictors were found to be 500 hPa geo potential height, surface zonal velocity, relative humidity at 850 and 500 hPa and surface specific humidity. Those predictors are used to provide downscaled climate variables (predictand) that are applicable to those specific observed data sites.

From this model it was found the future scenario of temperature in Kathmandu Airport at different time periods was rising.