Some Aspects of Climatic Fluctuation at Four Stations on the Tibetan Plateau During the Last 40 Years

Abstract

Making use of 40 years data, 1951–1990, at four stations (Lhasa, Changdou, Deqin and Ganzi) on the Tibetan Plateau, the fluctuations of air temperature and precipitation were analyzed. From the 1950s to the 1980s a warming and drying tendency is predominant, particularly in summer and in mid-winter. A seasonal change of different tendencies from March, April to May occurs in a diametrically opposite way from October, November to December. In the second part of the study, anomalies of air temperature and precipitation were analyzed in the cases of El Niño and La Niña. Distributions of the anomalies were shown by season for air temperature and precipitation separately. It was indicated that the anomalies at Lhasa are of different sign in most cases from those at the other three stations located in the eastern part of the Plateau in summer. The anomaly conditions are the same from October to December. This can be attributed to the influence of monsoonal atmospheric circulation systems in summer. It is also noted that the distributions of precipitation anomaly in the El Niño case are not opposite to those in the La Niña case. In the last part of study, combinations of negative/positive anomalies of air temperature/precipitation were clarified. Anomalies with combinations of negative (air temperature) and negative (precipitation) dominated in the cases of El Niño summer and La Niña winter, but combinations of positive (air temperature) and positive (precipitation) dominated in the cases of El Niño winter and La Niña summer, and a combination of anomalies with negative (air temperature) and positive (precipitation) predominated in the case of La Niña winter.