Circulation Indices And Distribution Characteristic Quantities Of Summer South Asian High

Three circulation indices which are area index S,intensity index P,center location index(λ_c,φ_c)and three characteristic quantities of system centers which are average distance r,compression coefficientμ,maximum anomaly directionβ,are defined for South Asian High(SAH).Their 60-year(1948～2007)series in June,July and August are calculated,by use of 100hPa NCEP/NCAR monthly mean geopotential height reanalysis data,which are used to the preliminary analysis for the climatic and anomalous characteristics of Summer SAH,the relationship with the climatic anomalies of China and its application on the climatic analysis.The results show that:1)SAH is the weakest,covers an minimum area,and the center is located in the Nepal southwest border in June;it is the strongest with maximum area and the center located in the northern of Pakistan in July;it is weaker and smaller in August than that in July,but stronger and bigger than that in June,the center located in the northern of India.2)S＇can be replaced with P＇in anomaly analysis due to the interannual quasi-synchronized variations of the intensity and area for SAH in each month.P＇of June,July and August have an intraseasonal consistenty,and their same sign ratio reaches 41/60 in the same year.The wavelet power spectrums of slow-variation components of SAH's intensity in June,July and August all pass the statistical significance test(α=0.05)in the end of 70's or so,thus the interdecadal variations of P＇are significantly.3)The climatic variability of SAH's center locations are quasi-latitudinal distribution and their longtitudinal(latitudinal) extended areas are in direct(inverse)proportion to the climatological intensity.The climatic variability and average distancer are maximum in June,mediacy in July, minimum in August,contrary the situation of compression coefficientμ.Maximum anomaly directionβall point to the southeastern.The interdecadal variations of center locations are apparent.4)The distribution of the correlation between the intensity of SAH and the SST is similar to that when El Nino happened.It indicate that SAH may Strengthen or weaken when El Nino or La Nina happens.The intensity in June,July,August has contrary extend with the SOI,so it can be used to predict the intensity of SAH.5)The relationship between the center location index of SAH and the temperature of China,the precipitation of Asia and the surrouding are obviously.So the South Asian High is a atmospheric action center which has great importantace to the climatic anomalies.