Study On The Intraseason Oscillation At The Stratospheric Atmosphere Of The Northern Hemisphere And Its Relationship With The Troposphere

Based on the NCEP/NCAR reanalysis data (geopotential height field and wind field data from1970 to1999), at first, by using morlet wave analysis, the dominant period of the intraseason oscillation(ISO) in the wintertime stratospheric atmosphere of the Northern Hemisphere(NH) is examined distinctly. In the wintertime stratospheric atmosphere of the northern Hemisphere, the space structure, the direction of the horizontal propagation , the most active areas and the annual variety of the low frequency oscillation are related in detail. Compared to that of the troposphere atmosphere, the space structure, propagation, regional distribution and the annual variety of the low frequency oscillation of the stratospheric atmosphere are different but connected. Then, the Arctic Oscillation (AO) is described as the leading mode at the stratospheric atmosphere of NH, its distributions are figured out and is compared with AO in the tropospheric atmosphere. At last the spatial patterns of teleconnection of the low frequency oscillation are also showed in the paper. By using daily data at many levels, the wavelet analysis suggests that there is a remarkable low frequency oscillation (a dominant period of 60-day) existing in the wintertime stratospheric atmosphere of the northern Hemisphere. By the way, the results show that there is another period of 20-day, but the period of 60-day is more distinct. So we choose the period of the band-pass filter in the text is 15 to 90 days. The low frequency oscillation has a barotropic structure on the vertical plane and a westward propagation on the horizontal plane by using daily filtered data at many levels. At high latitude area, variability of ISO is driven primarily by the zonal momentum of waves with zonal wavenumbers 1~2, and at middle latitude zonal wavenumbers is 2~3, at low latitude it is 3~5. Through the calculation of the kinetic energy by using the filtered wind data, ISO generally exists in atmosphere in NH, it is more remarkable in high latitude at horizontal plane. And ISO at middle stratosphere is more active than at low stratosphere. The annual variety of ISO is showed in paper. After realized the characters of ISO in the stratospheric atmosphere of NH, we compare them with ISO in the troposphere. They are absolutely similar at most region in NH except for the low latitude zone. It maybe the reason caused this difference between troposphere and stratosphere that the ISO in tropic tropospheric atmosphere is driven by CISK. Results show that the spatial patterns of the low frequency oscillation by using the singular value decomposition (SVD) and the empirical orthogonal function(EOF) of the geopotential height fields at many levels. The leading mode is AO. By calculating the correlation coefficients of the geopotential height fields at many levels, the figures show the same result as the figures of SVD. In the wintertime stratospheric atmosphere of the northern Hemisphere, the negative correlation between the extratropical regions and the other fields. And AO remarkably has the annual variety. The lag correlation is done with the principal component (PC) time series between troposphere and stratosphere from EOF decomposition. It shows that the ISO in the stratospheric atmosphere change faster than the ISO in the tropospheric atmosphere about 33 days. The spatial patterns of teleconnection of the low frequency oscillation are also showed in the paper. There is a wave from the Middle Eurasia (the Iran Altiplano) to the Pacific Ocean. And the Iran Altiplano, Siberia and the Pacific Ocean make up of the EUP teleconnection in the stratospheric atmosphere.