南半球中高纬大气环流年代际变率的研究

DECADAL VARIABILITY OF ATMOSPHERIC CIRCULATION IN THE SOUTHERN MIDDLE AND HIGH LATITUDES

中文关键词:  南半球中高纬  大气环流  年代际变率

英文关键词:Southern middle-high latitudes  Atmospheric circulation  Decadal variability  Anterctic Oscillatron Index

中文摘要:

      利用近百年全球海平面气压图和再分析海平面气压等资料,建立了自1871年以来1,4,7和10月份的南极涛动指数(AOI)序列。近百年来1月AOI有明显增强的趋势,7月AOI则有明显减弱的趋势。最近40多年来,1,4和10月AOI都有较强的上升趋势。4个月份的AOI都有20～30a左右的准周期波动,表现出显著的年代际尺度的变化。用1,4,7和10月的平均可以近似反映年平均南极涛动指数的变化。在年代际尺度上,年平均指数在1894～1901年、1910～1935年左右是强的负指数时期。1880～1893年、1936～1945年左右是较强的正指数时期,1980年代以来,强的正指数已经持续了近20a,且1990年代以来还有加强的趋势。模拟结果的功率谱显示气候系统内部产生的低频变化主要体现在年际尺度变率上,年代际尺度变率的谱值则远远低于观测结果,但不排除在个别情况下,通过Hasselmann机制产生AOI年代际变率的可能性。

英文摘要:

      This paper summarizes the long-term and decadal time scale fluctuations of atmospheric circulation in the southern middle and high latitudes. The long time series of Antarctic Oscillation Indices (AOIs) were established for January, April, July and October 4 months based on the historical sea level pressure map and NCAR/NCEP reanalysis surface pressure data set. It was found that the AOI of January increased in a rate of 1.17 hPa/100 a, and July decreased in a rate of -1.49 hPa/100 a since 1871. The method of wavelet analysis was applied to detect the low frequency characteristics of AOIs, and it's clear that there are decadal variations in the time scale of about 20-30 years in all 4 months.Since the averaged value of 4 months could explain most variance of annual AOI, so it's reasonable using the mean AOI of January, April, July and October to represent the annual AOI. The values of annual AOI was much lower in periods of about 1894-1901, 1910-1935, and was much higher in periods of about 1880-1893, 1936-1945. The positive anomaly was significant since 1980 s. Power spectrum of modeled AOIs from Hadley Center Control Integration(HCCI) were compared with the observations, it's found that the inter-annual time scale frequencies were much significant than decadal frequencies. But, there also had the possibility for generating weak decadal fluctuations in some special months and years by the mechanism of Hasselmann.