摘要
臭氧的时空分布特征对气候和环境变化具有显著影响,随着臭氧资料数量的增加和质量的提高,有必要对臭氧时空分布特征及其与气候变化的关系进行详细研究.本文利用欧洲中期天气预报中心提供的1979—2013年的全球月平均臭氧总量资料、平流层温度场资料,采用旋转经验正交函数分解(REOF)、Morlet小波分析、合成分析等方法研究了20°N以北的北半球冬季(12—2月)臭氧总量异常的主要空间分布结构与时间演变特征,并进一步分析了主要模态与平流层上层(2hPa)、中层(30hPa)以及下层(100hPa)温度异常的关系.结果表明:近30年北半球冬季臭氧总量异常变化最显著的区域主要有5个,分别位于极地地区(75°N—90°N,0°—360°)、北半球副热带地区(20°N—40°N,0°—360°)、阿拉斯加地区(60°N—75°N,180°—260°E)、北大西洋地区(45°N—60°N,310°E—360°E)及西伯利亚地区(50°N—65°N,80°E—130°E).5个区域的冬季臭氧总量异常具有明显的年际和年代际变化特征.1980年代后期是各个区域的臭氧总量异常由年代际偏多转为偏少的转换时段.此外,各区域存在显著的年际变化周期,而且各个区域的年际周期存在明显的差异.臭氧总量异常变化与平流层温度异常变化的关系表明,臭氧总量异常的增加(减少)能够导致平流层上层温度异常偏冷(暖)和平流层中、下层温度异常偏暖(冷),其中平流层中层温度异常的偏暖(冷)程度要比下层更加明显.
It is well known that ozone is one of the most important trace gases in the atmosphere.Stratospheric ozone can directly affect levels of ultraviolet radiation reaching the Earth′s surface and stratospheric temperature structure,while tropospheric ozone is an air pollutant,which is harmful to human health and ecosystems.Therefore,it can be inferred that ozone has a significant impact on the variability of climate and environment.As the increase of the high quality and quantity of ozone datasets,it is necessary to provide a detailed investigation of spatiotemporal distribution characteristics of total ozone and its relationship with climate variability.Besides,because most of ozone is observed in the stratosphere,it is also necessary to examine the relationship between ozone and stratospheric temperature.Ozone and temperature data are taken from monthly mean European Center for Medium Range Weather Forecasting（ECMWF）reanalysis data（ERA-Interim）from 1979 to 2013.ERAInterim has assimilated satellite observations（reprocessed Global Ozone Monitoring Experiment data from the Rutherford Appleton Laboratory provides ozone profile information from 1995onwards）at a 2°×2°horizontal resolution and relatively high vertical resolution（37levels）.To study the general features of ozone,we first apply the empirical orthogonal function（EOF）to the ozone data.And then the rotated EOF（REOF）method is used to extract the dominant modes of ozone,meaning that the initial EOF modes are linearly transformed using the varimax method,which maximizes the variance of the squared correlation coefficients between the time series of each REOF mode and each original EOF mode.The method increases the spatial variability of the obtained modes.Besides,the continuous wavelet transform method is used to study the periodicity of the rotated principal components（RPC）time series.We use the Morlet wavelet in the current study.The spatiotemporal structure of dominant total ozone pattern in the Northern Hemisphere（north of 20°N）during boreal winter is studied using REOF analysis and Morlet wavelet analysis.Besides,the relationship of the dominant total ozone pattern with the temperature anomalies in the upper（2hPa）,middle（30hPa）and lower（100hPa）stratosphere is further studied using composite analysis.The results show that the variability of total ozone in the Northern Hemisphere during boreal winter is characterized by five significant dominant patterns during the recent 30years（1979—2013）.The first REOF mode accounts for 34.5% of the total variance.It is centred mainly in the Arctic region（75°N—90°N,0°—360°）.The ozone of this region decreases during 1979—1995,while increases during 1995—2001.However,the ozone of this region shows significant interannual time scale since 2002.The local wavelet power spectrum analysis shows that the power spectrum of the normalized RPC1 has high power in about 3year for the period 1983—1993and about 2～7year for the period 1990—2005.The second mode is centred in the subtropics of Northern Hemisphere（20°N—40°N,0°—360°）,accounting for 32%of the total variance.The ozone in this region is above normal during the period 1979—1995but below normal thereafter.The power spectrum of RPC2 shows high power in about 2～3year for the period 1983—2000.The third REOF mode is centred in the Alaska region（60°N—75°N,180°—260°E）,accounting for 10% of the total variance.The ozone in this region is above normal during 1979—1985,while below normal during 1985—1995.After 2000,it shows interannual variability.The power spectrum of RPC3 shows high power in about 2～8year for the period1990—2000.The fourth REOF mode is centred in the North Atlantic region（45°N—60°N,310°E—360°E）,accounting for 5.6% of the total variance.The ozone in this region is above normal during 1979—1990,while below normal during 1991—2005.It shows interannual variability to some extent since 2005.The power spectrum of RPC4 shows high power in about 2～3yearduring 1979—1984,1989—1995and 2005—2012.The fifth REOF mode is centred in the Siberia region（50°N—65°N,80°E—130°E）.The ozone in this region is above normal during 1979—1987and 2002—2012,while below normal during 1988—2002.The power spectrum of RPC5 shows high power in about 2～4year during 1985—1995.On the other hand,it also shows high power in about 5～7 year during 1985—2003.The relationship between the dominant total ozone patterns and the stratospheric temperature indicates that,when the total ozone is increased（reduced）,the upper stratosphere will be cooled（warmed）,while the middle and lower stratosphere will be warmed（cooled）.Furthermore,the middle stratosphere is warmer（cooler）than the lower stratosphere.The results of this study show that the five dominant REOF modes show significant variability on the interannual and interdecadal time scales.On the interdecadal timescale,the total ozone over these five regions is above normal before late 1980,whereas less than normal during the period of 1990—2000.On the interannual time scale,total ozone over the five regions shows pronounced periodicity.In addition,their periodicities show significant difference.We have also examined the relationship between total ozone and stratospheric temperature.It is suggested that the upper stratospheric temperature has out-of-phase relationship with total ozone,while the middle and lower stratospheric temperature has in-phase relationship with total ozone.This study focuses only on the DJF season（boreal winter）simply because it is an important season for ozone in the Northern Hemisphere.However,the seasonality of the total ozone in the Northern Hemisphere and related impact on stratospheric and tropospheric climate is the major focus of a following study that is underway.Finally,we have only studied the relationship between the total ozone and stratospheric temperature based on analysis of observations.Therefore,further study using simulations in numerical model is needed to fully understand the mechanism by which the total ozone influences the stratospheric temperature.
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2015年第5期1475-1491,共17页
Chinese Journal of Geophysics
基金
国家重点基础研究发展计划项目(2013CB956203)
国家自然科学基金项目(41475070)共同资助
关键词
臭氧总量
平流层温度
分布特征
旋转经验正交函数
Total ozone
Stratospheric temperature
Distribution characteristics
Rotated empirical orthogonal function（REOF）
