青藏高原臭氧谷极端事件的定义及其特征

Definition and characteristics of extreme events of ozone valley over the Tibetan Plateau

利用1979—2016年ERA-interim逐日再分析资料,定义了青藏高原臭氧谷(Ozone Valley over the Tibetan Plateau,OVTP)极端和普通强(弱)事件,并讨论了其特征。结果表明:1) OVTP极端强事件在夏秋季节多发,10月最多,频率达2. 0%; OVTP普通强事件在春夏季多发,7月最多,频率达1. 7%。OVTP极端弱事件在秋冬季多发,12月最多,频率达3. 8%; OVTP普通弱事件在冬季多发,1月最多,频率达2. 0%。2) OVTP极端强事件出现频率显著增加(0. 004%·a^(-1)),极端弱事件出现频率显著减少(-0. 015%·a^(-1))。OVTP普通事件的变化均不显著。3) OVTP极端强事件的面积和强度均在秋季最大,10月达到最大值,面积为4. 3×10~5km^2,强度为1. 5×10~5t; OVTP普通强事件的面积和强度均在夏季最大,7月达到峰值,面积为1. 7×105km^2,强度为4. 1×10~3t。OVTP极端弱事件的面积和强度在春夏较小,4月达到最小值,面积为3. 2×10~4km^2,强度为1. 1×10~2t; OVTP普通弱事件的面积和强度在春夏秋均较小,4月和10月达到极小值,4月面积为2. 5×10~4km^2,强度为68 t,10月面积为2. 2×10~4km^2,强度为97t。4) OVTP极端和普通强事件的面积(强度)均呈显著增大(增强)趋势,极端强事件的面积达2. 5×10~2km^2·a^(-1),强度达2. 5×10~2t·a^(-1),普通强事件的面积达4. 5×10~2km^2·a^(-1),强度达4. 5 t·a^(-1)。极端和普通弱事件的面积(强度)均呈显著减小(减弱)趋势,极端弱事件的面积达-1. 7×10~4km^2·a^(-1),强度达-7. 0×10~3t·a^(-1),普通弱事件的面积达-2. 3×10~3km^2·a^(-1),强度达-2. 7×102t·a^(-1)。

Studies on the extreme events of ozone depletion in the polar region are many but studies on the ozone extreme events of ozone valley over the Tibetan Plateau(OVTP) are few and mainly focus on case analysis.Therefore,this paper defined the extreme and ordinary events of OVTP and analyzed their characteristics based on the ERA-interim daily reanalysis data from 1979 to 2016.Firstly,this paper selected the characteristic isolines of extreme(ordinary) strong and weak OVTP according to total column ozone(TCO) and zonal deviation of TCO (TCO^*) after plus or minus 1.96(1.29) standard deviation of TCO and TCO^*,respectively.Secondly,this paper defined the extreme strong OVTP with TCO≤250 DU and TCO^*≤-55 DU,the ordinary strong OVTP with 250 DU<TCO≤260 DU and-55 DU<TCO^*≤-40 DU,the ordinary weak OVTP with 285 DU<TCO≤293 DU and-10 DU<TCO^*≤-6 DU,and the extreme weak OVTP with-6 DU<TCO^*≤0 DU.Then this paper analyzed the characteristics of the extreme and ordinary OVTP.The results as follows:1) Extreme strong OVTP frequently occurs in summer and autumn,and it appears most in October when the occurrence is up to 2.0%.Ordinary strong OVTP frequently occurs in spring and summer,with the most occurrences in July when the occurrence is up to 1.7%.Extreme weak OVTP frequently occurs in autumn and winter,with the most occurrences in December when the frequency is up to 3.8%.Ordinary weak OVTP frequently occurs in winter,with the most occurrences in January when the frequency is up to 2.0%.2) Trends of extreme OVTP are significant,while trends of ordinary OVTP are not significant.Extreme strong OVTP increased significantly with 0.004%·a^-1.Extreme weak OVTP decreased significantly with 0.015%·a^-1.3) Area and strength of extreme strong OVTP are the largest in autumn and reach the maxima in October,with 4.3×10 5 km 2 and 1.5×10^5 t.Area and strength of ordinary strong OVTP are the highest in summer and peak in July,with 1.7×10^5 km^2 and 4.1×10^3 t.Area and strength of extreme weak OVTP are small in spring and summer and reach the minima in April,with 3.2×10^4 km^2 and 1.1×10^2 t.Area and strength of ordinary weak OVTP are small in spring,summer and autumn,and reach the minima in April (October),with 2.5×10^4 km^2 and 68 t (2.2×10^4 km^2 and 97 t).4) The significant trends of area and strength of extreme (ordinary) strong OVTP are 2.5×10^2 (4.5×10^2) km^2·a^-1 and 2.5×10^2(4.5) t·a^-1 ,respectively.On the other hand,the significant trends of area and strength of extreme (ordinary) weak OVTP are -1.7×10^4 (-2.3×10^3) km^2·a^-1 and -7.0×10^3 (-2.7×10^2) t·a^-1.