北半球中高纬度对流层顶转换层中O_3/H_2O混合关系的结构形态

The structure of O_3/H_2O mixing relationships in the tropopause transition layer in middle and high latitudes of the Northern Hemisphere

利用北半球40°N～50°N纬度带上HALOE实验测量的O_3和H_2O廓线资料,根据示踪成分O_3和H_2O空间分布的化学寿命以及输运特征时间常数等性质,在等熵坐标中构建了对流层顶附近及最低平流层300～390K等熵面间,O_3/H_2O混合关系的结构形态和季节特征.结果表明:(1)在对流层顶转换层的320～380K等熵面间O_3混合比廓线的斜率具有空间转折"突变",而H_2O混合比廓线的斜率则出现空间渐变转折.在对流层顶附近O_3和H_2O的源分别是平流层与对流层,使O_3混合比和H_2O混合比在320～380K等熵面的两侧显现出截然不同的垂直分布梯度.(2)在对流层顶附近O_3/H_2O达到最小二乘意义上的最佳拟合时,两者参考关系的对流层支与平流层支呈现出非规则"L"结构形态的季节与季节内变化,其中对流层支的斜率为负,而平流层支的斜率可随季节出现正负变化.同时,由"L"形态的转角处可确定随季节变化的化学对流层顶(chemopause)特征.(3)由O_3/H_2O混合关系反映出对流层不同区域空气携带的物质成分分别与平流层空气混合而形成混合层,而且可使混合层的混合线不恒定.混合层的表现在2003年、2005年1月和2003年4月的混合程度相当,混合的等熵厚度大约是30K,即在320～350K等熵面间.2005年11月的混合高度有所增高,进入平流层的H_2O混合比要比2003年和2005年1月的小,混合的等熵厚度大约为30K,在330～360K等熵面间.不同季节混合的等熵厚度变化较小,但高度可随季节而变化.O_3/H_2O混合关系的平流层支随季节的变化很明显,1月最低平流层空气脱水是引起平流层支季节变化的重要原因.

Using HALOE O3 and H2O vertical profiles in 40°N - 50°N of the Northern Hemisphere, considering chemical lifetime and transport temporal constant of O3and H2O, the structure and seasonal characteristic of O3/H20 mixing relationships between 300 K to 390 K near the tropopause and the lowest stratosphere have been constructed in the isentropic coordinates. The results are as follows ： （1）The slope of O3 mixing ratios profile have a spatial sudden change between 320-380 K isentropic surfaces of the tropopause translation layer, while the slope of H2O mixing ratios profile have a spatial gradual change. The source region of 03 is stratosphere but H20 is troposphere near tropopause. So on the two sides of 320 - 380 K isentropic surfaces, mixing ratios of 03 and H20 show distinctly different vertical gradient. （2） In the vicinity of the tropopause where O3/H20 relationships reach best least square fitting, the troposphere and stratosphere branch of the non-regular ＂L＂ relationship show seasonal and intraseasonal changes with a negative slope in the troposphere branch, but positive and negative slopes altering with seasons in stratosphere branch. At the same time, based on the ＂L＂ corner, the characteristic of chemopause with seasons can be confirmed. （3） The O3/H2O mixing relationship indicates that the transition layer is formed by stratospheric mixing with tropospheric air masses from different regions, and the mixing line of the transition layer is not constant. The transition layer mixing is equivalent in January 2003 and 2005 and April 2003, about 30 K isentropic thickness, that is between 320-350 K isentropic surfaces. Mixing height increases in November 2005, and the H20 coming into the stratosphere is less than in January 2003 and 2005, with about 30 K isentropic thickness, between 330-360 K isentropic surfaces. The change of mixing isentropic thickness is small in different seasons, but mixing height changes with seasons. The stratosphere branch of O3/H2O mixing relationship obviously changes with seasons, for which the significant reason is the lowest stratospheric air dehydration in January.