北半球中高纬度对流层顶转换层中O3/H2O 混合关系的结构形态

利用北半球40°N～50°N纬度带上HALOE实验测量的O₃和H₂O廓线资料,根据示踪成分O₃和H₂O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300～390 K等熵面间,O₃/H₂O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320～380 K等熵面间O₃混合比廓线的斜率具有空间转折"突变",而H₂O混合比廓线的斜率则出现空间渐变转折.在对流层顶附近O₃和H₂O的源分别是平流层与对流层,使O₃混合比和H₂O混合比在320～380 K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O₃/H₂O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O₃/H₂O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30 K,即在320～350 K等熵面间.2005年11月的混合高度有所增高,进入平流层的H₂O混合比要比2003年和2005年1月的小,混合的等熵厚度大约为30 K,在330～360 K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.O₃/H₂O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.

The structure of O3/H2O mixing relationships in the tropopause transition layer in middle and high latitudes of the Northern Hemisphere

Using HALOE O₃ and H₂O vertical profiles in 40°N ～50°N of the Northern Hemisphere, considering chemical lifetime and transport temporal constant of O₃ and H₂O, the structure and seasonal characteristic of O₃/H₂O 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 O₃ is stratosphere but H₂O is troposphere near tropopause. So on the two sides of 320～380 K isentropic surfaces, mixing ratios of O₃ and H₂O show distinctly different vertical gradient. (2) In the vicinity of the tropopause where O₃/H₂O relationships reach best least square fitting, the troposphere and stratosphere branch of the non-regular "L" relationship show seasonal and intra-seasonal 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 H₂O 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.