Extending water vapor trend observations over Boulder into the tropopause region: Trend uncertainties and resulting radiative forcing.
Extending water vapor trend observations over Boulder into the tropopause region: Trend uncertainties and resulting radiative forcing.
复制标题
将博尔德上空的水汽趋势观测扩展到对流层顶区域：趋势不确定性和由此产生的辐射强迫。
DOI：
10.1002/jgrd.50831
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
Kunz A
中科院分区：
文献类型：
--
作者：
Kunz A
本文利用30年来在Boulder（40°N,105°W）上空的气球测量资料来研究对流层顶区域的水汽趋势。这一分析扩展了之前公布的趋势，通常集中在16公里以上的高度，到更低的高度。采用了两个新概念：(1)在对流层顶以下- 2 km至对流层顶以上10 km的相对坐标系中呈现趋势；(2)根据对流层顶高度选择探空剖面。热带气团（TPz<12km）、温带气团（TPz<12km）和过渡性气团类型（12km<TPz<14km）揭示了三种不同的水汽储层。基于这些概念的分析减少了TP的动态诱导的水汽变率，主要有利于对流层上层和平流层下层的精细水汽趋势研究。尽管如此，这项研究表明，在TP周围- 2至+4公里的高度，趋势是多么不确定。这种不确定性反过来又影响到TP的水汽辐射效应的不确定性和解释，在30年期间的局地估计是不确定的。在TP周围的- 2和2公里之间没有探测到2001年初讨论较多的水汽减少。在平流层下层等熵上，2001年初温带气团类型的水汽变化比热带气团类型更强烈。这表明可能与高空急流上方动态变化有关，如布鲁尔-多布森环流浅层分支的变化。
Thirty years of balloon‐borne measurements over Boulder (40°N,105°W) are used to investigate the water vapor trend in the tropopause region. This analysis extends previously published trends, usually focusing on altitudes greater than 16 km, to lower altitudes. Two new concepts are applied: (1) Trends are presented in a thermal tropopause (TP) relative coordinate system from −2 km below to 10 km above the TP, and (2) sonde profiles are selected according to TP height. Tropical (TPz>14km), extratropical (TPz<12km), and transitional air mass types (12km<TPz<14km) reveal three different water vapor reservoirs. The analysis based on these concepts reduces the dynamically induced water vapor variability at the TP and principally favors refined water vapor trend studies in the upper troposphere and lower stratosphere. Nonetheless, this study shows how uncertain trends are at altitudes −2 to +4 km around the TP. This uncertainty in turn has an influence on the uncertainty and interpretation of water vapor radiative effects at the TP, which are locally estimated for the 30 year period to be of uncertain sign. The much discussed decrease in water vapor at the beginning of 2001 is not detectable between −2 and 2 km around the TP. On lower stratospheric isentropes, the water vapor change at the beginning of 2001 is more intense for extratropical than for tropical air mass types. This suggests a possible link with changing dynamics above the jet stream such as changes in the shallow branch of the Brewer‐Dobson circulation.