Vertical structure of stratospheric water vapour trends derived from merged satellite data
Vertical structure of stratospheric water vapour trends derived from merged satellite data
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DOI：
10.1038/ngeo2236
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发表时间：
2014-10-01
影响因子：
18.3
通讯作者：
Weigel, K.
中科院分区：
文献类型：
--
作者：
Hegglin, M. I.;Plummer, D. A.;Weigel, K.
平流层水蒸气是一种强大的温室气体。美国科罗拉多州博尔德市上空气球观测的最长记录显示，平流层水蒸气浓度增加，这不能用观测到的主要驱动因素热带对流层顶温度和甲烷的变化完全解释。卫星观测可以帮助解决这个问题，但从单个短卫星记录构建可靠的长期数据记录是具有挑战性的。在这里，我们提出了一种方法来合并卫星数据集的帮助下，化学-气候模式轻推到观测气象学。我们使用模型的水汽作为数据集之间的传递函数，以克服仪器漂移和短重叠周期引起的问题。在平流层下部，我们的水蒸气记录可追溯到1988年，水蒸气浓度主要跟随热带对流层顶温度。平流层低层和中层的长期趋势是负面的，来自博尔德的趋势被证明不具有全球代表性。在平流层上层，我们的记录可以追溯到1986年，并显示出积极的长期趋势。这种趋势的海拔差异是由甲烷氧化、平流层下层加强和平流层上层环流减弱来解释的。我们的结果质疑了以前基于平流层低层水蒸气浓度的全球长期增加而对地面辐射强迫的估计。
Stratospheric water vapour is a powerful greenhouse gas. The longest available record from balloon observations over Boulder, Colorado, USA shows increases in stratospheric water vapour concentrations that cannot be fully explained by observed changes in the main drivers, tropical tropopause temperatures and methane. Satellite observations could help resolve the issue, but constructing a reliable long-term data record from individual short satellite records is challenging. Here we present an approach to merge satellite data sets with the help of a chemistry-climate model nudged to observed meteorology. We use the models' water vapour as a transfer function between data sets that overcomes issues arising from instrument drift and short overlap periods. In the lower stratosphere, our water vapour record extends back to 1988 and water vapour concentrations largely follow tropical tropopause temperatures. Lower and mid-stratospheric long-term trends are negative, and the trends from Boulder are shown not to be globally representative. In the upper stratosphere, our record extends back to 1986 and shows positive long-term trends. The altitudinal differences in the trends are explained by methane oxidation together with a strengthened lower-stratospheric and a weakened upper-stratospheric circulation inferred by this analysis. Our results call into question previous estimates of surface radiative forcing based on presumed global long-term increases in water vapour concentrations in the lower stratosphere.