The impact of temperature vertical structure on trajectory modeling of stratospheric water vapor
Item
Title (Dublin Core)
The impact of temperature vertical structure on trajectory modeling of stratospheric water vapor
Description (Dublin Core)
Lagrangian trajectories driven by reanalysis meteorological fields are frequently used to study water vapor (H<sub>2</sub>O) in the stratosphere, in which the tropical cold-point temperatures regulate the amount of H<sub>2</sub>O entering the stratosphere. Therefore, the accuracy of temperatures in the tropical tropopause layer (TTL) is of great importance for understanding stratospheric H<sub>2</sub>O abundances. Currently, most reanalyses, such as the NASA MERRA (Modern Era Retrospective – analysis for Research and Applications), only provide temperatures with ~ 1.2 km vertical resolution in the TTL, which has been argued to miss finer vertical structure in the tropopause and therefore introduce uncertainties in our understanding of stratospheric H<sub>2</sub>O. In this paper, we quantify this uncertainty by comparing the Lagrangian trajectory prediction of H<sub>2</sub>O using MERRA temperatures on standard model levels (<i>traj.MER-T</i>) to those using GPS temperatures at finer vertical resolution (<i>traj.GPS-T</i>), and those using adjusted MERRA temperatures with finer vertical structures induced by waves (<i>traj.MER-Twave</i>). It turns out that by using temperatures with finer vertical structure in the tropopause, the trajectory model more realistically simulates the dehydration of air entering the stratosphere. But the effect on H<sub>2</sub>O abundances is relatively minor: compared with <i>traj.MER-T</i>, <i>traj.GPS-T</i> tends to dry air by ~ 0.1 ppmv, while <i>traj.MER-Twave</i> tends to dry air by 0.2–0.3 ppmv. Despite these differences in absolute values of predicted H<sub>2</sub>O and vertical dehydration patterns, there is virtually no difference in the interannual variability in different runs. Overall, we find that a tropopause temperature with finer vertical structure has limited impact on predicted stratospheric H<sub>2</sub>O.
Creator (Dublin Core)
Wang, T.
Dessler, A. E.
Schoeberl, M. R.
Randel, W. J.
Kim, J.-E.
Date (Dublin Core)
2018-09-10
Type (Dublin Core)
Text
Format (Dublin Core)
application/pdf
Identifier (Dublin Core)
10.5194/acp-15-3517-2015
https://acp.copernicus.org/articles/15/3517/2015/
Source (Dublin Core)
eISSN: 1680-7324
Language (Dublin Core)
eng
