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Convectively Transported Water Vapor Plumes in the Midlatitude Lower Stratosphere.

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Title: Convectively Transported Water Vapor Plumes in the Midlatitude Lower Stratosphere.
Authors: Wang, Xun1 (AUTHOR) xun.wang@mcgill.ca, Huang, Yi1 (AUTHOR), Qu, Zhipeng2 (AUTHOR), Vaillancourt, Paul A.3 (AUTHOR), Yau, Man‐Kong1 (AUTHOR), Feng, Jing1 (AUTHOR), Langille, Jeffery4 (AUTHOR), Bourassa, Adam5 (AUTHOR)
Source: Journal of Geophysical Research. Atmospheres. 2/27/2023, Vol. 128 Issue 4, p1-22. 22p.
Subject Terms: *Stratosphere, *Water masses, Water vapor, Numerical weather forecasting, Atmospheric water vapor measurement, Water vapor transport
Geographic Terms: North America
Abstract: Deep convective overshooting has been shown to transport water vapor into the midlatitude lower stratosphere. However, it has not been demonstrated how the convective water vapor plumes evolve after the overshoots collapse. Furthermore, there is a lack of characterization of the convective water vapor plumes, nor is it clear whether satellite instruments can observe the characteristics. We use a high‐resolution numerical weather prediction model to study a convective system over North America. Multiple overshoots transport water vapor in the overworld stratosphere, forming a moist layer between 16.2 and 16.8 km (389.8–399.7 K), with horizontal diameters of about 300–400 km, and a maximum water vapor mixing ratio of 10.0 ppmv (4.3 ppmv anomaly). Lagrangian trajectories and mass integrations show the overworld water vapor plumes are maintained after the convective system weakens. In the lowermost stratosphere (LMS), water vapor plumes are less stable and ice is present, because there is perturbation by ongoing convection. Lagrangian trajectories and mass integrations show the LMS parcels partly return to the troposphere, and that the LMS water vapor mass is reduced by half after the convection weakens. On average, the LMS moistening is between 15.0 and 15.8 km (362.6–382.0 K), with horizontal diameters of about 150 km, and a maximum water vapor mixing ratio of 31.1 ppmv (18.4 ppmv anomaly). Although current satellites have difficulty observing the fine structure of the convective water vapor plumes, a new satellite instrument under development (SHOW) with 1‐km vertical and 100‐km horizontal resolution will be able to verify the plume characteristics. Plain Language Summary: We use a high‐resolution numerical model to study convective moistening in the midlatitude lower stratosphere, including their evolution after the convection weakens, their observable characteristics, and whether their characteristics can be detected by satellite instruments. Our results show that the convective water vapor plumes above 380‐K potential temperature are stable in the stratosphere. They form a thin moist layer of 0.6 km with a horizontal size of about 300–400 km. The convective water vapor plumes closer to the tropopause and cloud tops contain ice, with vertical sizes of 0.8 km and horizontal sizes of about 150 km. They are less stable in the stratosphere, and their mass is reduced by half after the convection weakens. Current satellite instruments are limited by their resolutions in observing the characteristics of convective water vapor plumes. We show that new satellite instruments with a vertical resolution of 1 km will be able to observe the fine structures of convective water vapor plumes. Key Points: Water vapor plumes in the overworld stratosphere are more stable and maintain the mass in the stratosphere after the convection weakensWater vapor plumes in the lowermost stratosphere partly return to troposphere due to ongoing convective perturbationNew satellites with ≤ $\le $1‐km vertical resolution are required for observing the fine structure of the water vapor plumes [ABSTRACT FROM AUTHOR]
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Abstract:Deep convective overshooting has been shown to transport water vapor into the midlatitude lower stratosphere. However, it has not been demonstrated how the convective water vapor plumes evolve after the overshoots collapse. Furthermore, there is a lack of characterization of the convective water vapor plumes, nor is it clear whether satellite instruments can observe the characteristics. We use a high‐resolution numerical weather prediction model to study a convective system over North America. Multiple overshoots transport water vapor in the overworld stratosphere, forming a moist layer between 16.2 and 16.8 km (389.8–399.7 K), with horizontal diameters of about 300–400 km, and a maximum water vapor mixing ratio of 10.0 ppmv (4.3 ppmv anomaly). Lagrangian trajectories and mass integrations show the overworld water vapor plumes are maintained after the convective system weakens. In the lowermost stratosphere (LMS), water vapor plumes are less stable and ice is present, because there is perturbation by ongoing convection. Lagrangian trajectories and mass integrations show the LMS parcels partly return to the troposphere, and that the LMS water vapor mass is reduced by half after the convection weakens. On average, the LMS moistening is between 15.0 and 15.8 km (362.6–382.0 K), with horizontal diameters of about 150 km, and a maximum water vapor mixing ratio of 31.1 ppmv (18.4 ppmv anomaly). Although current satellites have difficulty observing the fine structure of the convective water vapor plumes, a new satellite instrument under development (SHOW) with 1‐km vertical and 100‐km horizontal resolution will be able to verify the plume characteristics. Plain Language Summary: We use a high‐resolution numerical model to study convective moistening in the midlatitude lower stratosphere, including their evolution after the convection weakens, their observable characteristics, and whether their characteristics can be detected by satellite instruments. Our results show that the convective water vapor plumes above 380‐K potential temperature are stable in the stratosphere. They form a thin moist layer of 0.6 km with a horizontal size of about 300–400 km. The convective water vapor plumes closer to the tropopause and cloud tops contain ice, with vertical sizes of 0.8 km and horizontal sizes of about 150 km. They are less stable in the stratosphere, and their mass is reduced by half after the convection weakens. Current satellite instruments are limited by their resolutions in observing the characteristics of convective water vapor plumes. We show that new satellite instruments with a vertical resolution of 1 km will be able to observe the fine structures of convective water vapor plumes. Key Points: Water vapor plumes in the overworld stratosphere are more stable and maintain the mass in the stratosphere after the convection weakensWater vapor plumes in the lowermost stratosphere partly return to troposphere due to ongoing convective perturbationNew satellites with ≤ $\le $1‐km vertical resolution are required for observing the fine structure of the water vapor plumes [ABSTRACT FROM AUTHOR]
ISSN:2169897X
DOI:10.1029/2022JD037699