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Abstract In the tropics, the tropopause is exceptionally cold and air entering the stratosphere is dehydrated down to a few parts per million leading to the extreme dryness of Earth’s stratosphere. Deep convection typically detrains a few kilometers below the tropopause, but the few storms that may reach up to the tropopause could have an outsize effect on water vapor, other chemically important trace species, and clouds. However, little progress has been made to quantify the role of these storms due to challenging conditions for observations, and computational limitations. Here we provide the first global observational estimate of the convective ice flux at near tropical tropopause levels by using spaceborne lidar measurements and pioneering a method to convert from lidar measurement to ice flux information. Our estimate indicates that the upward ice flux in deep convection dominates moisture transport almost all the way up to the cold point tropopause.
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Persistence of moist plumes from overshooting convection in the Asian monsoon anticyclone
Abstract. The Asian monsoon anticyclone (AMA) represents one of thewettest regions in the lower stratosphere (LS) and is a key contributor tothe global annual maximum in LS water vapour. While the AMA wet pool islinked with persistent convection in the region and horizontal confinementof the anticyclone, there remain ambiguities regarding the role oftropopause-overshooting convection in maintaining the regional LS watervapour maximum. This study tackles this issue using a unique set ofobservations from aboard the high-altitude M55-Geophysica aircraft deployedin Nepal in summer 2017 within the EU StratoClim project. We use acombination of airborne measurements (water vapour, ice water, waterisotopes, cloud backscatter) together with ensemble trajectory modellingcoupled with satellite observations to characterize the processescontrolling water vapour and clouds in the confined lower stratosphere (CLS)of the AMA. Our analysis puts in evidence the dual role of overshootingconvection, which may lead to hydration or dehydration depending on thesynoptic-scale tropopause temperatures in the AMA. We show that all of theobserved CLS water vapour enhancements are traceable to convective eventswithin the AMA and furthermore bear an isotopic signature of the overshootingprocess. A surprising result is that the plumes of moist air with mixingratios nearly twice the background level can persist for weeks whilstrecirculating within the anticyclone, without being subject to irreversibledehydration through ice settling. Our findings highlight the importance ofconvection and recirculation within the AMA for the transport of water into thestratosphere.
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- Award ID(s):
- 1743753
- PAR ID:
- 10378637
- Date Published:
- Journal Name:
- Atmospheric Chemistry and Physics
- Volume:
- 22
- Issue:
- 5
- ISSN:
- 1680-7324
- Page Range / eLocation ID:
- 3169 to 3189
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.5194/acp-22-3169-2022
