Preprints
https://doi.org/10.5194/egusphere-2024-3260
https://doi.org/10.5194/egusphere-2024-3260
18 Nov 2024
 | 18 Nov 2024
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

Understanding Boreal Summer UTLS Water Vapor Variations in Monsoon Regions: A Lagrangian Perspective

Hongyue Wang, Mijeong Park, Mengchu Tao, Cristina Peña-Ortiz, Nuria Pilar Plaza, Felix Ploeger, and Paul Konopka

Abstract. Water vapor in the Upper Troposphere and Lower Stratosphere (UTLS) plays a crucial role in climate feedback by influencing radiation, chemistry, and atmospheric dynamics. The amount of water vapor entering the stratosphere is sensitive to cold point temperatures (CPT), making Northern Hemisphere summer monsoons more favorable for transporting water vapor into the stratosphere. This study uses a Lagrangian method to reconstruct water vapor over the Asian (ASM) and North American (NAM) monsoons, investigating their contributions to stratospheric water vapor. The Lagrangian method tracks air parcels and identifies the coldest temperature along each trajectory, contrasting with local methods that rely on vertical temperature profiles. The reconstructed water vapor fields are validated against satellite observations from SAGE III/ISS and NASA’s Aura MLS. SAGE III/ISS shows stronger moisture enhancements than MLS, but both datasets reveal similar water vapor anomalies within the ASM and NAM anticyclones. Although the Lagrangian method is dry-biased compared to observations, it effectively reconstructs UTLS water vapor (correlation coefficient 0.75), capturing moist anomalies in the ASM but performing less well in the NAM. Our analysis shows that, large-scale cold point tropopause temperatures in the vicinity of the monsoons primarily drive the moisture anomalies, with NAM water vapor significantly influenced by long-range transport from South Asia. Some convection-related processes, such as east-west shifts within the ASM, are not fully captured due to unresolved temperature variability in ERA5 and missing ice microphysics. Despite biases and computational challenges, the Lagrangian method provides valuable insights into UTLS water vapor transport.

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Hongyue Wang, Mijeong Park, Mengchu Tao, Cristina Peña-Ortiz, Nuria Pilar Plaza, Felix Ploeger, and Paul Konopka

Status: open (until 30 Dec 2024)

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Hongyue Wang, Mijeong Park, Mengchu Tao, Cristina Peña-Ortiz, Nuria Pilar Plaza, Felix Ploeger, and Paul Konopka
Hongyue Wang, Mijeong Park, Mengchu Tao, Cristina Peña-Ortiz, Nuria Pilar Plaza, Felix Ploeger, and Paul Konopka

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Short summary
We investigated how stratospheric water vapor behaves over the Asian and North American monsoons. Using a method that tracks air movement, we recreated the moisture patterns. Our results show that the moisture in monsoon regions is primarily controlled by largescale air temperatures, while the North American monsoon is influenced by distant transport. These findings enhance our understanding of summertime stratospheric water vapor changes and offer insights into climate feedback mechanisms.