A Multimodel Investigation of Asian Summer Monsoon UTLS Transport Over the Western Pacific

Pan, Laura L.; Kinnison, Douglas E.; Liang, Qing; Chin, Mian; Santee, M. L.; Flemming, Johannes; Smith, Warren P.; Honomichl, Shawn; Bresch, James F.; Lait, Leslie R.; Zhu, Yunqian; Tilmes, Simone; Colarco, Peter R.; Warner, J. X.; Clerbaux, Cathy; Atlas, Elliot L.; Newman, Paul A.; Thornberry, T. D.; Randel, William J.; Toon, B.

doi:10.1029/2022jd037511

Cited by 9 publications

(8 citation statements)

References 105 publications

(209 reference statements)

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“…The higher frequency of large-scale TST over the Asian monsoon region (>80% in some places) is consistent with recent studies that have shown the importance of monsoon dynamics in stratospheric moistening over Asia, where monsoon convection often moistens the upper troposphere but additonal monsoon-driven isentropic cross-tropopause transport is required to extend these impacts to the stratosphere (e.g., Randel et al, 2010;Pan et al, 2016;Honomichl and Pan, 2020;Pan et al, 2022). Alternatively, the lower percentages common throughout the rest of the Northern Hemisphere subtropics and extratropics suggest that direct convective moistening via overshooting is the primary driver of these extreme concentrations.…”

Section: Transport Characteristicssupporting

confidence: 89%

“…Large-scale cross-tropopause transport can also be facilitated by isentropic assent along the warm conveyor belts of midlatitude cyclones, which has been shown to transport H 2 O and boundary-layer pollutants into the LMS (Roiger et al, 2011;Stohl, 2001;Wernli and Bourqui, 2002). Isentropic transport related to monsoon dynamics -which is intrinsically linked with smaller-scale monsoon convection -has also been shown to substantially contribute to LMS H 2 O enhancements (e.g., Randel et al, 2010;Pan et al, 2016;Honomichl and Pan, 2020;Pan et al, 2022).…”

Section: Introductionmentioning

confidence: 99%

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Climatology, sources, and transport characteristics of observed water vapor extrema in the lower stratosphere

Tinney

Homeyer

2023

Preprint

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Abstract. Stratospheric water vapor (H2O) is a substantial component of the global radiation budget, and therefore important to variability of the climate system. Efforts to understand the distribution, transport, and sources of stratospheric water vapor have increased in recent years, with many studies utilizing long-term satellite observations. Previous work to examine stratospheric H2O extrema has typically focused on the stratospheric overworld (pressures ≤ 100 hPa) to ensure the observations used are truly stratospheric. However, this leads to the broad exclusion of the lowermost stratosphere, which can extend over depths more than 5 km below the 100 hPa level in the midlatitudes and polar regions and has been shown to be the largest contributing layer to the stratospheric H2O feedback. Moreover, focusing on the overworld only can lead to a large underestimation of stratospheric H2O extrema occurrence. Therefore, we expand on previous work by examining 16 years of Microwave Limb Sounder (MLS) observations of water vapor extrema (≥ 8 ppmv) in both the stratospheric overworld and the lowermost stratosphere to create a new lower stratosphere climatology. The resulting frequency of H2O extrema increases by more than 300 % globally compared to extrema frequencies within stratospheric overworld observations only, though the percentage increase varies substantially by region and season. Additional context is provided to this climatology through a backward isentropic trajectory analysis to identify potential sources of the extrema. We show that, in general, tropopause-overshooting convection presents as a likely source of H2O extrema in much of the world, while meridional isentropic transport of air from the tropical upper troposphere to the extratropical lower stratosphere is also possible.

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Section: Transport Characteristicssupporting

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Climatology, sources, and transport characteristics of observed water vapor extrema in the lower stratosphere

Tinney

Homeyer

2023

Preprint

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“…Although the three species show loosely correlated maxima in the UT indicating the influence of convectively lofted PBL pollution, their emission sources are quite different (e.g., Baker et al, 2012). With the relative short lifetime of 1-2 months (Duncan et al, 2007;Pan et al, 2022), CO is considered a good marker for convective transport. The CO maxima Geophysical Research Letters 10.1029/2024GL109256 near 13-14 km (360-370 K θ) indicate the level of convective outflow.…”

Section: Chemical Structures Of the Anticyclone Northern Edgementioning

confidence: 99%

“…These data, therefore, provide complementary information to the airborne activities from other parts of the ASM system. In particular, the recent airborne campaigns, StratoClim (http://www.stratoclim.org/) project conducted high‐altitude research flights over the southern flank of the ASM anticyclone (Bucci et al., 2020; Höpfner et al., 2019; Mahnke et al., 2021; von Hobe et al., 2021), and the ACCLIP campaign sampled the ASM air from the eastern edge of the anticyclone (Pan et al., 2022). These data also extend the existing sounding data from southern flank of the TP, which includes ozone, water vapor, particles, and clouds (Bian et al., 2012; Brunamonti et al., 2018; He et al., 2019; Ma et al., 2022; Yu et al., 2017).…”

Section: Introductionmentioning

confidence: 99%

AirCore Observations at Northern Tibetan Plateau During the Asian Summer Monsoon

Yi,

Cai,

Liu

et al. 2024

Geophysical Research Letters

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We present data and analysis of a set of balloon‐borne sounding profiles, which includes co‐located O3, CO, CH4, and particles, over the northern Tibetan Plateau during an Asian summer monsoon (ASM) season. These novel measurements shed light on the ASM transport behavior near the northern edge of the anticyclone. Joint analyses of these species with the temperature and wind profiles and supported by back trajectory modeling identify three distinct transport processes that dominate the vertical chemical structure in the middle troposphere, upper troposphere (UT), and the tropopause region. The correlated changes in profile structures in the middle troposphere highlight the influence of the strong westerly jet. Elevated constituent concentrations in the UT identify the main level of convective transport at the upstream source regions. Observed higher altitude maxima for CH4 characterize the airmasses' continued ascent following convection. These data complement constituent observations from other parts of the ASM anticyclone.

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“…Short‐lived halogenated species transported to the UTLS by this mechanism may delay the recovery of stratospheric ozone (Bednarz et al., 2022), with the modeled impact depending on the complexity of the chemical mechanism or treatment considered (Fernandez et al., 2021). The application of chemical and transport modeling techniques to predict ASM impacts on global atmospheric composition remains an active research area (e.g., Ploeger et al., 2017; Vogel et al., 2019; Yan et al., 2019; Pan et al., 2016, 2022; Clemens et al., 2023).…”

Section: Introductionmentioning

confidence: 99%

Evaluating the Model Representation of Asian Summer Monsoon Upper Troposphere and Lower Stratosphere Transport and Composition Using Airborne In Situ Observations

Smith,

Pan,

Kinnison

et al. 2024

JGR Atmospheres

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Chemistry Climate Models (CCMs) are essential tools for characterizing and predicting the role of atmospheric composition and chemistry in Earth's climate system. This study demonstrates the use of airborne in situ observations to diagnose the representation of chemical composition and transport by CCMs. Process‐based diagnostics using dynamical and chemical coordinates are presented which minimize the spatial and temporal sampling differences between airborne in situ measurements and CCM grid points. The chosen process is the chemical impact of the Asian summer monsoon (ASM), where deep convection serves as a rapid transport pathway for surface emissions to reach the upper troposphere and lower stratosphere (UTLS). We examine two CCM configurations for their representation of the ASM UTLS using a set of airborne observations from south Asia. The diagnostics reveal good model performance at representing tropospheric tracer distribution throughout the troposphere and lower stratosphere, and excellent representation of chemical aging in the lower stratosphere when chemical loss is dominated by photolysis. Identified model limitations include the use of zonally averaged mole fraction boundary conditions for species with sufficiently short tropospheric lifetimes, which may obscure enhanced regional emissions sources. Overall, the diagnostics underscore the skill of current‐generation models at representing pollution transport from the boundary layer to the stratosphere via the ASM mechanism, and demonstrate the strength of airborne in situ observations toward characterizing this representation.

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A Multimodel Investigation of Asian Summer Monsoon UTLS Transport Over the Western Pacific

Cited by 9 publications

References 105 publications

Climatology, sources, and transport characteristics of observed water vapor extrema in the lower stratosphere

Climatology, sources, and transport characteristics of observed water vapor extrema in the lower stratosphere

AirCore Observations at Northern Tibetan Plateau During the Asian Summer Monsoon

Evaluating the Model Representation of Asian Summer Monsoon Upper Troposphere and Lower Stratosphere Transport and Composition Using Airborne In Situ Observations

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