Effects of convective ice evaporation on interannual variability of tropical tropopause layer water vapor

Ye, Hao; Dessler, A. E.; Yu, Wandi

doi:10.5194/acp-18-4425-2018

Cited by 16 publications

(52 citation statements)

References 73 publications

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“…As a final caveat, we have focused mostly on the winter TWP during normal conditions. Our conclusions about the role of convection mostly describe that region and are not likely to apply to anomalous situations such as El Niño (Avery et al, ; Ye et al, ), to the summer TTL nor to saturated regions observed near the Asian monsoon. Indeed, Figure b suggests that in the summer months, convection in the Asian monsoon region is more closely tied to the highest RHi region consistent with the findings of Ueyama et al ().…”

Section: Discussionmentioning

confidence: 78%

“…It is well understood that convection is the primary source of water in the midtroposphere (Corti et al, 2006;Folkins et al, 2002;Minschwaner & Dessler, 2004;Romps, 2014) and convection is occasionally observed to detrain even above the tropopause (e.g., Avery et al, 2017;Corti et al, 2008;Kelly et al, 1993;Wang & Dessler, 2012). There is clear evidence that it is playing a role in the TTL's water vapor budget, both in direct measurements of water vapor (Schoeberl et al, 2018;Ye et al, 2018) and in other tracers, such as HDO (Dessler et al, 2007;Moyer et al, 1996).…”

Section: Introductionmentioning

confidence: 99%

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Water Vapor, Clouds, and Saturation in the Tropical Tropopause Layer

et al. 2019

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The goal of this investigation is to understand the mechanism behind the observed high relative humidity with respect to ice (RHi) in the tropical region between ~14 km (150 hPa) and the tropopause, often referred to as the tropical tropopause layer (TTL). As shown by satellite, aircraft, and balloon observations, high (>80%) RHi regions are widespread within the TTL. Regions with the highest RHi are colocated with extensive cirrus. During boreal winter, the TTL RHi is highest over the Tropical Western Pacific (TWP) with a weaker maximum over South America and Africa. In the winter, TTL temperatures are coldest and upward motion is the greatest in the TWP. It is this upward motion, driving humid air into the colder upper troposphere that produces the persistent high RHi and cirrus formation. Back trajectory calculations show that comparable adiabatic and diabatic processes contribute to this upward motion. We construct a bulk model of TWP TTL water vapor transport that includes cloud nucleation and ice microphysics that quantifies how upward motion drives the persistent high RHi in the TTL region. We find that atmospheric waves triggering cloud formation regulate the RHi and that convection dehydrates the TTL. Our forward domain‐filling trajectory model is used to more precisely simulate the TTL spatial and vertical distribution of RHi. The observed RHi distribution is reproduced by the model, and we show that convection increases RHi below the base of the TTL with little impact on the RHi in the TTL region.

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Section: Discussionmentioning

confidence: 78%

Section: Introductionmentioning

confidence: 99%

Water Vapor, Clouds, and Saturation in the Tropical Tropopause Layer

et al. 2019

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“…This is the hydrating effect due to underestimating of total water when the laminar cirrus ice is not visible to the MLS. Note that this hydrating effect is different from those caused by the convectively lofted ice in current (Ye et al, ) and future climate (Dessler et al, ).…”

Section: Conclusion Remarksmentioning

confidence: 91%

“…This regression model is similar to the one used in Dessler et al (2013) and Ye et al (2018). Here, ΔT is the tropical average 500-hPa temperature anomaly in kelvin, which is superior to the El Niño-Southern Oscillation index, because it captures more subtle variability of clouds (see Figure 7a).…”

Section: Laminar Cirrus Frequencymentioning

confidence: 99%

Tropopause Laminar Cirrus and Its Role in the Lower Stratosphere Total Water Budget

Wang

Gong

et al. 2019

JGR Atmospheres

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Laminar cirrus are thin, extensive, isolated layers of ice clouds frequently observed in the tropical tropopause layer. Widespread laminar cirrus significantly affects tropical tropopause layer total water and thermal budget. In this study, we extract laminar cirrus from the Cloud‐Aerosol Lidar with Orthogonal Polarization Level 1 attenuated total backscatter images for January 2009, in order to characterize statistical properties of laminar cirrus cloud length, base, thickness, optical depth, and layer partial ice water path. These characteristics are used to develop an algorithm identifying laminar cirrus automatically from the Cloud‐Aerosol Lidar with Orthogonal Polarization Level 2 layer product for 2008–2017. The nearly 10‐year records reveal that tropopause laminar cirrus occurrence (30–40% of total cirrus) is strongly anticorrelated with the tropopause temperatures in that colder tropopause in frequent (super)saturation during boreal winter favors in situ formation of clouds. Interannually, anomalously warmer troposphere temperature (ΔT), easterly shear of the quasi‐biennial oscillation, and stronger upwelling branch of the Brewer‐Dobson circulation enhance laminar cirrus formation via cooling of the tropopause. The tropopause laminar cirrus carries ~0.05 mg/m3 (~0.5 ppmv) of ice water content during boreal winter and <0.01 mg/m3 during summer, which is anticorrelated with the seasonal variations of water vapor (H2O) observed by the Microwave Lime Sounder, indicating a temperature‐regulated partition between vapor and ice. Interannually, in cirrus‐rich region 1 ppmv decrease in H2O corresponds to 0.2–0.3 ppmv increase in ice water content. Frequently situated in (super)saturated air, tropopause laminar cirrus are likely to survive multiple lifecycles of the sublimation‐deposition processes, and may contribute up to 10% to the total water budget in the lower stratosphere.

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“…Large interannual variations of water vapor in the tropical UTLMS have been observed and shown to be important for both climate and chemical reasons (e.g., Dessler et al, 2013;20 Fueglistaler and Haynes, 2005;Liang et al, 2011;Liess and Geller, 2012;Randel and Jensen, 2013;Tao et al, 2015;Ye et al, 2018). Several well-known interannual climate modes are found to modulate the interannual variations of tropical UTLMS water vapor, such as the El Nino Southern Oscillation (ENSO) (e.g., Dessler et al, 2014;Liang et al, 2011;Randel et al, Atmos.…”

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confidence: 99%

Interannual variations of water vapor in the tropical upper troposphere and the lower and middle stratosphere and their connections to ENSO and QBO

Tian¹,

Shen²,

Tian³

et al. 2018

Preprint

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<p><strong>Abstract.</strong> In this study, we analyze the Aura Microwave Limb Sounder water vapor data in the tropical upper troposphere and the lower and middle stratosphere (UTLMS) (from 215&#8201;hPa to 6&#8201;hPa) for the period from August 2004 to September 2017 using time-lag regression analysis and composite analysis to explore the interannual variations of tropical UTLMS water vapor and their connections to El Nino Southern Oscillation (ENSO) and quasi-biennial oscillation (QBO). Our analysis shows that ENSO&#8217;s impact on the interannual tropical water vapor anomalies is strong in the upper troposphere (~215 to ~120&#8201;hPa) and near the tropopause (~110 to ~90&#8201;hPa) with a ~3-month lag but weak in the lower and middle stratosphere (~80 to ~6&#8201;hPa). In contrast, QBO has a large impact on the interannual tropical water vapor anomalies in the lower and middle stratosphere with an upward propagating signal starting at the tropopause (100 hPa), peaking first in the lower stratosphere near 68 hPa with a ~7-month lag and then in the middle stratosphere near 15 hPa with a ~24-month lag. The phase lag is based on the 30-hPa QBO index and should be different from that found by previous studies based on the 50-hPa QBO index. In the upper troposphere, interannual tropical water vapor anomalies are positive during the warm ENSO phases but negative during the cold ENSO phases no matter what QBO phases are. Near the tropopause, interannual tropical water vapor anomalies are different depending on different ENSO and QBO phase combinations. In the lower and middle stratosphere, interannual tropical water vapor anomalies are mainly determined by QBO instead of ENSO. For the easterly QBO phases, interannual tropical water vapor anomalies are positive in the lower stratosphere but negative in the middle stratosphere. Vice versa for the westerly QBO phases.</p>

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Effects of convective ice evaporation on interannual variability of tropical tropopause layer water vapor

Cited by 16 publications

References 73 publications

Water Vapor, Clouds, and Saturation in the Tropical Tropopause Layer

Water Vapor, Clouds, and Saturation in the Tropical Tropopause Layer

Tropopause Laminar Cirrus and Its Role in the Lower Stratosphere Total Water Budget

Interannual variations of water vapor in the tropical upper troposphere and the lower and middle stratosphere and their connections to ENSO and QBO

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