Water vapor transport and dehydration above convective outflow during Asian monsoon

James, R.; Bonazzola, M.; Legras, Bernard; Surbled, K.; Fueglistaler, S.

doi:10.1029/2008gl035441

Cited by 113 publications

(139 citation statements)

References 27 publications

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“…1) based on condensation and complete fall-out of the condensate along the trajectory. It is known that stratospheric water vapour predictions based on the minimum saturation mixing ratio from ERA-Interim data are drier than observed (James et al, 2008;Liu et al, 2010). Following the approach of James et al (2008) condensation in our model occurs every time relative humidity exceeds 130%.…”

Section: Water Vapour Modelmentioning

confidence: 99%

“…It is known that stratospheric water vapour predictions based on the minimum saturation mixing ratio from ERA-Interim data are drier than observed (James et al, 2008;Liu et al, 2010). Following the approach of James et al (2008) condensation in our model occurs every time relative humidity exceeds 130%. This threshold is well within the uncertainties of ice nucleation, and supersaturation with respect to ice is frequently observed (e.g., Krämer et al, 2009).…”

Section: Water Vapour Modelmentioning

confidence: 99%

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Insight from ozone and water vapour on transport in the tropical tropopause layer (TTL)

et al. 2011

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Abstract. We explore the potential of ozone observations to constrain transport processes in the tropical tropopause layer (TTL), and contrast it with insights that can be obtained from water vapour. Global fields from Halogen Occultation Experiment (HALOE) and in-situ observations are predicted using a backtrajectory approach that captures advection, instantaneous freeze-drying and photolytical ozone production. Two different representations of transport (kinematic and diabatic 3-month backtrajectories based on ERAInterim data) are used to evaluate the sensitivity to differences in transport. Results show that mean profiles and seasonality of both tracers can be reasonably reconstructed. Water vapour predictions are similar for both transport representations, but predictions for ozone are systematically higher for kinematic transport. Compared to global HALOE observations, the diabatic model prediction underestimates the vertical ozone gradient. Comparison of the kinematic prediction with observations obtained during the tropical SCOUT-O3 campaign shows a large high bias above 390 K potential temperature. We show that ozone predictions and vertical dispersion of the trajectories are highly correlated, rendering ozone an interesting tracer for aspects of transport to which water vapour is not sensitive. We show that dispersion and mean upwelling have similar effects on ozone profiles, with slower upwelling and larger dispersion both leading to higher ozone concentrations. Analyses of tropical upwelling basedCorrespondence to: F. Ploeger (f.ploeger@fz-juelich.de) on mean transport characteristics, and model validation have to take into account this ambiguity between tropical ozone production and in-mixing from the stratosphere. In turn, ozone provides constraints on transport in the TTL and lower stratosphere that cannot be obtained from water vapour.

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Section: Water Vapour Modelmentioning

confidence: 99%

Section: Water Vapour Modelmentioning

confidence: 99%

Insight from ozone and water vapour on transport in the tropical tropopause layer (TTL)

et al. 2011

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“…Several studies have emphasised the role of the NH summer Asian monsoon anticyclone, with the relative isolation in the interior of the upper anticyclone leading to coherent features in water vapour (e.g. James et al, 2008) and in a variety of chemical species including CO, HCN, C 2 H 6 and C 2 H 2 (Park et al, 2008). Indeed Randel et al (2010) have used HCN measurements to argue for a special role for the Asian monsoon anticyclone system in bringing polluted air from the south and east Asian region to the stratosphere in NH summer.…”

Section: Methodsmentioning

confidence: 99%

Emission location dependent ozone depletion potentials for very short-lived halogenated species

2010

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Abstract. We present trajectory-based estimates of Ozone Depletion Potentials (ODPs) for very short-lived halogenated source gases as a function of surface emission location. The ODPs are determined by the fraction of source gas and its degradation products which reach the stratosphere, depending primarily on tropospheric transport and chemistry, and the effect of the resulting reactive halogen in the stratosphere, which is determined by stratospheric transport and chemistry, in particular by stratospheric residence time. Reflecting the different timescales and physico-chemical processes in the troposphere and stratosphere, the estimates are based on calculation of separate ensembles of trajectories for the troposphere and stratosphere. A methodology is described by which information from the two ensembles can be combined to give the ODPs.The ODP estimates for a species with a fixed 20 d lifetime, representing a compound like n-propyl bromide, are presented as an example. The estimated ODPs show strong geographical and seasonal variation, particularly within the tropics. The values of the ODPs are sensitive to the inclusion of a convective parametrization in the trajectory calculations, but the relative spatial and seasonal variation is not. The results imply that ODPs are largest for emissions from south and south-east Asia during Northern Hemisphere summer and from the western Pacific during Northern Hemisphere winter. Large ODPs are also estimated for emissions throughout the tropics with non-negligible values also extending into northern mid-latitudes, particularly in the summer. These first estimates, whilst made under some simplifying assumptions, show larger ODPs for certain emission Correspondence to: I. Pisso (ignacio@jamstec.go.jp) regions, particularly south Asia in NH summer, than have typically been reported by previous studies which used emissions distributed evenly over land surfaces.

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“…Very deep and overshooting convective clouds bring moisture to the upper troposphere lower stratosphere region. The critical issues like possible mechanisms/pathways of moistening or drying of the lower stratosphere are still undergoing research (Danielsen, 1982;Highwood and Hoskins, 1998;Sherwood and Dessler, 2000;Dessler, 2002;Gettelman et al, 2002;Sherwood and Dessler, 2003;Jain et al, 2006;Jensen et al, 2007;Lelieveld et al, 2007;Rossow and Pearl, 2007;Horvath and Soden, 2008;James et al, 2008). But the first step in investigating these issues further is to pinpoint the locations and frequency of the events when convection reaches and/or penetrates the TTL (Rossow and Pearl, 2007).…”

Section: Convection Reaching the Tropical Tropopause Layer (Ttl)mentioning

confidence: 99%

A daytime climatological distribution of high opaque ice cloud classes over the Indian summer monsoon region observed from 25-year AVHRR data

Devasthale

Graßl

2009

Atmos. Chem. Phys.

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Abstract.A daytime climatological spatio-temporal distribution of high opaque ice cloud (HOIC) classes over the Indian subcontinent (0-40 • N, 60 • E-100 • E) is presented using 25-year data from the Advanced Very High Resolution Radiometers (AVHRRs) for the summer monsoon months. The HOICs are important for regional radiative balance, precipitation and troposphere-stratosphere exchange. In this study, HOICs are sub-divided into three classes based on their cloud top brightness temperatures (BT ). Class I represents very deep convection (BT <220 K). Class II represents deep convection (220 K<=BT <233 K) and Class III background convection (233 K<=BT <253 K). Apart from presenting finest spatial resolution (0.1×0.1 degrees) and long-term climatology of such cloud classes from AVHRRs to date, this study for the first time illustrates on (1) how these three cloud classes are climatologically distributed during monsoon months, and (2) how their distribution changes during active and break monsoon conditions. It is also investigated that how many deep convective clouds reach the tropopause layer during individual monsoon months. It is seen that Class I and Class II clouds dominate the Indian subcontinent during monsoon. The movement of monsoon over continent is very well reflected in these cloud classes. During monsoon breaks strong suppression of convective activity is observed over the Arabian Sea and the western coast of India. On the other hand, the presence of such convective activity is crucial for active monsoon conditions and all-IndiaCorrespondence to: A. Devasthale (abhay.devasthale@smhi.se) rainfall. It is found that a significant fraction of HOICs (3-5%) reach the tropopause layer over the Bay of Bengal during June and over the north and northeast India during July and August. Many cases are observed when clouds penetrate the tropopause layer and reach the lower stratosphere. Such cases mostly occur during June compared to the other months.

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Water vapor transport and dehydration above convective outflow during Asian monsoon

Cited by 113 publications

References 27 publications

Insight from ozone and water vapour on transport in the tropical tropopause layer (TTL)

Insight from ozone and water vapour on transport in the tropical tropopause layer (TTL)

Emission location dependent ozone depletion potentials for very short-lived halogenated species

A daytime climatological distribution of high opaque ice cloud classes over the Indian summer monsoon region observed from 25-year AVHRR data

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