Tropopause and hygropause variability over the equatorial Indian Ocean during February and March 1999

Mackenzie, Adrian; Schiller, C.; Peter, Thomas; Adriani, A.; Beuermann, J.; Bujok, O.; Cairo, F.; Corti, T.; Didonfrancesco, G.; Gensch, I.; Kiemle, Christoph; Krämer, M.; Kröger, C.; Merkulov, S. G.; Oulanovsky, A.; Ravegnani, F.; Rohs, Susanne; Rudakov, V. V.; Salter, P. R. S.; Santacesaria, V.; Stefanutti, L.; Yushkov, V.

doi:10.1029/2005jd006639

Cited by 24 publications

(23 citation statements)

References 56 publications

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“…These conditions are quite comparable to those encountered during the APE-THESEO campaign conducted over the equatorial Indian Ocean in February and March 1999 using the same aircraft (MacKenzie et al, 2006). Average cold point temperatures were about 1.5 • C warmer during APE-THESEO and more variable.…”

Section: Local Conditions During Campaignsupporting

confidence: 65%

The SCOUT-O3 Darwin Aircraft Campaign: rationale and meteorology

et al. 2009

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Abstract. An aircraft measurement campaign involving the Russian high-altitude aircraft M55 Geophysica and the German DLR Falcon was conducted in Darwin, Australia in November and December 2005 as part of the European integrated project SCOUT-O3. The overall objectives of the campaign were to study the transport of trace gases through the tropical tropopause layer (TTL), mechanisms of dehydration close to the tropopause, and the role of deep convection in these processes. In this paper a detailed roadmap of the campaign is presented, including rationales for each flight, and an analysis of the local and large-scale meteorological context in which they were embedded. The campaign took place during the pre-monsoon season which is characterized by a pronounced diurnal evolution of deep convection including a mesoscale system over the Tiwi Islands north of Darwin known as "Hector". This allowed studying in detail the role of deep convection in structuring the tropical tropopause region, in situ sampling convective overshoots above storm anvils, and probing the structure of anvils and cirrus clouds by Lidar and a suite of in situ instruments onboard the two aircraft. The large-scale flow during the first half of the campaign was such that local flights, away from convection, samCorrespondence to: D. Brunner (dominik.brunner@empa.ch) pled air masses downstream of the "cold trap" region over Indonesia. Abundant cirrus clouds enabled the study of active dehydration, in particular during two TTL survey flights. The campaign period also encompassed a Rossby wave breaking event transporting stratospheric air to the tropical middle troposphere and an equatorial Kelvin wave modulating tropopause temperatures and hence the conditions for dehydration.

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Section: Local Conditions During Campaignsupporting

confidence: 65%

The SCOUT-O3 Darwin Aircraft Campaign: rationale and meteorology

et al. 2009

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“…Figure 4 also shows that the tropopause (dash-dotted line) is dryer during the NH winter (APE-THESEO, SCOUTDarwin and TROCCINOX campaigns) while it is moister during the NH summer (SCOUT-AMMA). This also agrees with previous observational studies: MacKenzie et al (2006), for example, combined the in-situ measurements of temperature, water vapour, total water, clear-sky relative humidity, and cloud from APE-THESEO to show evidence of active dehydration in the TTL down to very low water vapour mixing ratios (mean measured hygropause was 2.4 ppmv) over the western equatorial indian ocean. As already mentioned in Sects.…”

Section: Water Vapoursupporting

confidence: 79%

Diagnostics of the Tropical Tropopause Layer from in-situ observations and CCM data

et al. 2009

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Abstract.A suite of diagnostics is applied to in-situ aircraft measurements and one Chemistry-Climate Model (CCM) data to characterize the vertical structure of the Tropical Tropopause Layer (TTL). The diagnostics are based on vertical tracer profiles and relative vertical tracer gradients, using tropopause-referenced coordinates, and tracer-tracer relationships in the tropical Upper Troposphere/Lower Stratosphere (UT/LS).Observations were obtained during four tropical campaigns performed from 1999 to 2006 with the research aircraft Geophysica and have been compared to the output of the ECHAM5/MESSy CCM. The model vertical resolution in the TTL (∼500 m) allows for appropriate comparison with high-resolution aircraft observations and the diagnostics used highlight common TTL features between the model and the observational data.The analysis of the vertical profiles of water vapour, ozone, and nitrous oxide, in both the observations and the model, shows that concentration mixing ratios exhibit a strong gradient change across the tropical tropopause, due to the role of this latter as a transport barrier and that transition between the tropospheric and stratospheric regimes occurs within a finite layer. The use of relative vertical ozone and carbon monoxide gradients, in addition to the vertical profiles, helps to highlight the region where this transition occurs and alCorrespondence to: E. Palazzi (e.palazzi@isac.cnr.it) lows to give an estimate of its thickness. The analysis of the CO-O 3 and H 2 O-O 3 scatter plots and of the Probability Distribution Function (PDF) of the H 2 O-O 3 pair completes this picture as it allows to better distinguish tropospheric and stratospheric regimes that can be identified by their different chemical composition.The joint analysis and comparison of observed and modelled data allows to state that the model can represent the background TTL structure and its seasonal variability rather accurately. The model estimate of the thickness of the interface region between tropospheric and stratospheric regimes agrees well with average values inferred from observations. On the other hand, the measurements can be influenced by regional scale variability, local transport processes as well as deep convection, that can not be captured by the model.

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“…There, the orange line represents the non-Davina mean saturation mixing ratio while the pink line represents the non-Davina mean water vapour mixing ratio, in cloudfree airmasses. As can be seen comparing the two profiles, in general during the campaign the air in the TTL was predominantly under-saturated, as reported in the analysis of MacKenzie et al (2006). The Davina A, B and C saturation mixing ratio profiles -blue, red and purple lines respectively -are lower than the corresponding non-Davina means, and closer to the actual mean water vapour mixing ratio observed during the campaign.…”

Section: Below 385 K: Dehydration Effectsmentioning

confidence: 66%

“…The general meteorological setting for the campaign is given in Stefanutti et al (2004). An analysis of the temperature, ozone, clouds and water vapour profiles acquired during the campaign has been reported in MacKenzie et al (2006). In the present work the focus is on the specific effects of tropical cyclones on the UTLS.…”

Section: Instruments and Methodsmentioning

confidence: 99%

“…Cumulus tops are rarely observed above 14 km, and this implies an abrupt reduction of convective mass flux above that level. The ozone concentration starts to increase there well below the cold point tropopause (Folkins et al, 1999;Fujiwara et al, 2000;Mackenzie et al, 2006;Vaughan et al, 2008) and the lapse rate starts to move away from the moist adiabatic below 14 km (Folkins and Braun, 2001). In the lower part of the TTL a mixing barrier exists (Folkins et al, 1999;Folkins et al, 2000) so that the residence time of air in the TTL is greater than in any other level of the troposphere.…”

Section: Introductionmentioning

confidence: 99%

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Morphology of the tropopause layer and lower stratosphere above a tropical cyclone: a case study on cyclone Davina (1999)

et al. 2008

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Abstract. During the APE-THESEO mission in the Indian Ocean the Myasishchev Design Bureau stratospheric research aircraft M55 Geophysica performed a flight over and within the inner core region of tropical cyclone Davina. Measurements of total water, water vapour, temperature, aerosol backscattering, ozone and tracers were made and are discussed here in comparison with the averages of those quantities acquired during the campaign time frame.Temperature anomalies in the tropical tropopause layer (TTL), warmer than average in the lower part and colder than average in the upper TTL were observed. Ozone was strongly reduced compared to its average value, and thick cirrus decks were present up to the cold point, sometimes topped by a layer of very dry air. Evidence for meridional transport of trace gases in the stratosphere above the cyclone was observed and perturbed water distribution in the TTL was documented. The paper discuss possible processes of dehydration induced by the cirrus forming above the cyclone, and change in the chemical tracer and water distribution in the lower stratosphere 400-430 K due to meridional transport from the mid-latitudes and link with Davina. Moreover it compares the data prior and after the cyclone passage to discuss its actual impact on the atmospheric chemistry and thermodynamics.

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Tropopause and hygropause variability over the equatorial Indian Ocean during February and March 1999

Cited by 24 publications

References 56 publications

The SCOUT-O3 Darwin Aircraft Campaign: rationale and meteorology

The SCOUT-O3 Darwin Aircraft Campaign: rationale and meteorology

Diagnostics of the Tropical Tropopause Layer from in-situ observations and CCM data

Morphology of the tropopause layer and lower stratosphere above a tropical cyclone: a case study on cyclone Davina (1999)

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