An introduction to the SCOUT-AMMA stratospheric aircraft, balloons and sondes campaign in West Africa, August 2006: rationale and roadmap

Cairo, F.; Pommereau, Jean‐Pierre; Law, Kathy S.; Schläger, Hans; Garnier, Anne; Fierli, F.; Ern, Manfred; Streibel, M.; Arabas, Sylwester; Borrmann, Stephan; Berthelier, Jean‐Jacques; Blom, C. E.; Christensen, T.; D’Amato, Francesco; Donfrancesco, G. Di; Deshler, Terry; Diedhiou, Arona; Durry, Georges; Engelsen, Ola; Goutail, Florence; Harris, Neil; Kerstel, Erik; Khaykin, Sergey; Konopka, Paul; Kylling, Arve; Larsen, N.; Lebel, Thierry; Liu, X.; Mackenzie, Adrian; Nielsen, Johannes K.; Oulanowski, A.; Parker, Douglas J.; Pelon, Jacques; Polcher, Jan; Pyle, J. A.; Ravegnani, F.; Rivière, Emmanuel; Robinson, A. D.; Röckmann, T.; Schiller, C.; Simões, F.; Stefanutti, L.; Stroh, F.; Some, L.; Siegmund, P.; Sitnikov, N.; Vernier, Jean‐Paul; Volk, C. M.; Voigt, Christiane; Hobe, Marc von; Viciani, Silvia; Yushkov, V.

doi:10.5194/acp-10-2237-2010

Cited by 67 publications

(75 citation statements)

References 96 publications

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“…Lower pollutant concentrations in the UT are mainly due to more dilution with cleaner air masses during upward transport. The same UT:MT fraction was evaluated over a larger period: 1-15 August and a mean value of 0.6 was simulated showing that even if injection of pollutants into the UT over West Africa is less frequent and plumes more diluted, it is significant, at least in the studied period (August 2006). This fraction is higher than previously suggested (Mari et al, 2008).…”

Section: Discussionmentioning

confidence: 99%

Cross-hemispheric transport of central African biomass burning pollutants: implications for downwind ozone production

et al. 2010

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Abstract. Pollutant plumes with enhanced concentrations of trace gases and aerosols were observed over the southern coast of West Africa during August 2006 as part of the AMMA wet season field campaign. Plumes were observed both in the mid and upper troposphere. In this study we examined the origin of these pollutant plumes, and their potential to photochemically produce ozone (O 3 ) downwind over the Atlantic Ocean. Their possible contribution to the Atlantic O 3 maximum is also discussed. Runs using the BOLAM mesoscale model including biomass burning carbon monoxide (CO) tracers were used to confirm an origin from central African biomass burning fires. The plumes measured in the mid troposphere (MT) had significantly higher pollutant concentrations over West Africa compared to the upper tropospheric (UT) plume. The mesoscale modelCorrespondence to: E. Real (elsa.real@aero.jussieu.fr) reproduces these differences and the two different pathways for the plumes at different altitudes: transport to the northeast of the fire region, moist convective uplift and transport to West Africa for the upper tropospheric plume versus north-west transport over the Gulf of Guinea for the mid-tropospheric plume. Lower concentrations in the upper troposphere are mainly due to enhanced mixing during upward transport. Model simulations suggest that MT and UT plumes are 16 and 14 days old respectively when measured over West Africa. The ratio of tracer concentrations at 600 hPa and 250 hPa was estimated for 14-15 August in the region of the observed plumes and compares well with the same ratio derived from observed carbon dioxide (CO 2 ) enhancements in both plumes. It is estimated that, for the period 1-15 August, the ratio of Biomass Burning (BB) tracer concentration transported in the UT to the ones transported in the MT is 0.6 over West Africa and the equatorial South Atlantic.Published by Copernicus Publications on behalf of the European Geosciences Union. E. Real et al.: Cross-hemispheric transport of african biomass burningRuns using a photochemical trajectory model, CiTTy-CAT, initialized with the observations, were used to estimate in-situ net photochemical O 3 production rates in these plumes during transport downwind of West Africa. The mid-troposphere plume spreads over altitude between 1.5 and 6 km over the Atlantic Ocean. Even though the plume was old, it was still very photochemically active (mean net O 3 production rates over 10 days of 2.6 ppbv/day and up to 7 ppbv/day during the first days) above 3 km especially during the first few days of transport westward. It is also shown that the impact of high aerosol loads in the MT plume on photolysis rates serves to delay the peak in modelled O 3 concentrations. These results suggest that a significant fraction of enhanced O 3 in mid-troposphere over the Atlantic comes from BB sources during the summer monsoon period. According to simulated occurrence of such transport, BB may be the main source for O 3 enhancement in the equatorial south Atlantic MT, at least in August 2...

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Section: Discussionmentioning

confidence: 99%

Cross-hemispheric transport of central African biomass burning pollutants: implications for downwind ozone production

et al. 2010

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“…There is a considerable amount of observational evidence of local cooling of the lower stratosphere over land convective systems, ranging from 2 K to 10 K (e.g. Johnson and Kriete, 1982;Danielsen, 1993;Sherwood and Dessler, 2003;Pommereau and Held, 2007;Cairo et al, 2010;Biondi et al, 2012). However the contributions of various processes to the TTL thermal structure are still unclear.…”

Section: S M Khaykin Et Al: Impact Of Land Convection On Temperatumentioning

confidence: 99%

Impact of land convection on temperature diurnal variation in the tropical lower stratosphere inferred from COSMIC GPS radio occultations

2013

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Following recent studies evidencing the influence of deep convection on the chemical composition and thermal structure of the tropical lower stratosphere, we explore its impact on the temperature diurnal variation in the upper troposphere and lower stratosphere using the high-resolution COSMIC GPS radio-occultation temperature measurements spanning from 2006 through 2011. The temperature in the lowermost stratosphere over land during summer displays a marked diurnal cycle characterized by an afternoon cooling. This diurnal cycle is shown collocated with most intense land convective areas observed by the Tropical Rainfall Measurement Mission (TRMM) precipitation radar and in phase with the maximum overshooting occurrence frequency in late afternoon. Two processes potentially responsible for that are identified: (i) non-migrating tides, whose physical nature is internal gravity waves, and (ii) local cross-tropopause mass transport of adiabatically cooled air by overshooting turrets. Although both processes can contribute, only the lofting of adiabatically cooled air is well captured by models, making it difficult to characterize the contribution of non-migrating tides. The impact of deep convection on the temperature diurnal cycle is found larger in the southern tropics, suggesting more vigorous convection over clean rain forest continents than desert areas and polluted continents in the northern tropics

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“…The approximate regional extent of the 148 flight missions is shown in Fig. 1 Large-scale transport into the UTLS e.g., Cairo et al (2010) Lightning and NO x production 1. ERA-Interim specific humidity fields are interpolated to the positions (latitude, longitude, altitude) of the FISH measurements.…”

Section: Era-interim Datamentioning

confidence: 99%

Comparison of Fast In situ Stratospheric Hygrometer (FISH) measurements of water vapor in the upper troposphere and lower stratosphere (UTLS) with ECMWF (re)analysis data

Kunz

Spelten²,

Konopka³

et al. 2014

Atmos. Chem. Phys.

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Abstract. An evaluation of water vapor in the upper troposphere and lower stratosphere (UTLS) of the ERA-Interim, the global atmospheric reanalysis produced by the European Centre for Medium-Range Weather Forecasts (ECMWF), is presented. Water vapor measurements are derived from the Fast In situ Stratospheric Hygrometer (FISH) during a large set of airborne measurement campaigns from 2001 to 2011 in the tropics, midlatitudes and polar regions, covering isentropic layers from 300 to 400 K (5-18 km).The comparison shows around 87 % of the reanalysis data are within a factor of 2 of the FISH water vapor measurements and around 30 % have a nearly perfect agreement with an over-and underestimation lower than 10 %. Nevertheless, strong over-and underestimations can occur both in the UT and LS, in particularly in the extratropical LS and in the tropical UT, where severe over-and underestimations up to 10 times can occur.The analysis data from the evolving ECMWF operational system is also evaluated, and the FISH measurements are divided into time periods representing different cycles of the Integrated Forecast System (IFS). The agreement with FISH improves over the time, in particular when comparing water vapor fields for time periods before 2004 and after 2010. It appears that influences of tropical tropospheric and extratropical UTLS processes, e.g., convective and quasiisentropic exchange processes, are particularly challenging for the simulation of the UTLS water vapor distribution. Both the reanalysis and operational analysis data show the tendency of an overestimation of low water vapor mixing ratio ( 10 ppmv) in the LS and underestimation of high water vapor mixing ratio ( 300 ppmv) in the UT.

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An introduction to the SCOUT-AMMA stratospheric aircraft, balloons and sondes campaign in West Africa, August 2006: rationale and roadmap

Cited by 67 publications

References 96 publications

Cross-hemispheric transport of central African biomass burning pollutants: implications for downwind ozone production

Cross-hemispheric transport of central African biomass burning pollutants: implications for downwind ozone production

Impact of land convection on temperature diurnal variation in the tropical lower stratosphere inferred from COSMIC GPS radio occultations

Comparison of Fast In situ Stratospheric Hygrometer (FISH) measurements of water vapor in the upper troposphere and lower stratosphere (UTLS) with ECMWF (re)analysis data

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