Space-borne observations link the tropical atlantic ozone maximum and paradox to lightning

Abstract. The potential enhancement of tropospheric column ozone values over the Tropical Atlantic Ocean on a seasonal basis by lightning is investigated using satellite derived ozone data, TRMM lightning data, ozonesonde data and NCEP reanalysis during 1998-2001. Our results show that the number of lightning flashes in Africa and South America reach a maximum during September, October and November (SON). The spatial patterns of winds in combination with lightning from West Africa, Central Africa and South America is likely responsible for enriching middle/upper troposphere ozone over the Tropical South Atlantic during SON. Moreover, lightning flashes are high in the hemisphere opposite to biomass burning during December, January, and February (DJF) and June, July and August (JJA). This pattern leads to an enrichment of ozone in the middle/upper troposphere in the Southern Hemisphere Tropics during DJF and the Northern Hemisphere Tropics during JJA. During JJA the largest numbers of lightning flashes are observed in West Africa, enriching tropospheric column ozone to the north of 5S in the absence of biomass burning. During DJF, lightning is concentrated in South America and Central Africa enriching tropospheric column ozone south of the Equator in the absence of biomass burning.

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Space-borne observations link the tropical Atlantic ozone maximum and paradox to lightning

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-3-5725-2003 ◽

2003 ◽

Vol 3 (6) ◽

pp. 5725-5754 ◽

Cited By ~ 2

Author(s):

G. S. Jenkins ◽

J.-H. Ryu

Keyword(s):

South America ◽

West Africa ◽

Atlantic Ocean ◽

Biomass Burning ◽

Central Africa ◽

Tropical Atlantic ◽

Tropical Atlantic Ocean ◽

The North ◽

June July ◽

Column Ozone

Abstract. The causes of high tropospheric column ozone values over the Tropical Atlantic Ocean during September, October, and November (SON) are investigated by examining lightning during 1998–2001. The cause for high tropospheric column ozone in the hemisphere opposite of biomass burning (tropical ozone paradox) is also examined. Our results show that lightning is central to high tropospheric column ozone during SON and responsible for the tropical ozone paradox during December, January, and February (DJF) and June, July and August (JJA). During SON large numbers of flashes are observed in South America, Central and West Africa enriching the tropospheric column ozone over the Tropical Atlantic Ocean. During JJA the largest numbers of lightning flashes are observed in West Africa, enriching tropospheric column ozone to the north of 5° S in the absence biomass burning. During DJF, lightning is concentrated in South America and Central Africa enriching tropospheric column ozone south of the Equator in the absence of biomass burning.

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

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-9-17385-2009 ◽

2009 ◽

Vol 9 (4) ◽

pp. 17385-17427 ◽

Cited By ~ 7

Author(s):

E. Real ◽

E. Orlandi ◽

K. S. Law ◽

F. Fierli ◽

D. Josset ◽

...

Keyword(s):

West Africa ◽

Atlantic Ocean ◽

Biomass Burning ◽

Mesoscale Model ◽

Central Africa ◽

Ozone Production ◽

Wet Season ◽

Upper Troposphere ◽

North East ◽

The North

Abstract. Pollutant plumes with enhanced levels 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 both the origin of these pollutant plumes and their potential to produce O3 downwind over the Atlantic Ocean. Runs using the BOLAM mesoscale model including biomass burning CO tracers were used to confirm an origin from central African fires. The plumes in the mid troposphere had significantly higher pollutant concentrations due to the fact that transport occurred from a region nearer or even over the fire region. In contrast, plumes transported into the upper troposphere over West Africa had been transported to the north-east of the fire region before being uplifted. Modelled tracer results showed that pollutants resided for between 9 and 12 days over Central Africa before being transported for 4 days, in the case of the mid-troposphere plume and 2 days in the case of the upper tropospheric plume to the measurement location over the southern part of West Africa. Around 35% of the biomass burning tracer was transported into the upper troposphere compared to that remaining in the mid troposphere. Runs using a photochemical trajectory model, CiTTyCAT, were used to estimate the net photochemical O3 production potential of these plumes. The mid tropospheric plume was still very photochemically active (up to 7 ppbv/day) especially during the first few days of transport westward over the Atlantic Ocean. The upper tropospheric plume was also still photochemically active, although at a slower rate (1–2 ppbv/day). Trajectories show this plume being recirculated around an upper tropospheric anticyclone back towards the African continent (around 20° S). The potential of theses plumes to produce O3 supports the hypothesis that biomass burning pollutants are contributing to the observed O3 maxima over the southern Atlantic at this time of year.

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Linking horizontal and vertical transports of biomass fire emissionsto the tropical Atlantic ozone paradox during the Northern Hemisphere winter season: climatology

Atmospheric Chemistry and Physics ◽

10.5194/acp-4-449-2004 ◽

2004 ◽

Vol 4 (2) ◽

pp. 449-469 ◽

Cited By ~ 17

Author(s):

G. S. Jenkins ◽

J.-H. Ryu

Keyword(s):

South America ◽

West Africa ◽

Northern Hemisphere ◽

Outgoing Longwave Radiation ◽

Winter Season ◽

Longwave Radiation ◽

Tropical Atlantic ◽

Hemisphere Winter ◽

Column Ozone ◽

Northern Hemisphere Winter

Abstract. During the Northern hemisphere winter season, biomass burning is widespread in West Africa, yet the total tropospheric column ozone values (<30DU) over much of the Tropical Atlantic Ocean (15°N-5°S) are relatively low. At the same time, the tropospheric column ozone values in the Southern Tropical Atlantic are higher than those in the Northern Hemisphere (ozone paradox). We examine the causes for low tropospheric column ozone values by considering the horizontal and vertical transport of biomass fire emissions in West Africa during November through March, using observed data which characterizes fires, aerosols, horizontal winds, precipitation, lightning and outgoing longwave radiation. We have found that easterly winds prevail in the lower troposphere but transition to westerly winds at pressure levels lower than 500hPa. A persistent anticyclone over West Africa at 700hPa is responsible for strong easterly winds, which causes a net outflow of ozone/ozone precursors from biomass burning in West Africa across the Atlantic Ocean towards South America. The lowest outgoing longwave radiation (OLR) and highest precipitation rates are generally found over the central Atlantic, some distance downstream of fires in West Africa making the vertical transport of ozone and ozone precursors less likely and ozone destruction more likely. However, lightning over land areas in Central Africa and South America can lead to enhanced ozone levels in the upper troposphere especially over the Southern tropical Atlantic during the Northern Hemisphere winter season.

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Anomalies of continental precipitation associated with El Niño Southern Oscillation: the role of moisture contribution from oceanic and terrestrial sources

10.5194/egusphere-egu21-12386 ◽

2021 ◽

Author(s):

Rogert Sorí ◽

Raquel Nieto ◽

Margarida L.R. Liberato ◽

Luis Gimeno

Keyword(s):

South America ◽

Southern Oscillation ◽

The United States ◽

Precipitation Pattern ◽

Two Phase ◽

The North ◽

Terrestrial Origin ◽

Precipitation Anomalies ◽

June July

The regional and global precipitation pattern is highly modulated by the influence of El Ni&#241;o Southern Oscillation (ENSO), which is considered the most important mode of climate variability on the planet. In this study was investigated the asymmetry of the continental precipitation anomalies during El Ni&#241;o and La Ni&#241;a. To do it, a Lagrangian approach already validated was used to determine the proportion of the total Lagrangian precipitation that is of oceanic and terrestrial origin. During both, El Ni&#241;o and La Ni&#241;a, the Lagrangian precipitation in regions such as the northeast of South America, the east and west coast of North America, Europe, the south of West Africa, Southeast Asia, and Oceania is generally determined by the oceanic component of the precipitation, while that from terrestrial origin provides a major percentage of the average Lagrangian precipitation towards the interior of the continents. The role of the moisture contribution to precipitation from terrestrial and oceanic origin was evaluated in regions with statistically significant precipitation anomalies during El Ni&#241;o and La Ni&#241;a. Two-phase asymmetric behavior of the precipitation was found in regions such the northeast of South America, South Africa, the north of Mexico, and southeast of the United States, etc. principally for December-January-February and June-July-August. For some of these regions was also calculated the anomalies of the precipitation from other datasets to confirm the changes. Besides, for these regions was calculated the anomaly of the Lagrangian precipitation, which agrees in all the cases with the precipitation change. For these regions, it was determined which component of the Lagrangian precipitation, whether oceanic or terrestrial, controlled the precipitation anomalies. A schematic figure represents the extent of the most important seasonal oceanic and terrestrial sources for each subregion during El Ni&#241;o and La Ni&#241;a.

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Secondary ozone peaks in the troposphere over the Himalayas

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-6743-2017 ◽

2017 ◽

Vol 17 (11) ◽

pp. 6743-6757 ◽

Cited By ~ 13

Author(s):

Narendra Ojha ◽

Andrea Pozzer ◽

Dimitris Akritidis ◽

Jos Lelieveld

Keyword(s):

Atmospheric Chemistry ◽

North Atlantic Ocean ◽

Monsoon Season ◽

Stratospheric Ozone ◽

Central Himalayas ◽

Air Masses ◽

Upper Troposphere ◽

The North ◽

Column Ozone ◽

Year 2000

Abstract. Layers with strongly enhanced ozone concentrations in the middle–upper troposphere, referred to as secondary ozone peaks (SOPs), have been observed in different regions of the world. Here we use the global ECHAM5/MESSy atmospheric chemistry model (EMAC) to (i) investigate the processes causing SOPs, (ii) explore both their frequency of occurrence and seasonality, and (iii) assess their effects on the tropospheric ozone budget over the Himalayas. The vertical profiles of potential vorticity (PV) and a stratospheric ozone tracer (O3s) in EMAC simulations, in conjunction with the structure of SOPs, suggest that SOPs over the Himalayas are formed by stratosphere-to-troposphere transport (STT) of ozone. The spatial distribution of O3s further shows that such effects are in general most pronounced in the northern part of India. Model simulated ozone distributions and backward air trajectories show that ozone rich air masses, associated with STT, originate as far as northern Africa and the North Atlantic Ocean, the Middle East, as well as in nearby regions in Afghanistan and Pakistan, and are rapidly (within 2–3 days) transported to the Himalayas. Analysis of a 15-year (2000–2014) EMAC simulation shows that the frequency of SOPs is highest during the pre-monsoon season (e.g. 11 % of the time in May), while no intense SOP events are found during the July–October period. The SOPs are estimated to enhance the tropospheric column ozone (TCO) over the central Himalayas by up to 21 %.

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Entrainment and its dependency on environmental conditions and convective organization in convection-permitting simulations

Monthly Weather Review ◽

10.1175/mwr-d-20-0229.1 ◽

2021 ◽

Author(s):

Tobias Becker ◽

Cathy Hohenegger

Keyword(s):

South America ◽

West Africa ◽

Deep Convection ◽

Static Stability ◽

Tropical Atlantic ◽

Shallow Convection ◽

Squall Lines ◽

Environmental Humidity ◽

Turbulence Generation ◽

Convective Organization

AbstractIn this study, we estimate bulk entrainment rates for deep convection in convection-permitting simulations, conducted over the tropical Atlantic Ocean, encompassing parts of Africa and South America. We find that, even though entrainment rates decrease with height in all regions, they are, when averaging between 600 and 800 hPa, generally higher over land than over ocean. This is so because, over Amazonia, shallow convection causes an increase of bulk entrainment rates at lower levels and because, over West Africa, where entrainment rates are highest, convection is organized in squall lines. These squall lines are associated with strong mesoscale convergence, causing more intense updrafts and stronger turbulence generation in the vicinity of updrafts, increasing the entrainment rates. With the exception of West Africa, entrainment rates differ less across regions than across different environments within the regions. In contrast to what is usually assumed in convective parameterizations, entrainment rates increase with environmental humidity. Moreover, over ocean, they increase with static stability, while over land, they decrease. In addition, confirming the results of a recent idealized study, entrainment rates increase with convective aggregation, except in regions dominated by squall lines, like over West Africa.

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Biomass burning in the southern hemisphere UTLS: GLORIA trace gas observations during SouthTRAC 2019 to evaluate the CAMS model

10.5194/egusphere-egu21-4717 ◽

2021 ◽

Author(s):

Sören Johansson ◽

Michael Höpfner ◽

Felix Friedl-Vallon ◽

Norbert Glatthor ◽

Jörn Ungermann ◽

...

Keyword(s):

South America ◽

Biomass Burning ◽

Large Scale ◽

Central Africa ◽

South Atlantic ◽

Trace Gas ◽

The South ◽

Hysplit Model ◽

Mixing Ratios ◽

Airborne Imaging

We present trace gas measurements obtained by the airborne imaging limb sounder GLORIA&#160;(Gimballed Limb Observer for Radiance Imaging of the Atmosphere) that has been operated onboard the German HALO (High Altitude and Long Range) research aircraft above the South Atlantic during the SouthTRAC campaign between September and November 2019. We show retrieval results as two-dimensional trace-gas distributions derived from GLORIA observations in the UTLS (Upper Troposphere Lower Stratosphere) region above South America and the Atlantic Ocean. Targeted gases are, amongst others, O3, HNO3, PAN, C2H6, and HCOOH. Using trajectories from the HYSPLIT model, measured pollution trace gas plumes are linked to possible regions of origin. Emission sources are connected to large scale biomass burning events in central Africa, South America and Australia. In our contribution, we compare these GLORIA measurements with results of the CAMS (Copernicus Atmosphere Monitoring Service) reanalysis model. We show that there are very delicate structures of pollutant trace gas distributions in the South Atlantic UTLS, and that CAMS generally is able to reproduce measured distributions of pollutants. Quantitatively, PAN volume mixing ratios are captured quite well by the model, which however underestimates the concentrations of C2H6 and in particular of HCOOH. Furthermore, biomass burning emissions from the beginning of the intensive Australian fires in November 2019, which are measured by GLORIA in thin filaments are not reproduced by the model.

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New simple approach to understand the spatial and vertical distribution of biomass burning CO emission based on the MOPITT vertical measurements

10.5194/egusphere-egu2020-9220 ◽

2020 ◽

Author(s):

Chuyong Lin ◽

Jason Cohen

Keyword(s):

South America ◽

Biomass Burning ◽

Large Scale ◽

Central Africa ◽

Western Africa ◽

Moderate Resolution ◽

Resolution Imaging ◽

Moderate Resolution Imaging Spectroradiometer ◽

Significant Spread ◽

Spatial And Vertical Distribution

A simple variance-maximization approach, based on 19 years of weekly Moderate Resolution Imaging spectroradiometer (MOPITT) CO vertical measurements, was employed to quantify the spatial distribution of the global seasonal biomass burning region. Results demonstrate there are a few large-scale and typical biomass burning regions responsible for most of the biomass burning emissions throughout the world, with the largest of these such regions located in Amazonian South America, Western Africa, Indonesia, and Northern Southeast Asia (Eastern India, Northern Myanmar, Laos, Vietnam and Eastern Bangladesh), which are highly associated with the results of Global Fire Emission Database(GFED). The CO is primarily lofted to and spreads downwind at 800mb or 700mb with three exceptions: The Maritime Continent and South America where there is significant spread at 300mb consistent with known deep- and pyro-convection; and Southern Africa where there is significant spread at 600mb. The total mass of CO lofted into the free troposphere ranges from 46% over Central Africa to 92% over Australia.

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Secondary ozone peaks in the troposphere over the Himalayas

10.5194/acp-2016-908 ◽

2016 ◽

Author(s):

Narendra Ojha ◽

Andrea Pozzer ◽

Dimitris Akritidis ◽

Jos Lelieveld

Keyword(s):

Atmospheric Chemistry ◽

North Atlantic Ocean ◽

Monsoon Season ◽

Stratospheric Ozone ◽

Central Himalayas ◽

Air Masses ◽

Upper Troposphere ◽

The North ◽

Column Ozone ◽

Year 2000

Abstract. Layers with strongly enhanced ozone concentrations in the middle-upper troposphere, referred to as Secondary Ozone Peaks (SOPs), have been observed in different regions of the world. Here we use the global ECHAM5/MESSy atmospheric chemistry model (EMAC) to (i) investigate the processes causing SOPs, (ii) explore both their frequency of occurrence and seasonality, and (iii) assess their effects on the tropospheric ozone budget over the Himalayas. The vertical profiles of potential vorticity (PV) and a stratospheric ozone tracer (O3s) in EMAC simulations, in conjunction with the structure of SOPs, suggest that SOPs over the Himalayas are formed by Stratosphere-to-Troposphere Transport (STT) of ozone. The spatial distribution of O3s further shows that such effects are in general confined to the northern part of India. Model simulated ozone distributions and backward air trajectories show that ozone rich air masses, associated with STT, originate as far as northern Africa and the North Atlantic Ocean, the Middle-East, as well as nearby regions in Afghanistan and Pakistan, and are rapidly (within 2–3 days) transported to the Himalayas. Analysis of a 15-year (2000–2014) EMAC simulation shows that the frequency of SOPs is highest during the pre-monsoon season (e.g. 11 % of the time in May), while no intense SOP events are found during the July–October period. The SOPs are estimated to enhance the Tropospheric Column Ozone (TCO) over the central Himalayas by up to 26 %.

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In situ observations of new particle formation in the tropical upper troposphere: the role of clouds and the nucleation mechanism

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-9983-2011 ◽

2011 ◽

Vol 11 (18) ◽

pp. 9983-10010 ◽

Cited By ~ 45

Author(s):

R. Weigel ◽

S. Borrmann ◽

J. Kazil ◽

A. Minikin ◽

A. Stohl ◽

...

Keyword(s):

South America ◽

West Africa ◽

Central America ◽

Particle Formation ◽

Tropical Convection ◽

New Particle Formation ◽

Upper Troposphere ◽

Nucleation Mode ◽

In Situ Observations

Abstract. New particle formation (NPF), which generates nucleation mode aerosol, was observed in the tropical Upper Troposphere (UT) and Tropical Tropopause Layer (TTL) by in situ airborne measurements over South America (January–March 2005), Australia (November–December 2005), West Africa (August 2006) and Central America (2004–2007). Particularly intense NPF was found at the bottom of the TTL. Measurements with a set of condensation particle counters (CPCs) with different dp50 (50% lower size detection efficiency diameter or "cut-off diameter") were conducted on board the M-55 Geophysica in the altitude range of 12.0–20.5 km and on board the DLR Falcon-20 at up to 11.5 km altitude. On board the NASA WB-57F size distributions were measured over Central America in the 4 to 1000 nm diameter range with a system of nucleation mode aerosol spectrometers. Nucleation mode particle concentrations (NNM) were derived from these measurements which allow for identifying many NPF events with NNM in the range of thousands of particles per cm3. Over Australia and West Africa, we identified NPF in the outflow of tropical convection, in particular of a Mesoscale Convective System (MCS). Newly formed particles with NNM > 1000 cm−3 were found to coexist with ice cloud particles (dp > 2 μm) as long as cloud particle concentrations remained below 2 cm−3. The occurrence of NPF within the upper troposphere and the TTL was generally confined within 340 K to 380 K potential temperature, but NPF was of particular strength between 350 K and 370 K (i.e. ~1–4 km below the cold point tropopause). Analyses of the aerosol volatility (at 250 °C) show that in the TTL on average 75–90% of the particles were volatile, compared to typically only 50% in the extra-tropical UT, indicative for the particles to mainly consist of H2SO4-H2O and possibly organic compounds. Along two flight segments over Central and South America (24 February 2005 and 7 August 2006, at 12.5 km altitude) in cloud free air, above thin cirrus, particularly high NNM were observed. Recent lifting had influenced the probed air masses, and NNM reached up to 16 000 particles cm−3 (ambient concentration). A sensitivity study using an aerosol model, which includes neutral and ion induced nucleation processes, simulates NNM in reasonable agreement with the in situ observations of clear-air NPF. Based on new, stringent multi-CPC criteria, our measurements corroborate the hypothesis that the tropical UT and the TTL are regions supplying freshly nucleated particles. Our findings narrow the altitude of the main source region to the bottom TTL, i.e. to the level of main tropical convection outflow, and, by means of measurements of carbon monoxide, they indicate the importance of anthropogenic emissions in NPF. After growth and/or coalescence the nucleation mode particles may act as cloud condensation nuclei in the tropical UT, or, upon ascent into the stratosphere, contribute to maintain the stratospheric background aerosol.

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