scholarly journals Seasonal and interannual variations in HCN amounts in the upper troposphere and lower stratosphere observed by MIPAS

2015 ◽  
Vol 15 (2) ◽  
pp. 563-582 ◽  
Author(s):  
N. Glatthor ◽  
M. Höpfner ◽  
G. P. Stiller ◽  
T. von Clarmann ◽  
B. Funke ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Annual Cycle ◽  
Lower Stratosphere ◽  
Tape Recorder ◽  
Time Shift ◽  
Interannual Variations ◽  
High Latitudes ◽  
Tropical Africa ◽  
Upper Troposphere ◽  
Fire Emissions

Abstract. We present a HCN climatology of the years 2002–2012, derived from FTIR limb emission spectra measured with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on the ENVISAT satellite, with the main focus on biomass burning signatures in the upper troposphere and lower stratosphere. HCN is an almost unambiguous tracer of biomass burning with a tropospheric lifetime of 5–6 months and a stratospheric lifetime of about 2 years. The MIPAS climatology is in good agreement with the HCN distribution obtained by the spaceborne ACE-FTS experiment and with airborne in situ measurements performed during the INTEX-B campaign. The HCN amounts observed by MIPAS in the southern tropical and subtropical upper troposphere have an annual cycle peaking in October–November, i.e. 1–2 months after the maximum of southern hemispheric fire emissions. The probable reason for the time shift is the delayed onset of deep convection towards austral summer. Because of overlap of varying biomass burning emissions from South America and southern Africa with sporadically strong contributions from Indonesia, the size and strength of the southern hemispheric plume have considerable interannual variations, with monthly mean maxima at, for example, 14 km between 400 and more than 700 pptv. Within 1–2 months after appearance of the plume, a considerable portion of the enhanced HCN is transported southward to as far as Antarctic latitudes. The fundamental period of HCN variability in the northern upper troposphere is also an annual cycle with varying amplitude, which in the tropics peaks in May after and during the biomass burning seasons in northern tropical Africa and southern Asia, and in the subtropics peaks in July due to trapping of pollutants in the Asian monsoon anticyclone (AMA). However, caused by extensive biomass burning in Indonesia and by northward transport of part of the southern hemispheric plume, northern HCN maxima also occur around October/November in several years, which leads to semi-annual cycles. There is also a temporal shift between enhanced HCN in northern low and mid- to high latitudes, indicating northward transport of pollutants. Due to additional biomass burning at mid- and high latitudes, this meridional transport pattern is not as clear as in the Southern Hemisphere. Upper tropospheric HCN volume mixing ratios (VMRs) above the tropical oceans decrease to below 200 pptv, presumably caused by ocean uptake, especially during boreal winter and spring. The tropical stratospheric tape recorder signal with an apparently biennial period, which was detected in MLS and ACE-FTS data from mid-2004 to mid-2007, is corroborated by MIPAS HCN data. The tape recorder signal in the whole MIPAS data set exhibits periodicities of 2 and 4 years, which are generated by interannual variations in biomass burning. The positive anomalies of the years 2003, 2007 and 2011 are caused by succession of strongly enhanced HCN from southern hemispheric and Indonesian biomass burning in boreal autumn and of elevated HCN from northern tropical Africa and the AMA in subsequent spring and summer. The anomaly of 2005 seems to be due to springtime emissions from tropical Africa followed by release from the summertime AMA. The vertical transport time of the anomalies is 1 month or less between 14 and 17 km in the upper troposphere and 8–11 months between 17 and 25 km in the lower stratosphere.

scholarly journals Seasonal and interannual variations of HCN amounts in the upper troposphere and lower stratosphere observed by MIPAS

2014 ◽  
Vol 14 (7) ◽  
pp. 8997-9040
Author(s):  
N. Glatthor ◽  
M. Höpfner ◽  
G. P. Stiller ◽  
T. von Clarmann ◽  
B. Funke ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Biomass Burning ◽  
Annual Cycle ◽  
Asian Monsoon ◽  
Lower Stratosphere ◽  
Tape Recorder ◽  
Positive Anomaly ◽  
Interannual Variations ◽  
High Latitudes ◽  
Upper Troposphere

Abstract. A global HCN dataset covering nearly the complete period June 2002 to April 2012 has been derived from FTIR limb emission spectra measured with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on the ENVISAT satellite. HCN is an almost unambiguous tracer of biomass burning with a tropospheric lifetime of 5–6 months and a stratospheric lifetime of about two years. We present a MIPAS HCN climatology with the main focus on biomass burning signatures in the upper troposphere and lower stratosphere. HCN observed by MIPAS in the southern tropical and subtropical upper troposphere has an annual cycle peaking in October–November during or shortly after the maximum of the southern hemispheric biomass burning season. Within 1–2 months after the burning season, a considerable portion of the enhanced HCN is transported southward to Antarctic latitudes. The fundamental period in the northern upper troposphere is also an annual cycle, which in the tropics peaks in May after the biomass burning seasons in northern tropical Africa and South Asia, and in the subtropics in July due to trapping of pollutants in the Asian monsoon anticyclone. However, caused by extensive biomass burning in Indonesia and Northern Africa together with northward transport of parts of the southern hemispheric plume, in several years HCN maxima are also found around October/November, which leads to semi-annual cycles in the northern tropics and subtropics. Because of overlap of interannually varying burning activities in different source regions, both southern and northern low-latitude maxima have considerable interannual variations. There is also a temporal shift between enhanced HCN in northern low and mid-to-high latitudes, indicating northward transport of pollutants. Due to additional biomass burning at mid and high latitudes this meridional transport pattern is not as clear as in the Southern Hemisphere. Presumably caused by ocean uptake, upper tropospheric HCN above the tropical oceans decreases to below 200 pptv especially during boreal winter and spring. HCN time series at 10 km altitude indicate a negative trend, which is more distinct in the northern (−1.3 to −2.1% yr−1) than in the Southern Hemisphere (−0.1 to −0.7% yr−1). The tropical stratospheric tape recorder signal with an apparently biennial period, which has been detected in MLS and ACE-FTS data from mid-2004 to mid-2007, is corroborated by MIPAS HCN data. The tape recorder signal in the whole MIPAS dataset exhibits periodicities of 2 and 4 yr, generated by interannual variations in biomass burning. The strongest positive anomaly in the year 2007 is caused by superposition of enhanced HCN from southern hemispheric and Indonesian biomass burning at the end of the year 2006 and from African sources in spring and the Asian monsoon during summer. The vertical transport time of the anomalies is 1 month or less between 14 and 17 km in the upper troposphere and about 9 months between 17 and 25 km in the lower stratosphere.

scholarly journals The impact of organic pollutants from Indonesian peatland fires on the tropospheric and lower stratospheric composition

2021 ◽  
Vol 21 (14) ◽  
pp. 11257-11288
Author(s):  
Simon Rosanka ◽  
Bruno Franco ◽  
Lieven Clarisse ◽  
Pierre-François Coheur ◽  
Andrea Pozzer ◽  
...  
Keyword(s):  
Biomass Burning ◽  
El Niño ◽  
Lower Stratosphere ◽  
El Nino ◽  
Lower Troposphere ◽  
Atmospheric Composition ◽  
Voc Emissions ◽  
Upper Troposphere ◽  
Upward Transport ◽  
The Impact

Abstract. The particularly strong dry season in Indonesia in 2015, caused by an exceptionally strong El Niño, led to severe peatland fires resulting in high volatile organic compound (VOC) biomass burning emissions. At the same time, the developing Asian monsoon anticyclone (ASMA) and the general upward transport in the Intertropical Convergence Zone (ITCZ) efficiently transported the resulting primary and secondary pollutants to the upper troposphere and lower stratosphere (UTLS). In this study, we assess the importance of these VOC emissions for the composition of the lower troposphere and the UTLS and investigate the effect of in-cloud oxygenated VOC (OVOC) oxidation during such a strong pollution event. This is achieved by performing multiple chemistry simulations using the global atmospheric model ECHAM/MESSy (EMAC). By comparing modelled columns of the biomass burning marker hydrogen cyanide (HCN) and carbon monoxide (CO) to spaceborne measurements from the Infrared Atmospheric Sounding Interferometer (IASI), we find that EMAC properly captures the exceptional strength of the Indonesian fires. In the lower troposphere, the increase in VOC levels is higher in Indonesia compared to other biomass burning regions. This has a direct impact on the oxidation capacity, resulting in the largest regional reduction in the hydroxyl radical (OH) and nitrogen oxides (NOx). While an increase in ozone (O3) is predicted close to the peatland fires, simulated O3 decreases in eastern Indonesia due to particularly high phenol concentrations. In the ASMA and the ITCZ, the upward transport leads to elevated VOC concentrations in the lower stratosphere, which results in the reduction of OH and NOx and the increase in the hydroperoxyl radical (HO2). In addition, the degradation of VOC emissions from the Indonesian fires becomes a major source of lower stratospheric nitrate radicals (NO3), which increase by up to 20 %. Enhanced phenol levels in the upper troposphere result in a 20 % increase in the contribution of phenoxy radicals to the chemical destruction of O3, which is predicted to be as large as 40 % of the total chemical O3 loss in the UTLS. In the months following the fires, this loss propagates into the lower stratosphere and potentially contributes to the variability of lower stratospheric O3 observed by satellite retrievals. The Indonesian peatland fires regularly occur during El Niño years, and the largest perturbations of radical concentrations in the lower stratosphere are predicted for particularly strong El Niño years. By activating the detailed in-cloud OVOC oxidation scheme Jülich Aqueous-phase Mechanism of Organic Chemistry (JAMOC), we find that the predicted changes are dampened. Global models that neglect in-cloud OVOC oxidation tend to overestimate the impact of such extreme pollution events on the atmospheric composition.

scholarly journals Spectrum of Wave Forcing Associated with the Annual Cycle of Upwelling at the Tropical Tropopause

2016 ◽  
Vol 73 (2) ◽  
pp. 855-868 ◽  
Author(s):  
Joowan Kim ◽  
William J. Randel ◽  
Thomas Birner ◽  
Marta Abalos
Keyword(s):  
Annual Cycle ◽  
Lower Stratosphere ◽  
Mass Conservation ◽  
Upper Troposphere ◽  
Wave Forcing ◽  
Planetary Scale ◽  
Tropical Tropopause ◽  
Zonal Wavenumber ◽  
Wavenumber Spectrum ◽  
Transformed Eulerian Mean

Abstract The zonal wavenumber spectrum of atmospheric wave forcing in the lower stratosphere is examined to understand the annual cycle of upwelling at the tropical tropopause. Tropopause upwelling is derived based on the wave forcing computed from ERA-Interim using the momentum and mass conservation equations in the transformed Eulerian-mean framework. The calculated upwelling agrees well with other upwelling estimates and successfully captures the annual cycle, with a maximum during Northern Hemisphere (NH) winter. The spectrum of wave forcing reveals that the zonal wavenumber-3 component drives a large portion of the annual cycle in upwelling. The wave activity flux (Eliassen–Palm flux) shows that the associated waves originate from the NH extratropics and the Southern Hemisphere tropics during December–February, with both regions contributing significant wavenumber-3 fluxes. These wave fluxes are nearly absent during June–August. Wavenumbers 1 and 2 and synoptic-scale waves have a notable contribution to tropopause upwelling but have little influence on the annual cycle, except the wavenumber-4 component. The quasigeostrophic refractive index suggests that the NH extratropical wavenumber-3 component can enhance tropopause upwelling because these planetary-scale waves are largely trapped in the vertical, while being refracted toward the subtropical upper troposphere and lower stratosphere. Regression analysis based on interannual variability suggests that the wavenumber-3 waves are related to tropical convection and wave breaking along the subtropical jet in the NH extratropics.

scholarly journals Transport analysis and source attribution of seasonal and interannual variability of CO in the tropical upper troposphere and lower stratosphere

2013 ◽  
Vol 13 (1) ◽  
pp. 129-146 ◽  
Author(s):  
J. Liu ◽  
J. A. Logan ◽  
L. T. Murray ◽  
H. C. Pumphrey ◽  
M. J. Schwartz ◽  
...  
Keyword(s):  
Annual Cycle ◽  
Annual Variation ◽  
Lower Stratosphere ◽  
Transport Model ◽  
Boreal Summer ◽  
Lower Altitude ◽  
Model Simulations ◽  
Upper Troposphere ◽  
Annual Variations ◽  
Upward Transport

Abstract. We used the GEOS-Chem chemistry-transport model to investigate impacts of surface emissions and dynamical processes on the spatial and temporal patterns of CO observed by the Microwave Limb Sounder (MLS) in the upper troposphere (UT) and lower stratosphere (LS). Model simulations driven by GEOS-4 and GEOS-5 assimilated fields present many features of the seasonal and inter-annual variation of CO in the upper troposphere and lower stratosphere. Both model simulations and the MLS data show a transition from semi-annual variations in the UT to annual variations in the LS. Tagged CO simulations indicate that the semi-annual variation of CO in the UT is determined mainly by the temporal overlapping of surface biomass burning from different continents as well as the north-south shifts of deep convection. Both GEOS-4 and GEOS-5 have maximum upward transport in April and May with a minimum in July to September. The CO peaks from the Northern Hemisphere (NH) fires propagate faster to the LS than do those from the Southern Hemisphere (SH) fires. Thus the transition from a semi-annual to an annual cycle around 80 hPa is induced by a combination of the CO signal at the tropopause and the annual cycle of the Brewer-Dobson circulation. In GEOS-5, the shift to an annual cycle occurs at a lower altitude than in MLS CO, a result of inadequate upward transport. We deduce vertical velocities from MLS CO, and use them to evaluate the velocities derived from the archived GEOS meteorological fields. We find that GEOS-4 velocities are similar to those from MLS CO between 215 hPa and 125 hPa, while the velocities in GEOS-5 are too low in spring and summer. The mean tropical vertical velocities from both models are lower than those inferred from MLS CO above 100 hPa, particularly in GEOS-5, with mean downward, rather than upward motion in boreal summer. Thus the models' CO maxima from SH burning are transported less effectively than those in MLS CO above 147 hPa and almost disappear by 100 hPa. The strongest peaks in the CO tape-recorder are in late 2004, 2006, and 2010, with the first two resulting from major fires in Indonesia and the last from severe burning in South America, all associated with intense droughts.

scholarly journals Transport analysis and source attribution of seasonal and interannual variability of CO in the tropical upper troposphere and lower stratosphere

2012 ◽  
Vol 12 (7) ◽  
pp. 17397-17442 ◽  
Author(s):  
Junhua Liu ◽  
J. A. Logan ◽  
L. T. Murray ◽  
H. C. Pumphrey ◽  
M. J. Schwartz ◽  
...  
Keyword(s):  
Annual Cycle ◽  
Annual Variation ◽  
Lower Stratosphere ◽  
Transport Model ◽  
Boreal Summer ◽  
Lower Altitude ◽  
Model Simulations ◽  
Upper Troposphere ◽  
Annual Variations ◽  
Upward Transport

Abstract. We used the GEOS-Chem chemistry-transport model to investigate impacts of surface emissions and dynamical processes on the spatial and temporal patterns of CO observed by the Microwave Limb Sounder (MLS) in the upper troposphere and lower stratosphere (UTLS). Model simulations driven by GEOS-4 and GEOS-5 assimilated fields present many features of the seasonal and inter-annual variation of CO in the UTLS. Both model simulations and the MLS data show a transition from semi-annual variations in the UT to annual variations in the LS. Tagged CO simulations indicate that the semi-annual variation of CO in the UT is determined mainly by the temporal overlapping of surface biomass burning from different continents as well as the north-south shifts of deep convection. Both GEOS-4 and GEOS-5 have maximum upward transport in April and May with a minimum in July to September. The CO peaks from NH fires propagate faster to the LS than do those from SH fires. Thus the transition from a semi-annual to an annual cycle around 80 hPa is induced by a combination of the CO signal at the tropopause and the annual cycle of the Brewer-Dobson circulation. In GEOS-5, the shift to an annual cycle occurs at a lower altitude than in MLS CO, a result of inadequate upward transport. We deduce vertical velocities from MLS CO, and find that those in GEOS-4 agree well with them between 215 hPa and 125 hPa in boreal summer, fall and winter, while the velocities in GEOS-5 are too low in all seasons. The mean tropical vertical velocities from both models are lower than those inferred from MLS CO above 100 hPa in June to November, particularly in GEOS-5, with mean downward, rather than upward motion in boreal summer. Thus the models' CO maxima from SH burning are transported less effectively than those in MLS CO above 147 hPa and almost disappear by 100 hPa. The strongest peaks in the CO tape-recorder are in late 2004, 2006, and 2010, with the first two resulting from major fires in Indonesia and the last from severe burning in South America, all associated with intense droughts.

scholarly journals Observations of peroxyacetyl nitrate (PAN) in the upper troposphere by the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS)

2013 ◽  
Vol 13 (1) ◽  
pp. 1575-1607 ◽  
Author(s):  
K. A. Tereszchuk ◽  
D. P. Moore ◽  
J. J. Harrison ◽  
C. D. Boone ◽  
M. Park ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Biomass Burning ◽  
Atmospheric Chemistry ◽  
Lower Stratosphere ◽  
Fourier Transform Spectrometer ◽  
Data Set ◽  
Upper Troposphere ◽  
Volatile Organic ◽  
The Impact ◽  
Chemistry Experiment

Abstract. Peroxyacetyl nitrate (CH3CO·O2NO2, abbreviated as PAN) is a trace molecular species present in the troposphere and lower stratosphere due primarily to pollution from fuel combustion and the pyrogenic outflows from biomass burning. In the lower troposphere, PAN has a relatively short life-time and is principally destroyed within a few hours through thermolysis, but it can act as a reservoir and carrier of NOx in the colder temperatures of the upper troposphere where UV photolysis becomes the dominant loss mechanism. Pyroconvective updrafts from large biomass burning events can inject PAN into the upper troposphere and lower stratosphere (UTLS), providing a means for the long-range transport of NOx. Given the extended lifetimes at these higher altitudes, PAN is readily detectable via satellite remote sensing. A new PAN data product is now available for the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) Version 3.0 data set. We report measurements of PAN in Boreal biomass burning plumes recorded during the Quantifying the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites (BORTAS) campaign. The retrieval method employed and errors analysis are described in full detail. The retrieved volume mixing ratio (VMR) profiles are compared to coincident measurements made by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instrument on the European Space Agency (ESA) ENVIronmental SATellite (ENVISAT). Three ACE-FTS occultations containing measurements of Boreal biomass burning outflows, recorded during BORTAS, were identified as having coincident measurements with MIPAS. In each case, the MIPAS measurements demonstrated good agreement with the ACE-FTS VMR profiles for PAN. The ACE-FTS PAN data set is used to obtain zonal mean distributions of seasonal averages from ~5 to 20 km. A strong seasonality is clearly observed for PAN concentrations in the global UTLS. Since the principal source of PAN in the UTLS is due to lofted biomass burning emissions from the pyroconvective updrafts created by large fires, the observed seasonality in enhanced PAN coincides with fire activity in different geographical regions throughout the year. This work is part of an in-depth investigation that is being conducted in an effort to study the aging and chemical evolution of biomass burning emissions in the UTLS by remote, space-borne measurements made by ACE-FTS to further our understanding of the impact of pyrogenic emissions on atmospheric chemistry. Included in this study will be the addition of new, pyrogenic, volatile organic hydrocarbons (VOCs) and oxygenated volatile organic compounds (OVOCs) to expand upon the already extensive suite of molecules retrieved by ACE-FTS to aid in elucidating biomass burning plume chemistry in the free troposphere.

scholarly journals The impact of biomass burning on upper tropospheric carbon monoxide: A study using MOCAGE global model and IAGOS airborne data

2020 ◽  
Author(s):  
Martin Cussac ◽  
Virginie Marécal ◽  
Valérie Thouret ◽  
Béatrice Josse ◽  
Bastien Sauvage
Keyword(s):  
Carbon Monoxide ◽  
Biomass Burning ◽  
Boreal Forests ◽  
Transport Model ◽  
Deep Convection ◽  
High Latitudes ◽  
Upper Troposphere ◽  
Airborne Measurements ◽  
Fire Plumes ◽  
The Impact

Abstract. In this paper the fate of biomass burning emissions of carbon monoxide is studied with the global chemistry transport model MOCAGE and IAGOS airborne measurements for the year of 2013. The objectives are firstly to improve their representation within the model and secondly to analyse their contribution to carbon monoxide concentrations in the upper troposphere. At first, a new implementation of biomass burning injection is developed for MOCAGE, using the latest products available in GFAS biomass burning inventory on plume altitude and injection height. This method is validated against IAGOS observations of CO made in fire plumes, identified thanks to the SOFT-IO source attribution data. The use of these GFAS products lead to improved MOCAGE skill to simulate fire plumes originating from boreal forests wildfires. It was also shown that this new biomass burning injection method did not change upper tropospheric carbon monoxide concentrations elsewhere on the globe as the previous one was already satisfying. Then, MOCAGE performances were evaluated in general in the upper troposphere in comparison to the IAGOS database, and were shown to be very good, with very little bias and good correlations between the model and the observations. Finally, we analyse the contribution of biomass burning to upper tropospheric carbon monoxide concentrations. This was done by comparing simulations were biomass were toggled on and off in different source regions of the world to assess their individual influence. The two regions contributing the most to upper tropospheric CO were found to be the boreal forests and equatorial Africa, in accordance with the quantities of CO they emit each year and the fact that they undergo fast vertical transport: deep convection in the tropics and pyroconvection at high latitudes. It was found that biomass burning contributes for more than 11 % on average on the CO concentrations in the upper troposphere, and up to 50 % at high latitudes during the wildfire season.

scholarly journals Overshooting of clean tropospheric air in the tropical lower stratosphere as seen by the CALIPSO lidar

2011 ◽  
Vol 11 (18) ◽  
pp. 9683-9696 ◽  
Author(s):  
J.-P. Vernier ◽  
J.-P. Pommereau ◽  
L. W. Thomason ◽  
J. Pelon ◽  
A. Garnier ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Lower Stratosphere ◽  
Thermal Structure ◽  
Radiative Heating ◽  
Major Contributor ◽  
Upper Troposphere ◽  
Tropical Tropopause Layer ◽  
Volcanic Plumes ◽  
Tropical Tropopause ◽  
Organic Particles

Abstract. The evolution of aerosols in the tropical upper troposphere/lower stratosphere between June 2006 and October 2009 is examined using the observations of the space borne CALIOP lidar aboard the CALIPSO satellite. Superimposed on several volcanic plumes and soot from an extreme biomass-burning event in 2009, the measurements reveal the existence of fast-cleansing episodes in the lower stratosphere to altitudes as high as 20 km. The cleansing of the layer, which extends from 14 to 20 km, takes place within 1 to 4 months during the southern tropics convective season that transports aerosol-poor tropospheric air into the lower stratosphere. In contrast, the convective season of the Northern Hemisphere summer shows an increase in the particle load at the tropopause consistent with a lofting of air rich with aerosols. These aerosols can consist of surface-derived material such as mineral dust and soot as well as liquid sulfate and organic particles. The flux of tropospheric air during the Southern Hemisphere convective season derived from CALIOP observations is shown to be 5 times at 16 km and 20 times at 19 km larger, respectively, than that associated with flux caused by slow ascent through radiative heating. These results suggest that convective overshooting is a major contributor to troposphere-to-stratosphere transport with concomitant implications for the Tropical Tropopause Layer top height, the humidity, the photochemistry and the thermal structure of the layer.

scholarly journals The outflow of Asian biomass burning carbonaceous aerosol into the upper troposphere and lower stratosphere in spring: radiative effects seen in a global model

2021 ◽  
Vol 21 (18) ◽  
pp. 14371-14384
Author(s):  
Prashant Chavan ◽  
Suvarna Fadnavis ◽  
Tanusri Chakroborty ◽  
Christopher E. Sioris ◽  
Sabine Griessbach ◽  
...  
Keyword(s):  
Water Vapor ◽  
Biomass Burning ◽  
Radiative Forcing ◽  
Lower Stratosphere ◽  
Carbonaceous Aerosol ◽  
The Arctic ◽  
Carbonaceous Aerosols ◽  
Maximum Enhancement ◽  
Model Simulations ◽  
Upper Troposphere

Abstract. Biomass burning (BB) over Asia is a strong source of carbonaceous aerosols during spring. From ECHAM6–HAMMOZ model simulations and satellite observations, we show that there is an outflow of Asian BB carbonaceous aerosols into the upper troposphere and lower stratosphere (UTLS) (black carbon: 0.1 to 6 ng m−3 and organic carbon: 0.2 to 10 ng m−3) during the spring season. The model simulations show that the greatest transport of BB carbonaceous aerosols into the UTLS occurs from the Indochina and East Asia region by deep convection over the Malay Peninsula and Indonesia. The increase in BB carbonaceous aerosols enhances atmospheric heating by 0.001 to 0.02 K d−1 in the UTLS. The aerosol-induced heating and circulation changes increase the water vapor mixing ratios in the upper troposphere (by 20–80 ppmv) and in the lowermost stratosphere (by 0.02–0.3 ppmv) over the tropics. Once in the lower stratosphere, water vapor is further transported to the South Pole by the lowermost branch of the Brewer–Dobson circulation. These aerosols enhance the in-atmosphere radiative forcing (0.68±0.25 to 5.30±0.37 W m−2), exacerbating atmospheric warming, but produce a cooling effect on climate (top of the atmosphere – TOA: -2.38±0.12 to -7.08±0.72 W m−2). The model simulations also show that Asian carbonaceous aerosols are transported to the Arctic in the troposphere. The maximum enhancement in aerosol extinction is seen at 400 hPa (by 0.0093 km−1) and associated heating rates at 300 hPa (by 0.032 K d−1) in the Arctic.

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