scholarly journals Model study of the cross-tropopause transport of biomass burning pollution

2007 ◽  
Vol 7 (14) ◽  
pp. 3713-3736 ◽  
Author(s):  
B. N. Duncan ◽  
S. E. Strahan ◽  
Y. Yoshida ◽  
S. D. Steenrod ◽  
N. Livesey
Keyword(s):  
Biomass Burning ◽  
El Niño ◽  
Fossil Fuels ◽  
Extreme Event ◽  
El Nino ◽  
Deep Convection ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
El Niño Event ◽  
The Impact

Abstract. We present a modeling study of the troposphere-to-stratosphere transport (TST) of pollution from major biomass burning regions to the tropical upper troposphere and lower stratosphere (UT/LS). TST occurs predominately through 1) slow ascent in the tropical tropopause layer (TTL) to the LS and 2) quasi-horizontal exchange to the lowermost stratosphere (LMS). We show that biomass burning pollution regularly and significantly impacts the composition of the TTL, LS, and LMS. Carbon monoxide (CO) in the LS in our simulation and data from the Aura Microwave Limb Sounder (MLS) shows an annual oscillation in its composition that results from the interaction of an annual oscillation in slow ascent from the TTL to the LS and seasonal variations in sources, including a semi-annual oscillation in CO from biomass burning. The impacts of CO sources that peak when ascent is seasonally low are damped (e.g. Southern Hemisphere biomass burning) and vice-versa for sources that peak when ascent is seasonally high (e.g. extra-tropical fossil fuels). Interannual variation of CO in the UT/LS is caused primarily by year-to-year variations in biomass burning and the locations of deep convection. During our study period, 1994–1998, we find that the highest concentrations of CO in the UT/LS occurred during the strong 1997–1998 El Niño event for two reasons: i. tropical deep convection shifted to the eastern Pacific Ocean, closer to South American and African CO sources, and ii. emissions from Indonesian biomass burning were higher. This extreme event can be seen as an upper bound on the impact of biomass burning pollution on the UT/LS. We estimate that the 1997 Indonesian wildfires increased CO in the entire TTL and tropical LS (>60 mb) by more than 40% and 10%, respectively, for several months. Zonal mean ozone increased and the hydroxyl radical decreased by as much as 20%, increasing the lifetimes and, subsequently TST, of trace gases. Our results indicate that the impact of biomass burning pollution on the UT/LS is likely greatest during an El Niño event due to favorable dynamics and historically higher burning rates.

scholarly journals Model study of the cross-tropopause transport of biomass burning pollution

2007 ◽  
Vol 7 (1) ◽  
pp. 2197-2248 ◽  
Author(s):  
B. N. Duncan ◽  
S. E. Strahan ◽  
Y. Yoshida
Keyword(s):  
Biomass Burning ◽  
El Niño ◽  
Fossil Fuels ◽  
Extreme Event ◽  
El Nino ◽  
Deep Convection ◽  
Tape Recorder ◽  
Boreal Winter ◽  
El Niño Event ◽  
The Impact

Abstract. We present a modeling study of the troposphere-to-stratosphere transport (TST) of pollution from major biomass burning regions to the tropical tropopause layer (TTL) and lower stratosphere (LS). We show that biomass burning pollution regularly and significantly impacts the composition of the TTL/LS. TST occurs through 1) slow ascent in the TTL and 2) quasi-horizontal exchange in the regions of the subtropical jets; we find both pathways to be important. The seasonal oscillation in CO in the TTL/LS (i.e., the CO "tape recorder") is caused largely by seasonal changes in biomass burning. Another contributing factor is the long-range transport of northern hemispheric pollution (e.g., biofuels and fossil fuels) to the northern tropics in boreal winter. Other tropical sources of CO (e.g., methane oxidation) have insignificant seasonal variation, contributing little to the tape recorder. Interannual variation of CO in the TTL/LS is caused by year-to-year variations in biomass burning and the strength, frequency, and locations of deep convection, which lofts pollution to the upper troposphere. During our study period, 1994–1998, we find that the highest concentrations of CO in the TTL/LS occur during the strong 1997/98 El Niño event for two reasons: i.~tropical deep convection was stronger and ii.~emissions were higher. This extreme event can be seen as an upper bound on the impact of biomass burning pollution on the TTL/LS. We estimate that the 1997 Indonesian wildfires increased CO in the entire TTL and tropical LS (<60 mb) by more than 40% and 10%, respectively, for several months. Zonal mean ozone increased and the hydroxyl radical decreased by as much as 20%, increasing the lifetimes and, subsequently TST, of trace gases. Our results indicate that the impact of biomass burning pollution on the TTL/LS is likely greatest during an El Niño event due to favorable dynamics and historically higher burning rates.

scholarly journals The impact of overshooting deep convection on local transport and mixing in the tropical upper troposphere/lower stratosphere (UTLS)

2015 ◽  
Vol 15 (11) ◽  
pp. 6467-6486 ◽  
Author(s):  
W. Frey ◽  
R. Schofield ◽  
P. Hoor ◽  
D. Kunkel ◽  
F. Ravegnani ◽  
...  
Keyword(s):  
Lower Stratosphere ◽  
Deep Convection ◽  
Horizontal Resolution ◽  
Transport Processes ◽  
Convective System ◽  
Upper Troposphere ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Transport And Mixing ◽  
The Impact

Abstract. In this study we examine the simulated downward transport and mixing of stratospheric air into the upper tropical troposphere as observed on a research flight during the SCOUT-O3 campaign in connection with a deep convective system. We use the Advanced Research Weather and Research Forecasting (WRF-ARW) model with a horizontal resolution of 333 m to examine this downward transport. The simulation reproduces the deep convective system, its timing and overshooting altitudes reasonably well compared to radar and aircraft observations. Passive tracers initialised at pre-storm times indicate the downward transport of air from the stratosphere to the upper troposphere as well as upward transport from the boundary layer into the cloud anvils and overshooting tops. For example, a passive ozone tracer (i.e. a tracer not undergoing chemical processing) shows an enhancement in the upper troposphere of up to about 30 ppbv locally in the cloud, while the in situ measurements show an increase of 50 ppbv. However, the passive carbon monoxide tracer exhibits an increase, while the observations show a decrease of about 10 ppbv, indicative of an erroneous model representation of the transport processes in the tropical tropopause layer. Furthermore, it could point to insufficient entrainment and detrainment in the model. The simulation shows a general moistening of air in the lower stratosphere, but it also exhibits local dehydration features. Here we use the model to explain the processes causing the transport and also expose areas of inconsistencies between the model and observations.

On Abnormally Strong Currents Observed on the Northern Coast of Peru during the 2015-2016 El Niño

2021 ◽  
Vol 8 (4) ◽  
pp. 205-210
Author(s):  
Chang-Woong Shin ◽  
Dimitri Gutiérrez
Keyword(s):  
Mixed Layer ◽  
El Niño ◽  
El Nino ◽  
Current Data ◽  
Kelvin Waves ◽  
Coastal Current ◽  
Northern Coast ◽  
El Niño Event ◽  
Strong Current ◽  
The Impact

The northern coast of Peru is a region that can rapidly detect the impact of an El Niño. To investigate the effects of the 2015-2016 El Niño on the oceanographic environment of the northern coast of Peru, the temperature and current data obtained from moored equipment at an oil platform were analyzed. Strong coastal along-shore currents of more than 0.60 m·s-1 were observed three times, although the mean current speed was 0.10 m·s-1 flowing toward the south-southwest. After the first strong current, the bottom temperature increased and the mixed layer deepened and remained there during the El Niño event. The temperature reached a maximum after the strong coastal current, then decreased gradually. An analysis of wind and sea surface height anomalies revealed that the coastal strong current was caused by Kelvin waves and the deepening of the mixed layer was not related to local winds, but to coastal Kelvin waves from the equator during the El Niño event.

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 Spatial and Temporal Analysis of El Niño Impact on Land and Forest Fire in Kalimantan and Sumatra

Agromet ◽  
2021 ◽  
Vol 35 (1) ◽  
pp. 1-10
Author(s):  
Sri Nurdiati ◽  
Ardhasena Sopaheluwakan ◽  
Pandu Septiawan
Keyword(s):  
Forest Fire ◽  
Forest Fires ◽  
El Niño ◽  
Fire Regime ◽  
El Nino ◽  
Function Analysis ◽  
Spatial And Temporal Patterns ◽  
El Niño Event ◽  
Dry Spell ◽  
The Impact

Land and forest fires in Kalimantan and Sumatra, Indonesia occurred annually at different magnitude and duration. Climate and sea interaction, like El Niño, influences the severity of dry seasons preceding the fires. However, research on the influence of El Niño intensity to fire regime in Kalimantan and Sumatra is limited. Therefore, this study aims to analyze the spatial and temporal patterns of the effects of El Niño intensity on land and forest fires in fire-prone provinces in Indonesia. Here, we applied the empirical orthogonal function analysis based on singular value decomposition to determine the dominant patterns of hotspots and rainfall data that evolve spatially and temporally. For analysis, the study required the following data: fire hotspots, dry-spell, and rainfall for period 2001-2019. This study revealed that El Niño intensity had a different impacts for each province. Generally, El Niño will influence the severity of forest fire events in Indonesia. However, we found that the impact of El Niño intensity varied for Kalimantan, South Sumatra, and Riau Province. Kalimantan was the most sensitive province to the El Niño event. The duration and number of hotspots in Kalimantan increased significantly even in moderate El Niño event. This was different for South Sumatra, where the duration and number of hotspots only increased significantly when a strong El Niño event occurred.

scholarly journals Organic pollutants from tropical peatland fires: regional influences and its impact on lower stratospheric ozone

2020 ◽  
Author(s):  
Simon Rosanka ◽  
Bruno Franco ◽  
Lieven Clarisse ◽  
Pierre-François Coheur ◽  
Andreas Wahner ◽  
...  
Keyword(s):  
Biomass Burning ◽  
El Niño ◽  
El Nino ◽  
Stratospheric Ozone ◽  
Lower Troposphere ◽  
Atmospheric Model ◽  
Chemical Production ◽  
Global Models ◽  
Upward Transport ◽  
The Impact

Abstract. The particularly strong dry season in Indonesia in 2015, caused by an exceptional 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/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 we 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) 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 hydroxyl radicals (OH) and nitrogen oxides (NOx). Even though an increase in ozone (O3) is predicted close to the peatland fires, particular high concentrations of phenols lead to an O3 depletion in eastern Indonesia. By employing the detailed in-cloud OVOC oxidation scheme Jülich Aqueous-phase Mechanism of Organic Chemistry (JAMOC), we find that the predicted changes are dampened and that by ignoring these processes, global models tend to overestimate the impact of such extreme pollution events. In the ASMA and the ITCZ, the upward transport leads to elevated VOC concentrations in the UTLS region, which results in a depletion of lower stratospheric O3. We find that this is caused by a high destruction of O3 by phenoxy radicals and by the increased formation of NOx reservoir species, which dampen the chemical production of O3. The Indonesian peatland fires regularly occur during El Niño years and contribute to the depletion of O3. In the time period from 2001 to 2016, we find that the lower stratospheric O3 is reduced by about 0.38 DU and contributes to about 25 % to the lower stratospheric O3 reduction observed by remote sensing. By not considering these processes, global models might not be able to reproduce this variability in lower stratospheric O3.

scholarly journals An overview of the HIBISCUS campaign

2007 ◽  
Vol 7 (1) ◽  
pp. 2389-2475 ◽  
Author(s):  
J.-P. Pommereau ◽  
A. Garnier ◽  
G. Held ◽  
A.-M. Gomes ◽  
F. Goutail ◽  
...  
Keyword(s):  
Lower Stratosphere ◽  
Deep Convection ◽  
Global Scale ◽  
South Atlantic Convergence Zone ◽  
Lapse Rate ◽  
Tropical Tropopause Layer ◽  
Convective Systems ◽  
Major Mechanism ◽  
Tropical Tropopause ◽  
The Impact

Abstract. HIBISCUS was a field campaign for investigating the impact of deep convection on the Tropical Tropopause Layer (TTL) and the Lower Stratosphere, which took place during the Southern Hemisphere summer in February–March 2004 in the State of São Paulo, Brazil. Its objective was to provide a set of new observational data on meteorology, tracers of horizontal and vertical transport, water vapour, clouds, and chemistry in the tropical UT/LS from balloon observations at local scale over a land convective area, as well as at global scale using circumnavigating long-duration balloons. Overall, the composition of the TTL, the region between 14 and 19 km of intermediate lapse rate between the almost adiabatic upper troposphere and the stable stratosphere, appears highly variable. Tracers and ozone measurements performed at both the local and the global scale indicate a strong quasi-horizontal isentropic exchange with the lowermost mid-latitude stratosphere suggesting that the barrier associated to the tropical jet is highly permeable at these levels in summer. But the project also provides clear indications of strong episodic updraught of cold air, short-lived tracers, low ozone, humidity and ice particles across the lapse rate tropopause at about 15 km, up to 18 or 19 km at 420–440 K potential levels in the lower stratosphere, suggesting that, in contrast to oceanic convection penetrating little the stratosphere, fast daytime developing land convective systems could be a major mechanism in the troposphere-stratosphere exchange at the global scale. The present overview is meant to provide the background of the project, as well as overall information on the instrumental tools available, on the way they have been used within the highly convective context of the South Atlantic Convergence Zone, and a brief summary of the results, which will be detailed in several other papers of this special issue.

scholarly journals Small-Scale Wind Fluctuations in the Tropical Tropopause Layer from Aircraft Measurements: Occurrence, Nature, and Impact on Vertical Mixing

2017 ◽  
Vol 74 (11) ◽  
pp. 3847-3869 ◽  
Author(s):  
Aurélien Podglajen ◽  
T. Paul Bui ◽  
Jonathan M. Dean-Day ◽  
Leonhard Pfister ◽  
Eric J. Jensen ◽  
...  
Keyword(s):  
Deep Convection ◽  
Vertical Mixing ◽  
Turbulence Theory ◽  
Small Scale ◽  
Tracer Transport ◽  
Tropical Tropopause Layer ◽  
Airborne Measurements ◽  
Tropical Tropopause ◽  
Vertical Scale ◽  
The Impact

Abstract The contribution of turbulent mixing to heat and tracer transport in the tropical tropopause layer (TTL) is poorly constrained, partly owing to a lack of direct observations. Here, the authors use high-resolution (20 Hz) airborne measurements to study the occurrence and properties of small-scale (&lt;100 m) wind fluctuations in the TTL (14–19 km) over the tropical Pacific. The fluctuations are highly intermittent and appear localized within shallow (100 m) patches. Furthermore, active turbulent events are more frequent at low altitude, near deep convection, and within layers of low gradient Richardson number. A case study emphasizes the link between the turbulent events and the occurrence of inertio-gravity waves having small horizontal or vertical scale. To evaluate the impact of the observed fluctuations on tracer mixing, their characteristics are examined. During active events, they are in broad agreement with inertial-range turbulence theory: the motions are close to 3D isotropic and the spectra follow a −5/3 power-law scaling. The diffusivity induced by turbulent bursts is estimated to be on the order of 10−1 m2 s−1 and increases from the top to the bottom of the TTL (from ~2 × 10−2 to ~3 × 10−1 m2 s−1). Given the uncertainties involved in the estimate, this is in reasonable agreement (about a factor of 3–4 lower) with the parameterized turbulent diffusivity in ERA-Interim, but it disagrees with other observational estimates from radar and radiosondes. The magnitude of the consequent vertical transport depends on the altitude and the tracer; for the species considered, it is generally smaller than that induced by the mean tropical upwelling.

scholarly journals The impact of solar activity on the 2015/16 El Niño event

2016 ◽  
Vol 9 (6) ◽  
pp. 428-435 ◽  
Author(s):  
Wen-Juan HUO ◽  
Zi-Niu XIAO
Keyword(s):  
Solar Activity ◽  
El Niño ◽  
El Nino ◽  
El Niño Event ◽  
The Impact
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