Modeling the solar radiative impact of aerosols from biomass burning during the Southern African Regional Science Initiative (SAFARI‐2000) experiment

Myhre, Gunnar; Berntsen, Terje; Haywood, Jim M.; Sundet, Jostein K.; Holben, B. N.; Johnsrud, Mona; Stordal, Frøde

doi:10.1029/2002jd002313

Cited by 89 publications

(128 citation statements)

References 36 publications

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“…3b and 4b), which would suggest that the variation in the AOD is dominated by the variation in coarse aerosol particles, most likely dust. A similar relationship was found previously for Banizoumbou Ogunjobi et al, 2008;Rajot et al, 2008). This relationship is prominent at Agoufou, Banizoumbou, Zinder Airport, Maine Soroa, and Ougadougou.…”

Section: Western African Aeronet Aod and α Ext Observationssupporting

confidence: 71%

“…In Fig. 4a and b, values of α ext below 0.4 are indicative of aerosols dominated by coarse particles (e.g., mineral dust or coarse sea salt particles) (shaded gray area), while higher values show a contribution from predominantly fine, submicron aerosols, indicative of biomass burning or anthropogenic sources Ogunjobi et al, 2008;Rajot et al, 2008). Table 1 displays the multiyear daily average and median AOD and α ext , which were calculated using all available data points per site.…”

Section: Model-observation Comparisonsmentioning

confidence: 99%

“…In Ilorin, which is south of the other sites, the AOD peaks in January-March, while the α ext is at a minimum value in March-May. Previous work found that minimum values of α ext are related to dust storms at Ouagadougou, Dakar, and Agoufou and clearly linked to dust at Ilorin and Banizoumbou based on air mass back trajectories and observed seasonality (Ogunjobi et al, 2008). While Dakar is frequently influenced by air transported over the Atlantic Ocean (Ogunjobi et al, 2008), analysis off the coast of Dakar at Cape Verde found the AOD and aerosol mass loading were dominated by desert dust, with sea salt minimally contributing to AOD (6 %) in part due to its small extinction (Chiapello et al, 1999), which would also imply a minor influence on α ext .…”

Section: Western African Aeronet Aod and α Ext Observationsmentioning

confidence: 99%

“…The mean AERONET AOD in the northern African and Middle Eastern sites ( Ogunjobi et al, 2008). Whiskers are ±1 standard deviation across daily means within a given month.…”

Section: Northern Africa and Middle East Aeronet Aod And α Ext Observmentioning

confidence: 99%

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Evaluation of climate model aerosol seasonal and spatial variability over Africa using AERONET

et al. 2017

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Abstract. The sensitivity of climate models to the characterization of African aerosol particles is poorly understood. Africa is a major source of dust and biomass burning aerosols and this represents an important research gap in understanding the impact of aerosols on radiative forcing of the climate system. Here we evaluate the current representation of aerosol particles in the Conformal Cubic Atmospheric Model (CCAM) with ground-based remote retrievals across Africa, and additionally provide an analysis of observed aerosol optical depth at 550 nm (AOD 550 nm ) and Ångström exponent data from 34 Aerosol Robotic Network (AERONET) sites. Analysis of the 34 long-term AERONET sites confirms the importance of dust and biomass burning emissions to the seasonal cycle and magnitude of AOD 550 nm across the continent and the transport of these emissions to regions outside of the continent. In general, CCAM captures the seasonality of the AERONET data across the continent. The magnitude of modeled and observed multiyear monthly average AOD 550 nm overlap within ±1 standard deviation of each other for at least 7 months at all sites except the Réunion St Denis Island site (Réunion St. Denis). The timing of modeled peak AOD 550 nm in southern Africa occurs 1 month prior to the observed peak, which does not align with the timing of maximum fire counts in the region. For the western and northern African sites, it is evident that CCAM currently overestimates dust in some regions while others (e.g., the Arabian Peninsula) are better characterized. This may be due to overestimated dust lifetime, or that the characterization of the soil for these areas needs to be updated with local information. The CCAM simulated AOD 550 nm for the global domain is within the spread of previously published results from CMIP5 and AeroCom experiments for black carbon, organic carbon, and sulfate aerosols. The model's performance provides confidence for using the model to estimate largescale regional impacts of African aerosols on radiative forcing, but local feedbacks between dust aerosols and climate over northern Africa and the Mediterranean may be overestimated.

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Section: Western African Aeronet Aod and α Ext Observationssupporting

confidence: 71%

Section: Model-observation Comparisonsmentioning

confidence: 99%

Section: Western African Aeronet Aod and α Ext Observationsmentioning

confidence: 99%

“…The mean AERONET AOD in the northern African and Middle Eastern sites ( Ogunjobi et al, 2008). Whiskers are ±1 standard deviation across daily means within a given month.…”

Section: Northern Africa and Middle East Aeronet Aod And α Ext Observmentioning

confidence: 99%

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Evaluation of climate model aerosol seasonal and spatial variability over Africa using AERONET

et al. 2017

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“…Further, there may be strong local effects in regions with high aerosol loadings Haywood et al, 1999;Kaufman et al, 2002;Myhre et al, 2007;Myhre et al, 2003a, b;Yu et al, 2006). The radiative effect of aerosols in the Arctic may differ from other regions due to the high surface albedo of snow and ice and during the summer period due to the high solar zenith angle that strengthen the radiative effect of scattering aerosols (Haywood and Shine, 1997;Myhre and Stordal, 2001).…”

Section: Direct Radiative Forcing Of the May 2006 Eventmentioning

confidence: 99%

Regional aerosol optical properties and radiative impact of the extreme smoke event in the European Arctic in spring 2006

et al. 2007

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Abstract. In spring 2006 a special meteorological situation occurred in the European Arctic region giving record high levels of air pollution. The synoptic situation resulted in extensive transport of pollution predominantly from agricultural fires in Eastern Europe into the Arctic region and record high air-pollution levels were measured at the Zeppelin observatory at Ny-Ålesund (78 • 54 N, 11 • 53 E) in the period from 25 April to 12 May. In the present study we investigate the optical properties of the aerosols from this extreme event and we estimate the radiative forcing of this episode.We examine the aerosol optical properties from the source region and into the European Arctic and explore the evolution of the episode and the changes in the optical properties. A number of sites in Eastern Europe, Northern Scandinavia and Svalbard are included in the study. The observations show that the maximum AOD was from 2-3 May at all sites and varies from 0.52 to 0.87, and the correspondingÅngstrøm exponent was relatively large. Lidar measurements from Minsk, ALOMAR (Arctic Lidar Observatory for Middle Atmosphere Research at Andenes) and NyAlesund show that the aerosol layer was below 3 km at all sites the height is decreasing from the source region and into the Arctic. For the AERONET sites included (Minsk, Toravere, Hornsund) we have further studied the evolution of the aerosol size. The single scattering albedo at Svalbard is proCorrespondence to: C. Lund Myhre (clm@nilu.no) vided for two sites; Ny-Ålesund and Hornsund. Importantly the calculated single scattering albedo based on the aerosol chemical composition and size distribution from Ny-Ålesund and the AERONET measurements at Hornsund are consistent. We have found strong agreement between the satellite daily MODIS AOD and the ground-based AOD observations. This agreement is crucial for accurate radiative forcing calculations. We calculate a strong negative radiative forcing for the most polluted days employing the analysed ground based data, MODIS AOD and a multi-stream model for radiative transfer of solar radiation. During this specific pollution event the forcing reached values as low as −35 W m −2 in the region. For comparison, the direct forcing of a corresponding aerosol layer with a typical AOD of 0.05 for the season is around −5 W m −2 .

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Mesoscale modeling and satellite observation of transport and mixing of smoke and dust particles over northern sub‐Saharan African region

et al. 2013

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The transport and vertical distribution of smoke and dust aerosols over the northern sub‐Saharan African region are simulated in the Weather Research and Forecasting model with Chemistry (WRF‐Chem), which uses hourly dynamic smoke emissions from the Fire Locating and Modeling of Burning Emissions database derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) fire products. Model performance for February 2008 is evaluated using MODIS true color images, aerosol optical depth (AOD) measurements from the Aerosol Robotic Network, MODIS AOD retrievals, and the Cloud‐Aerosol Lidar data with Orthogonal Polarization (CALIOP) atmospheric backscattering and extinction products. Specification of smoke injection height of 650 m in WRF‐Chem yields aerosol vertical profiles that are most consistent with CALIOP observations of aerosol layer height. Between the equator and 10°N, Saharan dust is often mixed with smoke near the surface, and their transport patterns manifest the interplay of trade winds, subtropical highs, precipitation associated with the Intertropical Convergence Zone, and the high mountains located near the Great Rift Valley region. At the 700 hPa level and above, smoke layers spread farther to the north and south and are often above the dust layers over the Sahel region. In some cases, transported smoke can also be mixed with dust over the Saharan region. Statistically, 5% of the CALIOP valid measurements in February 2007–2011 show aerosol layers either above or between the clouds, reinforcing the importance of the aerosol vertical distribution for quantifying aerosol impact on climate in the Sahel region.

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Modeling the solar radiative impact of aerosols from biomass burning during the Southern African Regional Science Initiative (SAFARI‐2000) experiment

Cited by 89 publications

References 36 publications

Evaluation of climate model aerosol seasonal and spatial variability over Africa using AERONET

Evaluation of climate model aerosol seasonal and spatial variability over Africa using AERONET

Regional aerosol optical properties and radiative impact of the extreme smoke event in the European Arctic in spring 2006

Mesoscale modeling and satellite observation of transport and mixing of smoke and dust particles over northern sub‐Saharan African region

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