Standard climate models radiation codes underestimate black carbon radiative forcing

Myhre, Gunnar; Samset, B. H.

doi:10.5194/acp-15-2883-2015

Cited by 31 publications

(15 citation statements)

References 28 publications

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“…First, the OsloCTM2 results are derived using an eight‐stream radiative transfer model, while the radiation scheme in CAM4 is two‐stream only. This was recently found to cause a 10% difference for global, annual mean modeled BC RF due to multiple scattering over high‐albedo surfaces [ Myhre and Samset , ]. For Figure a, we performed a calculation with the OsloCTM2 code in two‐stream mode.…”

Section: Discussionmentioning

confidence: 99%

Climate response to externally mixed black carbon as a function of altitude

Samset

Myhre

2015

JGR Atmospheres

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The climate response to the presence of black carbon (BC) aerosol at a given altitude in the atmosphere is investigated using a global circulation model. The vertical dependence of the efficiency with which BC exerts radiative forcing (RF) through the direct aerosol effect has previously been extensively studied. Here we use the Community Atmosphere Model version 4 atmospheric component of the National Center for Atmospheric Research Community Earth System model version 1.03 to calculate the three-dimensional response to a BC layer inserted at various altitudes. Simulations have been performed both for fixed sea surface temperatures and using a slab ocean setup to include the surface temperature response. We investigate the vertical profiles of RF exerted per gram of externally mixed BC due to both the direct and semidirect aerosol effects. Associated changes in cloud cover, relative humidity, and precipitation are discussed. The precipitation response to BC is decomposed into a fast, stability-related change and a slow, temperature-driven component. We find that while the efficiency of BC to exert positive RF due to the direct effect strengthens with altitude, as in previous studies, it is strongly offset by a negative semidirect effect. The net radiative perturbation of BC at top of atmosphere is found to be positive everywhere below the tropopause and negative above. The global, annual mean precipitation response to BC, after equilibration of a slab ocean, is found to be positive between the surface and 900 hPa but negative at all other altitudes.

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Section: Discussionmentioning

confidence: 99%

Climate response to externally mixed black carbon as a function of altitude

Samset

Myhre

2015

JGR Atmospheres

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“…The 1‐D radiative transfer equation was solved using a six‐stream discrete ordinates radiative transfer solver developed by Stamnes et al []. Myhre and Samset [] showed that the commonly used two‐stream codes lead to approximately 15% underestimation in absorbing aerosol DRE. Surface type and albedo were obtained from the International Geosphere‐Biosphere Programme library, which contains 20 surface types [ Loveland and Belward , ].…”

Section: Methodsmentioning

confidence: 99%

Contribution of brown carbon and lensing to the direct radiative effect of carbonaceous aerosols from biomass and biofuel burning emissions

et al. 2015

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We present global direct radiative effect (DRE) calculations of carbonaceous aerosols emitted from biomass/biofuel burning addressing the interplay between two poorly constrained contributions to DRE: mixing state of black carbon (lensing) and light absorption by organic aerosol (OA) due to the presence of brown carbon (BrC). We use the parameterization of Saleh et al. (2014) which captures the variability in biomass/biofuel OA absorption. The global mean effect of OA absorption is +0.22 W/m2 and +0.12 W/m2 for externally and internally mixed cases, while the effect of lensing is +0.39 W/m2 and +0.29 W/m2 for nonabsorbing and absorbing OA cases, signifying the nonlinear interplay between OA absorption and lensing. These two effects can be overestimated if not treated simultaneously in radiative transfer calculations. The combined effect of OA absorption and lensing increases the global mean DRE of biomass/biofuel aerosols from −0.46 W/m2 to +0.05 W/m2 and appears to reduce the gap between existing model‐based and observationally constrained DRE estimates. We observed a strong sensitivity to these parameters in key regions, where DRE shifts from strongly negative (< −1 W/m2) to strongly positive (> +1 W/m2) when accounting for lensing and OA absorption.

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“…Elevating small sensors above ground level has significant benefits for atmosphere physics, especially when it comes to aerosol research. Complex interactions between aerosols and solar radiation, together with very limited measurement options of vertical profiles of aerosols' optical and microphysical properties, make understanding and modeling Earth's climate difficult (Bond et al 2013;IPCC 2013;Koch and Del Genio 2010;Myhre and Samset 2015). Columnar integrated data are available for many properties, but it is important to remember that for some aerosols, such as absorption of black carbon (BC), vertical distribution is even more important than total columnar values (Samset and Myhre 2011;Samset et al 2013;Zarzycki and Bond 2010;Cook and Highwood 2004).…”

Section: Introductionmentioning

confidence: 99%

UAS as a Support for Atmospheric Aerosols Research: Case Study

Chiliński

Markowicz

Kubicki

2018

Pure Appl. Geophys.

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Abstract-Small drones (multi-copters) have the potential to deliver valuable data for atmospheric research. They are especially useful for collecting vertical profiles of optical and microphysical properties of atmospheric aerosols. Miniaturization of sensors, such as aethalometers and particle counters, allows for collecting profiles of black carbon concentration, absorption coefficient, and particle size distribution. Vertical variability of single-scattering properties has a significant impact on radiative transfer and Earth's climate, but the base of global measurements is very limited. This results in high uncertainties of climate/radiation models. Vertical range of modern multi-copters is up to 2000 m, which is usually enough to study aerosols up to the top of planetary boundary layer on middle latitudes. In this study, we present the benefits coming from usage of small drones in atmospheric research. The experiment, described as a case study, was conducted at two stations (Swider and Warsaw) in Poland, from October 2014 to March 2015. For over 6 months, photoacoustic extinctiometers collected data at both stations. This enabled us to compare the stations and to establish ground reference of black carbon concentrations for vertical profiles collected by ceilometer and drone. At Swider station, we used Vaisala CL-31 ceilometer. It delivered vertical profiles of range corrected signal, which were analysed together with profiles acquired by micro-aethalometer AE-51 and Vaisala RS92-SGP radiosonde carried by a hexacopter drone. Near to the surface, black carbon gradient of % 400 (lg/m 3 )/100 m was detected, which was below the ceilometer minimal altitude of detection. This confirmed the usefulness of drones and potential of their support for remote sensing techniques.

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Standard climate models radiation codes underestimate black carbon radiative forcing

Cited by 31 publications

References 28 publications

Climate response to externally mixed black carbon as a function of altitude

Climate response to externally mixed black carbon as a function of altitude

Contribution of brown carbon and lensing to the direct radiative effect of carbonaceous aerosols from biomass and biofuel burning emissions

UAS as a Support for Atmospheric Aerosols Research: Case Study

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