scholarly journals Effective radiative forcing in a GCM with fixed surface temperatures

2020 ◽  
Author(s):  
Timothy Andrews ◽  
Christopher J Smith ◽  
Gunnar Myhre ◽  
Piers Forster ◽  
Robin Chadwick
Keyword(s):  
Radiative Forcing ◽  
Surface Temperatures ◽  
Effective Radiative Forcing

scholarly journals Effective radiative forcing in a GCM with fixed surface temperatures

2020 ◽  
Author(s):  
Timothy Andrews ◽  
Christopher J Smith ◽  
Gunnar Myhre ◽  
Piers Forster ◽  
Robin Chadwick ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Surface Temperatures ◽  
Effective Radiative Forcing

scholarly journals Effective Radiative Forcing in a GCM With Fixed Surface Temperatures

2021 ◽  
Vol 126 (4) ◽  
Author(s):  
Timothy Andrews ◽  
Christopher J. Smith ◽  
Gunnar Myhre ◽  
Piers M. Forster ◽  
Robin Chadwick ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Surface Temperatures ◽  
Effective Radiative Forcing

scholarly journals A new approach for retrieving the UV–vis optical properties of ambient aerosols

2016 ◽  
Vol 9 (8) ◽  
pp. 3477-3490 ◽  
Author(s):  
Nir Bluvshtein ◽  
J. Michel Flores ◽  
Lior Segev ◽  
Yinon Rudich
Keyword(s):  
Optical Properties ◽  
Atmospheric Aerosols ◽  
Radiative Forcing ◽  
Complex Refractive Index ◽  
Single Scattering ◽  
Aerosol Size Distribution ◽  
Distribution Data ◽  
Ambient Aerosols ◽  
New Approach ◽  
Effective Radiative Forcing

Abstract. Atmospheric aerosols play an important part in the Earth's energy budget by scattering and absorbing incoming solar and outgoing terrestrial radiation. To quantify the effective radiative forcing due to aerosol–radiation interactions, researchers must obtain a detailed understanding of the spectrally dependent intensive and extensive optical properties of different aerosol types. Our new approach retrieves the optical coefficients and the single-scattering albedo of the total aerosol population over 300 to 650 nm wavelength, using extinction measurements from a broadband cavity-enhanced spectrometer at 315 to 345 nm and 390 to 420 nm, extinction and absorption measurements at 404 nm from a photoacoustic cell coupled to a cavity ring-down spectrometer, and scattering measurements from a three-wavelength integrating nephelometer. By combining these measurements with aerosol size distribution data, we retrieved the time- and wavelength-dependent effective complex refractive index of the aerosols. Retrieval simulations and laboratory measurements of brown carbon proxies showed low absolute errors and good agreement with expected and reported values. Finally, we implemented this new broadband method to achieve continuous spectral- and time-dependent monitoring of ambient aerosol population, including, for the first time, extinction measurements using cavity-enhanced spectrometry in the 315 to 345 nm UV range, in which significant light absorption may occur.

scholarly journals Improved Aerosol Processes and Effective Radiative Forcing in HadGEM3 and UKESM1

2018 ◽  
Vol 10 (11) ◽  
pp. 2786-2805 ◽  
Author(s):  
J. P. Mulcahy ◽  
C. Jones ◽  
A. Sellar ◽  
B. Johnson ◽  
I. A. Boutle ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Effective Radiative Forcing

scholarly journals Effective radiative forcing in the aerosol–climate model CAM5.3-MARC-ARG

2018 ◽  
Author(s):  
Benjamin S. Grandey ◽  
Daniel Rothenberg ◽  
Alexander Avramov ◽  
Qinjian Jin ◽  
Hsiang-He Lee ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Climate Model ◽  
Regional Distribution ◽  
Radiative Effect ◽  
Mixing State ◽  
Anthropogenic Aerosols ◽  
Effective Radiative Forcing ◽  
Aerosol Module ◽  
Aerosol Emissions ◽  
Global Mean

Abstract. We quantify the effective radiative forcing (ERF) of anthropogenic aerosols modelled by the aerosol–climate model CAM5.3-MARC-ARG. CAM5.3-MARC-ARG is a new configuration of the Community Atmosphere Model version 5.3 (CAM5.3) in which the default aerosol module has been replaced by the two-Moment, Multi-Modal, Mixing-state-resolving Aerosol model for Research of Climate (MARC). CAM5.3-MARC-ARG uses the default ARG aerosol activation scheme, consistent with the default configuration of CAM5.3. We compute differences between simulations using year-1850 aerosol emissions and simulations using year-2000 aerosol emissions in order to assess the radiative effects of anthropogenic aerosols. We compare the aerosol column burdens, cloud properties, and radiative effects produced by CAM5.3-MARC-ARG with those produced by the default configuration of CAM5.3, which uses the modal aerosol module with three log-normal modes (MAM3). Compared with MAM3, we find that MARC produces stronger cooling via the direct radiative effect, stronger cooling via the surface albedo radiative effect, and stronger warming via the cloud longwave radiative effect. The global mean cloud shortwave radiative effect is similar between MARC and MAM3, although the regional distributions differ. Overall, MARC produces a global mean net ERF of −1.75 ± 0.04 W m−2, which is stronger than the global mean net ERF of −1.57 ± 0.04 W m−2 produced by MAM3. The regional distribution of ERF also differs between MARC and MAM3, largely due to differences in the regional distribution of the cloud shortwave radiative effect. We conclude that the specific representation of aerosols in global climate models, including aerosol mixing state, has important implications for climate modelling.

scholarly journals Quantifying cloud adjustments and the radiative forcing due to aerosol–cloud interactions in satellite observations of warm marine clouds

2020 ◽  
Vol 20 (10) ◽  
pp. 6225-6241 ◽  
Author(s):  
Alyson Douglas ◽  
Tristan L'Ecuyer
Keyword(s):  
Radiative Forcing ◽  
Local Environment ◽  
Satellite Observations ◽  
Cloud Environment ◽  
Climate Scenarios ◽  
Liquid Water Path ◽  
Sources Of Uncertainty ◽  
Aerosol Cloud ◽  
Effective Radiative Forcing ◽  
Aerosol Cloud Interactions

Abstract. Aerosol–cloud interactions and their resultant forcing remains one of the largest sources of uncertainty in future climate scenarios. The effective radiative forcing due to aerosol–cloud interactions (ERFaci) is a combination of two different effects, namely how aerosols modify cloud brightness (RFaci, intrinsic) and how cloud extent reacts to aerosol (cloud adjustments CA; extrinsic). Using satellite observations of warm clouds from the NASA A-Train constellation from 2007 to 2010 along with MERRA-2 Reanalysis and aerosol from the SPRINTARS model, we evaluate the ERFaci in warm, marine clouds and its components, the RFaciwarm and CAwarm, while accounting for the liquid water path and local environment. We estimate the ERFaciwarm to be -0.32±0.16 Wm−2. The RFaciwarm dominates the ERFaciwarm contributing 80 % (-0.21±0.15 Wm−2), while the CAwarm enhances this cooling by 20 % (-0.05±0.03 Wm−2). Both the RFaciwarm and CAwarm vary in magnitude and sign regionally and can lead to opposite, negating effects under certain environmental conditions. Without considering the two terms separately and without constraining cloud–environment interactions, weak regional ERFaciwarm signals may be erroneously attributed to a damped susceptibility to aerosol.

scholarly journals Investigation of short-term effective radiative forcing of fire aerosols over North America using nudged hindcast ensembles

2017 ◽  
Author(s):  
Yawen Liu ◽  
Kai Zhang ◽  
Yun Qian ◽  
Yuhang Wang ◽  
Yufei Zou ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Climate Model ◽  
Analysis Data ◽  
Ensemble Spread ◽  
Short Term ◽  
Large Ensemble ◽  
Southern Mexico ◽  
Aerosol Radiative Forcing ◽  
Fire Emissions ◽  
Effective Radiative Forcing

Abstract. Aerosols from fire emissions can potentially have large impact on clouds and radiation. However, fire aerosol sources are often intermittent and their effect on weather and climate is difficult to quantify. Here we investigated the short-term effective radiative forcing of fire aerosols using the global aerosol-climate model Community Atmosphere Model Version 5 (CAM5). Different from previous studies, we used nudged hindcast ensembles to quantify the forcing uncertainty due to the chaotic response to small perturbations in the atmosphere state. Daily mean emissions from three fire inventories were used to consider the uncertainty in emission strength and injection heights. The simulated aerosol optical depth (AOD) and mass concentrations were evaluated against in-situ measurements and re-analysis data. Overall, the results show the model has reasonably good predicting skills. Short (10-day) nudged ensemble simulations were then performed with and without fire emissions to estimate the effective radiative forcing. Results show fire aerosols have large effects on both liquid and ice clouds over the two selected regions in April 2009. For the 10-day average, we found a large ensemble spread of regional mean shortwave cloud radiative effect over Southern Mexico (15.6 %) and the Central U.S. (64.3 %), despite that the regional mean AOD time series are almost indistinguishable during the 10-day period. Moreover, the ensemble spread is much larger when using daily averages instead of 10-day averages. For the case investigated here, a minimum of 9 ensemble members is necessary to get a reasonable estimate of the ensemble mean and spread of the forcing on individual days. This demonstrates the importance of using a large ensemble of simulations to estimate the short-term effective aerosol radiative forcing.

scholarly journals Snow-induced buffering in aerosol–cloud interactions

2020 ◽  
Author(s):  
Takuro Michibata ◽  
Kentaroh Suzuki ◽  
Toshihiko Takemura
Keyword(s):  
Radiative Forcing ◽  
General Circulation ◽  
State Of The Art ◽  
General Circulation Models ◽  
Regional Pattern ◽  
Cloud Droplets ◽  
Microphysical Process ◽  
Aerosol Cloud ◽  
Effective Radiative Forcing ◽  
Aerosol Cloud Interactions

Abstract. Complex aerosol–cloud–precipitation interactions lead to large differences in estimates of aerosol impacts on climate among general circulation models (GCMs) and satellite retrievals. Typically, precipitating hydrometeors are treated diagnostically in most GCMs, and their radiative effects are ignored. Here, we quantify how the treatment of precipitation influences the simulated effective radiative forcing due to aerosol–cloud interactions (ERFaci) using a state-of-the-art GCM with a two-moment prognostic precipitation scheme that incorporates the radiative effect of precipitating particles, and investigate how microphysical process representations are related to macroscopic climate effects. Prognostic precipitation substantially weakens the magnitude of ERFaci (by approximately 75 %) compared with the traditional diagnostic scheme, and this is the result of the increased longwave (warming) and weakened shortwave (cooling) components of ERFaci. The former is attributed to additional adjustment processes induced by falling snow, and the latter stems largely from riming of snow by collection of cloud droplets. The significant reduction in ERFaci does not occur without prognostic snow, which contributes mainly by buffering the cloud response to aerosol perturbations through depleting cloud water via collection. Prognostic precipitation also alters the regional pattern of ERFaci, particularly over northern mid-latitudes where snow is abundant. The treatment of precipitation is thus a highly influential controlling factor of ERFaci, contributing more than other uncertain tunable processes related to aerosol–cloud–precipitation interactions. This change in ERFaci caused by the treatment of precipitation is large enough to explain the existing difference in ERFaci between GCMs and observations.

scholarly journals Response to marine cloud brightening in a multi-model ensemble

2018 ◽  
Vol 18 (2) ◽  
pp. 621-634 ◽  
Author(s):  
Camilla W. Stjern ◽  
Helene Muri ◽  
Lars Ahlm ◽  
Olivier Boucher ◽  
Jason N. S. Cole ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Cloud Droplet ◽  
Model Ensemble ◽  
Low Clouds ◽  
Precipitation Decrease ◽  
Intercomparison Project ◽  
Cloud Droplet Number Concentration ◽  
Significant Temperature ◽  
Effective Radiative Forcing ◽  
Subtropical Oceans

Abstract. Here we show results from Earth system model simulations from the marine cloud brightening experiment G4cdnc of the Geoengineering Model Intercomparison Project (GeoMIP). The nine contributing models prescribe a 50 % increase in the cloud droplet number concentration (CDNC) of low clouds over the global oceans in an experiment dubbed G4cdnc, with the purpose of counteracting the radiative forcing due to anthropogenic greenhouse gases under the RCP4.5 scenario. The model ensemble median effective radiative forcing (ERF) amounts to −1.9 W m−2, with a substantial inter-model spread of −0.6 to −2.5 W m−2. The large spread is partly related to the considerable differences in clouds and their representation between the models, with an underestimation of low clouds in several of the models. All models predict a statistically significant temperature decrease with a median of (for years 2020–2069) −0.96 [−0.17 to −1.21] K relative to the RCP4.5 scenario, with particularly strong cooling over low-latitude continents. Globally averaged there is a weak but significant precipitation decrease of −2.35 [−0.57 to −2.96] % due to a colder climate, but at low latitudes there is a 1.19 % increase over land. This increase is part of a circulation change where a strong negative top-of-atmosphere (TOA) shortwave forcing over subtropical oceans, caused by increased albedo associated with the increasing CDNC, is compensated for by rising motion and positive TOA longwave signals over adjacent land regions.

Effective radiative forcing from historical land use change

2016 ◽  
Vol 48 (11-12) ◽  
pp. 3489-3505 ◽  
Author(s):  
Timothy Andrews ◽  
Richard A. Betts ◽  
Ben B. B. Booth ◽  
Chris D. Jones ◽  
Gareth S. Jones
Keyword(s):  
Land Use ◽  
Land Use Change ◽  
Radiative Forcing ◽  
Effective Radiative Forcing ◽  
Historical Land Use
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