scholarly journals A multimodel assessment of the influence of regional anthropogenic emission reductions on aerosol direct radiative forcing and the role of intercontinental transport

2013 ◽  
Vol 118 (2) ◽  
pp. 700-720 ◽  
Author(s):  
Hongbin Yu ◽  
Mian Chin ◽  
J. Jason West ◽  
Cynthia S. Atherton ◽  
Nicolas Bellouin ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Anthropogenic Emission ◽  
Emission Reductions ◽  
Direct Radiative Forcing ◽  
Intercontinental Transport

scholarly journals Effects of black carbon mitigation on Arctic climate

2020 ◽  
Vol 20 (9) ◽  
pp. 5527-5546
Author(s):  
Thomas Kühn ◽  
Kaarle Kupiainen ◽  
Tuuli Miinalainen ◽  
Harri Kokkola ◽  
Ville-Veikko Paunu ◽  
...  
Keyword(s):  
Emission Reduction ◽  
Radiative Forcing ◽  
Arctic Climate ◽  
The Arctic ◽  
Arctic Council ◽  
Emission Reductions ◽  
Member States ◽  
Premature Deaths ◽  
Direct Radiative Forcing ◽  
Effective Radiative Forcing

Abstract. We use the ECHAM-HAMMOZ aerosol-climate model to assess the effects of black carbon (BC) mitigation measures on Arctic climate. To this end we constructed several mitigation scenarios that implement all currently existing legislation and then implement further reductions of BC in a successively increasing global area, starting from the eight member states of the Arctic Council, expanding to its active observer states, then to all observer states, and finally to the entire globe. These scenarios also account for the reduction of the co-emitted organic carbon (OC) and sulfate (SU). We find that, even though the additional BC emission reductions in the member states of the Arctic Council are small, the resulting reductions in Arctic BC mass burdens can be substantial, especially in the lower troposphere close to the surface. This in turn means that reducing BC emissions only in the Arctic Council member states can reduce BC deposition in the Arctic by about 30 % compared to the current legislation, which is about 60 % of what could be achieved if emissions were reduced globally. Emission reductions further south affect Arctic BC concentrations at higher altitudes and thus only have small additional effects on BC deposition in the Arctic. The direct radiative forcing scales fairly well with the total amount of BC emission reduction, independent of the location of the emission source, with a maximum direct radiative forcing in the Arctic of about −0.4 W m−2 for a global BC emission reduction. On the other hand, the Arctic effective radiative forcing due to the BC emission reductions, which accounts for aerosol–cloud interactions, is small compared to the direct aerosol radiative forcing. This happens because BC- and OC-containing particles can act as cloud condensation nuclei, which affects cloud reflectivity and lifetime and counteracts the direct radiative forcing of BC. Additionally, the effective radiative forcing is accompanied by very large uncertainties that originate from the strong natural variability of meteorology, cloud cover, and surface albedo in the Arctic. We further used the TM5-FASST model to assess the benefits of the aerosol emission reductions for human health. We found that a full implementation in all Arctic Council member and observer states could reduce the annual global number of premature deaths by 329 000 by the year 2030, which amounts to 9 % of the total global premature deaths due to particulate matter.

scholarly journals Snow-darkening versus direct radiative effects of mineral dust aerosol on the Indian summer monsoon onset: role of temperature change over dust sources

2019 ◽  
Vol 19 (3) ◽  
pp. 1605-1622 ◽  
Author(s):  
Zhengguo Shi ◽  
Xiaoning Xie ◽  
Xinzhou Li ◽  
Liu Yang ◽  
Xiaoxun Xie ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Central Asia ◽  
Black Carbon ◽  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Radiative Forcing ◽  
Indian Monsoon ◽  
Indian Subcontinent ◽  
Direct Radiative Forcing

Abstract. Atmospheric absorptive aerosols exert complicated effects on the climate system, two of which are through their direct radiative forcing and snow-darkening forcing. Compared to black carbon, the snow-darkening effect of dust on climate has been scarcely explored till now. When depositing in snow, dust can reduce the albedo of snow by darkening it and increasing the snowmelt. In this study, the snow-darkening effect of dust, as well as the direct radiative effect, on the Indian summer monsoon are evaluated by atmospheric general circulation model experiments. The results show that the snow-darkening and direct radiative forcing of dust both have significant impacts on the onset of the Indian monsoon, but they are distinctly opposite. The snow-darkening effect of dust weakens the Indian monsoon precipitation during May and June, opposite to black carbon. The surface temperature over central Asia and the western Tibetan Plateau becomes warmer due to the dust-induced decrease in snow cover, which leads to a local low-level cyclonic anomaly as well as an anticyclonic anomaly over the Indian subcontinent and Arabian Sea. This circulation pattern allows air currents penetrating into the Indian subcontinent more from central Asia but less from the Indian Ocean. In contrast, the direct radiative forcing of dust warms the low troposphere over the Arabian Peninsula, which intensifies moisture convergence and precipitation over the Indian monsoon region. The upper tropospheric atmospheric circulation over Asia is also sensitive to both effects. Compared to previous studies which emphasized the temperature over the Tibetan Plateau, our results further highlight an important role of surface/low tropospheric temperature changes over dust source areas, which can also significantly modify the response of summer monsoon. Thus, links between the climatic impact of dust and complicated thermal conditions over Asia are of importance and need to be clarified accurately.

scholarly journals Effects of Black Carbon Mitigation on Arctic Climate

2019 ◽  
Author(s):  
Thomas Kühn ◽  
Kaarle Kupiainen ◽  
Tuuli Miinalainen ◽  
Harri Kokkola ◽  
Ville-Veikko Paunu ◽  
...  
Keyword(s):  
Emission Reduction ◽  
Radiative Forcing ◽  
Arctic Climate ◽  
The Arctic ◽  
Council Member ◽  
Arctic Council ◽  
Emission Reductions ◽  
Member States ◽  
Direct Radiative Forcing ◽  
Effective Radiative Forcing

Abstract. We use the aerosol-climate model ECHAM-HAMMOZ to assess the effects of black carbon (BC) mitigation measures on Arctic climate. To this end we constructed several mitigation scenarios that implement all currently existing legislation and then implement further reductions of BC in a successively increasing global area, starting from the eight member states of the Arctic Council, expanding to its active observer states, then to all observer states, and finally to the entire globe. These scenarios also account for the reduction of the co-emitted organic carbon (OC) and sulphate (SU). We find that, even though the additional BC emission reductions in the member states of the Arctic Council are small, the resulting reductions in Arctic BC mass burdens can be substantial, especially in the lower atmosphere close to the surface. This in turn means that reducing BC emissions only in the Arctic Council member states can reduce BC deposition in the Arctic by about 30 % compared to the current legislation, which is about 60 % of what could be achieved if emissions were reduced globally. Emission reductions further south affect Arctic BC concentrations at higher altitudes and thus only have small additional effects on BC deposition in the Arctic. The direct radiative forcing scales fairly well with the total amount of BC emission reduction, independent of the location of the emission source, with a maximum direct radiative forcing in the Arctic of about 0.4 W/m2 for a global BC emission reduction. On the other hand, the Arctic effective radiative forcing due to the BC emission reductions, which accounts for aerosol-cloud interactions, is small compared to the direct aerosol radiative forcing. This happens because BC and OC containing particles can act as cloud condensation nuclei, which affects cloud reflectivity and lifetime, and counter-acts the direct radiative forcing of BC. Additionally the effective radiative forcing is accompanied by very large uncertainties that origin from the strong natural variability of meteorology, cloud cover, and surface albedo in the Arctic. We further used the model TM5-FASST to assess the benefits of the aerosol emission reductions on human health. We found that a full implementation in all Arctic Council member and observer states could reduce the annual global amount of premature deaths by 339 000 by 2030.

scholarly journals Snow-darkening versus direct radiative effects of mineral dust aerosol on the Indian summer monsoon: role of the Tibetan Plateau

2018 ◽  
Author(s):  
Zhengguo Shi ◽  
Xiaoning Xie ◽  
Xinzhou Li ◽  
Liu Yang ◽  
Xiaoxun Xie ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Central Asia ◽  
Snow Cover ◽  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Radiative Forcing ◽  
Indian Monsoon ◽  
Indian Subcontinent ◽  
Direct Radiative Forcing

Abstract. Mineral dust aerosol exerts complicated effects on the climate system and two of which are through their direct radiative forcing and snow-darkening forcing. Especially, the snow-darkening effect of dust on climate have been scarcely explored till now. When depositing in snow, dust can reduce the albedo of snow by darkening it and increase the snow melt. In this study, the snow-darkening effect of dust, as well as the direct radiative effect, on the Indian summer monsoon are evaluated by atmospheric general circulation model experiments, with a special focus on the role of Tibetan Plateau. The results show that, the snow-darkening and direct radiative forcing of dust have both significant impacts on the onset of Indian monsoon but they are distinctly opposite. The snow-darkening effect weakens the Indian monsoon precipitation during May and June while the direct radiative forcing intensifies it. The surface temperature over western Tibetan Plateau and Central Asia becomes warmer due to the dust-induced decrease in snow cover, which leads to a local low-level cyclonic anomaly as well as an anticyclonic anomaly over Indian subcontinent and Arabian Sea. This circulation pattern allows air current penetrating into Indian subcontinent more from Central Asia but less from Indian Ocean. In contrast, the direct radiative forcing of dust cools Tibetan Plateau and adjacent areas but warms Arabian Peninsular, which intensifies the moisture convergence and upward motion over Indian monsoon region. The upper tropospheric atmospheric circulation over Asia is also sensitive to both effects. Our results highlight a potential role of snow-albedo feedback in the effects of dust, which significantly amplifies the response of temperature over Tibetan Plateau. Thus, links between the climatic impact of dust, Tibetan Plateau thermal condition and surface snow cover are of importance and require to be clarified accurately.

scholarly journals Estimates of direct radiative forcing due to aerosols from the MERRA-2 reanalysis over the Amazon region

2018 ◽  
Author(s):  
Brunna Penna ◽  
Dirceu Herdies ◽  
Simone Costa
Keyword(s):  
Radiative Forcing ◽  
Reanalysis Data ◽  
Amazon Region ◽  
Reference State ◽  
Aerosol Radiative Forcing ◽  
Aerosol Loading ◽  
Direct Radiative Forcing ◽  
Direct Forcing ◽  
The Difference ◽  
Natural Aerosols

Abstract. Sixteen years of analysis of clear-sky direct aerosol radiative forcing is presented for the Amazon region, with calculations of AERONET network, MODIS sensor and MERRA-2 reanalysis data. The results showed that MERRA-2 reanalysis is an excellent tool for calculating and providing the spatial distribution of aerosol direct radiative forcing. In addition, the difference between considering the reference state of the atmosphere without aerosol loading and with natural aerosol to obtain the aerosol direct radiative forcing is discussed. During the dry season, the monthly average direct forcing at the top of atmosphere varied from −9.60 to −4.20 Wm−2, and at the surface, it varied from −29.81 to −9.24 Wm−2, according to MERRA-2 reanalysis data and the reference state of atmosphere without aerosol loading. Already with the state of reference being the natural aerosols, the average direct forcing at the top of atmosphere varied from −5.15 to −1.18 Wm−2, and at the surface, it varied from −21.28 to −5.25 Wm−2; this difference was associated with the absorption of aerosols.

scholarly journals Impact of Desert Dust Radiative Forcing on Sahel Precipitation: Relative Importance of Dust Compared to Sea Surface Temperature Variations, Vegetation Changes, and Greenhouse Gas Warming

2007 ◽  
Vol 20 (8) ◽  
pp. 1445-1467 ◽  
Author(s):  
Masaru Yoshioka ◽  
Natalie M. Mahowald ◽  
Andrew J. Conley ◽  
William D. Collins ◽  
David W. Fillmore ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
North Africa ◽  
Radiative Forcing ◽  
Sea Surface ◽  
Desert Dust ◽  
Direct Radiative Forcing ◽  
Sahel Region ◽  
Precipitation Reduction ◽  
Sahel Precipitation

Abstract The role of direct radiative forcing of desert dust aerosol in the change from wet to dry climate observed in the African Sahel region in the last half of the twentieth century is investigated using simulations with an atmospheric general circulation model. The model simulations are conducted either forced by the observed sea surface temperature (SST) or coupled with the interactive SST using the Slab Ocean Model (SOM). The simulation model uses dust that is less absorbing in the solar wavelengths and has larger particle sizes than other simulation studies. As a result, simulations show less shortwave absorption within the atmosphere and larger longwave radiative forcing by dust. Simulations using SOM show reduced precipitation over the intertropical convergence zone (ITCZ) including the Sahel region and increased precipitation south of the ITCZ when dust radiative forcing is included. In SST-forced simulations, on the other hand, significant precipitation changes are restricted to over North Africa. These changes are considered to be due to the cooling of global tropical oceans as well as the cooling of the troposphere over North Africa in response to dust radiative forcing. The model simulation of dust cannot capture the magnitude of the observed increase of desert dust when allowing dust to respond to changes in simulated climate, even including changes in vegetation, similar to previous studies. If the model is forced to capture observed changes in desert dust, the direct radiative forcing by the increase of North African dust can explain up to 30% of the observed precipitation reduction in the Sahel between wet and dry periods. A large part of this effect comes through atmospheric forcing of dust, and dust forcing on the Atlantic Ocean SST appears to have a smaller impact. The changes in the North and South Atlantic SSTs may account for up to 50% of the Sahel precipitation reduction. Vegetation loss in the Sahel region may explain about 10% of the observed drying, but this effect is statistically insignificant because of the small number of years in the simulation. Greenhouse gas warming seems to have an impact to increase Sahel precipitation that is opposite to the observed change. Although the estimated values of impacts are likely to be model dependent, analyses suggest the importance of direct radiative forcing of dust and feedbacks in modulating Sahel precipitation.

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