scholarly journals Influence of anthropogenic aerosols on the Asian monsoon: a case study using the WRF-Chem model

2013 ◽  
Vol 13 (8) ◽  
pp. 21383-21425 ◽  
Author(s):  
X. Jiang ◽  
M. C. Barth ◽  
C. Wiedinmyer ◽  
S. T. Massie
Keyword(s):  
East Asia ◽  
Radiative Forcing ◽  
Asian Monsoon ◽  
Anthropogenic Activities ◽  
Cloud Droplet ◽  
Cloud Base ◽  
Monsoon Precipitation ◽  
Anthropogenic Aerosols ◽  
Source Regions ◽  
Local Emissions

Abstract. Aerosols, in particular those related to anthropogenic activities, including black carbon, organic carbon, and sulfate aerosols, have been found to affect the Asian monsoon through direct and indirect aerosol radiative forcing. In this work, we use the coupled regional Weather Research and Forecasting model with Chemistry (WRF-Chem) to understand how aerosol changes from local emission sources could modulate the Asian monsoon precipitation through aerosol direct and indirect radiative effects. Our modeling results with the consideration of the local emissions show an improvement in simulated monsoon precipitation, when compared to reanalysis data and satellite observations. Aerosols generally induce a reduction in pre-monsoon and monsoon precipitation in East Asia. Over the Indian region, local anthropogenic emissions tend to reduce precipitation in the source regions while slightly increasing precipitation outside of the emission source regions. The increase in precipitation corresponds to a decrease in the cloud base level or lifting condensation level. Analysis of vertical cloud properties suggests that the increased cloud droplet number and prolonged cloud lifetime/reduced precipitation efficiency due to the local aerosol emissions are responsible for the precipitation reduction over East Asia. Aerosols from local emissions also play a very important role in the simulated surface temperature, radiation, and monsoon circulations.

scholarly journals Global and regional radiative forcing from 20 % reductions in BC, OC and SO<sub>4</sub> – an HTAP2 multi-model study

2016 ◽  
Author(s):  
Camilla Weum Stjern ◽  
Bjørn Hallvard Samset ◽  
Gunnar Myhre ◽  
Huisheng Bian ◽  
Mian Chin ◽  
...  
Keyword(s):  
East Asia ◽  
Radiative Forcing ◽  
General Circulation ◽  
Anthropogenic Aerosols ◽  
Aerosol Forcing ◽  
Source Regions ◽  
Model Study ◽  
Range Transport ◽  
Emission Changes ◽  
The Impact

Abstract. In the Hemispheric Transport of Air Pollution Phase 2 (HTAP) exercise, a range of global atmospheric general circulation and chemical transport models performed coordinated perturbation experiments with 20 % reductions in emissions of anthropogenic aerosols, or aerosol precursors, in a number of source regions. Here, we compare the resulting changes in the atmospheric load and vertically resolved profiles of black carbon (BC), organic aerosols (OA) and sulfate (SO4) from 10 models that include treatment of aerosols. We use a set of temporally, horizontally and vertically resolved profiles of aerosol forcing efficiency (AFE) to estimate the impact of emission changes in six major source regions on global radiative forcing (RF) pertaining to the direct aerosol effect. Results show that mitigations in South and East Asia have substantial impacts on the radiative budget in all investigated receptor regions, especially for BC. In Russia and the Middle East, more than 80 % of the forcing for BC and OA is due to extra-regional emission reductions. Similarly, for North America, BC emissions control in East Asia is found to be more important than domestic mitigations, which is consistent with previous findings. Comparing fully resolved RF calculations to RF estimates based on vertically averaged AFE profiles allows us to quantify the importance of vertical resolution to RF estimates. We find that locally in the source regions, a 20 % emission reduction strengthens the radiative forcing associated with SO4 by 25 % when including the vertical dimension, as the AFE for SO4 is strongest near the surface. Conversely, the local RF from BC weakens by 37 % since BC AFE is low close to the ground. The influence of inter-continental transport on BC forcing, however, is enhanced by one third when accounting for the vertical aspect, because long-range transport leads primarily to aerosol changes at high altitudes, where the BC AFE is strong.

scholarly journals Global and regional radiative forcing from 20 % reductions in BC, OC and SO<sub>4</sub> – an HTAP2 multi-model study

2016 ◽  
Vol 16 (21) ◽  
pp. 13579-13599 ◽  
Author(s):  
Camilla Weum Stjern ◽  
Bjørn Hallvard Samset ◽  
Gunnar Myhre ◽  
Huisheng Bian ◽  
Mian Chin ◽  
...  
Keyword(s):  
East Asia ◽  
Radiative Forcing ◽  
General Circulation ◽  
Temperature Response ◽  
Anthropogenic Aerosols ◽  
Aerosol Forcing ◽  
Source Regions ◽  
Intercontinental Transport ◽  
Emission Changes ◽  
The Impact

Abstract. In the Hemispheric Transport of Air Pollution Phase 2 (HTAP2) exercise, a range of global atmospheric general circulation and chemical transport models performed coordinated perturbation experiments with 20 % reductions in emissions of anthropogenic aerosols, or aerosol precursors, in a number of source regions. Here, we compare the resulting changes in the atmospheric load and vertically resolved profiles of black carbon (BC), organic aerosols (OA) and sulfate (SO4) from 10 models that include treatment of aerosols. We use a set of temporally, horizontally and vertically resolved profiles of aerosol forcing efficiency (AFE) to estimate the impact of emission changes in six major source regions on global radiative forcing (RF) pertaining to the direct aerosol effect, finding values between. 51.9 and 210.8 mW m−2 Tg−1 for BC, between −2.4 and −17.9 mW m−2 Tg−1 for OA and between −3.6 and −10.3 W m−2 Tg−1 for SO4. In most cases, the local influence dominates, but results show that mitigations in south and east Asia have substantial impacts on the radiative budget in all investigated receptor regions, especially for BC. In Russia and the Middle East, more than 80 % of the forcing for BC and OA is due to extra-regional emission reductions. Similarly, for North America, BC emissions control in east Asia is found to be more important than domestic mitigations, which is consistent with previous findings. Comparing fully resolved RF calculations to RF estimates based on vertically averaged AFE profiles allows us to quantify the importance of vertical resolution to RF estimates. We find that locally in the source regions, a 20 % emission reduction strengthens the radiative forcing associated with SO4 by 25 % when including the vertical dimension, as the AFE for SO4 is strongest near the surface. Conversely, the local RF from BC weakens by 37 % since BC AFE is low close to the ground. The fraction of BC direct effect forcing attributable to intercontinental transport, on the other hand, is enhanced by one-third when accounting for the vertical aspect, because long-range transport primarily leads to aerosol changes at high altitudes, where the BC AFE is strong. While the surface temperature response may vary with the altitude of aerosol change, the analysis in the present study is not extended to estimates of temperature or precipitation changes.

scholarly journals Simulation of dust aerosol and its regional feedbacks over East Asia using a regional climate model

2008 ◽  
Vol 8 (2) ◽  
pp. 4625-4667 ◽  
Author(s):  
D. F. Zhang ◽  
A. S. Zakey ◽  
X. J. Gao ◽  
F. Giorgi
Keyword(s):  
East Asia ◽  
Regional Climate Model ◽  
Radiative Forcing ◽  
Climate Model ◽  
Regional Climate ◽  
Surface Cooling ◽  
Near Surface ◽  
Dust Aerosols ◽  
Source Regions ◽  
Mass Load

Abstract. The ICTP regional climate model (RegCM3) coupled with a desert dust model is used to simulate the radiative forcing and related climate effects of dust aerosols over East Asia. Two sets of experiments encompassing the main dust producing months, February to May, for 10 years (1997–2006) are conducted and inter-compared, one without (Exp. 1) and one with (Exp. 2) the radiative effects of dust aerosols. The simulation results are evaluated against ground station and satellite data. The model captures the basic observed climatology over the area of interest. The spatial and temporal variations of near surface concentration, mass load, and emission of dust aerosols from the main source regions are reproduced by model, with the main model deficiency being an overestimate of dust amount over the source regions and underestimate downwind of these source areas. Both the top-of-the-atmosphere (TOA) and surface radiative fluxes are decreased by dust and this causes a surface cooling locally up to −1°C. The inclusion of dust radiative forcing leads to a reduction of dust emission in the East Asia source regions, which is mainly caused by an increase in local stability and a corresponding decrease in dust lifting. Our results indicate that dust effects should be included in the assessment of climate change over East Asia.

scholarly journals The effects of aerosols on water cloud microphysics and macrophysics based on satellite observations over East Asia and the North Pacific

2014 ◽  
Vol 14 (7) ◽  
pp. 10515-10541 ◽  
Author(s):  
T. Michibata ◽  
K. Kawamoto ◽  
T. Takemura
Keyword(s):  
East Asia ◽  
North Pacific ◽  
Vertical Structure ◽  
Cloud Droplet ◽  
Cloud Microphysics ◽  
Satellite Observations ◽  
Cloud Base ◽  
Seasonal Differences ◽  
The North ◽  
The North Pacific

Abstract. This study examines the characteristics of the microphysics and macrophysics of water clouds from East Asia to the North Pacific, using data from satellite observations. Our goals are to clarify differences in microphysics and macrophysics between land and oceanic clouds, seasonal differences unique to the mid-latitudes, characteristics of the drizzling process, and cloud vertical structure. In pristine oceanic areas, fractional occurrences of cloud optical thickness (COT) and cloud droplet effective radius (CDR) increase systematically with an increase in drizzle intensity, but in polluted land areas these characteristics of the COT and CDR transition are not as evident. Additionally, regional and seasonal differences are identified in terms of drizzle intensity as a function of the liquid water path (LWP) and cloud droplet number concentration (Nc). The correlations between drizzle intensity and LWP, and between drizzle intensity and Nc are both more robust over oceanic areas than over land areas. We also demonstrate regional and seasonal characteristics of the cloud vertical structure. As a result, we find aerosol–cloud interaction mainly occurs around the cloud base in polluted land areas during the winter season. In addition, a difference between polluted and pristine areas in the efficiency of cloud droplet growth is confirmed. These results suggest that water clouds over the mid-latitudes exhibit a different drizzle system to those over the tropics.

scholarly journals Long-range transport of anthropogenic air pollutants into the marine air: insight into fine particle transport and chloride depletion on sea salts

2021 ◽  
Vol 21 (23) ◽  
pp. 17715-17726
Author(s):  
Liang Xu ◽  
Xiaohuan Liu ◽  
Huiwang Gao ◽  
Xiaohong Yao ◽  
Daizhou Zhang ◽  
...  
Keyword(s):  
East Asia ◽  
Long Range ◽  
Air Pollutants ◽  
Radiative Forcing ◽  
Eastern China ◽  
Long Range Transport ◽  
Anthropogenic Aerosols ◽  
Range Transport ◽  
Anthropogenic Air Pollutants ◽  
Marine Air

Abstract. Long-range transport of anthropogenic air pollutants from East Asia can affect the downwind marine air quality during spring and winter. Long-range transport of continental air pollutants and their interaction with sea salt aerosol (SSA) significantly modify the radiative forcing of marine aerosols and influence ocean biogeochemical cycling. Previous studies poorly characterize variations of aerosol particles along with air mass transport from the continental edge to the remote ocean. Here, the research ship R/V Dongfanghong 2 traveled from the eastern China seas (ECS) to the northwestern Pacific Ocean (NWPO) to understand what and how air pollutants were transported from the highly polluted continental air to clean marine air in spring. A transmission electron microscope (TEM) was used to find the long-range transported anthropogenic particles and the possible Cl-depletion phenomenon of SSA in marine air. Anthropogenic aerosols (e.g., sulfur (S)-rich, S-soot, S-metal/fly ash, organic matter (OM)-S, and OM coating particles) were identified and dramatically declined from 87 % to 8 % by number from the ECS to remote NWPO. For the SSA aging, 87 % of SSA particles in the ECS were identified as fully aged, while the proportion of fully aged SSA particles in the NWPO decreased to 29 %. Our results highlight that anthropogenic acidic gases in the troposphere (e.g., SO2, NOx, and volatile organic compounds) could be transported to remote marine air and exert a significant impact on aging of SSA particles in the NWPO. The study shows that anthropogenic particles and gases from East Asia significantly perturb different aerosol chemistry from coastal to remote marine air. More attention should be given to the modification of SSA particles in remote marine areas due to the influence of anthropogenic gaseous pollutants.

scholarly journals Impact of natural and anthropogenic aerosols on stratocumulus and precipitation in the Southeast Pacific: a regional modelling study using WRF-Chem

2012 ◽  
Vol 12 (6) ◽  
pp. 14623-14667 ◽  
Author(s):  
Q. Yang ◽  
W. I. Gustafson ◽  
J. D. Fast ◽  
H. Wang ◽  
R. C. Easter ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Fold Increase ◽  
Sea Salt ◽  
Cloud Base ◽  
Anthropogenic Emissions ◽  
Entrainment Rate ◽  
Moderate Increase ◽  
Anthropogenic Aerosols ◽  
Aerosol Cloud ◽  
Southeast Pacific

Abstract. Cloud-system resolving simulations with the chemistry version of the Weather Research and Forecasting (WRF-Chem) model are used to quantify the relative impacts of regional anthropogenic and oceanic emissions on changes in aerosol properties, cloud macro- and microphysics, and cloud radiative forcing over the Southeast Pacific (SEP) during the VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx) (15 October–16 November 2008). Two distinct regions are identified. The near-coast polluted region is characterized by the strong suppression of non-sea-salt particle activation due to sea-salt particles, a dominant role of first over second indirect effects, low surface precipitation rates, and limited impact of aerosols associated with anthropogenic emissions on clouds. The effects of natural marine aerosols on cloud properties (e.g., cloud optical depth and cloud-top and cloud-base heights), precipitation, and the top of atmosphere and surface shortwave fluxes counteract those of anthropogenic aerosols over this region. The relatively clean remote region is characterized by large contributions of aerosols from non-local sources (lateral boundaries), much stronger drizzle at the surface, and high aerosol-cloud-precipitation interactions under a scenario of five-fold increase in anthropogenic emissions. Clouds in this clean region are quite sensitive (e.g., a 13% increase in cloud-top height and a 9% increase in surface albedo) to a moderate increase (25% of the reference case) in cloud condensation nuclei (CCN) concentration produced by a five-fold increase in regional anthropogenic emissions. The reduction of precipitation due to this increase in anthropogenic aerosols more than doubles the aerosol lifetime in the clean marine boundary layer. Therefore, the aerosol impacts on precipitation are amplified by the positive feedback of precipitation on aerosol, which ultimately alters the cloud micro- and macro-physical properties, leading to strong aerosol-cloud-precipitation interactions. The high sensitivity is also related to an increase in cloud-top entrainment rate (by 16% at night) due to the increased anthropogenic aerosols. The simulated aerosol-cloud-precipitation interactions due to the increased anthropogenic aerosols have a stronger diurnal cycle over the clean region compared to the near-coast region with stronger interactions at night. During the day, solar heating results in more frequent decoupling of the cloud and sub-cloud layers, thinner clouds, reduced precipitation, and reduced sensitivity to the increase in anthropogenic emissions. The results of this study imply that the energy balance perturbations from increased anthropogenic emissions are larger in the more susceptible clean environment than in already polluted environment and is larger than possible from first indirect effect alone.

scholarly journals Addressing the difficulties in quantifying the Twomey effect for marine warm clouds from multi-sensor satellite observations and reanalysis

2022 ◽  
Author(s):  
Hailing Jia ◽  
Johannes Quaas ◽  
Edward Gryspeerdt ◽  
Christoph Böhm ◽  
Odran Sourdeval
Keyword(s):  
Radiative Forcing ◽  
Cloud Droplet ◽  
Influential Factors ◽  
Satellite Observations ◽  
Cloud Base ◽  
Aerosol Cloud ◽  
Spatio Temporal ◽  
Observational Estimate ◽  
Aerosol Cloud Interactions ◽  
Aerosol Effects

Abstract. Aerosol–cloud interaction is the most uncertain component of the overall anthropogenic forcing of the climate, in which the Twomey effect plays a fundamental role. Satellite-based estimates of the Twomey effect are especially challenging, mainly due to the difficulty in disentangling aerosol effects on cloud droplet number concentration (Nd) from possible confounders. By combining multiple satellite observations and reanalysis, this study investigates the impacts of a) updraft, b) precipitation, c) retrieval errors, as well as (d) vertical co-location between aerosol and cloud, on the assessment of Nd-toaerosol sensitivity (S) in the context of marine warm (liquid) clouds. Our analysis suggests that S increases remarkably with both cloud base height and cloud geometric thickness (proxies for vertical velocity at cloud base), consistent with stronger aerosol-cloud interactions at larger updraft velocity. In turn, introducing the confounding effect of aerosol–precipitation interaction can artificially amplify S by an estimated 21 %, highlighting the necessity of removing precipitating clouds from analyses on the Twomey effect. It is noted that the retrieval biases in aerosol and cloud appear to underestimate S, in which cloud fraction acts as a key modulator, making it practically difficult to balance the accuracies of aerosol–cloud retrievals at aggregate scales (e.g., 1° × 1° grid). Moreover, we show that using column-integrated sulfate mass concentration (SO4C) to approximate sulfate concentration at cloud base (SO4B) can result in a degradation of correlation with Nd, along with a nearly twofold enhancement of S, mostly attributed to the inability of SO4C to capture the full spatio-temporal variability of SO4B. These findings point to several potential ways forward to account for the major influential factors practically by means of satellite observations and reanalysis, aiming at an optimal observational estimate of global radiative forcing due to the Twomey effect.

Addressing the difficulties in quantifying the Twomey effect for marine warm clouds from multi-sensor satellite observations and reanalysis

2021 ◽  
Author(s):  
Hailing Jia ◽  
Johannes Quaas
Keyword(s):  
Radiative Forcing ◽  
Cloud Droplet ◽  
Influential Factors ◽  
Satellite Observations ◽  
Cloud Base ◽  
Cloud Droplet Number Concentration ◽  
Spatio Temporal ◽  
Observational Estimate ◽  
Aerosol Cloud Interactions ◽  
Aerosol Effects

&lt;p&gt;Aerosol&amp;#8211;cloud interaction is the most uncertain component of the overall anthropogenic forcing of the climate, inwhich the Twomey effect plays a fundamental role. Satellite-based estimates of the Twomey effect are especially challenging, mainly due to the difficulty in disentangling aerosol effects on cloud droplet number concentration (Nd) from possible confounders. By combining multiple satellite observations and reanalysis, this study investigates the impacts of a) updraft, b) precipitation, c) retrieval errors, as well as (d) vertical co-location between aerosol and cloud, on the assessment of Nd-to-aerosol sensitivity (S) in the context of marine warm (liquid) clouds. Our analysis suggests that S increases remarkably with both cloud base height and cloud geometric thickness (proxies for vertical velocity at cloud base), consistent with stronger aerosol-cloud interactions at larger updraft velocity. In turn, introducing the confounding effect of aerosol&amp;#8211;precipitation interaction can artificially amplify S by an estimated 21 %, highlighting the necessity of removing precipitating clouds from analyses on the Twomey effect. It is noted that the retrieval biases in aerosol and cloud appear to underestimate S, in which cloud fraction acts as a key modulator, making it practically difficult to balance the accuracies of aerosol&amp;#8211;cloud retrievals at aggregate scales (e.g., 1&amp;#9702; &amp;#215; 1&amp;#9702; grid). Moreover, we show that using column-integrated sulfate mass concentration (SO4C) to approximate sulfate concentration at cloud base (SO4B) can result in a degradation of correlation with Nd, along with a nearly two fold enhancement of S, mostly attributed to the inability of SO4C to capture the full spatio-temporal variability of SO4B. These findings point to several potential ways forward to account for the major influential factors practically by means of satellite observations and reanalysis, aiming at an optimal observational estimate of global radiative forcing due to the Twomey effect.&lt;/p&gt;

Interaction between the Black Carbon Aerosol Warming Effect and East Asian Monsoon

2020 ◽  
Author(s):  
Bingliang Zhuang ◽  
Tijian Wang ◽  
Shu Li ◽  
Min Xie ◽  
Mengmeng Li ◽  
...  
Keyword(s):  
East Asia ◽  
Black Carbon ◽  
South China ◽  
Radiative Forcing ◽  
Asian Monsoon ◽  
Meridional Circulation ◽  
East Asian Monsoon ◽  
Regional Climate ◽  
East Asian ◽  
Black Carbon Aerosol

&lt;p&gt;Black carbon aerosol (BC) has a significant influence on regional climate changes due to its warming effect. Such changes will feedback to BC loadings. Here, the interactions between the BC warming effect and East Asian monsoon (EAM) in both winter (EAWM) and summer (EASM) are investigated using a regional climate model RegCM4, which essentially captures the EAM features and the BC variations in China. The seasonal mean BC optical depth is 0.021 over East Asia during winter, which is 10.5% higher than that during summer. Nevertheless, the BCs direct radiative forcing is 32% stronger during summer (+1.85 W/m&lt;sup&gt;2&lt;/sup&gt;). The BC direct effect would induce lower air to warm by 0.11-0.12 K, which causes an meridional circulation anomaly associated with a cyclone at 20-30 &lt;sup&gt;o&lt;/sup&gt;N and southerly anomalies at 850 hPa over East Asia. Consequently, the EAM circulation is weakened during winter but enhanced during summer. Precipitation is likely increased, especially in south China during summer (by 3.73%). Compared to BC changes due to EAM interannual variations, BC changes due to its warming effect are as important, but weaker. BC surface concentrations are decreased by 1~3% during both winter and summer, by 1~3%, while the columnar BC is increased in south China during winter. During the strongest monsoon years, the BC loadings are higher at lower latitudes than those during the weakest years, resulting in more southerly meridional circulation anomalies and BC feedbacks during both winter and summer. However, the interactions between the BC warming effect and EAWM/EASM are more intense during the weakest monsoon years.&lt;/p&gt;

scholarly journals The effects of aerosols on water cloud microphysics and macrophysics based on satellite-retrieved data over East Asia and the North Pacific

2014 ◽  
Vol 14 (21) ◽  
pp. 11935-11948 ◽  
Author(s):  
T. Michibata ◽  
K. Kawamoto ◽  
T. Takemura
Keyword(s):  
East Asia ◽  
North Pacific ◽  
Vertical Structure ◽  
Cloud Droplet ◽  
Cloud Microphysics ◽  
Cloud Base ◽  
Droplet Growth ◽  
Seasonal Differences ◽  
The North ◽  
The North Pacific

Abstract. This study examines the characteristics of the microphysics and macrophysics of water clouds from East Asia to the North Pacific, using data from active CloudSat radar measurements and passive MODerate-resolution Imaging Spectroradiometer (MODIS) retrievals. Our goals are to clarify differences in microphysics and macrophysics between land and oceanic clouds, seasonal differences unique to the midlatitudes, characteristics of the drizzling process, and cloud vertical structure. In pristine oceanic areas, fractional occurrences of cloud optical thickness (COT) and cloud droplet effective radius (CDR) increase systematically with an increase in drizzle intensity, but these characteristics of the COT and CDR transition are less evident in polluted land areas. In addition, regional and seasonal differences are identified in terms of drizzle intensity as a function of the liquid water path (LWP) and cloud droplet number concentration (Nc). The correlations between drizzle intensity and LWP, and between drizzle intensity and Nc, are both more robust over oceanic areas than over land areas. We also demonstrate regional and seasonal characteristics of the cloud vertical structure. Our results suggest that aerosol–cloud interaction mainly occurs around the cloud base in polluted land areas during the winter season. In addition, a difference between polluted and pristine areas in the efficiency of cloud droplet growth is confirmed. These results suggest that water clouds over the midlatitudes exhibit a different drizzle system to those over the tropics.

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