scholarly journals East Asian climate response to COVID-19 lockdown measures in China

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sun-Seon Lee ◽  
Jung-Eun Chu ◽  
Axel Timmermann ◽  
Eui-Seok Chung ◽  
June-Yi Lee
Keyword(s):  
Air Pollution ◽  
Atmospheric Chemistry ◽  
Cloud Condensation Nuclei ◽  
Cloud Formation ◽  
Atmospheric Conditions ◽  
Anthropogenic Aerosol ◽  
Surface Warming ◽  
Anomalous Surface ◽  
Additional Perturbation ◽  
Aerosol Emissions

AbstractThe COVID-19 pandemic caused disruptions of public life and imposed lockdown measures in 2020 resulted in considerable reductions of anthropogenic aerosol emissions. It still remains unclear how the associated short-term changes in atmospheric chemistry influenced weather and climate on regional scales. To understand the underlying physical mechanisms, we conduct ensemble aerosol perturbation experiments with the Community Earth System Model, version 2. In the simulations reduced anthropogenic aerosol emissions in February generate anomalous surface warming and warm-moist air advection which promotes low-level cloud formation over China. Although the simulated response is weak, it is detectable in some areas, in qualitative agreement with the observations. The negative dynamical cloud feedback offsets the effect from reduced cloud condensation nuclei. Additional perturbation experiments with strongly amplified air pollution over China reveal a nonlinear sensitivity of regional atmospheric conditions to chemical/radiative perturbations. COVID-19-related changes in anthropogenic aerosol emissions provide an excellent testbed to elucidate the interaction between air pollution and climate.

scholarly journals Analysis of polarimetric satellite measurements suggests stronger cooling due to aerosol-cloud interactions

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Otto P. Hasekamp ◽  
Edward Gryspeerdt ◽  
Johannes Quaas
Keyword(s):  
Radiative Forcing ◽  
Cloud Condensation Nuclei ◽  
Cloud Droplet ◽  
Cloud Formation ◽  
Anthropogenic Aerosol ◽  
Intergovernmental Panel ◽  
Aerosol Cloud ◽  
Cloud Properties ◽  
Aerosol Cloud Interactions ◽  
Aerosol Emissions

AbstractAnthropogenic aerosol emissions lead to an increase in the amount of cloud condensation nuclei and consequently an increase in cloud droplet number concentration and cloud albedo. The corresponding negative radiative forcing due to aerosol cloud interactions (RF$${}_{{\rm{aci}}}$$aci) is one of the most uncertain radiative forcing terms as reported in the 5th Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). Here we show that previous observation-based studies underestimate aerosol-cloud interactions because they used measurements of aerosol optical properties that are not directly related to cloud formation and are hampered by measurement uncertainties. We have overcome this problem by the use of new polarimetric satellite retrievals of the relevant aerosol properties (aerosol number, size, shape). The resulting estimate of RF$${}_{{\rm{aci}}}$$aci = −1.14 Wm$${}^{{\rm{-2}}}$$-2 (range between −0.84 and −1.72 Wm$${}^{{\rm{-2}}}$$-2) is more than a factor 2 stronger than the IPCC estimate that includes also other aerosol induced changes in cloud properties.

scholarly journals Weaker cooling by aerosols due to dust–pollution interactions

2020 ◽  
Vol 20 (23) ◽  
pp. 15285-15295
Author(s):  
Klaus Klingmüller ◽  
Vlassis A. Karydis ◽  
Sara Bacer ◽  
Georgiy L. Stenchikov ◽  
Jos Lelieveld
Keyword(s):  
Atmospheric Chemistry ◽  
Climate Model ◽  
Cloud Condensation Nuclei ◽  
Radiative Effect ◽  
Dust Pollution ◽  
Aerosol Composition ◽  
Anthropogenic Aerosol ◽  
Aerosol Forcing ◽  
Condensed Water ◽  
Chemical Ageing

Abstract. The interactions between aeolian dust and anthropogenic air pollution, notably chemical ageing of mineral dust and coagulation of dust and pollution particles, modify the atmospheric aerosol composition and burden. Since the aerosol particles can act as cloud condensation nuclei, this affects the radiative transfer not only directly via aerosol–radiation interactions, but also indirectly through cloud adjustments. We study both radiative effects using the global ECHAM/MESSy atmospheric chemistry-climate model (EMAC) which combines the Modular Earth Submodel System (MESSy) with the European Centre/Hamburg (ECHAM) climate model. Our simulations show that dust–pollution–cloud interactions reduce the condensed water path and hence the reflection of solar radiation. The associated climate warming outweighs the cooling that the dust–pollution interactions exert through the direct radiative effect. In total, this results in a net warming by dust–pollution interactions which moderates the negative global anthropogenic aerosol forcing at the top of the atmosphere by (0.2 ± 0.1) W m−2.

scholarly journals Air pollution control and decreasing new particle formation lead to strong climate warming

2011 ◽  
Vol 11 (9) ◽  
pp. 25991-26007 ◽  
Author(s):  
R. Makkonen ◽  
A. Asmi ◽  
V.-M. Kerminen ◽  
M. Boy ◽  
A. Arneth ◽  
...  
Keyword(s):  
Air Pollution ◽  
Pollution Control ◽  
Cloud Condensation Nuclei ◽  
Particle Formation ◽  
Control Measures ◽  
Air Pollution Control ◽  
New Particle Formation ◽  
Anthropogenic Aerosol ◽  
Aerosol Forcing ◽  
Year 2000

Abstract. The number of cloud droplets determines several climatically relevant cloud properties. A major cause for the high uncertainty in the indirect aerosol forcing is the availability of cloud condensation nuclei (CCN), which in turn is highly sensitive to atmospheric new particle formation. Here we present the effect of new particle formation on anthropogenic aerosol forcing in present-day (year 2000) and future (year 2100) conditions. The total aerosol forcing (−1.61 W m−2 in year 2000) is simulated to be greatly reduced in the future, to −0.23 W m−2, mainly due to decrease in SO2 emissions and resulting decrease in new particle formation. With the total aerosol forcing decreasing in response to air pollution control measures taking effect, warming from increased greenhouse gas concentrations can potentially increase at a very rapid rate.

scholarly journals Weaker cooling by aerosols due to dust-pollution interactions

2020 ◽  
Author(s):  
Klaus Klingmüller ◽  
Vlassis A. Karydis ◽  
Sara Bacer ◽  
Georgiy L. Stenchikov ◽  
Jos Lelieveld
Keyword(s):  
Atmospheric Chemistry ◽  
Climate Model ◽  
Cloud Condensation Nuclei ◽  
Cloud Water ◽  
Radiative Effect ◽  
Dust Pollution ◽  
Aerosol Composition ◽  
Anthropogenic Aerosol ◽  
Aerosol Forcing ◽  
Chemical Ageing

Abstract. The interactions between aeolian dust and anthropogenic air pollution, notably chemical ageing of mineral dust and coagulation of dust and pollution particles, modify the atmospheric aerosol composition and burden. Since the aerosol particles can act as cloud condensation nuclei, this not only affects the radiative transfer directly via aerosol-radiation interactions, but also indirectly through cloud adjustments. We study both radiative effects using the global ECHAM/MESSy atmospheric chemistry-climate model (EMAC) which combines the Modular Earth Submodel System (MESSy) with the European Centre/Hamburg (ECHAM) climate model. Our simulations show that dust-pollution interactions reduce the cloud water path and hence the reflection of solar radiation. The associated climate warming outweighs the cooling which the dust-pollution interactions exert through the direct radiative effect. In total, this results in a net warming by dust-pollution interactions which moderates the negative global anthropogenic aerosol forcing at the top of the atmosphere by (0.2 ± 0.1) W m−2.

The Effects of Anthropogenic Aerosol Emissions from Chile and Mexico in ECHAM-HAMMOZ

2020 ◽  
Author(s):  
Tuuli Miinalainen ◽  
Harri Kokkola ◽  
Kari E. J. Lehtinen ◽  
Thomas Kühn
Keyword(s):  
Climate Model ◽  
Cloud Condensation Nuclei ◽  
Cloud Droplet ◽  
Radiative Properties ◽  
Reference Scenario ◽  
Climatic Effects ◽  
Anthropogenic Aerosol ◽  
Regional Effect ◽  
Radiative Balance ◽  
Aerosol Emissions

<p>In this research project we studied the climatic effects of anthropogenic aerosol emissions originating from Chile and Mexico. In particular, we studied black carbon (BC), organic carbon (OC) and sulfur dioxide (SO<sub>2</sub>).</p><p>By using aerosol-climate model ECHAM6.3.0-HAM2.3-MOZ1.0, we analyzed how each aerosol species affects the local cloud properties and radiative balance in the atmosphere. As we here are interested in the maximum impact, we simulated each aerosol species with separate model runs. The reference scenario (BASE) was simulated with the full representation of anthropogenic aerosol emissions from the ECLIPSEV6a emission inventory for the year 2015.Then, we constructed otherwise identical scenarios but the anthropogenic aerosol emissions from Chile and Mexico for each aerosol type were removed (NO_BC, NO_OC and NO_SO2). </p><p>The results indicate that for Chile the sulfur emissions seem to have the greatest impact on both cloud condensation nuclei (CCN) and cloud droplet number concentration. This result is plausible since there the SO<sub>2</sub> emissions are much higher than BC and OC emissions. For Mexico, the OC emissions had the most notable effect on CCN, but the cloud droplets are more affected by the SO<sub>2</sub> emissions. When looking at the radiative properties, we found out that the direct effects were rather minor compared to semi-direct and indirect effects. This indicates that aerosol-cloud interactions have much larger regional effect on radiation than the aerosol direct effect.</p>

scholarly journals The Amazon Tall Tower Observatory (ATTO): overview of pilot measurements on ecosystem ecology, meteorology, trace gases, and aerosols

2015 ◽  
Vol 15 (18) ◽  
pp. 10723-10776 ◽  
Author(s):  
M. O. Andreae ◽  
O. C. Acevedo ◽  
A. Araùjo ◽  
P. Artaxo ◽  
C. G. G. Barbosa ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Amazon Basin ◽  
Cloud Condensation Nuclei ◽  
Heat Fluxes ◽  
Atmospheric Conditions ◽  
Additional Species ◽  
Pilot Studies ◽  
Forest Region ◽  
Human Perturbations ◽  
Tall Tower

Abstract. The Amazon Basin plays key roles in the carbon and water cycles, climate change, atmospheric chemistry, and biodiversity. It has already been changed significantly by human activities, and more pervasive change is expected to occur in the coming decades. It is therefore essential to establish long-term measurement sites that provide a baseline record of present-day climatic, biogeochemical, and atmospheric conditions and that will be operated over coming decades to monitor change in the Amazon region, as human perturbations increase in the future. The Amazon Tall Tower Observatory (ATTO) has been set up in a pristine rain forest region in the central Amazon Basin, about 150 km northeast of the city of Manaus. Two 80 m towers have been operated at the site since 2012, and a 325 m tower is nearing completion in mid-2015. An ecological survey including a biodiversity assessment has been conducted in the forest region surrounding the site. Measurements of micrometeorological and atmospheric chemical variables were initiated in 2012, and their range has continued to broaden over the last few years. The meteorological and micrometeorological measurements include temperature and wind profiles, precipitation, water and energy fluxes, turbulence components, soil temperature profiles and soil heat fluxes, radiation fluxes, and visibility. A tree has been instrumented to measure stem profiles of temperature, light intensity, and water content in cryptogamic covers. The trace gas measurements comprise continuous monitoring of carbon dioxide, carbon monoxide, methane, and ozone at five to eight different heights, complemented by a variety of additional species measured during intensive campaigns (e.g., VOC, NO, NO2, and OH reactivity). Aerosol optical, microphysical, and chemical measurements are being made above the canopy as well as in the canopy space. They include aerosol light scattering and absorption, fluorescence, number and volume size distributions, chemical composition, cloud condensation nuclei (CCN) concentrations, and hygroscopicity. In this paper, we discuss the scientific context of the ATTO observatory and present an overview of results from ecological, meteorological, and chemical pilot studies at the ATTO site.

Composition and Properties of the Natural Aerosol over the Boreal and Tropical Forests

2020 ◽  
Author(s):  
Hans-Christen Hansson ◽  
Paulo Artaxo ◽  
Meinrat Andreae ◽  
Markku Kulmala
Keyword(s):  
Tropical Forests ◽  
Atmospheric Chemistry ◽  
Boreal Forests ◽  
Cloud Condensation Nuclei ◽  
Particle Formation ◽  
Climate System ◽  
Atmospheric Composition ◽  
Cloud Formation ◽  
Aerosol Composition ◽  
The Tropics

<p>We, together with 50 of our colleagues present a review on the interaction between tropical and boreal forests and the atmosphere, especially addressing their influence in the climate system. With its emissions of VOCs, aerosols and trace gases, with strong atmosphere interactions, forests are a key component of the climate system. These emissions and atmospheric processing regulates atmospheric chemistry and are the major source of cloud condensation nuclei (CCN) affecting cloud formation and development, and thus temperature and precipitation. Emissions from forests are thus closely connected to the hydrological and the carbon cycles, being  an essential integrated part of the climate system.</p><p>In terms of meteorology, tropical and boreal forests are very different. Temperature, solar radiation, precipitation, evapotranspiration, albedo, cloud structure and cover, convection etc., are all very different. However, the aerosols in the two systems show similarities as Primary Biological Aerosol Particles are the major component (70%) of coarse mode particles in Amazonia while Secondary Organic Aerosol in the tropics are mainly isoprene driven giving a slightly more hygroscopic SOA than the boreal monoterpene driven SOA. The organics constitutes 70 to 85% of PM1 mass for both boreal and tropical forests. In Amazonia, sulfates, nitrates and BC shows very low concentrations, while the boreal sites shows 2-3 times higher concentrations. The Siberian continental site and Amazonian site show remarkable similarities in the lack of new particle formation (NPF) which will be  discussed.</p><p>In the tropics dry season and boreal spring and early summer, increasing biomass burning emissions in both forest types dominates the aerosol composition, with high OC and BC concentrations while anthropogenic pollution influences boreal forest atmospheric composition during wintertime. The changes in diffuse to direct radiation due to scattering aerosols has important effects in tropical forests but minor in boreal, enhancing the net ecosystem exchange by 30% and 10% respectively. Thus the natural forest emissions affects the direct as well as the indirect forcing.</p><p>An Amazonia high altitude NPF process chain was recently observed at the top of the troposphere, and is an interesting interaction between forest emissions, cloud transport and processing and particle formation and aging at high altitudes that are brought back to the boundary layer, populating the CCN. For boreal forests, the complex relationship between GPP, BVOC, SOA, CCN, clouds, radiation, temperature and CO<sub>2</sub> show multiple pathways and feedbacks, and some of them can be quantified. All showing the complexity of the interaction between forests, atmosphere and climate.</p>

Blooming trees as a source of fine (< 5μm) aerosol particles

2020 ◽  
Author(s):  
Jürgen Gratzl ◽  
Teresa M Seifried ◽  
Paul Bieber ◽  
Hinrich Grothe ◽  
Julia Burkart
Keyword(s):  
Atmospheric Chemistry ◽  
Urban Areas ◽  
Clinical Immunology ◽  
Cloud Condensation Nuclei ◽  
Pollen Grains ◽  
Cloud Formation ◽  
British Society ◽  
Aerodynamic Diameter ◽  
Geophysical Research ◽  
Cytoplasmic Material

&lt;p&gt;During the blooming season of trees, pollen is an important component of the atmospheric aerosol, even in urban areas. Wind pollinated plants such as early flowering trees (e.g. birch, alder) release pollen grains in extremely large quantities. Once in the atmosphere pollen can impact human health and cloud formation (Sch&amp;#228;ppi et al. 1999, Pummer et al. 2012, Steiner et al. 2015). Intact pollen grains are rather large with geometrical diameters from 10-100 &amp;#956;m and therefore have short residence times in the atmosphere. However, it is known that under certain conditions (high humidity and after germination) pollen grains release cytoplasmic material including starch granules from their interior, commonly referred to as subpollen particles (SPP). Studies have shown that the cytoplasmic material contains cloud active substances and allergens (Steiner et al. 2015, Pummer et al. 2012, Basci et al. 2006). How and if this material becomes airborne and whether it distributes in the atmosphere is still an open question. Motivated by this question we took a detailed look at the particles shed from blooming catkins.&lt;/p&gt; &lt;p&gt;In this study freshly harvested branches with flowering catkins of different trees were put in an aerosol chamber. An Aerodynamic Particle Sizer (TSI Spectrometer 3321; 0.5 &amp;#8211; 20 &amp;#956;m) and a Cascade Impactor (Sioutas; 2.5 &amp;#956;m, 1.0 &amp;#956;m, 0.50 &amp;#956;m, 0.25 &amp;#956;m) were attached to the chamber to sample the released aerosol. The catkins were agitated with puffs of clean air to simulate wind. The aerodynamic diameters of the released particles were recorded and the filters of the impactor were analyzed with a Scanning Electron Microscope and a light microscope. We find that not only large pollen grains are released but also smaller particles. Up to 50% of all released particles were in the size range from (0.5 &amp;#8211; 5 &amp;#956;m). Additionally, we find that the aerodynamic diameter of pollen grains is in general smaller than their geometrical diameter. For instance, the aerodynamic diameter of pollen grains from birch is 30-70% smaller than the geometrical diameter.&lt;/p&gt; &lt;p&gt;&amp;#160;&lt;/p&gt; &lt;p&gt;References:&lt;br /&gt;Sch&amp;#228;ppi, G. F.; Taylor, P. E.; Pain, M. C.; Cameron, P. A.; Dent, A. W.; Staff, I. A. &amp; Suphioglu, C.; Concentrations of major grass group 5 allergens in pollen grains and atmospheric particles: implications for hay fever and allergic asthma sufferers sensitized to grass pollen allergens.; Clinical and experimental allergy: journal of the British Society for Allergy and Clinical Immunology, 1999, 29, 633-641&lt;br /&gt;Pummer, B. G.; Bauer, H.; Bernardi, J.; Bleicher, S. &amp; Grothe, H.; Suspendable macromolecules are responsible for ice nucleation activity of birch and conifer pollen; Atmospheric Chemistry and Physics, Copernicus GmbH, 2012, 12, 2541-2550&lt;br /&gt;Steiner, A. L.; Brooks, S. D.; Deng, C.; Thornton, D. C. O.; Pendleton, M. W. &amp; Bryant, V.; Pollen as atmospheric cloud condensation nuclei; Geophysical research letters, Wiley Online Library, 2015, 42, 3596-3602&lt;br /&gt;Bacsi, A.; Choudhury, B. K.; Dharajiya, N.; Sur, S. &amp; Boldogh, I.; Subpollen particles: carriers of allergenic proteins and oxidases; Journal of Allergy and Clinical Immunology, Elsevier, 2006 , 118 , 844-850&lt;/p&gt;

scholarly journals Weaker cooling by aerosols due to dust-pollution interactions

2020 ◽  
Author(s):  
Klaus Klingmueller ◽  
Vlassis Karydis ◽  
Sara Bacer ◽  
Georgiy Stenchikov ◽  
Jos Lelieveld
Keyword(s):  
Atmospheric Chemistry ◽  
Climate Model ◽  
Cloud Condensation Nuclei ◽  
Aerosol Particles ◽  
Cloud Water ◽  
Radiative Effect ◽  
Dust Pollution ◽  
Anthropogenic Aerosol ◽  
Aerosol Forcing ◽  
Chemical Ageing

&lt;p&gt;The interactions between aeolian dust and anthropogenic air pollution, notably chemical ageing of mineral dust and coagulation of dust and pollution particles, modify the atmospheric aerosol burden. Since the aerosol particles can act as cloud condensation nuclei, this not only affects the radiative transfer directly via aerosol radiation interactions, but also indirectly through cloud adjustments. We study both radiative effects using the global ECHAM/MESSy atmospheric chemistry-climate model (EMAC) which combines the Modular Earth Submodel System (MESSy) with the European Centre/Hamburg (ECHAM) climate model. Our simulations show that the dust-pollution interactions reduce the cloud water and hence the reflection of solar radiation. The associated climate warming outweighs the cooling which the dust-pollution interactions exert through the direct radiative effect. In total, this results in a net warming by dust-pollution interactions which we estimate to moderate the negative global anthropogenic aerosol forcing at the top of the atmosphere by more than 0.1 W / m&amp;#178;.&lt;/p&gt;

scholarly journals Estimating seasonal variations in cloud droplet number concentration over the boreal forest from satellite observations

2011 ◽  
Vol 11 (15) ◽  
pp. 7701-7713 ◽  
Author(s):  
R. H. H. Janssen ◽  
L. N. Ganzeveld ◽  
P. Kabat ◽  
M. Kulmala ◽  
T. Nieminen ◽  
...  
Keyword(s):  
Boreal Forest ◽  
Seasonal Variations ◽  
Cloud Model ◽  
Cloud Condensation Nuclei ◽  
Cloud Droplet ◽  
Number Concentration ◽  
Cloud Formation ◽  
Clear Correlation ◽  
Atmospheric Conditions ◽  
Cloud Droplet Number Concentration

Abstract. Seasonal variations in cloud droplet number concentration (NCD) in low-level stratiform clouds over the boreal forest are estimated from MODIS observations of cloud optical and microphysical properties, using a sub-adiabatic cloud model to interpret vertical profiles of cloud properties. An uncertainty analysis of the cloud model is included to reveal the main sensitivities of the cloud model. We compared the seasonal cycle in NCD, obtained using 9 yr of satellite data, to surface concentrations of potential cloud activating aerosols, measured at the SMEAR II station at Hyytiälä in Finland. The results show that NCD and cloud condensation nuclei (CCN) concentrations have no clear correlation at seasonal time scale. The fraction of aerosols that actually activate as cloud droplet decreases sharply with increasing aerosol concentrations. Furthermore, information on the stability of the atmosphere shows that low NCD is linked to stable atmospheric conditions. Combining these findings leads to the conclusion that cloud droplet activation for the studied clouds over the boreal forest is limited by convection. Our results suggest that it is important to take the strength of convection into account when studying the influence of aerosols from the boreal forest on cloud formation, although they do not rule out the possibility that aerosols from the boreal forest affect other types of clouds with a closer coupling to the surface.

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