[ { "id": "authors:9txaz-ptm62", "collection": "authors", "collection_id": "9txaz-ptm62", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20211214-987826000", "type": "article", "title": "Atmospheric Effects on the Isotopic Composition of Ozone", "author": [ { "family_name": "Liang", "given_name": "Mao-Chang", "orcid": "0000-0002-5294-9344", "clpid": "Liang-Mao-Chang" }, { "family_name": "Chen", "given_name": "Yi-Chun", "orcid": "0000-0001-7997-8578", "clpid": "Chen-Yi-Chun" }, { "family_name": "Gao", "given_name": "Yi-Qin", "clpid": "Gao-Yi-Qin" }, { "family_name": "Zhang", "given_name": "Xi", "clpid": "Zhang-Xi" }, { "family_name": "Yung", "given_name": "Yuk L.", "orcid": "0000-0002-4263-2562", "clpid": "Yung-Y-L" } ], "abstract": "The delta values of the isotope composition of atmospheric ozone is ~100\u2030 (referenced to atmospheric O\u2082). Previous photochemical models, which considered the isotope fractionation processes from both formation and photolysis of ozone, predicted \u03b4\u2074\u2079O\u2083 and \u03b4\u2075\u2070O\u2083 values, in \u03b4\u2074\u2079O\u2083 versus \u03b4\u2075\u2070O\u2083 space, that are >10\u2030 larger than the measurements. We propose that the difference between the model and observations could be explained either by the temperature variation, Chappuis band photolysis, or a combination of the two and examine them. The isotopic fractionation associated with ozone formation increases with temperature. Our model shows that a hypothetical reduction of ~20 K in the nominal temperature profile could reproduce the observations. However, this hypothesis is not consistent with temperatures obtained by in situ measurements and NCEP Reanalysis. Photolysis of O\u2083 in the Chappuis band causes O\u2083 to be isotopically depleted, which is supported by laboratory measurements for \u00b9\u2078O\u00b9\u2078O\u00b9\u2078O but not by recent new laboratory data made at several wavelengths for \u2074\u2079O\u2083 and \u2075\u2070O\u2083. Cloud reflection can significantly enhance the photolysis rate and affect the spectral distribution of photons, which could influence the isotopic composition of ozone. Sensitivity studies that modify the isotopic composition of ozone by the above two mechanisms are presented. We conclude isotopic fractionation occurring in photolysis in the Chappuis band remains the most plausible solution to the model-observation discrepancy. Implications of our results for using the oxygen isotopic signature for constraining atmospheric chemical processes related to ozone, such as CO\u2082, nitrate, and the hydroxyl radical, are discussed.", "doi": "10.3390/atmos12121673", "issn": "2073-4433", "publisher": "MDPI", "publication": "Atmosphere", "publication_date": "2021-12-14", "series_number": "12", "volume": "12", "issue": "12", "pages": "Art. No. 1673" }, { "id": "authors:hcmwp-vbj29", "collection": "authors", "collection_id": "hcmwp-vbj29", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190724-122707801", "type": "article", "title": "Satellite-Derived Correlation of SO_2, NO_2, and Aerosol Optical Depth with Meteorological Conditions over East Asia from 2005 to 2015", "author": [ { "family_name": "Lin", "given_name": "Chin-An", "clpid": "Lin-Chin-An" }, { "family_name": "Chen", "given_name": "Yi-Chun", "orcid": "0000-0001-7997-8578", "clpid": "Chen-Yi-Chun" }, { "family_name": "Liu", "given_name": "Chian-Yi", "orcid": "0000-0003-1725-4405", "clpid": "Liu-Chian-Yi" }, { "family_name": "Chen", "given_name": "Wei-Ting", "orcid": "0000-0002-9292-0933", "clpid": "Chen-Wei-Ting" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Chou", "given_name": "Charles C.-K.", "clpid": "Chou-Charles-C-K" } ], "abstract": "Intense economic and industrial development in China has been accompanied by severe local air pollution, as well as in other downwind countries in East Asia. This study analyzes satellite observational data of sulfur dioxide (SO_2), nitrogen dioxide (NO_2), and aerosol optical depth (AOD) to explore the spatial distribution, long-term temporal variation, and correlation to meteorological conditions over this region over the period 2005\u20132015. SO_2 and NO_2 data are retrieved from the ozone monitoring instrument (OMI) onboard the National Aeronautics and Space Administration (NASA) Aura satellite, while AOD data are from the moderate-resolution imaging spectroradiometer (MODIS) onboard the NASA Aqua satellite. Spatial distributions of SO_2, NO_2, and AOD show the highest levels in the North China Plain (NCP), with hotspots also in Southeastern China (SC) and the Sichuan Basin (SB). Biomass burning also contributes to a high level of AOD in Southeast Asia in spring and in Equatorial Asia in fall. Considering the correlation of pollutant levels to meteorological conditions, monitoring data show that higher temperature and higher relative humidity (RH) favor the conversion of SO_2 and NO_2 to sulfate and nitrate aerosol, respectively. The impact of stronger lower tropospheric stability facilitates the accumulation of SO_2 and NO_2 in NCP and SC. Transport of SO_2 and NO2 from intense source regions to relatively clean regions is highly influential over East Asia; such transport from the NCP leads to a considerable increase of pollutants in SC, SB, Taiwan Island (TW), and Taiwan Strait (TWS), particularly in winter. Aerosols generated by biomass burning in Southeast Asia and anthropogenic aerosol in SC are transported to TW and TWS and lead to the increase of AOD, with the highest levels of AOD in SC, TW, and TWS occurring in spring. Precipitation results in the removal of pollutants, especially in highly polluted regions, the effect of which is most significant in winter and spring.", "doi": "10.3390/rs11151738", "issn": "2072-4292", "publisher": "MDPI", "publication": "Remote Sensing", "publication_date": "2019-07-24", "series_number": "15", "volume": "11", "issue": "15", "pages": "Art. No. 1738" }, { "id": "authors:91mvg-bbx03", "collection": "authors", "collection_id": "91mvg-bbx03", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190501-161717861", "type": "article", "title": "Precipitation effects of giant cloud condensation nuclei artificially introduced into stratocumulus clouds", "author": [ { "family_name": "Jung", "given_name": "E.", "orcid": "0000-0003-0970-2730", "clpid": "Jung-Eunsil" }, { "family_name": "Albrecht", "given_name": "B. A.", "clpid": "Albrecht-B-A" }, { "family_name": "Jonsson", "given_name": "H. H.", "orcid": "0000-0003-3043-1074", "clpid": "Jonsson-H-H" }, { "family_name": "Chen", "given_name": "Y.-C.", "orcid": "0000-0001-7997-8578", "clpid": "Chen-Yi-Chun" }, { "family_name": "Seinfeld", "given_name": "J. H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Sorooshian", "given_name": "A.", "orcid": "0000-0002-2243-2264", "clpid": "Sorooshian-A" }, { "family_name": "Metcalf", "given_name": "A. R.", "orcid": "0000-0003-0385-1356", "clpid": "Metcalf-A-R" }, { "family_name": "Song", "given_name": "S.", "clpid": "Song-S" }, { "family_name": "Fang", "given_name": "M.", "clpid": "Fang-M" }, { "family_name": "Russell", "given_name": "L. M.", "orcid": "0000-0002-6108-2375", "clpid": "Russell-L-M" } ], "abstract": "To study the effect of giant cloud condensation nuclei (GCCN) on precipitation processes in stratocumulus clouds, 1\u201310 \u03bcm diameter salt particles (salt powder) were released from an aircraft while flying near the cloud top on 3 August 2011 off the central coast of California. The seeded area was subsequently sampled from the aircraft that was equipped with aerosol, cloud, and precipitation probes and an upward-facing cloud radar. During post-seeding sampling, made 30\u201360 min after seeding, the mean cloud droplet size increased, the droplet number concentration decreased, and large drop (e.g., diameter larger than 10 \u03bcm) concentration increased. Average drizzle rates increased from about 0.05 to 0.20 mm h^(\u22121), and the liquid water path decreased from about 52 to 43 g m^(\u22122). Strong radar returns associated with drizzle were observed on the post-seeding cloud-base level-leg flights and were accompanied by a substantial depletion of the cloud liquid water content. The changes were large enough to suggest that the salt particles with concentrations estimated to be 10^(\u22122) to 10^(-4) cm^(\u22123) resulted in a four-fold increase in the cloud-base rainfall rate and depletion of the cloud water due to rainout. In contrast, a case is shown where the cloud was already precipitating (on 10 August) and the effect of adding GCCN to the cloud was insignificant.", "doi": "10.5194/acp-15-5645-2015", "issn": "1680-7324", "publisher": "European Geosciences Union", "publication": "Atmospheric Chemistry and Physics", "publication_date": "2015-05-22", "series_number": "10", "volume": "15", "issue": "10", "pages": "5645-5658" }, { "id": "authors:c7gmd-mh993", "collection": "authors", "collection_id": "c7gmd-mh993", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140701-132233552", "type": "article", "title": "Satellite-based estimate of global aerosol\u2013cloud radiative forcing by marine warm clouds", "author": [ { "family_name": "Chen", "given_name": "Yi-Chun", "orcid": "0000-0001-7997-8578", "clpid": "Chen-Yi-Chun" }, { "family_name": "Christensen", "given_name": "Matthew W.", "clpid": "Christensen-M-W" }, { "family_name": "Stephens", "given_name": "Graeme L.", "clpid": "Stephens-G-L" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "abstract": "Changes in aerosol concentrations affect cloud albedo and Earth's radiative balance. Aerosol radiative forcing from pre-industrial time to the present due to the effect of atmospheric aerosol levels on the micro- and macrophysics of clouds bears the largest uncertainty among external influences on climate change. Of all cloud forms, low-level marine clouds exert the largest impact on the planet's albedo. For example, a 6% increase in the albedo of global marine stratiform clouds could offset the warming that would result from a doubling of atmospheric CO_2 concentrations. Marine warm cloud properties are thought to depend on aerosol levels and large-scale dynamic or thermodynamic states. Here we present a comprehensive analysis of multiple measurements from the A-Train constellation of Earth-observing satellites, to quantify the radiative forcing exerted by aerosols interacting with marine clouds. Specifically, we analyse observations of co-located aerosols and clouds over the world's oceans for the period August 2006\u2013April 2011, comprising over 7.3 million CloudSat single-layer marine warm cloud pixels. We find that thermodynamic conditions\u2014that is, tropospheric stability and humidity in the free troposphere\u2014and the state of precipitation act together to govern the cloud liquid water responses to the presence of aerosols and the strength of aerosol\u2013cloud radiative forcing.", "doi": "10.1038/ngeo2214", "issn": "1752-0894", "publisher": "Nature Publishing Group", "publication": "Nature Geoscience", "publication_date": "2014-09", "series_number": "9", "volume": "7", "issue": "9", "pages": "643-646" }, { "id": "authors:pcvfz-3c825", "collection": "authors", "collection_id": "pcvfz-3c825", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140310-102849450", "type": "book_section", "title": "Observed aerosol effects on marine cloud nucleation and supersaturation", "book_title": "Nucleation and Atmospheric Aerosols", "author": [ { "family_name": "Russell", "given_name": "Lynn M.", "orcid": "0000-0002-6108-2375", "clpid": "Russell-L-M" }, { "family_name": "Seinfeld", "given_name": "J. H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Chen", "given_name": "Yi-Chun", "orcid": "0000-0001-7997-8578", "clpid": "Chen-Yi-Chun" }, { "family_name": "Coggon", "given_name": "Matthew", "orcid": "0000-0002-5763-1925", "clpid": "Coggon-M-M" }, { "family_name": "Craven", "given_name": "Jill S.", "clpid": "Craven-J-S" }, { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" }, { "family_name": "Metcalf", "given_name": "Andrew R.", "orcid": "0000-0003-0385-1356", "clpid": "Metcalf-A-R" } ], "contributor": [ { "family_name": "DeMott", "given_name": "Paul J.", "clpid": "DeMott-P-J" }, { "family_name": "O'Dowd", "given_name": "Colin D.", "clpid": "O'Dowd-C-D" } ], "abstract": "Aerosol particles in the marine boundary layer include primary organic and salt particles from sea spray and combustion-derived particles from ships and coastal cities. These particle types serve as nuclei for marine cloud droplet activation, although the particles that activate depend on the particle size and composition as well as the supersaturation that results from cloud updraft velocities. The Eastern Pacific Emitted Aerosol Cloud Experiment (EPEACE) 2011 was a targeted aircraft campaign to assess how different particle types nucleate cloud droplets. As part of E-PEACE 2011, we studied the role of marine particles as cloud droplet nuclei and used emitted particle sources to separate particle-induced feedbacks from dynamical variability. The emitted particle sources included shipboard smoke-generated particles with 0.05-1 \u03bcm diameters (which produced tracks measured by satellite and had drop composition characteristic of organic smoke) and combustion particles from container ships with 0.05-0.2 \u03bcm diameters (which were measured in a variety of conditions with droplets containing both organic and sulfate components) [1]. Three central aspects of the collaborative E-PEACE results are: (1) the size and chemical composition of the emitted smoke particles compared to ship-track-forming cargo ship emissions as well as background marine particles, with particular attention to the role of organic particles, (2) the characteristics of cloud track formation for smoke and cargo ships, as well as the role of multi-layered low clouds, and (3) the implications of these findings for quantifying aerosol indirect effects. For comparison with the E-PEACE results, the preliminary results of the Stratocumulus Observations of Los-Angeles Emissions Derived Aerosol-Droplets (SOLEDAD) 2012 provided evidence of the cloud-nucleating roles of both marine organic particles and coastal urban pollution, with simultaneous measurements of the effective supersaturations of the clouds in the California coastal region.", "doi": "10.1063/1.4803366", "isbn": "978-0-7354-1152-4", "publisher": "Melville, NY", "place_of_publication": "American Institute of Physics", "publication_date": "2013-06", "pages": "696-701" }, { "id": "authors:082gf-bdv27", "collection": "authors", "collection_id": "082gf-bdv27", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130708-131056964", "type": "article", "title": "Eastern Pacific Emitted Aerosol Cloud Experiment", "author": [ { "family_name": "Russell", "given_name": "Lynn M.", "orcid": "0000-0002-6108-2375", "clpid": "Russell-Lynn-M" }, { "family_name": "Sorooshian", "given_name": "Armin", "orcid": "0000-0002-2243-2264", "clpid": "Sorooshian-Armin" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Albrecht", "given_name": "Bruce A.", "orcid": "0000-0001-5085-4272", "clpid": "Albrecht-Bruce-A" }, { "family_name": "Nenes", "given_name": "Athanasios", "orcid": "0000-0003-3873-9970", "clpid": "Nenes-Athanasios" }, { "family_name": "Ahlm", "given_name": "Lars", "clpid": "Ahlm-Lars" }, { "family_name": "Chen", "given_name": "Yi-Chun", "orcid": "0000-0001-7997-8578", "clpid": "Chen-Yi-Chun" }, { "family_name": "Coggon", "given_name": "Matthew", "orcid": "0000-0002-5763-1925", "clpid": "Coggon-Matthew-M" }, { "family_name": "Craven", "given_name": "Jill S.", "clpid": "Craven-Jill-S" }, { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" }, { "family_name": "Frossard", "given_name": "Amanda A.", "orcid": "0000-0002-5728-0854", "clpid": "Frossard-Amanda-A" }, { "family_name": "Jonsson", "given_name": "Haflidi", "orcid": "0000-0003-3043-1074", "clpid": "Jonsson-Haflidi-H" }, { "family_name": "Jung", "given_name": "Eunsil", "orcid": "0000-0003-0970-2730", "clpid": "Jung-Eunsil" }, { "family_name": "Lin", "given_name": "Jack J.", "orcid": "0000-0002-4453-1263", "clpid": "Lin-Jack-J" }, { "family_name": "Metcalfe", "given_name": "Andrew R.", "orcid": "0000-0003-0385-1356", "clpid": "Metcalf-Andrew-R" }, { "family_name": "Modini", "given_name": "Robin", "orcid": "0000-0002-2982-1369", "clpid": "Modini-Robin-L" }, { "family_name": "M\u00fclmenst\u00e4dt", "given_name": "Johannes", "orcid": "0000-0003-1105-6678", "clpid": "M\u00fclmenst\u00e4dt-Johannes" }, { "family_name": "Roberts", "given_name": "Greg C.", "orcid": "0000-0002-3636-8590", "clpid": "Roberts-Greg-C" }, { "family_name": "Shingler", "given_name": "Taylor", "orcid": "0000-0003-4596-1027", "clpid": "Shingler-Taylor" }, { "family_name": "Song", "given_name": "Siwon", "orcid": "0000-0002-2001-4106", "clpid": "Song-Siwon" }, { "family_name": "Wang", "given_name": "Zhen", "orcid": "0000-0002-7921-3134", "clpid": "Wang-Zhen" }, { "family_name": "Wonasch\u00fctz", "given_name": "Anna", "clpid": "Wonasch\u00fctz-Anna" } ], "abstract": "Aerosol\u2013cloud\u2013radiation interactions are widely held to be the largest single source of uncertainty in climate model projections of future radiative forcing due to increasing anthropogenic emissions. The underlying causes of this uncertainty among modeled predictions of climate are the gaps in our fundamental understanding of cloud processes. There has been significant progress with both observations and models in addressing these important questions but quantifying them correctly is nontrivial, thus limiting our ability to represent them in global climate models. The Eastern Pacific Emitted Aerosol Cloud Experiment (E-PEACE) 2011 was a targeted aircraft campaign with embedded modeling studies, using the Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter aircraft and the research vessel Point Sur in July and August 2011 off the central coast of California, with a full payload of instruments to measure particle and cloud number, mass, composition, and water uptake distributions. EPEACE used three emitted particle sources to separate particle-induced feedbacks from dynamical variability, namely 1) shipboard smoke-generated particles with 0.05\u20131-\u03bcm diameters (which produced tracks measured by satellite and had drop composition characteristic of organic smoke), 2) combustion particles from container ships with 0.05\u20130.2-\u03bcm diameters (which were measured in a variety of conditions with droplets containing both organic and sulfate components), and 3) aircraft-based milled salt particles with 3\u20135-\u03bcm diameters (which showed enhanced drizzle rates in some clouds). The aircraft observations were consistent with past large-eddy simulations of deeper clouds in ship tracks and aerosol\u2013 cloud parcel modeling of cloud drop number and composition, providing quantitative constraints on aerosol effects on warm-cloud microphysics.", "doi": "10.1175/BAMS-D-12-00015.1", "issn": "0003-0007", "publisher": "American Meteorological Society", "publication": "Bulletin of the American Meteorological Society", "publication_date": "2013-05", "series_number": "5", "volume": "94", "issue": "5", "pages": "709-729" }, { "id": "authors:fvz7q-vyx29", "collection": "authors", "collection_id": "fvz7q-vyx29", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200529-093434315", "type": "article", "title": "Occurrence of lower cloud albedo in ship tracks", "author": [ { "family_name": "Chen", "given_name": "Y.-C.", "orcid": "0000-0001-7997-8578", "clpid": "Chen-Yi-Chun" }, { "family_name": "Christensen", "given_name": "M. W.", "clpid": "Christensen-M-W" }, { "family_name": "Xue", "given_name": "L.", "clpid": "Xue-L" }, { "family_name": "Sorooshian", "given_name": "A.", "orcid": "0000-0002-2243-2264", "clpid": "Sorooshian-A" }, { "family_name": "Stephens", "given_name": "G. L.", "clpid": "Stephens-G-L" }, { "family_name": "Rasmussen", "given_name": "R. M.", "clpid": "Rasmussen-R-M" }, { "family_name": "Seinfeld", "given_name": "J. H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "abstract": "The concept of geoengineering by marine cloud brightening is based on seeding marine stratocumulus clouds with sub-micrometer sea-salt particles to enhance the cloud droplet number concentration and cloud albedo, thereby producing a climate cooling effect. The efficacy of this as a strategy for global cooling rests on the extent to which aerosol-perturbed marine clouds will respond with increased albedo. Ship tracks, quasi-linear cloud features prevalent in oceanic regions impacted by ship exhaust, are a well-known manifestation of the effect of aerosol injection on marine clouds. We present here an analysis of the albedo responses in ship tracks, based on in situ aircraft measurements and three years of satellite observations of 589 individual ship tracks. It is found that the sign (increase or decrease) and magnitude of the albedo response in ship tracks depends on the mesoscale cloud structure, the free tropospheric humidity, and cloud top height. In a closed cell structure (cloud cells ringed by a perimeter of clear air), nearly 30% of ship tracks exhibited a decreased albedo. Detailed cloud responses must be accounted for in global studies of the potential efficacy of sea-spray geoengineering as a means to counteract global warming.", "doi": "10.5194/acp-12-8223-2012", "issn": "1680-7324", "publisher": "European Geosciences Union", "publication": "Atmospheric Chemistry and Physics", "publication_date": "2012-09-12", "series_number": "17", "volume": "12", "issue": "17", "pages": "8223-8235" }, { "id": "authors:v7mwd-y8h76", "collection": "authors", "collection_id": "v7mwd-y8h76", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20111031-111332320", "type": "article", "title": "A comprehensive numerical study of \n aerosol-cloud-precipitation interactions in marine stratocumulus", "author": [ { "family_name": "Chen", "given_name": "Y.-C.", "orcid": "0000-0001-7997-8578", "clpid": "Chen-Yi-Chun" }, { "family_name": "Xue", "given_name": "L.", "clpid": "Xue-L" }, { "family_name": "Lebo", "given_name": "Z. J.", "orcid": "0000-0002-1064-4833", "clpid": "Lebo-Z-J" }, { "family_name": "Wang", "given_name": "H.", "clpid": "Wang-H" }, { "family_name": "Rasmussen", "given_name": "R. M.", "clpid": "Rasmussen-R-M" }, { "family_name": "Seinfeld", "given_name": "J. H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "abstract": "Three-dimensional large-eddy simulations (LES) with detailed bin-resolved microphysics are performed to explore the diurnal variation of marine stratocumulus (MSc) clouds under clean and polluted conditions. The sensitivity of the aerosol-cloud-precipitation interactions to variation of sea surface temperature, free tropospheric humidity, large-scale divergence rate, and wind speed is assessed. The comprehensive set of simulations corroborates previous studies that (1) with moderate/heavy drizzle, an increase in aerosol leads to an increase in cloud thickness; and (2) with non/light drizzle, an increase in aerosol results in a thinner cloud, due to the pronounced effect on entrainment. It is shown that for higher SST, stronger large-scale divergence, drier free troposphere, or lower wind speed, the cloud thins and precipitation decreases. The sign and magnitude of the Twomey effect, droplet dispersion effect, cloud thickness effect, and cloud optical depth susceptibility to aerosol perturbations (i.e., change in cloud optical depth to change in aerosol number concentration) are evaluated by LES experiments and compared with analytical formulations. The Twomey effect emerges as dominant in total cloud optical depth susceptibility to aerosol perturbations. The dispersion effect, that of aerosol perturbations on the cloud droplet size spectrum, is positive (i.e., increase in aerosol leads to spectral narrowing) and accounts for 3% to 10% of the total cloud optical depth susceptibility at nighttime, with greater influence in heavier drizzling clouds. The cloud thickness effect is negative (i.e., increase in aerosol leads to thinner cloud) for non/light drizzling cloud and positive for a moderate/heavy drizzling clouds; the cloud thickness effect contributes 5% to 22% of the nighttime total cloud susceptibility. Overall, the total cloud optical depth susceptibility ranges from ~0.28 to 0.53 at night; an increase in aerosol concentration enhances cloud optical depth, especially with heavier precipitation and in a more pristine environment. During the daytime, the range of magnitude for each effect is more variable owing to cloud thinning and decoupling. The good agreement between LES experiments and analytical formulations suggests that the latter may be useful in evaluations of the total cloud susceptibility. The ratio of the magnitude of the cloud thickness effect to that of the Twomey effect depends on cloud base height and cloud thickness in unperturbed (clean) clouds.", "doi": "10.5194/acp-11-9749-2011", "issn": "1680-7316", "publisher": "European Geosciences Union", "publication": "Atmospheric Chemistry and Physics", "publication_date": "2011-09-21", "series_number": "18", "volume": "11", "issue": "18", "pages": "9749-9769" } ]