The Impact of Aerosols on the Summer Rainfall Frequency in China

Choi, Yun-Sang; Ho, Chin Siong; Kim, Jinwon; Gong, D.; Park, Rokjin J.

doi:10.1175/2007jamc1745.1

Cited by 59 publications

(33 citation statements)

References 37 publications

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“…This trend for light rain is different from that of total rainfall observed in eastern China, which shows decreases in northern China and increases in southeastern China. Choi et al (2008) also showed that, over recent decades, increases in aerosol concentrations correlated negatively with the trend in light rain (< 5 mm d −1 ) and positively with changes in moderate rainfall (10-20 mm d −1 ) in China. A study by Rosenfeld et al (2008) proposed that interactions of aerosols with deep convective clouds could increase precipitation, which might be responsible for the observed increases in precipitation in southern China where aerosol concentrations were high and water vapor supply was adequate.…”

Section: Changes In Precipitation and Cloudsmentioning

confidence: 87%

Climatic effects of air pollutants over china: A review

2014

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Tropospheric ozone (O 3 ) and aerosols are major air pollutants in the atmosphere. They have also made significant contributions to radiative forcing of climate since preindustrial times. With its rapid economic development, concentrations of air pollutants are relatively high in China; hence, quantifying the role of air pollutants in China in regional climate change is especially important. This review summarizes existing knowledge with regard to impacts of air pollutants on climate change in China and defines critical gaps needed to reduce the associated uncertainties. Measured monthly, seasonal, and annual mean surface-layer concentrations of O 3 and aerosols over China are compiled in this work, with the aim to show the magnitude of concentrations of O 3 and aerosols over China and to provide datasets for evaluation of model results in future studies. Ground-based and satellite measurements of O 3 column burden and aerosol optical properties, as well as model estimates of radiative forcing by tropospheric O 3 and aerosols are summarized. We also review regional and global modeling studies that have investigated climate change driven by tropospheric O 3 and/or aerosols in China; the predicted sign and magnitude of the responses in temperature and precipitation to O 3 /aerosol forcings are presented. Based on this review, key priorities for future research on the climatic effects of air pollutants in China are highlighted.

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Section: Changes In Precipitation and Cloudsmentioning

confidence: 87%

Climatic effects of air pollutants over china: A review

2014

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“…This finding can serve to resolve many contradictions related to interactions between aerosols, clouds, and precipitation. For example, an increase in precipitation caused by an increase in aerosol concentrations is particularly dominant over China (29) and the Amazon region (19), whereas the opposite is true over other regions; the former process is known as the so-called "cold rain process by IN particles," whereas the latter is known as the "warm rain process by cloud condensation nuclei particles." In this respect, the observed regional distribution of SCF shown in Fig.…”

Section: Discussionmentioning

confidence: 99%

Space observations of cold-cloud phase change

Choi

Lindzen

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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129

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This study examines the vertically resolved cloud measurements from the cloud-aerosol lidar with orthogonal polarization instrument on Aqua satellite from June 2006 through May 2007 to estimate the extent to which the mixed cloud-phase composition can vary according to the ambient temperature, an important concern for the uncertainty in calculating cloud radiative effects. At −20°C, the global average fraction of supercooled clouds in the total cloud population is found to be about 50% in the data period. Between −10 and −40°C, the fraction is smaller at lower temperatures. However, there are appreciable regional and temporal deviations from the global mean (> AE 20%) at the isotherm. In the analysis with coincident dust aerosol data from the same instrument, it appears that the variation in the supercooled cloud fraction is negatively correlated with the frequencies of dust aerosols at the −20°C isotherm. This result suggests a possibility that dust particles lifted to the cold cloud layer effectively glaciate supercooled clouds. Observations of radiative flux from the clouds and earth's radiant energy system instrument aboard Terra satellite, as well as radiative transfer model simulations, show that the 20% variation in the supercooled cloud fraction is quantitatively important in cloud radiative effects, especially in shortwave, which are 10 − 20 W m −2 for regions of mixed-phase clouds affected by dust. In particular, our results demonstrate that dust, by glaciating supercooled water, can decrease albedo, thus compensating for the increase in albedo due to the dust aerosols themselves. This has important implications for the determination of climate sensitivity.aerosol-cloud interaction | ice nucleation | mixed cloud phase | super cooled water | cloud radiative effect C old clouds that consist of mixed-phase particles, are ubiquitous in the Earth's upper and middle troposphere. Changes in the liquid/ice-phase composition in such clouds may significantly affect the radiative balance of the earth atmosphere system because the cloud radiative properties for both the shortwave (SW) and longwave (LW) such as cloud optical depth, single-scattering albedo, and emissivity vary according to the phase of cloud particles (1-3). It is therefore of fundamental importance to examine the variation in the cloud-phase composition for accurate calculations of cloud radiative effects.In fact, the cloud-phase composition in mixed-phase clouds is complicatedly affected by several factors other than temperature; e.g., ice nuclei (IN) aerosols. Most of climate models, however, have calculated the cloud-phase composition with limited sophistication, simply as a function of grid-mean temperature (4). For example, it has been typically assumed that clouds are composed entirely of ice and liquid particles below −40°C and above 0°C, respectively, of a mixture of ice and liquid phases between −40 and 0°C. The fraction of supercooled liquid particles within mixed-phase clouds is represented as a linear function of temperatures in genera...

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“…PM 10 is easier to act as CCN and can impact low warm cloud. The enhancement of low-level warm cloud caused by lower PM 10 enriches warm-rain efficiency Choi et al, 2008b) and moderate rain is negligible, while the weak correlation coefficient shows that AOD and moderate rain have some relations. These results show very weak correlations between surface aerosols (e.g., PM 10 ) and moderate rain.…”

Section: Relation Between Precipitation and Aerosolmentioning

confidence: 95%

Inter-Annual Variations of Cloud and Precipitation and their Possible Relationships with Surface Aerosols in Shanghai

Zhang

Duan

et al. 2015

Aerosol Air Qual. Res.

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Aerosol-cloud-precipitation interactions have attracted much more attention for decades, but there still remain many uncertainties in assessing global climate. Long-term ground-based measurements of aerosol, cloud and precipitation in Shanghai were used to examine their inter-annual variations and possible relationships. During 1990-2010, the yearlyaveraged total cloud cover (TCC) and low cloud cover (LCC) decrease on average by 0.58% and 2.49% per year. LCC correlates to surface aerosols (e.g., PM 10 ), with a correlation coefficient (R) of 0.67. Aerosol optical depth (AOD), as an indicator of columnar aerosol loading, shows a non-significant correlation with cloud cover. The yearly-aggregated heavy and extreme rain days and their rainfall amount increase gradually. The moderate rain day enhances but its annual rainfall amount declines year by year, while the light rain exhibits an opposite pattern to the moderate rain. These results imply that local aerosols maybe exert somewhat enforcing on low cloud and light rain through possible entrainment or updraft that can bring up surface particles into free troposphere, whereas its influence to total cloud and precipitation is negligible at a small scale. Future studies are needed to ensure whether local aerosols to directly affect low cloud, and to explore how surface aerosols to enter into higher atmospheric layers and impact cloud and precipitation at larger scales.

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The Impact of Aerosols on the Summer Rainfall Frequency in China

Cited by 59 publications

References 37 publications

Climatic effects of air pollutants over china: A review

Climatic effects of air pollutants over china: A review

Space observations of cold-cloud phase change

Inter-Annual Variations of Cloud and Precipitation and their Possible Relationships with Surface Aerosols in Shanghai

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