Climate Modification by Atmospheric Aerosols

McCormick, Robert A.; Ludwig, John H.

doi:10.1126/science.156.3780.1358

Cited by 279 publications

(144 citation statements)

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“…Remote sensing of aerosols has been of considerable interest, because of the fact that increasing atmospheric aerosol concentrations scatters more sunlight back into space, increases planetary albedo and decreases the temperature of the Earth (McCormick and Ludwig 1967). Researchers have estimated that an increase in the tropospheric aerosol optical depth (AOD) of 0.1 would decrease the temperature about 1°C on Earth's surface (Hansen and Lacis 1990).…”

Section: Introductionmentioning

confidence: 99%

Error Analysis of Retrieved Aerosol Optical Depth due to Adjacency Effect for ROCSAT-2 RSI Bands

Liu¹

2005

Terr. Atmos. Ocean. Sci.

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The adjacency effect (AE), caused by the scattering of reflected radiance from an inhomogeneous surface, is known to introduce a blurring effect on remotely sensed data, especially for high spatial resolution data. The retrieval of aerosol optical depth (AOD) by the dark target (DT) method usually neglects the AE. Hence, significant errors may be induced in aerosol retrieval. In this study, the errors of retrieved AOD due to AE by the DT method for very high spatial resolution data of 8 m in the multi-spectral bands of ROCSAT-2 RSI are investigated. A fast, accurate simple atmospheric correction model is applied. Target size is considered the same as the spatial resolution. The errors are mainly studied for both low and medium contrasts, in both clear and hazy skies for both continental and urban aerosol models. The results indicate that for the continental model, AE may cause significant retrieval errors for AOD over DTs for medium contrast in both skies in blue and red bands. Error becomes negligible if the inhomogeneous surface is for low contrast in clear sky. It is larger for the urban model where there is more absorption than for the continental model, due to the less sensitivity of top-of-atmosphere reflectance to AOD for DTs in inhomogeneous surfaces. This suggests that AE be considered for medium contrast in both skies, especially for urban-industrial regions for ROCSAT-2 RSI.

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Section: Introductionmentioning

confidence: 99%

Error Analysis of Retrieved Aerosol Optical Depth due to Adjacency Effect for ROCSAT-2 RSI Bands

Liu¹

2005

Terr. Atmos. Ocean. Sci.

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“…First, they can directly alter the energy balance due to scattering and absorption of incoming solar radiation (e.g. McCormick and Ludwig, 1967). Second, they can act as cloud condensation nuclei (CCN) and thus modify the cloud micro-physical properties and lifetime as well as precipitation (Ramanathan et al, 2001;Krüger and Grassl, 2011).…”

Section: Introductionmentioning

confidence: 99%

Analysis of aerosol effects on warm clouds over the Yangtze River Delta from multi-sensor satellite observations

et al. 2017

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Abstract. Aerosol effects on low warm clouds over the Yangtze River Delta (YRD, eastern China) are examined using co-located MODIS, CALIOP and CloudSat observations. By taking the vertical locations of aerosol and cloud layers into account, we use simultaneously observed aerosol and cloud data to investigate relationships between cloud properties and the amount of aerosol particles (using aerosol optical depth, AOD, as a proxy). Also, we investigate the impact of aerosol types on the variation of cloud properties with AOD. Finally, we explore how meteorological conditions affect these relationships using ERA-Interim reanalysis data. This study shows that the relation between cloud properties and AOD depends on the aerosol abundance, with a different behaviour for low and high AOD (i.e. AOD < 0.35 and AOD > 0.35). This applies to cloud droplet effective radius (CDR) and cloud fraction (CF), but not to cloud optical thickness (COT) and cloud top pressure (CTP). COT is found to decrease when AOD increases, which may be due to radiative effects and retrieval artefacts caused by absorbing aerosol. Conversely, CTP tends to increase with elevated AOD, indicating that the aerosol is not always prone to expand the vertical extension. It also shows that the COT-CDR and CWP (cloud liquid water path)-CDR relationships are not unique, but affected by atmospheric aerosol loading. Furthermore, separation of cases with either polluted dust or smoke aerosol shows that aerosol-cloud interaction (ACI) is stronger for clouds mixed with smoke aerosol than for clouds mixed with dust, which is ascribed to the higher absorption efficiency of smoke than dust. The variation of cloud properties with AOD is analysed for various relative humidity and boundary layer thermodynamic and dynamic conditions, showing that high relative humidity favours larger cloud droplet particles and increases cloud formation, irrespective of vertical or horizontal level. Stable atmospheric conditions enhance cloud cover horizontally. However, unstable atmospheric conditions favour thicker and higher clouds. Dynamically, upward motion of air parcels can also facilitate the formation of thicker and higher clouds. Overall, the present study provides an understanding of the impact of aerosols on cloud properties over the YRD. In addition to the amount of aerosol particles (or AOD), evidence is provided that aerosol types and ambient environmental conditions need to be considered to understand the observed relationships between cloud properties and AOD.

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“…Aerosol affects the Earth and atmospheric radiation budget by directly scattering and absorbing the incoming solar radiation (McCormick and Ludwig, 1967;Charlson and Pilat, 1969;Atwater, 1970;Coakley Jr. et al, 1983) and by indirectly increasing the cloud albedo and suppressing precipitation by modifying cloud microphysical properties as cloud condensation nuclei (Twomey, 1977;Albrecht, 1989). The direct aerosol effect will influence the atmospheric temperature structure and cloud formation (Grassl, 1975;Hansen et al, 1997;Ackerman et al, 2000;Koren et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

A case study of dust aerosol radiative properties over Lanzhou, China

et al. 2010

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Abstract. The vertical distribution of dust aerosol and its radiative properties are analysed using the data measured by the micropulse lidar, profiling microwave radiometer, sunphotometer, particulate monitor, and nephelometer at the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL) during a dust storm from 27 March to 29 March 2007. The analysis shows that the dust aerosol mainly exists below 2 km in height, and the dust aerosol extinction coefficient decreases with height. The temporal evolution of aerosol optical depth (AOD) during the dust storm is characterized by a sub-maximum at 22:00 (Beijing Time), 27 March and a maximum at 12:00, 28 March. The AOD respectively derived by lidar and sunphotometer shows a good consistency. The PM 10 concentration and aerosol scattering coefficient share similar variation trends, and their maximums both appear at 22:00, 27 March.The aerosol extinction coefficient and relative humidity have the similar trends and their maximums almost appear at the same heights, which presents a correlation between extinction coefficient and relative humidity known as aerosol hygroscopicity. The relative humidity is related with temperature, and then the temperature will affect the aerosol extinction properties by modifying the relative humidity condition.The aerosol extinction coefficient, scattering coefficient, and PM 10 concentration present good linear correlations. The correlation coefficients of the aerosol scattering coefficients of 450, 520, and 700 nm and PM 10 concentration, of aerosol extinction coefficient retrieved by lidar at 532 nm and PM 10 concentration, and of aerosol extinction and scattering coefficient are respectively 0.98, 0.94, and 0.96.

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Climate Modification by Atmospheric Aerosols

Cited by 279 publications

References 6 publications

Error Analysis of Retrieved Aerosol Optical Depth due to Adjacency Effect for ROCSAT-2 RSI Bands

Error Analysis of Retrieved Aerosol Optical Depth due to Adjacency Effect for ROCSAT-2 RSI Bands

Analysis of aerosol effects on warm clouds over the Yangtze River Delta from multi-sensor satellite observations

A case study of dust aerosol radiative properties over Lanzhou, China

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