Satellite-derived direct radiative effect of aerosols dependent on cloud cover

Chand, D.; Wood, Robert; Anderson, Theodore L.; Satheesh, S. K.; Charlson, Robert J.

doi:10.1038/ngeo437

Cited by 286 publications

(356 citation statements)

References 29 publications

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“…Such aerosol plumes, which are common during the biomass burning season off the west coast of Africa, are clearly evident based on CALIPSO observations (e.g. Chand et al, 2009).…”

Section: Above-cloud Aerosol Layersmentioning

confidence: 99%

Investigating potential biases in observed and modeled metrics of aerosol-cloud-precipitation interactions

2011

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Abstract. This study utilizes large eddy simulation, aircraft measurements, and satellite observations to identify factors that bias the absolute magnitude of metrics of aerosol-cloudprecipitation interactions for warm clouds. The metrics considered are precipitation susceptibility S o , which examines rain rate sensitivity to changes in drop number, and a cloudprecipitation metric, χ, which relates changes in rain rate to those in drop size. While wide ranges in rain rate exist at fixed cloud drop concentration for different cloud liquid water amounts, χ and S o are shown to be relatively insensitive to the growth phase of the cloud for large datasets that include data representing the full spectrum of cloud lifetime. Spatial resolution of measurements is shown to influence the liquid water path-dependent behavior of S o and χ. Other factors of importance are the choice of the minimum rain rate threshold, and how to quantify rain rate, drop size, and the cloud condensation nucleus proxy. Finally, low biases in retrieved aerosol amounts owing to wet scavenging and high biases associated with above-cloud aerosol layers should be accounted for. The paper explores the impact of these effects for model, satellite, and aircraft data.

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“…Such aerosol plumes, which are common during the biomass burning season off the west coast of Africa, are clearly evident based on CALIPSO observations (e.g. Chand et al, 2009).…”

Section: Above-cloud Aerosol Layersmentioning

confidence: 99%

Investigating potential biases in observed and modeled metrics of aerosol-cloud-precipitation interactions

2011

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“…The peak heating rate in the aerosol layer is 2 K d −1 and 3.5 K d −1 for AOD of 0.4 and 1.0 respectively. Seasonal-mean AOD values for cloudy conditions over the southeast Atlantic Ocean are presented by Chand et al (2009). The mean value reaches as high as 0.5 near the coast and instantaneous values can reach as high as 1.0 (see Chand et al, 2009, Supplement Fig.…”

Section: Methodsmentioning

confidence: 99%

“…The level of cloud cover corresponding to the change in sign of the forcing depends on the aerosol optical thickness, aerosol single-scattering albedo, and whether the aerosol layer resides above the cloud or in the cloud. Chand et al (2009) determine that this critical cloud fraction is about 0.4 for the southeast Atlantic region considered here based on satellite remote sensing observations. Therefore, the direct radiative forcing at the top-of-atmosphere of the smoke aerosol is expected to be positive for the overcast scenes explored here.…”

Section: Lower Tropospheric Warming and Cloud Thickeningmentioning

confidence: 99%

Stratocumulus cloud thickening beneath layers of absorbing smoke aerosol

2010

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Abstract. Marine stratocumulus cloud properties, and the free-tropospheric environment above them, are examined in NASA A-Train satellite data for cases where smoke from seasonal burning of the West African savannah overlay the persistent southeast Atlantic stratocumulus cloud deck. CALIPSO space-borne lidar observations show that features identified as layers of aerosol occur predominantly between 2 km and 4 km. Layers identified as cloud features occur predominantly below 1.5 km altitude and beneath the layer of elevated smoke aerosol. The diurnal mean shortwave heating rates attributable to the absorption of solar energy in the aerosol layer is nearly 1.5 K d −1 for an aerosol optical thickness value of 1, and increases to 1.8 K d −1 when the smoke resides above clouds owing to the additional component of upward solar radiation reflected by the cloud. As a consequence of this heating, the 700 hPa air temperature above the cloud deck is warmer by approximately 1 K on average for cases where smoke is present above the cloud compared to cases without smoke above cloud. The warmer conditions in the free-troposphere above the cloud during smoke events coincide with cloud liquid water path values that are greater by 20 g m −2 and cloud tops that are lower for overcast conditions compared to periods with low amounts of smoke. The observed thickening and subsidence of the cloud layer are consistent with published results of large-eddy simulations showing that solar absorption by smoke above stratocumulus clouds increases the buoyancy of free-tropospheric air above the temperature inversion capping the boundary layer. Increased buoyancy inhibits the entrainment of dry air through the cloud-top, thereby helping to preserve humidity and cloud cover in the boundary layer. The direct radiative effect of absorbing aerosols residing over a bright cloud deck is a positive radiative forcing (warming) at the top of the atCorrespondence to: E. M. Wilcox (eric.wilcox@dri.edu) mosphere. However, the greater liquid water path for cases of smoke overlaying cloud contributes an additional negative semi-direct radiative forcing (cooling) of climate in locations such as the southeast Atlantic Ocean owing to the enhanced albedo of the thicker cloud.

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“…[2] Recent studies have found correlations between cloud and aerosol properties [Kaufman et al, 2005;Loeb and Schuster, 2008] along with the potential impact on global radiative forcing [Chand et al, 2009]. These correlations may be caused by passive remote sensing artifacts, aerosol and cloud dependence on large scale meteorology, aerosol influence on cloud properties, or cloud influence on aerosol properties in the near cloud environment due to cloud processing.…”

Section: Introductionmentioning

confidence: 99%

Enhanced aerosol backscatter adjacent to tropical trade wind clouds revealed by satellite‐based lidar

Tackett¹,

Girolamo²

2009

Geophysical Research Letters

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[1] There have been many proposed processes by which clouds modify aerosol properties, suggesting that aerosol properties near clouds are different than far from clouds. We provide the first satellite-based lidar observations of backscatter and color ratio, quantities directly related to aerosol properties, as a function of distance to cloud edge for boundary layer clouds over the western tropical Atlantic. We show backscatter and color ratio are enhanced adjacent to cloud edge, particularly near cloud top and cloud base. Specifically, layer integrated median backscatter increases by 31 ± 3% and 42 ± 2%, at wavelengths of 532 nm, and 1,064 nm, respectively, and layer averaged color ratio increases by 15 ± 5%. Backscatter calculations suggest our observations adjacent to cloud are best explained by an aerosol size distribution with reduced number concentration, increased median radius, and decreased width compared to far from cloud.

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Satellite-derived direct radiative effect of aerosols dependent on cloud cover

Cited by 286 publications

References 29 publications

Investigating potential biases in observed and modeled metrics of aerosol-cloud-precipitation interactions

Investigating potential biases in observed and modeled metrics of aerosol-cloud-precipitation interactions

Stratocumulus cloud thickening beneath layers of absorbing smoke aerosol

Enhanced aerosol backscatter adjacent to tropical trade wind clouds revealed by satellite‐based lidar

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