Distinct Impacts of Increased Aerosols on Cloud Droplet Number Concentration of Stratus/Stratocumulus and Cumulus

Jia, Hui; Ma, Xiaoyan; Yu, Fangqun; Liu, Y.; Yin, Yan

doi:10.1029/2019gl085081

Cited by 24 publications

(19 citation statements)

References 55 publications

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“…In the cross-section of Figure 9b, no decrease in the rain water in the lee side of the Pyrenees is observed, as the cross-section orientation does not include the area characterized by significant rainfall suppression (Figure 8b). The above procedure confirms the fact that cloud and rain water production are two inverse processes [106,107], highly dependent on the impact of the CCN to the atmospheric conditions.…”

Section: Impact On the Precipitation Patternsupporting

confidence: 77%

“…Apart from the enhanced evaporation, high amounts of relative humidity contribute to the above mechanism. On the contrary, pristine conditions lead to the exact opposite results, as limited evaporation conditions, lower relative humidity amounts and decreased cloud water mixing ratios lead to important cloud to rain water conversion and enhancement of precipitation [106,107]. It is remarkable that the prognostic treatment of dust particles enhances significantly the precipitation over areas far away from the dust event.…”

Section: Discussionmentioning

confidence: 99%

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Assessing Desert Dust Indirect Effects on Cloud Microphysics through a Cloud Nucleation Scheme: A Case Study over the Western Mediterranean

et al. 2020

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In this study, the performance and characteristics of the advanced cloud nucleation scheme of Fountoukis and Nenes, embedded in the fully coupled Weather Research and Forecasting/Chemistry (WRF/Chem) model, are investigated. Furthermore, the impact of dust particles on the distribution of the cloud condensation nuclei (CCN) and the way they modify the pattern of the precipitation are also examined. For the simulation of dust particle concentration, the Georgia Tech Goddard Global Ozone Chemistry Aerosol Radiation and Transport of Air Force Weather Agency (GOCART-AFWA) is used as it includes components for the representation of dust emission and transport. The aerosol activation parameterization scheme of Fountoukis and Nenes has been implemented in the six-class WRF double-moment (WDM6) microphysics scheme, which treats the CCN distribution as a prognostic variable, but does not take into account the concentration of dust aerosols. Additionally, the presence of dust particles that may facilitate the activation of CCN into cloud or rain droplets has also been incorporated in the cumulus scheme of Grell and Freitas. The embedded scheme is assessed through a case study of significant dust advection over the Western Mediterranean, characterized by severe rainfall. Inclusion of CCN based on prognostic dust particles leads to the suppression of precipitation over hazy areas. On the contrary, precipitation is enhanced over areas away from the dust event. The new prognostic CCN distribution improves in general the forecasting skill of the model as bias scores, the root mean square error (RMSE), false alarm ratio (FAR) and frequencies of missed forecasts (FOM) are limited when modelled data are compared against satellite, LIDAR and aircraft observations.

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Section: Impact On the Precipitation Patternsupporting

confidence: 77%

Section: Discussionmentioning

confidence: 99%

Assessing Desert Dust Indirect Effects on Cloud Microphysics through a Cloud Nucleation Scheme: A Case Study over the Western Mediterranean

et al. 2020

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“…Note that the Southern Oceans only has a limited impact on the global-averaged RF aci due to its low anthropogenic fraction 35 . In situ observations have demonstrated that the response of N d to aerosols is more sensitive for stratiform clouds than cumuliform clouds 26 . Also, stratiform ones have smaller retrieval biases for the N d retrieval than cumulus ones 16 , thus suffer less AIE underestimation caused by partly cloudy retrievals 17,25 .…”

Section: Resultsmentioning

confidence: 99%

Significant underestimation of radiative forcing by aerosol–cloud interactions derived from satellite-based methods

Jia

et al. 2021

Nat Commun

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Satellite-based estimates of radiative forcing by aerosol–cloud interactions (RFaci) are consistently smaller than those from global models, hampering accurate projections of future climate change. Here we show that the discrepancy can be substantially reduced by correcting sampling biases induced by inherent limitations of satellite measurements, which tend to artificially discard the clouds with high cloud fraction. Those missed clouds exert a stronger cooling effect, and are more sensitive to aerosol perturbations. By accounting for the sampling biases, the magnitude of RFaci (from −0.38 to −0.59 W m−2) increases by 55 % globally (133 % over land and 33 % over ocean). Notably, the RFaci further increases to −1.09 W m−2 when switching total aerosol optical depth (AOD) to fine-mode AOD that is a better proxy for CCN than AOD. In contrast to previous weak satellite-based RFaci, the improved one substantially increases (especially over land), resolving a major difference with models.

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“…For instance, the marine boundary layer is deeper and more likely to be decoupled in this region, so the aerosols and precursor gases emitted by ships near the surface may not be efficiently transported to the subcloud layer. Additionally, it is possible that cumuliform clouds are less susceptible to aerosol‐driven increased in N d than stratiform clouds for physical reasons, such as differences in supersaturation adjustments between the two regimes (Jia et al, ).…”

Section: The Issue Of Detectability and Its Policy Implicationsmentioning

confidence: 99%

Substantial Cloud Brightening From Shipping in Subtropical Low Clouds

et al. 2020

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The influence of aerosol particles on cloud reflectivity remains one of the largest sources of uncertainty in our understanding of anthropogenic climate change. Commercial shipping constitutes a large and concentrated aerosol perturbation in a meteorological regime where clouds have a disproportionally large effect on climate. Yet, to date, studies have been unable to detect climatologically relevant cloud radiative effects from shipping, despite models indicating that the cloud response should produce a sizable negative radiative forcing (perturbation to Earth's energy balance). We attribute a significant increase in cloud reflectivity to enhanced cloud droplet number concentrations within a major shipping corridor in the southeast Atlantic. Prevailing winds constrain emissions around the corridor, which cuts through a climatically important region of expansive low cloud cover. We use universal kriging, a classic geostatistical method, to estimate what cloud properties would have been in the absence of shipping. In the morning, cloud brightening is consistent with changes in microphysics alone, whereas in the afternoon, increases in cloud brightness from microphysical changes are offset by decreases in the total amount of cloud water. We calculate an effective radiative forcing within the southeast Atlantic shipping corridor of approximately −2 W/m2. Several years of data are required to identify a clear signal. Extrapolating our results globally, we calculate an effective radiative forcing due to aerosol‐cloud interactions in low clouds of −1.0 W/m2 (95% confidence interval: −1.6 to −0.4 W/m2). The unique setup in the southeast Atlantic could be an ideal test for the representation of aerosol‐cloud interactions in climate models.

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Distinct Impacts of Increased Aerosols on Cloud Droplet Number Concentration of Stratus/Stratocumulus and Cumulus

Cited by 24 publications

References 55 publications

Assessing Desert Dust Indirect Effects on Cloud Microphysics through a Cloud Nucleation Scheme: A Case Study over the Western Mediterranean

Assessing Desert Dust Indirect Effects on Cloud Microphysics through a Cloud Nucleation Scheme: A Case Study over the Western Mediterranean

Significant underestimation of radiative forcing by aerosol–cloud interactions derived from satellite-based methods

Substantial Cloud Brightening From Shipping in Subtropical Low Clouds

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