scholarly journals Wet scavenging limits the detection of aerosol effects on precipitation

2015 ◽  
Vol 15 (13) ◽  
pp. 7557-7570 ◽  
Author(s):  
E. Gryspeerdt ◽  
P. Stier ◽  
B. A. White ◽  
Z. Kipling
Keyword(s):  
Spatial Variability ◽  
General Circulation ◽  
Regional Scale ◽  
General Circulation Models ◽  
Satellite Observations ◽  
Scale Model ◽  
Convective Clouds ◽  
Aerosol Cloud ◽  
Wet Scavenging ◽  
Aerosol Properties

Abstract. Satellite studies of aerosol–cloud interactions usually make use of retrievals of both aerosol and cloud properties, but these retrievals are rarely spatially co-located. While it is possible to retrieve aerosol properties above clouds under certain circumstances, aerosol properties are usually only retrieved in cloud-free scenes. Generally, the smaller spatial variability of aerosols compared to clouds reduces the importance of this sampling difference. However, as precipitation generates an increase in spatial variability of aerosols, the imperfect co-location of aerosol and cloud property retrievals may lead to changes in observed aerosol–cloud–precipitation relationships in precipitating environments. In this work, we use a regional-scale model, satellite observations and reanalysis data to investigate how the non-coincidence of aerosol, cloud and precipitation retrievals affects correlations between them. We show that the difference in the aerosol optical depth (AOD)–precipitation relationship between general circulation models (GCMs) and satellite observations can be explained by the wet scavenging of aerosol. Using observations of the development of precipitation from cloud regimes, we show how the influence of wet scavenging can obscure possible aerosol influences on precipitation from convective clouds. This obscuring of aerosol–cloud–precipitation interactions by wet scavenging suggests that even if GCMs contained a perfect representation of aerosol influences on convective clouds, the difficulty of separating the "clear-sky" aerosol from the "all-sky" aerosol in GCMs may prevent them from reproducing the correlations seen in satellite data.

scholarly journals Wet scavenging limits the detection of aerosol–cloud–precipitation interactions

2015 ◽  
Vol 15 (5) ◽  
pp. 6851-6886 ◽  
Author(s):  
E. Gryspeerdt ◽  
P. Stier ◽  
B. A. White ◽  
Z. Kipling
Keyword(s):  
Spatial Variability ◽  
General Circulation ◽  
Regional Scale ◽  
General Circulation Models ◽  
Satellite Observations ◽  
Scale Model ◽  
Convective Clouds ◽  
Aerosol Cloud ◽  
Wet Scavenging ◽  
Aerosol Properties

Abstract. Satellite studies of aerosol–cloud interactions usually make use of retrievals of both aerosol and cloud properties, but these retrievals are rarely spatially co-located. While it is possible to retrieve aerosol properties above clouds under certain circumstances, aerosol properties are usually only retrieved in cloud free scenes. Generally, the smaller spatial variability of aerosols compared to clouds reduces the importance of this sampling difference. However, as precipitation generates an increase in spatial variability, the imperfect co-location of aerosol and cloud property retrievals may lead to changes in observed aerosol–cloud–precipitation relationships in precipitating environments. In this work, we use a regional-scale model, satellite observations and reanalysis data to investigate how the non-coincidence of aerosol, cloud and precipitation retrievals affects correlations between them. We show that the difference in the aerosol optical depth (AOD)-precipitation relationship between general circulation models (GCMs) and satellite observations can be explained by the wet scavenging of aerosol. Using observations of the development of precipitation from cloud regimes, we show how the influence of wet scavenging can obscure possible aerosol influences on precipitation from convective clouds. This obscuring of aerosol–cloud–precipitation interactions by wet scavenging suggests that even if GCMs contained a perfect representation of aerosol influences on convective clouds, the difficulty of separating the "clear-sky" aerosol from the "all-sky" aerosol in GCMs may prevent them from reproducing the correlations seen in satellite data.

scholarly journals A global satellite view of aerosol cloud interactions

2004 ◽  
Vol 4 (5) ◽  
pp. 6823-6836 ◽  
Author(s):  
C. Luo
Keyword(s):  
North Africa ◽  
North Atlantic ◽  
Radiative Forcing ◽  
General Circulation ◽  
Large Scale ◽  
Regional Scale ◽  
Cloud Amount ◽  
General Circulation Models ◽  
Aerosol Cloud ◽  
Aerosol Cloud Interactions

Abstract. Long-term and large-scale correlations between Advanced Very High-Resolution Radiometer (AVHRR) aerosol optical depth and International Satellite Cloud Climatology Project (ISCCP) monthly cloud amount data show significant regional scale relationships between cloud amount and aerosols, consistent with aerosol-cloud interactions. Positive correlations between aerosols and cloud amount are associated with North American and Asian aerosols in the North Atlantic and Pacific storm tracks, and mineral aerosols in the tropical North Atlantic. Negative correlations are seen near biomass burning regions of North Africa and Indonesia, as well as south of the main mineral aerosol source of North Africa. These results suggest that there are relationships between aerosols and clouds in the observations that can be used by general circulation models to verify the correct forcing mechanisms for both direct and indirect radiative forcing by clouds.

scholarly journals Retrieval of Model Grid-Scale Heat Capacity Using Geostationary Satellite Products. Part I: First Case-Study Application

2005 ◽  
Vol 44 (9) ◽  
pp. 1346-1360 ◽  
Author(s):  
Richard T. McNider ◽  
William M. Lapenta ◽  
Arastoo P. Biazar ◽  
Gary J. Jedlovec ◽  
Ronnie J. Suggs ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Heat Capacity ◽  
General Circulation ◽  
Mesoscale Model ◽  
Regional Scale ◽  
Model Performance ◽  
General Circulation Models ◽  
Surface Energy Budget ◽  
Scale Model ◽  
First Case

Abstract In weather forecast and general circulation models the behavior of the atmospheric boundary layer, especially the nocturnal boundary layer, can be critically dependent on the magnitude of the effective model grid-scale bulk heat capacity. Yet, this model parameter is uncertain both in its value and in its conceptual meaning for a model grid in heterogeneous conditions. Current methods for estimating the grid-scale heat capacity involve the areal/volume weighting of heat capacity (resistance) of various, often ill-defined, components. This can lead to errors in model performance in certain parameter spaces. Here, a technique is proposed and tested for recovering bulk heat capacity using time tendencies in satellite-retrieved surface skin temperature (SST). The technique builds upon sensitivity studies that show that surface temperature is most sensitive to thermal inertia in the early evening hours. The retrievals are made within the context of a surface energy budget in a regional-scale model [the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5)]. The retrieved heat capacities are used in the forecast model, and it is shown that the model predictions of temperature are improved in the nighttime during the forecast periods.

scholarly journals The importance of considering sub-grid cloud variability when using satellite observations to evaluate the cloud and precipitation simulations in climate models

2018 ◽  
Vol 11 (8) ◽  
pp. 3147-3158 ◽  
Author(s):  
Hua Song ◽  
Zhibo Zhang ◽  
Po-Lun Ma ◽  
Steven Ghan ◽  
Minghuai Wang
Keyword(s):  
General Circulation ◽  
Climate Models ◽  
General Circulation Models ◽  
Satellite Observations ◽  
Community Atmosphere Model ◽  
Cloud Resolving Model ◽  
Moderate Resolution ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Indispensable Tool ◽  
Probability Of Precipitation

Abstract. Satellite cloud observations have become an indispensable tool for evaluating general circulation models (GCMs). To facilitate the satellite and GCM comparisons, the CFMIP (Cloud Feedback Model Inter-comparison Project) Observation Simulator Package (COSP) has been developed and is now increasingly used in GCM evaluations. Real-world clouds and precipitation can have significant sub-grid variations, which, however, are often ignored or oversimplified in the COSP simulation. In this study, we use COSP cloud simulations from the Super-Parameterized Community Atmosphere Model (SPCAM5) and satellite observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) and CloudSat to demonstrate the importance of considering the sub-grid variability of cloud and precipitation when using the COSP to evaluate GCM simulations. We carry out two sensitivity tests: SPCAM5 COSP and SPCAM5-Homogeneous COSP. In the SPCAM5 COSP run, the sub-grid cloud and precipitation properties from the embedded cloud-resolving model (CRM) of SPCAM5 are used to drive the COSP simulation, while in the SPCAM5-Homogeneous COSP run only grid-mean cloud and precipitation properties (i.e., no sub-grid variations) are given to the COSP. We find that the warm rain signatures in the SPCAM5 COSP run agree with the MODIS and CloudSat observations quite well. In contrast, the SPCAM5-Homogeneous COSP run which ignores the sub-grid cloud variations substantially overestimates the radar reflectivity and probability of precipitation compared to the satellite observations, as well as the results from the SPCAM5 COSP run. The significant differences between the two COSP runs demonstrate that it is important to take into account the sub-grid variations of cloud and precipitation when using COSP to evaluate the GCM to avoid confusing and misleading results.

scholarly journals Snow-induced buffering in aerosol–cloud interactions

2020 ◽  
Author(s):  
Takuro Michibata ◽  
Kentaroh Suzuki ◽  
Toshihiko Takemura
Keyword(s):  
Radiative Forcing ◽  
General Circulation ◽  
State Of The Art ◽  
General Circulation Models ◽  
Regional Pattern ◽  
Cloud Droplets ◽  
Microphysical Process ◽  
Aerosol Cloud ◽  
Effective Radiative Forcing ◽  
Aerosol Cloud Interactions

Abstract. Complex aerosol–cloud–precipitation interactions lead to large differences in estimates of aerosol impacts on climate among general circulation models (GCMs) and satellite retrievals. Typically, precipitating hydrometeors are treated diagnostically in most GCMs, and their radiative effects are ignored. Here, we quantify how the treatment of precipitation influences the simulated effective radiative forcing due to aerosol–cloud interactions (ERFaci) using a state-of-the-art GCM with a two-moment prognostic precipitation scheme that incorporates the radiative effect of precipitating particles, and investigate how microphysical process representations are related to macroscopic climate effects. Prognostic precipitation substantially weakens the magnitude of ERFaci (by approximately 75 %) compared with the traditional diagnostic scheme, and this is the result of the increased longwave (warming) and weakened shortwave (cooling) components of ERFaci. The former is attributed to additional adjustment processes induced by falling snow, and the latter stems largely from riming of snow by collection of cloud droplets. The significant reduction in ERFaci does not occur without prognostic snow, which contributes mainly by buffering the cloud response to aerosol perturbations through depleting cloud water via collection. Prognostic precipitation also alters the regional pattern of ERFaci, particularly over northern mid-latitudes where snow is abundant. The treatment of precipitation is thus a highly influential controlling factor of ERFaci, contributing more than other uncertain tunable processes related to aerosol–cloud–precipitation interactions. This change in ERFaci caused by the treatment of precipitation is large enough to explain the existing difference in ERFaci between GCMs and observations.

scholarly journals Shepard and Hardy Multiquadric Interpolation Methods for Multicomponent Aerosol–Cloud Parameterization

2009 ◽  
Vol 66 (1) ◽  
pp. 105-115 ◽  
Author(s):  
Alexandru Rap ◽  
Satyajit Ghosh ◽  
Michael H. Smith
Keyword(s):  
General Circulation ◽  
Interpolation Method ◽  
Global Climate ◽  
Cloud Droplet ◽  
General Circulation Models ◽  
Aerosol Cloud ◽  
Aerosol Mass ◽  
Wide Range ◽  
Interpolation Techniques ◽  
Cloud Parameterization

Abstract This paper presents a novel method based on the application of interpolation techniques to the multicomponent aerosol–cloud parameterization for global climate modeling. Quantifying the aerosol indirect effect still remains a difficult task, and thus developing parameterizations for general circulation models (GCMs) of the microphysics of clouds and their interactions with aerosols is a major challenge for climate modelers. Three aerosol species are considered in this paper—namely sulfate, sea salt, and biomass smoke—and a detailed microphysical chemical parcel model is used to obtain a dataset of points relating the cloud droplet number concentration (CDNC) to the three aerosol input masses. The resulting variation of CDNC with the aerosol mass has some nonlinear features that require a complex but efficient parameterization to be easily incorporated into GCMs. In bicomponent systems, simple interpolation techniques may be sufficient to relate the CDNC to the aerosol mass, but with increasing components, simple methods fail. The parameterization technique proposed in this study employs either the modified Shepard interpolation method or the Hardy multiquadrics interpolation method, and the numerical results obtained show that both methods provide realistic results for a wide range of aerosol mass loadings. This is the first application of these two interpolation techniques to aerosol–cloud interaction studies.

scholarly journals New approaches to quantifying aerosol influence on the cloud radiative effect

2016 ◽  
Vol 113 (21) ◽  
pp. 5812-5819 ◽  
Author(s):  
Graham Feingold ◽  
Allison McComiskey ◽  
Takanobu Yamaguchi ◽  
Jill S. Johnson ◽  
Kenneth S. Carslaw ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
General Circulation ◽  
General Circulation Models ◽  
Shortwave Radiation ◽  
Emergent Properties ◽  
Radiative Effect ◽  
Aerosol Composition ◽  
Aerosol Cloud ◽  
Cloud Radiative Effect ◽  
Aerosol Cloud Interactions

The topic of cloud radiative forcing associated with the atmospheric aerosol has been the focus of intense scrutiny for decades. The enormity of the problem is reflected in the need to understand aspects such as aerosol composition, optical properties, cloud condensation, and ice nucleation potential, along with the global distribution of these properties, controlled by emissions, transport, transformation, and sinks. Equally daunting is that clouds themselves are complex, turbulent, microphysical entities and, by their very nature, ephemeral and hard to predict. Atmospheric general circulation models represent aerosol−cloud interactions at ever-increasing levels of detail, but these models lack the resolution to represent clouds and aerosol−cloud interactions adequately. There is a dearth of observational constraints on aerosol−cloud interactions. We develop a conceptual approach to systematically constrain the aerosol−cloud radiative effect in shallow clouds through a combination of routine process modeling and satellite and surface-based shortwave radiation measurements. We heed the call to merge Darwinian and Newtonian strategies by balancing microphysical detail with scaling and emergent properties of the aerosol−cloud radiation system.

scholarly journals Improving our fundamental understanding of the role of aerosol−cloud interactions in the climate system

2016 ◽  
Vol 113 (21) ◽  
pp. 5781-5790 ◽  
Author(s):  
John H. Seinfeld ◽  
Christopher Bretherton ◽  
Kenneth S. Carslaw ◽  
Hugh Coe ◽  
Paul J. DeMott ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Radiative Forcing ◽  
General Circulation ◽  
Climate Models ◽  
Large Range ◽  
General Circulation Models ◽  
Radiative Properties ◽  
Aerosol Cloud ◽  
Aerosol Cloud Interactions

The effect of an increase in atmospheric aerosol concentrations on the distribution and radiative properties of Earth’s clouds is the most uncertain component of the overall global radiative forcing from preindustrial time. General circulation models (GCMs) are the tool for predicting future climate, but the treatment of aerosols, clouds, and aerosol−cloud radiative effects carries large uncertainties that directly affect GCM predictions, such as climate sensitivity. Predictions are hampered by the large range of scales of interaction between various components that need to be captured. Observation systems (remote sensing, in situ) are increasingly being used to constrain predictions, but significant challenges exist, to some extent because of the large range of scales and the fact that the various measuring systems tend to address different scales. Fine-scale models represent clouds, aerosols, and aerosol−cloud interactions with high fidelity but do not include interactions with the larger scale and are therefore limited from a climatic point of view. We suggest strategies for improving estimates of aerosol−cloud relationships in climate models, for new remote sensing and in situ measurements, and for quantifying and reducing model uncertainty.

A Comparison of the Water Budgets between Clouds from AMMA and TWP-ICE

2013 ◽  
Vol 70 (2) ◽  
pp. 487-503 ◽  
Author(s):  
Xiping Zeng ◽  
Wei-Kuo Tao ◽  
Scott W. Powell ◽  
Robert A. Houze ◽  
Paul Ciesielski ◽  
...  
Keyword(s):  
General Circulation ◽  
Three Dimensional ◽  
Vertical Wind Shear ◽  
General Circulation Models ◽  
Warm Pool ◽  
Water Budgets ◽  
Convective Systems ◽  
Convective Clouds ◽  
Distinct Structure ◽  
Multidisciplinary Analysis

Abstract Two field campaigns, the African Monsoon Multidisciplinary Analysis (AMMA) and the Tropical Warm Pool–International Cloud Experiment (TWP-ICE), took place in 2006 near Niamey, Niger, and Darwin, Northern Territory, Australia, providing extensive observations of mesoscale convective systems (MCSs) near a desert and a tropical coast, respectively. Under the constraint of their observations, three-dimensional cloud-resolving model simulations are carried out and presented in this paper to replicate the basic characteristics of the observed MCSs. All of the modeled MCSs exhibit a distinct structure having deep convective clouds accompanied by stratiform and anvil clouds. In contrast to the approximately 100-km-scale MCSs observed in TWP-ICE, the MCSs in AMMA have been successfully simulated with a scale of about 400 km. These modeled AMMA and TWP-ICE MCSs offer an opportunity to understand the structure and mechanism of MCSs. Comparing the water budgets between AMMA and TWP-ICE MCSs suggests that TWP-ICE convective clouds have stronger ascent while the mesoscale ascent outside convective clouds in AMMA is stronger. A case comparison, with the aid of sensitivity experiments, also suggests that vertical wind shear and ice crystal (or dust aerosol) concentration can significantly impact stratiform and anvil clouds (e.g., their areas) in MCSs. In addition, the obtained water budgets quantitatively describe the transport of water between convective, stratiform, and anvil regions as well as water sources/sinks from microphysical processes, providing information that can be used to help determine parameters in the convective and cloud parameterizations in general circulation models (GCMs).

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