scholarly journals A new two-moment bulk stratiform cloud microphysics scheme in the NCAR Community Atmosphere Model (CAM3), Part II: Single-Column and Global Results

2007 ◽  
Vol preprint (2008) ◽  
pp. 1 ◽  
Author(s):  
A. Gettelman ◽  
H. Morrison ◽  
S. J. Ghan
Keyword(s):  
Cloud Microphysics ◽  
Stratiform Cloud ◽  
Microphysics Scheme ◽  
Community Atmosphere Model ◽  
Single Column ◽  
Atmosphere Model

A New Two-Moment Bulk Stratiform Cloud Microphysics Scheme in the Community Atmosphere Model, Version 3 (CAM3). Part II: Single-Column and Global Results

2008 ◽  
Vol 21 (15) ◽  
pp. 3660-3679 ◽  
Author(s):  
A. Gettelman ◽  
H. Morrison ◽  
S. J. Ghan
Keyword(s):  
General Circulation ◽  
Circulation Model ◽  
Cloud Microphysics ◽  
Number Concentration ◽  
Radiation Budget ◽  
Cloud Particle ◽  
Microphysics Scheme ◽  
Community Atmosphere Model ◽  
Single Column ◽  
Rain Drops

Abstract The global performance of a new two-moment cloud microphysics scheme for a general circulation model (GCM) is presented and evaluated relative to observations. The scheme produces reasonable representations of cloud particle size and number concentration when compared to observations, and it represents expected and observed spatial variations in cloud microphysical quantities. The scheme has smaller particles and higher number concentrations over land than the standard bulk microphysics in the GCM and is able to balance the top-of-atmosphere radiation budget with 60% the liquid water of the standard scheme, in better agreement with retrieved values. The new scheme diagnostically treats both the mixing ratio and number concentration of rain and snow, and it is therefore able to differentiate the two key regimes, consisting of drizzle in shallow, warm clouds and larger rain drops in deeper cloud systems. The modeled rain and snow size distributions are consistent with observations.

scholarly journals A sensitivity study of radiative fluxes at the top of atmosphere to cloud-microphysics and aerosol parameters in the community atmosphere model CAM5

2013 ◽  
Vol 13 (21) ◽  
pp. 10969-10987 ◽  
Author(s):  
C. Zhao ◽  
X. Liu ◽  
Y. Qian ◽  
J. Yoon ◽  
Z. Hou ◽  
...  
Keyword(s):  
Regional Scale ◽  
Cloud Microphysics ◽  
Model Parameters ◽  
Parameter Uncertainties ◽  
Dimensional Parameter ◽  
Individual Parameter ◽  
Radiative Fluxes ◽  
Community Atmosphere Model ◽  
Atmosphere Model ◽  
Global Mean

Abstract. In this study, we investigated the sensitivity of net radiative fluxes (FNET) at the top of atmosphere (TOA) to 16 selected uncertain parameters mainly related to the cloud microphysics and aerosol schemes in the Community Atmosphere Model version 5 (CAM5). We adopted a quasi-Monte Carlo (QMC) sampling approach to effectively explore the high-dimensional parameter space. The output response variables (e.g., FNET) are simulated using CAM5 for each parameter set, and then evaluated using the generalized linear model analysis. In response to the perturbations of these 16 parameters, the CAM5-simulated global annual mean FNET ranges from −9.8 to 3.5 W m−2 compared to 1.9 W m−2 with the default parameter values. Variance-based sensitivity analysis is conducted to show the relative contributions of individual parameter perturbations to the global FNET variance. The results indicate that the changes in the global mean FNET are dominated by changes in net cloud forcing (CF) within the parameter ranges being investigated. The threshold size parameter related to auto-conversion of cloud ice to snow is identified as one of the most influential parameters for FNET in CAM5 simulations. The strong heterogeneous geographic distribution of FNET variance shows that parameters have a clear localized effect over regions where they are acting. However, some parameters also have non-local impacts on FNET variance. Although external factors, such as perturbations of anthropogenic and natural emissions, largely affect FNET variance at the regional scale, their impact is weaker than that of model internal parameters in terms of simulating global mean FNET. The interactions among the 16 selected parameters contribute a relatively small portion to the total FNET variance over most regions of the globe. This study helps us better understand the parameter uncertainties in the CAM5 model, and thus provides information for further calibrating uncertain model parameters with the largest sensitivity.

scholarly journals A sensitivity study of radiative fluxes at the top of atmosphere to cloud-microphysics and aerosol parameters in the Community Atmosphere Model CAM5

2013 ◽  
Vol 13 (5) ◽  
pp. 12135-12176 ◽  
Author(s):  
C. Zhao ◽  
X. Liu ◽  
Y. Qian ◽  
J. Yoon ◽  
Z. Hou ◽  
...  
Keyword(s):  
Regional Scale ◽  
Cloud Microphysics ◽  
Model Parameters ◽  
Parameter Uncertainties ◽  
Dimensional Parameter ◽  
Individual Parameter ◽  
Radiative Fluxes ◽  
Community Atmosphere Model ◽  
Atmosphere Model ◽  
Global Mean

Abstract. In this study, we investigated the sensitivity of net radiative fluxes (FNET) at the top of atmosphere (TOA) to 16 selected uncertain parameters mainly related to the cloud microphysics and aerosol schemes in the Community Atmosphere Model version 5 (CAM5). We adopted a quasi-Monte Carlo (QMC) sampling approach to effectively explore the high dimensional parameter space. The output response variables (e.g., FNET) were simulated using CAM5 for each parameter set, and then evaluated using the generalized linear model analysis. In response to the perturbations of these 16 parameters, the CAM5-simulated global annual mean FNET ranges from −9.8 to 3.5 W m−2 compared to the CAM5-simulated FNET of 1.9 W m−2 with the default parameter values. Variance-based sensitivity analysis was conducted to show the relative contributions of individual parameter perturbation to the global FNET variance. The results indicate that the changes in the global mean FNET are dominated by those of net cloud forcing (CF) within the parameter ranges being investigated. The threshold size parameter related to auto-conversion of cloud ice to snow is identified as one of the most influential parameters for FNET in CAM5 simulations. The strong heterogeneous geographic distribution of FNET variance shows parameters have a clear localized effect over regions where they are acting. However, some parameters also have non-local impacts on FNET variance. Although external factors, such as perturbations of anthropogenic and natural emissions, largely affect FNET variance at the regional scale, their impact is weaker than that of model internal parameters in terms of simulating global mean FNET. The interactions among the 16 selected parameters contribute a relatively small portion to the total FNET variance over most regions of the globe. This study helps us better understand the parameter uncertainties in the CAM5 model, and thus provides information for further calibrating uncertain model parameters with the largest sensitivity.

scholarly journals Evaluation of Microphysics Parameterization for Convective Clouds in the NCAR Community Atmosphere Model CAM5

2012 ◽  
Vol 25 (24) ◽  
pp. 8568-8590 ◽  
Author(s):  
Xiaoliang Song ◽  
Guang J. Zhang ◽  
J.-L. F. Li
Keyword(s):  
Large Scale ◽  
Convective Cloud ◽  
Number Concentration ◽  
Liquid Water Path ◽  
Microphysics Scheme ◽  
Convective Clouds ◽  
Community Atmosphere Model ◽  
Atmosphere Model ◽  
Subtropical Oceans ◽  
The Impact

Abstract A physically based two-moment microphysics parameterization scheme for convective clouds is implemented in the NCAR Community Atmosphere Model version 5 (CAM5) to improve the representation of convective clouds and their interaction with large-scale clouds and aerosols. The explicit treatment of mass mixing ratio and number concentration of cloud and precipitation particles enables the scheme to account for the impact of aerosols on convection. The scheme is linked to aerosols through cloud droplet activation and ice nucleation processes and to stratiform cloud parameterization through convective detrainment of cloud liquid/ice water content (LWC/IWC) and droplet/crystal number concentration (DNC/CNC). A 5-yr simulation with the new convective microphysics scheme shows that both cloud LWC/IWC and DNC/CNC are in good agreement with observations, indicating the scheme describes microphysical processes in convection well. Moreover, the microphysics scheme is able to represent the aerosol effects on convective clouds such as the suppression of warm rain formation and enhancement of freezing when aerosol loading is increased. With more realistic simulations of convective cloud microphysical properties and their detrainment, the mid- and low-level cloud fraction is increased significantly over the ITCZ–southern Pacific convergence zone (SPCZ) and subtropical oceans, making it much closer to the observations. Correspondingly, the serious negative bias in cloud liquid water path over subtropical oceans observed in the standard CAM5 is reduced markedly. The large-scale precipitation is increased and precipitation distribution is improved as well. The long-standing precipitation bias in the western Pacific is significantly alleviated because of microphysics–thermodynamics feedbacks.

scholarly journals Unified parameterization of the planetary boundary layer and shallow convection with a higher-order turbulence closure in the Community Atmosphere Model: single-column experiments

2012 ◽  
Vol 5 (6) ◽  
pp. 1407-1423 ◽  
Author(s):  
P. A. Bogenschutz ◽  
A. Gettelman ◽  
H. Morrison ◽  
V. E. Larson ◽  
D. P. Schanen ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Higher Order ◽  
Turbulence Closure ◽  
Shallow Convection ◽  
Liquid Water Path ◽  
Community Atmosphere Model ◽  
Single Column ◽  
Atmosphere Model ◽  
Similar Accuracy

Abstract. This paper describes the coupling of the Community Atmosphere Model (CAM) version 5 with a unified multi-variate probability density function (PDF) parameterization, Cloud Layers Unified by Binormals (CLUBB). CLUBB replaces the planetary boundary layer (PBL), shallow convection, and cloud macrophysics schemes in CAM5 with a higher-order turbulence closure based on an assumed PDF. Comparisons of single-column versions of CAM5 and CAM-CLUBB are provided in this paper for several boundary layer regimes. As compared to large eddy simulations (LESs), CAM-CLUBB and CAM5 simulate marine stratocumulus regimes with similar accuracy. For shallow convective regimes, CAM-CLUBB improves the representation of cloud cover and liquid water path (LWP). In addition, for shallow convection CAM-CLUBB offers better fidelity for subgrid-scale vertical velocity, which is an important input for aerosol activation. Finally, CAM-CLUBB results are more robust to changes in vertical and temporal resolution when compared to CAM5.

scholarly journals Unified parameterization of the planetary boundary layer and shallow convection with a higher-order turbulence closure in the community atmosphere model: single column experiments

2012 ◽  
Vol 5 (3) ◽  
pp. 1743-1780 ◽  
Author(s):  
P. A. Bogenschutz ◽  
A. Gettelman ◽  
H. Morrison ◽  
V. E. Larson ◽  
D. P. Schanen ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Higher Order ◽  
Turbulence Closure ◽  
Shallow Convection ◽  
Liquid Water Path ◽  
Community Atmosphere Model ◽  
Single Column ◽  
Atmosphere Model ◽  
Similar Accuracy

Abstract. This paper describes the coupling of the Community Atmosphere Model (CAM) version 5 with a unified multi-variate probability density function (PDF) parameterization, Cloud Layers Unified by Binormals (CLUBB). CLUBB replaces the planetary boundary layer (PBL), shallow convection, and cloud macrophysics schemes in CAM5 with a higher-order turbulence closure based on an assumed PDF. Comparisons of single-column versions of CAM5 and CAM-CLUBB are provided in this paper for several boundary layer regimes. As compared to Large Eddy Simulations (LES), CAM-CLUBB and CAM5 simulate marine stratocumulus regimes with similar accuracy. For shallow convective regimes, CAM-CLUBB improves the representation of cloud cover and liquid water path (LWP). In addition, for shallow convection CAM-CLUBB offers better fidelity for sub-grid scale vertical velocity, which is an important input for aerosol activation. Finally, CAM-CLUBB results are more robust to changes in vertical and temporal resolution when compared to CAM5.

scholarly journals Improvement of the Cloud Microphysics Scheme of the Mesoscale Model at the Japan Meteorological Agency using Space-borne Radar and Microwave Imager of the Global Precipitation Measurement as Reference

2021 ◽  
Author(s):  
Yasutaka Ikuta ◽  
Masaki Satoh ◽  
Masahiro Sawada ◽  
Hiroshi Kusabiraki ◽  
Takuji Kubota
Keyword(s):  
Cloud Microphysics ◽  
Japan Meteorological Agency ◽  
Dual Frequency ◽  
Microphysics Scheme ◽  
Precipitation Measurement ◽  
Single Column ◽  
Microwave Imager ◽  
Cloud Ice ◽  
Global Precipitation Measurement ◽  
Global Precipitation

AbstractIn this study, the single-moment 6-class bulk cloud microphysics scheme used in the operational numerical weather prediction system at the Japan Meteorological Agency was improved using the observations of the Global Precipitation Measurement (GPM) core satellite as reference values. The original cloud microphysics scheme has the following biases: underestimation of cloud ice compared to the brightness temperature of the GPM Microwave Imager (GMI) and underestimation of the lower troposphere rain compared to the reflectivity of GPM Dual-frequency Precipitation Radar (DPR). Furthermore, validation of the dual-frequency rate of reflectivity revealed that the dominant particles in the solid phase of simulation were graupel and deviated from DPR observation. The causes of these issues were investigated using a single-column kinematic model. The underestimation of cloud ice was caused by a high ice-to-snow conversion rate, and the underestimation of precipitation in the lower layers was caused by an excessive number of small-diameter rain particles. The parameterization of microphysics scheme is improved to eliminate the biases in the single-column model. In the forecast obtained using the improved scheme, the underestimation of cloud ice and rain is reduced. Consequently, the prediction errors of hydrometeors were reduced against the GPM satellite observations, and the atmospheric profiles and precipitation forecasts were improved.

scholarly journals A unified parameterization of clouds and turbulence using CLUBB and subcolumns in the Community Atmosphere Model

2015 ◽  
Vol 8 (6) ◽  
pp. 5041-5088 ◽  
Author(s):  
K. Thayer-Calder ◽  
A. Gettelman ◽  
C. Craig ◽  
S. Goldhaber ◽  
P. A. Bogenschutz ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Climate Models ◽  
Convective Cloud ◽  
Global Climate Models ◽  
Liquid Water Path ◽  
Microphysics Scheme ◽  
Cloud Forcing ◽  
Community Atmosphere Model ◽  
Atmosphere Model ◽  
Cloud Parameterization

Abstract. Most global climate models parameterize separate cloud types using separate parameterizations. This approach has several disadvantages, including obscure interactions between parameterizations and inaccurate triggering of cumulus parameterizations. Alternatively, a unified cloud parameterization uses one equation set to represent all cloud types. Such cloud types include stratiform liquid and ice cloud, shallow convective cloud, and deep convective cloud. Vital to the success of a unified parameterization is a general interface between clouds and microphysics. One such interface involves drawing Monte Carlo samples of subgrid variability of temperature, water vapor, cloud liquid, and cloud ice, and feeding the sample points into a microphysics scheme. This study evaluates a unified cloud parameterization and a Monte Carlo microphysics interface that has been implemented in the Community Atmosphere Model (CAM) version 5.3. Results describing the mean climate and tropical variability from global simulations are presented. The new model shows a degradation in precipitation skill but improvements in short-wave cloud forcing, liquid water path, long-wave cloud forcing, precipitable water, and tropical wave simulation. Also presented are estimations of computational expense and investigation of sensitivity to number of subcolumns.

scholarly journals Advanced Two-Moment Bulk Microphysics for Global Models. Part II: Global Model Solutions and Aerosol–Cloud Interactions*

2015 ◽  
Vol 28 (3) ◽  
pp. 1288-1307 ◽  
Author(s):  
A. Gettelman ◽  
H. Morrison ◽  
S. Santos ◽  
P. Bogenschutz ◽  
P. M. Caldwell
Keyword(s):  
Horizontal Resolution ◽  
Liquid Water Path ◽  
Anthropogenic Aerosols ◽  
Time Step ◽  
Microphysics Scheme ◽  
Aerosol Cloud ◽  
Community Atmosphere Model ◽  
Single Column ◽  
Cloud Resolving Model ◽  
Aerosol Cloud Interactions

Abstract A modified microphysics scheme is implemented in the Community Atmosphere Model, version 5 (CAM5). The new scheme features prognostic precipitation. The coupling between the microphysics and the rest of the model is modified to make it more flexible. Single-column tests show the new microphysics can simulate a constrained drizzling stratocumulus case. Substepping the cloud condensation (macrophysics) within a time step improves single-column results. Simulations of mixed-phase cases are strongly sensitive to ice nucleation. The new microphysics alters process rates in both single-column and global simulations, even at low (200 km) horizontal resolution. Thus, prognostic precipitation can be important, even in low-resolution simulations where advection of precipitation is not important. Accretion dominates as liquid water path increases in agreement with cloud-resolving model simulations and estimates from observations. The new microphysics with prognostic precipitation increases the ratio of accretion over autoconversion. The change in process rates appears to significantly reduce aerosol–cloud interactions and indirect radiative effects of anthropogenic aerosols by up to 33% (depending on substepping) to below 1 W m−2 of cooling between simulations with preindustrial (1850) and present-day (2000) aerosol emissions.

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