scholarly journals Assessment of NASA GISS CMIP5 and Post-CMIP5 Simulated Clouds and TOA Radiation Budgets Using Satellite Observations. Part I: Cloud Fraction and Properties

2014 ◽  
Vol 27 (11) ◽  
pp. 4189-4208 ◽  
Author(s):  
Ryan E. Stanfield ◽  
Xiquan Dong ◽  
Baike Xi ◽  
Aaron Kennedy ◽  
Anthony D. Del Genio ◽  
...  
Keyword(s):  
Boundary Layer ◽  
General Circulation ◽  
Radiant Energy ◽  
Strong Support ◽  
Cloud Microphysics ◽  
Cloud Fraction ◽  
Satellite Observations ◽  
Moist Convection ◽  
Water Path ◽  
Total Column

Abstract Although many improvements have been made in phase 5 of the Coupled Model Intercomparison Project (CMIP5), clouds remain a significant source of uncertainty in general circulation models (GCMs) because their structural and optical properties are strongly dependent upon interactions between aerosol/cloud microphysics and dynamics that are unresolved in such models. Recent changes to the planetary boundary layer (PBL) turbulence and moist convection parameterizations in the NASA GISS Model E2 atmospheric GCM (post-CMIP5, hereafter P5) have improved cloud simulations significantly compared to its CMIP5 (hereafter C5) predecessor. A study has been performed to evaluate these changes between the P5 and C5 versions of the GCM, both of which used prescribed sea surface temperatures. P5 and C5 simulated cloud fraction (CF), liquid water path (LWP), ice water path (IWP), cloud water path (CWP), precipitable water vapor (PWV), and relative humidity (RH) have been compared to multiple satellite observations including the Clouds and the Earth’s Radiant Energy System–Moderate Resolution Imaging Spectroradiometer (CERES-MODIS, hereafter CM), CloudSat–Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO; hereafter CC), Atmospheric Infrared Sounder (AIRS), and Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E). Although some improvements are observed in the P5 simulation on a global scale, large improvements have been found over the southern midlatitudes (SMLs), where correlations increased and both bias and root-mean-square error (RMSE) significantly decreased, in relation to the previous C5 simulation, when compared to observations. Changes to the PBL scheme have resulted in improved total column CFs, particularly over the SMLs where marine boundary layer (MBL) CFs have increased by nearly 20% relative to the previous C5 simulation. Globally, the P5 simulated CWPs are 25 g m−2 lower than the previous C5 results. The P5 version of the GCM simulates PWV and RH higher than its C5 counterpart and agrees well with the AMSR-E and AIRS observations. The moister atmospheric conditions simulated by P5 are consistent with the CF comparison and provide a strong support for the increase in MBL clouds over the SMLs. Over the tropics, the P5 version of the GCM simulated total column CFs and CWPs are slightly lower than the previous C5 results, primarily as a result of the shallower tropical boundary layer in P5 relative to C5 in regions outside the marine stratocumulus decks.

Structure of the Madden–Julian Oscillation in the Superparameterized CAM

2009 ◽  
Vol 66 (11) ◽  
pp. 3277-3296 ◽  
Author(s):  
James J. Benedict ◽  
David A. Randall
Keyword(s):  
Boundary Layer ◽  
General Circulation ◽  
Deep Convection ◽  
Circulation Model ◽  
Grid Cell ◽  
Atmospheric Model ◽  
Space Time ◽  
Madden Julian Oscillation ◽  
Moist Convection ◽  
Time Structures

Abstract The detailed dynamic and thermodynamic space–time structures of the Madden–Julian oscillation (MJO) as simulated by the superparameterized Community Atmosphere Model version 3.0 (SP-CAM) are analyzed. Superparameterization involves substituting conventional boundary layer, moist convection, and cloud parameterizations with a configuration of cloud-resolving models (CRMs) embedded in each general circulation model (GCM) grid cell. Unlike most GCMs that implement conventional parameterizations, the SP-CAM displays robust atmospheric variability on intraseasonal space and time (30–60 days) scales. The authors examine a 19-yr SP-CAM simulation based on the Atmospheric Model Intercomparison Project protocol, forced by prescribed sea surface temperatures. Overall, the space–time structures of MJO convective disturbances are very well represented in the SP-CAM. Compared to observations, the model produces a similar vertical progression of increased moisture, warmth, and heating from the boundary layer to the upper troposphere as deep convection matures. Additionally, important advective and convective processes in the SP-CAM compare favorably with those in observations. A deficiency of the SP-CAM is that simulated convective intensity organized on intraseasonal space–time scales is overestimated, particularly in the west Pacific. These simulated convective biases are likely due to several factors including unrealistic boundary layer interactions, a lack of weakening of the simulated disturbance over the Maritime Continent, and mean state differences.

scholarly journals Statistical Analyses of Satellite Cloud Object Data from CERES. Part V: Relationships between Physical Properties of Marine Boundary Layer Clouds

2008 ◽  
Vol 21 (24) ◽  
pp. 6668-6688 ◽  
Author(s):  
Zachary A. Eitzen ◽  
Kuan-Man Xu ◽  
Takmeng Wong
Keyword(s):  
Boundary Layer ◽  
Cluster Analysis ◽  
Physical Properties ◽  
Radiative Forcing ◽  
Marine Boundary Layer ◽  
Radiant Energy ◽  
Cloud Fraction ◽  
Cloud Radiative Forcing ◽  
Boundary Layer Clouds ◽  
Shallow Cumulus

Abstract Relationships between physical properties are studied for three types of marine boundary layer cloud objects identified with the Clouds and the Earth’s Radiant Energy System (CERES) footprint data from the Tropical Rainfall Measuring Mission satellite between 30°S and 30°N. Each cloud object is a contiguous region of CERES footprints that have cloud-top heights below 3 km, and cloud fractions of 99%–100% (overcast type), 40%–99% (stratocumulus type), or 10%–40% (shallow cumulus type). These cloud fractions represent the fraction of ∼2 km × 2 km Visible/Infrared Scanner pixels that are cloudy within each ∼10 km × 10 km footprint. The cloud objects have effective diameters that are greater than 300 km for the overcast and stratocumulus types, and greater than 150 km for the shallow cumulus type. The Spearman rank correlation coefficient is calculated between many microphysical/optical [effective radius (re), cloud optical depth (τ), albedo, liquid water path, and shortwave cloud radiative forcing (SW CRF)] and macrophysical [outgoing longwave radiation (OLR), cloud fraction, cloud-top temperature, longwave cloud radiative forcing (LW CRF), and sea surface temperature (SST)] properties for each of the three cloud object types. When both physical properties are of the same category (microphysical/optical or macrophysical), the magnitude of the correlation tends to be higher than when they are from different categories. The magnitudes of the correlations also change with cloud object type, with the correlations for overcast and stratocumulus cloud objects tending to be higher than those for shallow cumulus cloud objects. Three pairs of physical properties are studied in detail, using a k-means cluster analysis: re and τ, OLR and SST, and LW CRF and SW CRF. The cluster analysis of re and τ reveals that for each of the cloud types, there is a cluster of cloud objects with negative slopes, a cluster with slopes near zero, and two clusters with positive slopes. The joint OLR and SST probability plots show that the OLR tends to decrease with SST in regions with boundary layer clouds for SSTs above approximately 298 K. When the cloud objects are split into “dry” and “moist” clusters based on the amount of precipitable water above 700 hPa, the associated OLRs increase with SST throughout the SST range for the dry clusters, but the OLRs are roughly constant with SST for the moist cluster. An analysis of the joint PDFs of LW CRF and SW CRF reveals that while the magnitudes of both LW and SW CRFs generally increase with cloud fraction, there is a cluster of overcast cloud objects that has low values of LW and SW CRF. These objects are generally located near the Sahara Desert, and may be contaminated with dust. Many of these overcast objects also appear in the re and τ cluster with negative slopes.

scholarly journals Aerosol Impacts on the Diurnal Cycle of Marine Stratocumulus

2008 ◽  
Vol 65 (8) ◽  
pp. 2705-2718 ◽  
Author(s):  
Irina Sandu ◽  
Jean-Louis Brenguier ◽  
Olivier Geoffroy ◽  
Odile Thouron ◽  
Valery Masson
Keyword(s):  
Boundary Layer ◽  
Diurnal Cycle ◽  
Liquid Water ◽  
Large Scale ◽  
Cloud Microphysics ◽  
Cloud Base ◽  
Liquid Water Path ◽  
Marine Stratocumulus ◽  
Water Path ◽  
The Impact

Abstract Recent large-eddy simulation (LES) studies of the impact of aerosol on the dynamics of nocturnal marine stratocumulus revealed that, depending on the large-scale forcings, an aerosol-induced increase of the droplet concentration can lead to either an increase or a decrease of the liquid water path, hence contrasting with the cloud thickening that is expected from a reduction of the precipitation efficiency. In this study, the aerosol impacts on cloud microphysics are examined in the context of the boundary-layer diurnal cycle using 36-h LES simulations of pristine and polluted clouds. These simulations corroborate previous findings that during nighttime aerosol-induced liquid water path changes are sensitive to the large-scale forcings via enhancement of cloud-top entrainment such that, ultimately, the liquid water path may be reduced when the free-tropospheric-entrained air is drier. During the day, however, enhanced entrainment, inhibition of drizzle evaporation below cloud base, and reduced sensible heat flux from the surface lead to a more pronounced decoupling of the boundary layer, which significantly amplifies the liquid water path reduction of the polluted clouds. At night the sign of the liquid water path difference between pristine and polluted clouds depends upon large-scale forcings, while during the day the liquid water path of polluted clouds is always smaller than the one of the pristine clouds. Suggestions are made on how observational studies could be designed for validation of these simulations.

scholarly journals Quantification of Monthly Mean Regional-Scale Albedo of Marine Stratiform Clouds in Satellite Observations and GCMs

2011 ◽  
Vol 50 (10) ◽  
pp. 2139-2148 ◽  
Author(s):  
Frida A.-M. Bender ◽  
Robert J. Charlson ◽  
Annica M. L. Ekman ◽  
Louise V. Leahy
Keyword(s):  
Climate Models ◽  
System Modeling ◽  
Regional Scale ◽  
Radiant Energy ◽  
Energy System ◽  
Cloud Fraction ◽  
Satellite Observations ◽  
Radiative Properties ◽  
Cloud Albedo ◽  
Stratiform Clouds

AbstractPlanetary albedo—the reflectivity for solar radiation—is of singular importance in determining the amount of solar energy taken in by the Earth–atmosphere system. Modeling albedo, and specifically cloud albedo, correctly is crucial for realistic climate simulations. A method is presented herein by which regional cloud albedo can be quantified from the relation between total albedo and cloud fraction, which in observations is found to be approximately linear on a monthly mean scale. This analysis is based primarily on the combination of cloud fraction data from the Moderate Resolution Imaging Spectroradiometer (MODIS) and albedo data from the Clouds and the Earth’s Radiant Energy System (CERES), but the results presented are also supported by the combination of cloud fraction and proxy albedo data from satelliteborne lidar [Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO)]. These data are measured and derived completely independently from the CERES–MODIS data. Applied to low-level marine stratiform clouds in three regions (off the coasts of South America, Africa, and North America), the analysis reveals regionally uniform monthly mean cloud albedos, indicating that the variation in cloud shortwave radiative properties is small on this scale. A coherent picture of low “effective” cloud albedo emerges, in the range from 0.35 to 0.42, on the basis of data from CERES and MODIS. In its simplicity, the method presented appears to be useful as a diagnostic tool and as a constraint on climate models. To demonstrate this, the same method is applied to cloud fraction and albedo output from several current-generation climate models [from the Coupled Model Intercomparison Project, phase 3 (CMIP3), archive]. Although the multimodel mean cloud albedo estimates agree to within 20% with the satellite-based estimates for the three focus regions, model-based estimates of cloud albedo are found to display much larger variability than do the observations, within individual models as well as between models.

scholarly journals Observational Evidence That Enhanced Subsidence Reduces Subtropical Marine Boundary Layer Cloudiness

2013 ◽  
Vol 26 (19) ◽  
pp. 7507-7524 ◽  
Author(s):  
Timothy A. Myers ◽  
Joel R. Norris
Keyword(s):  
Boundary Layer ◽  
Liquid Water ◽  
Marine Boundary Layer ◽  
Cloud Fraction ◽  
Liquid Water Path ◽  
Water Path ◽  
Cloud Data ◽  
Marine Stratus ◽  
Temperature Inversions ◽  
Cloud Thickness

Abstract Conventional wisdom suggests that subsidence favors the presence of marine stratus and stratocumulus because regions of enhanced boundary layer cloudiness are observed to climatologically co-occur with regions of enhanced subsidence. Here it is argued that the climatological positive correlation between subsidence and cloudiness is not the result of a direct physical mechanism connecting the two. Instead, it arises because enhanced subsidence is typically associated with stronger temperature inversions capping the marine boundary layer, and stronger temperature inversions favor greater cloudiness. Through statistical analysis of satellite cloud data and meteorological reanalyses for the subsidence regime over tropical (30°S–30°N) oceans, it is shown that enhanced subsidence promotes reduced cloudiness for the same value of inversion strength and that a stronger inversion favors greater cloudiness for the same value of subsidence. Using a simple conceptual model, it is argued that enhanced subsidence leads to reduced cloud thickness, liquid water path, and cloud fraction by pushing down the top of the marine boundary layer. Moreover, a stronger inversion reduces entrainment drying and warming, thus leading to a more humid boundary layer and greater cloud thickness, liquid water path, and cloud fraction. These two mechanisms typically oppose each other for geographical and seasonal cloud variability because enhanced subsidence is usually associated with stronger inversions. If global warming results in stronger inversions but weaker subsidence, the two mechanisms could both favor increased subtropical low-level cloudiness.

scholarly journals Synergy of Satellite- and Ground-Based Observations for Continuous Monitoring of Atmospheric Stability, Liquid Water Path, and Integrated Water Vapor: Theoretical Evaluations Using Reanalysis and Neural Networks

2020 ◽  
Vol 59 (7) ◽  
pp. 1153-1170
Author(s):  
Maria Toporov ◽  
Ulrich Löhnert
Keyword(s):  
Boundary Layer ◽  
Water Vapor ◽  
Temporal Resolution ◽  
Liquid Water ◽  
Atmospheric Stability ◽  
Satellite Observations ◽  
Liquid Water Path ◽  
Water Path ◽  
Atmospheric State ◽  
Humidity Profiles

AbstractAtmospheric stability plays an essential role in the evolution of weather events. While the upper troposphere is sampled by satellite sensors, and in situ sensors measure the atmospheric state close to the surface, only sporadic information from radiosondes or aircraft observations is available in the planetary boundary layer. Ground-based remote sensing offers the possibility to continuously and automatically monitor the atmospheric state in the boundary layer. Microwave radiometers (MWR) provide temporally resolved temperature and humidity profiles in the boundary layer and accurate values of integrated water vapor and liquid water path, and the differential absorption lidar (DIAL) measures humidity profiles with high vertical and temporal resolution up to 3000-m height. Both instruments have the potential to complement satellite observations by additional information from the lowest atmospheric layers, particularly under cloudy conditions. This study presents a neural network retrieval for stability indices, integrated water vapor, and liquid water path from simulated satellite- and ground-based measurements based on the COSMO regional reanalysis (COSMO-REA2). Focusing on the temporal resolution, the satellite-based instruments considered in the study are the currently operational Spinning Enhanced Visible and Infrared Imager (SEVIRI) and the future Infrared Sounder (IRS), both in geostationary orbit. Relative to the retrieval based on satellite observations, the additional ground-based MWR/DIAL measurements provide valuable improvements not only in the presence of clouds, which represent a limiting factor for infrared SEVIRI/IRS, but also under clear-sky conditions. The root-mean-square error for convective available potential energy, for instance, is reduced by 24% if IRS observations are complemented by ground-based MWR measurements.

scholarly journals Assessing the Impact of Meteorological History on Subtropical Cloud Fraction

2010 ◽  
Vol 23 (11) ◽  
pp. 2926-2940 ◽  
Author(s):  
Guillaume S. Mauger ◽  
Joel R. Norris
Keyword(s):  
Boundary Layer ◽  
Time Scales ◽  
Cloud Cover ◽  
Radiant Energy ◽  
Cloud Fraction ◽  
Meteorological Conditions ◽  
Surface Fluxes ◽  
Analysis Model ◽  
Cloud Properties ◽  
The Impact

Abstract This study presents findings from the application of a new Lagrangian method used to evaluate the meteorological sensitivities of subtropical clouds in the northeast Atlantic. Parcel back trajectories are used to account for the influence of previous meteorological conditions on cloud properties, whereas forward trajectories highlight the continued evolution of cloud state. Satellite retrievals from Moderate Resolution Imaging Spectroradiometer (MODIS), Clouds and the Earth’s Radiant Energy System (CERES), Quick Scatterometer (QuikSCAT), and Special Sensor Microwave Imager (SSM/I) provide measurements of cloud properties as well as atmospheric state. These are complemented by meteorological fields from the ECMWF operational analysis model. Observations are composited by cloud fraction, and mean trajectories are used to evaluate differences between each composite. Systematic differences in meteorological conditions are found to extend through the full 144-h trajectories, confirming the need to account for cloud history in assessing impacts on cloud properties. Most striking among these is the observation that strong synoptic-scale divergence is associated with reduced cloud fraction 0–12 h later. Consistent with prior work, the authors find that cloud cover variations correlate best with variations in lower-tropospheric stability (LTS) and SST that are 36 h upwind. In addition, the authors find that free-tropospheric humidity, along-trajectory SST gradient, and surface fluxes all correlate best at lags ranging from 0 to 12 h. Overall, cloud cover appears to be most strongly impacted by variations in surface divergence over short time scales (<12 h) and by factors influencing boundary layer stratification over longer time scales (12–48 h). Notably, in the early part of the trajectories several of the above associations are reversed. In particular, when trajectories computed for small cloud fraction scenes are traced back 72 h, they are found to originate in conditions of weaker surface divergence and stronger surface fluxes relative to those computed for large cloud fraction scenes. Coupled with a drier boundary layer and warmer SSTs, this suggests that a decoupling of the boundary layer precedes cloud dissipation. The authors develop an approximation for the stratification of the boundary layer and find further evidence that stratification plays a role in differentiating between developing and dissipating clouds.

scholarly journals Global anthropogenic aerosol effects on convective clouds in ECHAM5-HAM

2007 ◽  
Vol 7 (5) ◽  
pp. 14639-14674 ◽  
Author(s):  
U. Lohmann
Keyword(s):  
Liquid Water ◽  
General Circulation ◽  
Hydrological Cycle ◽  
Cloud Microphysics ◽  
Liquid Water Path ◽  
Anthropogenic Aerosol ◽  
Water Path ◽  
Convective Clouds ◽  
Stratiform Clouds ◽  
Aerosol Effects

Abstract. Aerosols affect the climate system by changing cloud characteristics in many ways. They act as cloud condensation and ice nuclei and may have an influence on the hydrological cycle. Here we investigate aerosol effects on convective clouds by extending the double moment cloud microphysics scheme developed for stratiform clouds to convective clouds in the ECHAM5 general circulation model. This increases the liquid water path in the tropics and reduces the sensitivity of the liquid water path with increasing aerosol optical depth in better agreement with observations and large-eddy simulation studies. In simulations in which greenhouse gases and aerosols emissions are increased since pre-industrial times, accounting for microphysics in convective clouds matches most closely the observed increase in precipitation. The total anthropogenic aerosol effect since pre-industrial time is slightly reduced from −1.6 to −1.9 W m−2 when microphysics are only included in stratiform clouds to −1.5 W m−2 when microphysics are included both in stratiform and convective clouds.

Modeling Water Vapor and Clouds as Passive Tracers in an Idealized GCM

2018 ◽  
Vol 31 (2) ◽  
pp. 775-786 ◽  
Author(s):  
Yi Ming ◽  
Isaac M. Held
Keyword(s):  
Water Vapor ◽  
General Circulation ◽  
Large Scale ◽  
Probability Distributions ◽  
Water Vapor Pressure ◽  
Substantial Reduction ◽  
Lower Troposphere ◽  
Circulation Model ◽  
Cloud Microphysics ◽  
Cloud Fraction

This paper introduces an idealized general circulation model (GCM) in which water vapor and clouds are tracked as tracers, but are not allowed to affect circulation through either latent heat release or cloud radiative effects. The cloud scheme includes an explicit treatment of cloud microphysics and diagnoses cloud fraction from a prescribed subgrid distribution of total water. The model is capable of qualitatively capturing many large-scale features of water vapor and cloud distributions outside of the boundary layer and deep tropics. The subtropical dry zones, midlatitude storm tracks, and upper-tropospheric cirrus are simulated reasonably well. The inclusion of cloud microphysics (namely rain re-evaporation) has a modest but significant effect of moistening the lower troposphere in this model. When being subjected to a uniform fractional increase of saturated water vapor pressure, the model produces little change in cloud fraction. A more realistic perturbation, which considers the nonlinearity of the Clausius–Clapeyron relation and spatial structure of CO2-induced warming, results in a substantial reduction in the free-tropospheric cloud fraction. This is reconciled with an increase of relative humidity by analyzing the probability distributions of both quantities, and may help explain partly similar decreases in cloud fraction in full GCMs. The model provides a means to isolate individual processes or model components for studying their influences on cloud simulation in the extratropical free troposphere.

scholarly journals The Effect of Environmental Conditions on Tropical Deep Convective Systems Observed from the TRMM Satellite

2006 ◽  
Vol 19 (22) ◽  
pp. 5745-5761 ◽  
Author(s):  
Bing Lin ◽  
Bruce A. Wielicki ◽  
Patrick Minnis ◽  
Lin Chambers ◽  
Kuan-Man Xu ◽  
...  
Keyword(s):  
Boundary Layer ◽  
General Circulation ◽  
Radiant Energy ◽  
Cloud Formation ◽  
Convective Systems ◽  
Cloud Properties ◽  
Areal Coverage ◽  
Deep Convective Systems ◽  
Ice Water ◽  
Formation Efficiency

Abstract This study uses measurements of radiation and cloud properties taken between January and August 1998 by three Tropical Rainfall Measuring Mission (TRMM) instruments, the Clouds and the Earth’s Radiant Energy System (CERES) scanner, the TRMM Microwave Imager (TMI), and the Visible and Infrared Scanner (VIRS), to evaluate the variations of tropical deep convective systems (DCSs) with sea surface temperature and precipitation. The authors find that DCS precipitation efficiency increases with SST at a rate of ∼2% K−1. Despite increasing rainfall efficiency, the cloud areal coverage rises with SST at a rate of about 7% K−1 in the warm tropical seas. There, the boundary layer moisture supply for deep convection and the moisture transported to the upper troposphere for cirrus anvil cloud formation increase by ∼6.3% and ∼4.0% K−1, respectively. The changes in cloud formation efficiency, along with the increased transport of moisture available for cloud formation, likely contribute to the large rate of increasing DCS areal coverage. Although no direct observations are available, the increase of cloud formation efficiency with rising SST is deduced indirectly from measurements of changes in the ratio of DCS ice water path and boundary layer water vapor amount with SST. Besides the cloud areal coverage, DCS cluster effective sizes also increase with precipitation. Furthermore, other cloud properties, such as cloud total water and ice water paths, increase with SST. These changes in DCS properties will produce a negative radiative feedback for the earth’s climate system due to strong reflection of shortwave radiation by the DCS. These results significantly differ from some previously hypothesized dehydration scenarios for warmer climates, partially support the thermostat hypothesis but indicate a smaller magnitude of the negative feedback, and have great potential in testing current cloud-system-resolving models and convective parameterizations of general circulation models.

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