Evaluation of ACCESS model cloud properties over the Southern Ocean area using multiple-satellite products

2015 ◽  
Vol 142 (694) ◽  
pp. 160-171 ◽  
Author(s):  
San Luo ◽  
Zhian Sun ◽  
Xiaogu Zheng ◽  
Lawrie Rikus ◽  
Charmaine Franklin
Keyword(s):  
Southern Ocean ◽  
Ocean Area ◽  
Cloud Properties ◽  
Model Cloud ◽  
Access Model

Influences of Recent Particle Formation on Southern Ocean Aerosol Variability and Low Cloud Properties

2021 ◽  
Author(s):  
Isabel L. McCoy ◽  
Christopher S. Bretherton ◽  
Robert Wood ◽  
Cynthia H. Twohy ◽  
Andrew Gettelman ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Particle Formation ◽  
Cloud Properties ◽  
Low Cloud

Influences of Recent Particle Formation on Southern Ocean Aerosol Variability and Low Cloud Properties

2021 ◽  
Author(s):  
Isabel L. McCoy ◽  
Christopher S. Bretherton ◽  
Robert Wood ◽  
Cynthia H. Twohy ◽  
Andrew Gettelman ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Particle Formation ◽  
Cloud Properties ◽  
Low Cloud

Observed Southern Ocean Cloud Properties and Shortwave Reflection. Part I: Calculation of SW Flux from Observed Cloud Properties*

2014 ◽  
Vol 27 (23) ◽  
pp. 8836-8857 ◽  
Author(s):  
Daniel T. McCoy ◽  
Dennis L. Hartmann ◽  
Daniel P. Grosvenor
Keyword(s):  
Seasonal Variation ◽  
Solar Radiation ◽  
Southern Ocean ◽  
Water Content ◽  
Liquid Water ◽  
Effective Radius ◽  
Shortwave Radiation ◽  
Liquid Water Path ◽  
Cloud Liquid Water ◽  
Cloud Properties

Abstract The sensitivity of the reflection of shortwave radiation over the Southern Ocean to the cloud properties there is estimated using observations from a suite of passive and active satellite instruments in combination with radiative transfer modeling. A composite cloud property observational data description is constructed that consistently incorporates mean cloud liquid water content, ice water content, liquid and ice particle radius information, vertical structure, vertical overlap, and spatial aggregation of cloud water as measured by optical depth versus cloud-top pressure histograms. The observational datasets used are Moderate Resolution Imaging Spectroradiometer (MODIS) effective radius filtered to mitigate solar zenith angle bias, the Multiangle Imaging Spectroradiometer (MISR) cloud-top height–optical depth (CTH–OD) histogram, the liquid water path from the University of Wisconsin dataset, and ice cloud properties from CloudSat. This cloud database is used to compute reflected shortwave radiation as a function of month and location over the ocean from 40° to 60°S, which compares well with observations of reflected shortwave radiation. This calculation is then used to test the sensitivity of the seasonal variation of shortwave reflection to the observed seasonal variation of cloud properties. Effective radius decreases during the summer season, which results in an increase in reflected solar radiation of 4–8 W m−2 during summer compared to what would be reflected if the effective radius remained constant at its annual-mean value. Summertime increases in low cloud fraction similarly increase the summertime reflection of solar radiation by 9–11 W m−2. In-cloud liquid water path is less in summertime, causing the reflected solar radiation to be 1–4 W m−2 less.

Exposing Global Cloud Biases in the Community Atmosphere Model (CAM) Using Satellite Observations and Their Corresponding Instrument Simulators

2012 ◽  
Vol 25 (15) ◽  
pp. 5190-5207 ◽  
Author(s):  
J. E. Kay ◽  
B. R. Hillman ◽  
S. A. Klein ◽  
Y. Zhang ◽  
B. Medeiros ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Marine Boundary Layer ◽  
Climate Model ◽  
Substantial Improvement ◽  
Satellite Observations ◽  
Cloud Properties ◽  
Community Atmosphere Model ◽  
Realistic Representation ◽  
Model Cloud ◽  
Atmosphere Model

Abstract Satellite observations and their corresponding instrument simulators are used to document global cloud biases in the Community Atmosphere Model (CAM) versions 4 and 5. The model–observation comparisons show that, despite having nearly identical cloud radiative forcing, CAM5 has a much more realistic representation of cloud properties than CAM4. In particular, CAM5 exhibits substantial improvement in three long-standing climate model cloud biases: 1) the underestimation of total cloud, 2) the overestimation of optically thick cloud, and 3) the underestimation of midlevel cloud. While the increased total cloud and decreased optically thick cloud in CAM5 result from improved physical process representation, the increased midlevel cloud in CAM5 results from the addition of radiatively active snow. Despite these improvements, both CAM versions have cloud deficiencies. Of particular concern, both models exhibit large but differing biases in the subtropical marine boundary layer cloud regimes that are known to explain intermodel differences in cloud feedbacks and climate sensitivity. More generally, this study demonstrates that simulator-facilitated evaluation of cloud properties, such as amount by vertical level and optical depth, can robustly expose large and at times radiatively compensating climate model cloud biases.

The Southern Ocean Cloud project

2021 ◽  
Author(s):  
Tom Lachlan-Cope ◽  
Amelie Kirchgaessner ◽  
Anna Jones ◽  
Jo Browse ◽  
David Topping ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Production Control ◽  
Size Spectrum ◽  
Climate Modelling ◽  
Oceanic Circulation ◽  
Aerosol Composition ◽  
Atlantic Sector ◽  
Cloud Properties ◽  
Cloud Development ◽  
The Uk

<p>The Southern Ocean Cloud (SOC) project is funded by the UK Natural Environment Research Council to investigate clouds, particularly mixed-phase, in the Atlantic sector of the Southern Ocean and how aerosol sources and production control clouds properties. Here we aim to introduce the community to the project and any associated opportunities that might be available. At high Southern latitudes models are relatively poor at representing clouds and this has an impact on the energy balance and hence atmospheric and oceanic circulation both locally and globally. This project will investigate those processes that control cloud development and will concentrate on the aerosol that act as cloud nuclei, the source of these nuclei and how aerosol and microphysical processes are modelled.</p><p> </p><p>It is planned to deploy instruments to the British Antarctic Survey (BAS) research stations Rothera and Bird Island research stations as well as on the BAS research vessel. These instruments will measure the aerosol size spectrum at all stations and in addition CCN and INP numbers, cloud properties (with a polarized lidar) and aerosol composition at Rothera. The instruments will be deployed for at least 3 years, although some instruments may be moved from Rothera to the ship for special observing periods.</p><p> </p><p>In addition to the long-term measurements there will be two special observing periods (SOPs), the first in the 2022/23 Antarctic season will consist of a dedicated ship cruise and an airborne campaign using the BAS instrumented twin otter aircraft along with enhanced observations at the surface stations. The second SOP will also have enhanced observations at the surface stations along with an airborne campaign.</p><p> </p><p>The observations will be backed up with a programme of aerosol, weather and climate modelling. The combination of modelling and observations should enable us to identify the major sources of cloud nuclei over the Southern Ocean, examine their role in cloud development, and improve the representation of these processes in models.</p><p> </p>

EVALUATION OF CLOUDS, RADIATION, AND PRECIPITATION IN CMIP6 MODELS USING GLOBAL WEATHER STATES DERIVED FROM ISCCP-H CLOUD PROPERTY DATA

2021 ◽  
pp. 1-42
Author(s):  
George Tselioudis ◽  
William. B. Rossow ◽  
Christian Jakob ◽  
Jasmine Remillard ◽  
Derek Tropf ◽  
...  
Keyword(s):  
Cumulus Clouds ◽  
Cloud Optical Depth ◽  
Cloud Properties ◽  
Shallow Cumulus ◽  
Property Data ◽  
Ensemble Mean ◽  
Stratocumulus Clouds ◽  
Model Cloud ◽  
Adequate Representation ◽  
Cloud Top Pressure

AbstractA clustering methodology is applied to cloud optical depth cloud top pressure (TAU-PC) histograms from the new, 1-degree resolution, ISCCP-H dataset, to derive an updated global Weather State (WS) dataset. Then, PC-TAU histograms from current-climate CMIP6 model simulations are assigned to the ISCCP-H WSs along with their concurrent radiation and precipitation properties, to evaluate model cloud, radiation, and precipitation properties in the context of the Weather States. The new ISCCP-H analysis produces WSs that are very similar to those previously found in the lower resolution ISCCP-D dataset. The main difference lies in the splitting of the ISCCP-D thin stratocumulus WS between the ISCCP-H shallow cumulus and stratocumulus WSs, which results in the reduction by one of the total WS number. The evaluation of the CMIP6 models against the ISCCP-H Weather States, shows that, in the ensemble mean, the models are producing an adequate representation of the frequency and geographical distribution of the WSs, with measurable improvements compared to the WSs derived for the CMIP5 ensemble. However, the frequency of shallow cumulus clouds continues to be underestimated, and, in some WSs the good agreement of the ensemble mean with observations comes from averaging models that significantly overpredict and underpredict the ISCCP-H WS frequency. In addition, significant biases exist in the internal cloud properties of the model WSs, such as the model underestimation of cloud fraction in middle-top clouds and secondarily in midlatitude storm and stratocumulus clouds, that result in an underestimation of cloud SW cooling in those regimes.

scholarly journals Natural aerosols explain seasonal and spatial patterns of Southern Ocean cloud albedo

2015 ◽  
Vol 1 (6) ◽  
pp. e1500157 ◽  
Author(s):  
Daniel T. McCoy ◽  
Susannah M. Burrows ◽  
Robert Wood ◽  
Daniel P. Grosvenor ◽  
Scott M. Elliott ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Atmospheric Aerosols ◽  
Suspended Solid ◽  
Spatiotemporal Variability ◽  
Anthropogenic Aerosols ◽  
Spatially Correlated ◽  
Cloud Properties ◽  
Planetary Albedo ◽  
High Concentrations ◽  
Natural Aerosols

Atmospheric aerosols, suspended solid and liquid particles, act as nucleation sites for cloud drop formation, affecting clouds and cloud properties—ultimately influencing the cloud dynamics, lifetime, water path, and areal extent that determine the reflectivity (albedo) of clouds. The concentration Nd of droplets in clouds that influences planetary albedo is sensitive to the availability of aerosol particles on which the droplets form. Natural aerosol concentrations affect not only cloud properties themselves but also modulate the sensitivity of clouds to changes in anthropogenic aerosols. It is shown that modeled natural aerosols, principally marine biogenic primary and secondary aerosol sources, explain more than half of the spatiotemporal variability in satellite-observed Nd. Enhanced Nd is spatially correlated with regions of high chlorophyll a, and the spatiotemporal variability in Nd is found to be driven primarily by high concentrations of sulfate aerosol at lower Southern Ocean latitudes (35o to 45oS) and by organic matter in sea spray aerosol at higher latitudes (45o to 55oS). Biogenic sources are estimated to increase the summertime mean reflected solar radiation in excess of 10 W m–2 over parts of the Southern Ocean, which is comparable to the annual mean increases expected from anthropogenic aerosols over heavily polluted regions of the Northern Hemisphere.

scholarly journals Southern Ocean Cloud Properties Derived from CAPRICORN and MARCUS Data

2020 ◽  
Author(s):  
Gerald Mace ◽  
Alain Protat ◽  
Ruhi S Humphries ◽  
Simon Peter Alexander ◽  
Ian McRobert ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Cloud Properties

scholarly journals The Surface Downwelling Solar Radiation Surplus over the Southern Ocean in the Met Office Model: The Role of Midlatitude Cyclone Clouds

2012 ◽  
Vol 25 (21) ◽  
pp. 7467-7486 ◽  
Author(s):  
A. Bodas-Salcedo ◽  
K. D. Williams ◽  
P. R. Field ◽  
A. P. Lock
Keyword(s):  
Southern Ocean ◽  
Optical Depth ◽  
Radiative Properties ◽  
Shortwave Radiation ◽  
Radiative Fluxes ◽  
Cloud Properties ◽  
Cloud Regime ◽  
New Diagnosis ◽  
Cloud Regimes

The authors study the role of clouds in the persistent bias of surface downwelling shortwave radiation (SDSR) in the Southern Ocean in the atmosphere-only version of the Met Office model. The reduction of this bias in the atmosphere-only version is important to minimize sea surface temperature biases when the atmosphere model is coupled to a dynamic ocean. The authors use cloud properties and radiative fluxes estimates from the International Satellite Cloud Climatology Project (ISCCP) and apply a clustering technique to classify clouds into different regimes over the Southern Ocean. Then, they composite the cloud regimes around cyclone centers, which allows them to study the role of each cloud regime in a mean composite cyclone. Low- and midlevel clouds in the cold-air sector of the cyclones are responsible for most of the bias. Based on this analysis, the authors develop and test a new diagnosis of shear-dominated boundary layers. This change improves the simulation of the SDSR through a better simulation of the frequency of occurrence of the cloud regimes in the cyclone composite. Substantial biases in the radiative properties of the midtop and stratocumulus regimes are still present, which suggests the need to increase the optical depth of the low-level cloud with moderate optical depth and cloud with tops at midlevels.

scholarly journals What is the Role of Sea Surface Temperature in Modulating Cloud and Precipitation Properties over the Southern Ocean?

2016 ◽  
Vol 29 (20) ◽  
pp. 7453-7476 ◽  
Author(s):  
Yi Huang ◽  
Steven T. Siems ◽  
Michael J. Manton ◽  
Daniel Rosenfeld ◽  
Roger Marchand ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Southern Ocean ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Liquid Water ◽  
Storm Track ◽  
Supercooled Liquid ◽  
Sea Surface ◽  
Liquid Water Path ◽  
Cloud Properties

Abstract This study employs four years of spatiotemporally collocated A-Train satellite observations to investigate cloud and precipitation characteristics in relation to the underlying properties of the Southern Ocean (SO). Results show that liquid-phase cloud properties strongly correlate with the sea surface temperature (SST). In summer, ubiquitous supercooled liquid water (SLW) is observed over SSTs less than about 4°C. Cloud-top temperature (CTT) and effective radius of liquid-phase clouds generally decrease for colder SSTs, whereas the opposite trend is observed for cloud-top height, cloud optical thickness, and liquid water path. The deduced cloud depth is larger over the colder oceans. Notable differences are observed between “precipitating” and “nonprecipitating” clouds and between different ocean sectors. Using a novel joint SST–CTT histogram, two distinct liquid-phase cloud types are identified, where the retrieved particle size appears to increase with decreasing CTT over warmer water (SSTs >~7°C), while the opposite is true over colder water. A comparison with the Northern Hemisphere (NH) storm-track regions suggests that the ubiquitous SLW with markedly smaller droplet size is a unique feature for the cold SO (occurring where SSTs <~4°C), while the presence of this cloud type is much less frequent over the NH counterparts, where the SSTs are rarely colder than about 4°C at any time of the year. This study also suggests that precipitation, which has a profound influence on cloud properties, remains poorly observed over the SO with the current spaceborne sensors. Large uncertainties in precipitation properties are associated with the ubiquitous boundary layer clouds within the lowest kilometer of the atmosphere.

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