Reassessing the Effect of Cloud Type on Earth’s Energy Balance in the Age of Active Spaceborne Observations. Part I: Top of Atmosphere and Surface

2019 ◽  
Vol 32 (19) ◽  
pp. 6197-6217 ◽  
Author(s):  
Tristan S. L’Ecuyer ◽  
Yun Hang ◽  
Alexander V. Matus ◽  
Zhien Wang
Keyword(s):  
Energy Balance ◽  
Vertical Structure ◽  
Classical Problem ◽  
Cloud Base ◽  
Radiative Effect ◽  
Radiative Effects ◽  
Solar Absorption ◽  
Structure Information ◽  
Cloud Radiative Effect ◽  
Cloud Radiative Effects

AbstractThis study revisits the classical problem of quantifying the radiative effects of unique cloud types in the era of spaceborne active observations. The radiative effects of nine cloud types, distinguished based on their vertical structure defined by CloudSat and CALIPSO observations, are assessed at both the top of the atmosphere and the surface. The contributions from single- and multilayered clouds are explicitly diagnosed. The global, annual mean net cloud radiative effect at the top of the atmosphere is found to be −17.1 ± 4.2 W m−2 owing to −44.2 ± 2 W m−2 of shortwave cooling and 27.1 ± 3.7 W m−2 of longwave heating. Leveraging explicit cloud base and vertical structure information, we further estimate the annual mean net cloud radiative effect at the surface to be −24.8 ± 8.7 W m−2 (−51.1 ± 7.8 W m−2 in the shortwave and 26.3 ± 3.8 W m−2 in the longwave). Multilayered clouds are found to exert the strongest influence on the top-of-atmosphere energy balance. However, a strong asymmetry in net cloud radiative cooling between the hemispheres (8.6 W m−2) is dominated by enhanced cooling from stratocumulus over the southern oceans. It is found that there is no corresponding asymmetry at the surface owing to enhanced longwave emission by southern ocean clouds in winter, which offsets a substantial fraction of their impact on solar absorption in summer. Thus the asymmetry in cloud radiative effects is entirely realized as an atmosphere heating imbalance between the hemispheres.

scholarly journals The Role of Cloud Radiative Heating in Determining the Location of the ITCZ in Aquaplanet Simulations

2016 ◽  
Vol 29 (8) ◽  
pp. 2741-2763 ◽  
Author(s):  
Bryce E. Harrop ◽  
Dennis L. Hartmann
Keyword(s):  
Hadley Circulation ◽  
Radiative Heating ◽  
Moisture Convergence ◽  
Radiative Effect ◽  
Radiative Effects ◽  
Onset Of Convection ◽  
Cloud Radiative Effect ◽  
Cloud Radiative Effects ◽  
The Mean ◽  
The Impact

Abstract The relationship between the tropical circulation and cloud radiative effect is investigated. Output from the Clouds On–Off Klimate Intercomparison Experiment (COOKIE) is used to examine the impact of cloud radiative effects on circulation and climate. In aquaplanet simulations with a fixed SST pattern, the cloud radiative effect leads to an equatorward contraction of the intertropical convergence zone (ITCZ) and a reduction of the double ITCZ problem. It is shown that the cloud radiative heating in the upper troposphere increases the temperature, weakens CAPE, and inhibits the onset of convection until it is closer to the equator, where SSTs are higher. Precipitation peaks at higher values in a narrower band when the cloud radiative effects are active, compared to when they are inactive, owing to the enhancement in moisture convergence. Additionally, cloud–radiation interactions strengthen the mean meridional circulation and consequently enhance the moisture convergence. Although the mean tropical precipitation decreases, the atmospheric cloud radiative effect has a strong meridional gradient, which supports stronger poleward energy flux and speeds up the Hadley circulation. Cloud radiative heating also enhances cloud water path (liquid plus ice), which, combined with the reduction in precipitation, suggests that the cloud radiative heating reduces precipitation efficiency in these models.

Regional and Seasonal Influence of Cloud Radiative Effects on CMIP6 Model Climate Sensitivity

2020 ◽  
Author(s):  
Bithi De ◽  
George Tselioudis
Keyword(s):  
Climate Sensitivity ◽  
Significant Contribution ◽  
Coupled Model ◽  
Radiative Effect ◽  
Radiative Effects ◽  
Seasonal Influence ◽  
Equilibrium Climate Sensitivity ◽  
Cloud Radiative Effect ◽  
Cloud Radiative Effects ◽  
The Relationship

<p>Recent analyses of Coupled Model Intercomparison Project phase 6 (CMIP6) models have shown higher climate sensitivities than previously reported, and this increase has been preliminary attributed to the simulation of anomalous Shortwave Cloud Radiative Effect (SWCRE) over the southern midlatitude regions. In this work, we further explore how the seasonal and annual SWCRE over different regions of the globe influence the model climate sensitivities. Our study suggests a significant contribution of SWCRE on climate sensitivities in both northern and southern midlatitudes; and the relationship remains robust across the seasons. Additionally, we assess the underlying physics of the inter-model spread to diagnose model biases. The results will contribute to quantify the severity of the Equilibrium Climate Sensitivity, as simulated by the CMIP6 models.</p>

scholarly journals The cloud-free global energy balance and inferred cloud radiative effects: an assessment based on direct observations and climate models

2018 ◽  
Vol 52 (7-8) ◽  
pp. 4787-4812 ◽  
Author(s):  
Martin Wild ◽  
Maria Z. Hakuba ◽  
Doris Folini ◽  
Patricia Dörig-Ott ◽  
Christoph Schär ◽  
...  
Keyword(s):  
Energy Balance ◽  
Climate Models ◽  
Radiative Effects ◽  
Global Energy ◽  
Global Energy Balance ◽  
Direct Observations ◽  
Cloud Radiative Effects

scholarly journals The efficacy of aerosol–cloud radiative perturbations from near-surface emissions in deep open-cell stratocumuli

2018 ◽  
Vol 18 (23) ◽  
pp. 17475-17488 ◽  
Author(s):  
Anna Possner ◽  
Hailong Wang ◽  
Robert Wood ◽  
Ken Caldeira ◽  
Thomas P. Ackerman
Keyword(s):  
Emission Line ◽  
Radiative Properties ◽  
Radiative Effect ◽  
Radiative Effects ◽  
Near Surface ◽  
Open Cell ◽  
Detection And Attribution ◽  
Cloud Radiative Effects ◽  
Ship Tracks ◽  
Cloud Radiative Properties

Abstract. Aerosol–cloud radiative effects are determined and quantified in simulations of deep open-cell stratocumuli observed during the VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx) campaign off the west coast of Chile. The cloud deck forms in a boundary layer 1.5 km deep, with cell sizes reaching 50 km in diameter. Global databases of ship tracks suggest that these linear structures are seldom found in boundary layers this deep. Here, we quantify the changes in cloud radiative properties to a continuous aerosol point source moving along a fixed emission line releasing 1017 particles per second. We show that a spatially coherent cloud perturbation is not evident along the emission line. Yet our model simulates an increase in domain-mean all-sky albedo of 0.05, corresponding to a diurnally averaged cloud radiative effect of 20 W m−2, given the annual mean solar insolation at the VOCALS-REx site. Therefore, marked changes in cloud radiative properties in precipitating deep open cells may be driven by anthropogenic near-surface aerosol perturbations, such as those generated by ships. Furthermore, we demonstrate that these changes in cloud radiative properties are masked by the naturally occurring variability within the organised cloud field. A clear detection and attribution of cloud radiative effects to a perturbation in aerosol concentrations becomes possible when sub-filtering of the cloud field is applied, using the spatio-temporal distribution of the aerosol perturbation. Therefore, this work has implications for the detection and attribution of effective cloud radiative forcing in marine stratocumuli, which constitutes one of the major physical uncertainties within the climate system. Our results suggest that ships may sometimes have a substantial radiative effect on marine clouds and albedo, even when ship tracks are not readily visible.

scholarly journals Radiative budget and cloud radiative effect over the Atlantic from ship based observations

2012 ◽  
Vol 5 (2) ◽  
pp. 2011-2042 ◽  
Author(s):  
J. Kalisch ◽  
A. Macke
Keyword(s):  
Cloud Type ◽  
Radiative Effects ◽  
Radiative Fluxes ◽  
Stratus Clouds ◽  
Solar Cooling ◽  
Cloud Radiative Effect ◽  
Single Column ◽  
Single Column Model ◽  
Cloud Radiative Effects ◽  
The Mean

Abstract. The aim of this study is to determine cloud-type resolved cloud radiative budgets and cloud radiative effects from surface measurements of broadband radiative fluxes over the Atlantic Ocean. Furthermore, based on simultaneous observations of the state of the cloudy atmosphere a radiative closure study has been performed by means of the ECHAM5 single column model in order to identify the models ability to realistically reproduce the effects of clouds on the climate system. An extensive data base of radiative and atmospheric measurements has been established along five meridional cruises of the German research icebreaker POLARSTERN. Besides pyranometer and pyrgeometer for downward broadband solar and thermal radiative fluxes, a sky imager and a microwave radiometer have been utilized to determine cloud fraction and cloud type on the one hand and temperature and humidity profiles as well as liquid water path for warm non-precipitating clouds on the other hand. Averaged over all cruise tracks we obtain a total net (solar + thermal) radiative flux of 144 W m−2 that is dominated by the solar component. In general, the solar contribution is large for cirrus clouds and small for stratus clouds. No significant meridional dependencies were found for the surface radiation budgets and cloud effects. The strongest surface longwave cloud effects were shown in the presence of low level clouds. Clouds with a high optical density induce strong negative solar radiative effects under high solar altitudes. The mean surface net cloud radiative effect is −34 W m−2. For the purpose of quickly estimating the mean surface longwave, shortwave and net cloud effects in moderate, subtropical and tropical climate regimes a new parameterisation was created, considering the total cloud amount and the solar zenith angle. The ECHAM5 single column model provides a surface net cloud effect that is more cooling by 16 W m−2 compared to the radiation observations. This overestimation in solar cooling is mostly caused by the shortwave impact of convective clouds. The latter show a large overestimation in solar cooling of up to 112 W m−2. Mean cloud radiative effects of cirrus and stratus clouds were simulated close to the observations.

scholarly journals How Well Are Clouds Simulated over Greenland in Climate Models? Consequences for the Surface Cloud Radiative Effect over the Ice Sheet

2018 ◽  
Vol 31 (22) ◽  
pp. 9293-9312 ◽  
Author(s):  
A. Lacour ◽  
H. Chepfer ◽  
N. B. Miller ◽  
M. D. Shupe ◽  
V. Noel ◽  
...  
Keyword(s):  
Cloud Cover ◽  
Climate Models ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ground Level ◽  
Radiative Effect ◽  
Cloud Properties ◽  
Cloud Radiative Effect ◽  
Primary Driver ◽  
Cloud Radiative Effects

Using lidar and radiative flux observations from space and ground, and a lidar simulator, we evaluate clouds simulated by climate models over the Greenland ice sheet, including predicted cloud cover, cloud fraction profile, cloud opacity, and surface cloud radiative effects. The representation of clouds over Greenland is a central concern for the models because clouds impact ice sheet surface melt. We find that over Greenland, most of the models have insufficient cloud cover during summer. In addition, all models create too few nonopaque, liquid-containing clouds optically thin enough to let direct solar radiation reach the surface (−1% to −3.5% at the ground level). Some models create too few opaque clouds. In most climate models, the cloud properties biases identified over all Greenland also apply at Summit, Greenland, proving the value of the ground observatory in model evaluation. At Summit, climate models underestimate cloud radiative effect (CRE) at the surface, especially in summer. The primary driver of the summer CRE biases compared to observations is the underestimation of the cloud cover in summer (−46% to −21%), which leads to an underestimated longwave radiative warming effect (CRELW = −35.7 to −13.6 W m−2 compared to the ground observations) and an underestimated shortwave cooling effect (CRESW = +1.5 to +10.5 W m−2 compared to the ground observations). Overall, the simulated clouds do not radiatively warm the surface as much as observed.

scholarly journals Quantifying the Contribution of Different Cloud Types to the Radiation Budget in Southern West Africa

2018 ◽  
Vol 31 (13) ◽  
pp. 5273-5291 ◽  
Author(s):  
Peter G. Hill ◽  
Richard P. Allan ◽  
J. Christine Chiu ◽  
Alejandro Bodas-Salcedo ◽  
Peter Knippertz
Keyword(s):  
West Africa ◽  
Vertical Structure ◽  
Climate Models ◽  
Radiation Budget ◽  
Radiative Effect ◽  
Satellite Measurements ◽  
Regional Energy ◽  
Cloud Radiative Effect ◽  
Low Cloud ◽  
Low Cloud Cover

The contribution of cloud to the radiation budget of southern West Africa (SWA) is poorly understood and yet it is important for understanding regional monsoon evolution and for evaluating and improving climate models, which have large biases in this region. Radiative transfer calculations applied to atmospheric profiles obtained from the CERES– CloudSat–CALIPSO–MODIS (CCCM) dataset are used to investigate the effects of 12 different cloud types (defined by their vertical structure) on the regional energy budget of SWA (5°–10°N, 8°W–8°E) during June–September. We show that the large regional mean cloud radiative effect in SWA is due to nonnegligible contributions from many different cloud types; eight cloud types have a cloud fraction larger than 5% and contribute at least 5% of the regional mean shortwave cloud radiative effect at the top of the atmosphere. Low clouds, which are poorly observed by passive satellite measurements, were found to cause net radiative cooling of the atmosphere, which reduces the heating from other cloud types by approximately 10%. The sensitivity of the radiation budget to underestimating low-cloud cover is also investigated. The radiative effect of missing low cloud is found to be up to approximately −25 W m−2 for upwelling shortwave irradiance at the top of the atmosphere and 35 W m−2 for downwelling shortwave irradiance at the surface.

scholarly journals Effectiveness and limitations of parameter tuning in reducing biases of top-of-atmosphere radiation and clouds in MIROC version 5

2017 ◽  
Author(s):  
Tomoo Ogura ◽  
Hideo Shiogama ◽  
Masahiro Watanabe ◽  
Masakazu Yoshimori ◽  
Tokuta Yokohata ◽  
...  
Keyword(s):  
General Circulation ◽  
Grid Point ◽  
Circulation Model ◽  
Cloud Amount ◽  
Parameter Tuning ◽  
The Arctic ◽  
Cloud Base ◽  
Observation Data ◽  
Radiative Effect ◽  
Cloud Radiative Effect

Abstract. This study discusses how much of the biases in top-of-atmosphere (TOA) radiation and clouds can be removed by parameter tuning in the present-day simulation of a climate model in the Coupled Model Inter-comparison Project phase 5 (CMIP5) generation. We used a low-resolution version of the Model for Interdisciplinary Research on Climate version 5 (MIROC5) Atmosphere-Ocean General Circulation Model (AOGCM) and compared the output of a perturbed parameter ensemble (PPE) experiment in the pre-industrial control setting with satellite observation data. The model biases and the parametric uncertainty of the biases are evaluated with respect to TOA radiation and clouds. We used the output of the PPE experiment without flux adjustment, which is consistent with the experimental design of the CMIP5. The results indicate that removing or changing the sign of the biases by parameter tuning alone is difficult. Especially, the cooling bias of the shortwave cloud radiative effect in low latitudes could not be removed, neither in the zonal mean nor at each latitude–longitude grid point. The bias was related to the overestimation of both cloud amount and cloud optical thickness, which could not be removed by the parameter tuning either. However, they could be alleviated by tuning parameters such as the maximum cumulus updraft velocity at the cloud base. On the other hand, the bias of the shortwave cloud radiative effect in the Arctic was sensitive to parameter tuning. It could be removed by tuning such parameters as albedo of ice and snow both in the zonal mean and at each grid point. The obtained results illustrate the benefit of PPE experiments which provide useful information regarding effectiveness and limitations of parameter tuning.

scholarly journals Cloud radiative effect, cloud fraction and cloud type at two stations in Switzerland using hemispherical sky cameras

2017 ◽  
Vol 10 (12) ◽  
pp. 4587-4600 ◽  
Author(s):  
Christine Aebi ◽  
Julian Gröbner ◽  
Niklaus Kämpfer ◽  
Laurent Vuilleumier
Keyword(s):  
Cloud Fraction ◽  
Cloud Base ◽  
Transfer Model ◽  
Radiative Effect ◽  
Cloud Type ◽  
Direct Radiation ◽  
Low Level ◽  
Cloud Coverage ◽  
Cloud Radiative Effect ◽  
Fractional Cloud

Abstract. The current study analyses the cloud radiative effect during the daytime depending on cloud fraction and cloud type at two stations in Switzerland over a time period of 3 to 5 years. Information on fractional cloud coverage and cloud type is retrieved from images taken by visible all-sky cameras. Cloud-base height (CBH) data are retrieved from a ceilometer and integrated water vapour (IWV) data from GPS measurements. The longwave cloud radiative effect (LCE) for low-level clouds and a cloud coverage of 8 oktas has a median value between 59 and 72 Wm−2. For mid- and high-level clouds the LCE is significantly lower. It is shown that the fractional cloud coverage, the CBH and IWV all have an influence on the magnitude of the LCE. These observed dependences have also been modelled with the radiative transfer model MODTRAN5. The relative values of the shortwave cloud radiative effect (SCErel) for low-level clouds and a cloud coverage of 8 oktas are between −90 and −62 %. Also here the higher the cloud is, the less negative the SCErel values are. In cases in which the measured direct radiation value is below the threshold of 120 Wm−2 (occulted sun) the SCErel decreases substantially, while cases in which the measured direct radiation value is larger than 120 Wm−2 (visible sun) lead to a SCErel of around 0 %. In 14 and 10 % of the cases in Davos and Payerne respectively a cloud enhancement has been observed with a maximum in the cloud class cirrocumulus–altocumulus at both stations. The calculated median total cloud radiative effect (TCE) values are negative for almost all cloud classes and cloud coverages.

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