Performance of CAMS-CSM in Simulating the Shortwave Cloud Radiative Effect over Global Stratus Cloud Regions: Baseline Evaluation and Sensitivity Test

The trades form an important link in the atmospheric energy supply, transporting moisture and momentum to the deep tropics and influencing the global hydrological cycle.&#160;Trade-wind cumuli are the most ubiquitous cloud type over tropical oceans, yet models disagree in simulating their response to warming.&#160;Our study takes advantage of extensive in-situ soundings performed&#160;during the EUREC4A campaign, which took place in the downstream&#160;trades of the North Atlantic in winter 2020. We employ 1068&#160;dropsondes&#160;made in a ca. 2deg x 2deg area&#160;to&#160;close the moisture and energy budgets of the subcloud layer and atmospheric column. Our motivation for closing moisture and energy budgets using EUREC4A data is two-fold. First, we try to understand which large-scale environmental factors control&#160;variability in subcloud layer moisture and moist static energy, given their influence on setting convective potential.&#160;Second,&#160;we quantify the interplay between clouds and their environment through an energetic lens. The&#160;cloud radiative effect emerges as a residual from the total column moist static energy budget,&#160;yielding an energetic estimate of clouds. We quantify how this cloud radiative effect compares with coincident satellite and geometric (i.e. cloud fraction) estimates of cloudiness,&#160;varies on different scales, and relates to large-scale environmental conditions.

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The Surface Longwave Cloud Radiative Effect from Space Lidar Observations

10.5194/egusphere-egu21-2064 ◽

2021 ◽

Author(s):

Assia Arouf

Keyword(s):

Cloud Cover ◽

Temporal Variations ◽

Radiative Effect ◽

Cloud Properties ◽

Cloud Radiative Effect ◽

Long Time ◽

The One ◽

Natural Climate ◽

The Impact ◽

Lidar Observations

Clouds exert important effects on Earth's surface energy balance through their effects on longwave (LW) and shortwave (SW) radiation. Indeed, clouds radiatively warm the surface in the LW domain by emitting LW radiation back to the ground. The surface LW cloud radiative effect (CRE) quantifies this warming effect. To study the impact of clouds on the interanual natural climate variability, we need to observe them on a long time scale over all kinds of surfaces. The CALIPSO space lidar provides these observations by sampling the atmosphere along its track over all kinds of surfaces for over than 14 years (2006-2020).In this work, we propose new estimates of the surface LW CRE from space-based lidar observations only. Indeed, we show from 1D atmospheric column radiative transfer calculations, that surface LW CRE at sea level linearly decreases with the cloud altitude. Thus, these computations allow to establish simple relationships between the surface LW CRE, and five cloud properties observed by the CALIPSO space lidar: the opaque cloud cover and altitude, the thin cloud cover, altitude, and emissivity. Over the 2008&#8211;2011, CALIPSO-based retrieval (27.7 W m-2) is 1.2 W m-2 larger than the one derived from combined space radar, lidar, and radiometer observations. Over the 2008&#8211;2018 period, the global mean CALIPSO-based retrieval (27.5 W m-2) is 0.1 W m-2 larger than the one derived from CERES space radiometer. Our estimates show that globally, opaque clouds warm the surface by 23.3 W m-2 and thin clouds contribute only by 4.2 W m-2. At high latitudes North and South over oceans, the largest surface LW opaque CRE occurs in fall (40.4 W m-2, 31.6 W m-2) due to the formation of additional opaque low clouds after sea ice melting over a warmer ocean.To quantify the cloud property that drives the temporal variations of the surface LW CRE, the surface LW CRE needs to be related by simple relationships to a finite number of cloud properties such as cloud opacity, cloud altitude and cloud cover. This study allows a decomposition and attribution approach of the surface LW CRE variations and shows that they are driven by the variations occurring in the opaque cloud properties. Moreover, opaque cloud cover drives over than 73% of global surface LW CRE interannual variations.

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Toward a Consistent Definition between Satellite and Model Clear-Sky Radiative Fluxes

Journal of Climate ◽

10.1175/jcli-d-19-0381.1 ◽

2020 ◽

Vol 33 (1) ◽

pp. 61-75 ◽

Cited By ~ 3

Author(s):

Norman G. Loeb ◽

Fred G. Rose ◽

Seiji Kato ◽

David A. Rutan ◽

Wenying Su ◽

...

Keyword(s):

Tropical Pacific ◽

Radiative Effect ◽

The West ◽

Model Calculations ◽

Radiative Fluxes ◽

Clear Sky ◽

Cloud Radiative Effect ◽

Adjustment Factors ◽

The Impact ◽

Global Mean

AbstractA new method of determining clear-sky radiative fluxes from satellite observations for climate model evaluation is presented. The method consists of applying adjustment factors to existing satellite clear-sky broadband radiative fluxes that make the observed and simulated clear-sky flux definitions more consistent. The adjustment factors are determined from the difference between observation-based radiative transfer model calculations of monthly mean clear-sky fluxes obtained by ignoring clouds in the atmospheric column and by weighting hourly mean clear-sky fluxes with imager-based clear-area fractions. The global mean longwave (LW) adjustment factor is −2.2 W m−2 at the top of the atmosphere and 2.7 W m−2 at the surface. The LW adjustment factors are pronounced at high latitudes during winter and in regions with high upper-tropospheric humidity and cirrus cloud cover, such as over the west tropical Pacific, and the South Pacific and intertropical convergence zones. In the shortwave (SW), global mean adjustment is 0.5 W m−2 at TOA and −1.9 W m−2 at the surface. It is most pronounced over sea ice off of Antarctica and over heavy aerosol regions, such as eastern China. However, interannual variations in the regional SW and LW adjustment factors are small compared to those in cloud radiative effect. After applying the LW adjustment factors, differences in zonal mean cloud radiative effect between observations and climate models decrease markedly between 60°S and 60°N and poleward of 65°N. The largest regional improvements occur over the west tropical Pacific and Indian Oceans. In contrast, the impact of the SW adjustment factors is much smaller.

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On the Relationships between Subtropical Clouds and Meteorology in Observations and CMIP3 and CMIP5 Models*

Journal of Climate ◽

10.1175/jcli-d-14-00475.1 ◽

2015 ◽

Vol 28 (8) ◽

pp. 2945-2967 ◽

Cited By ~ 47

Author(s):

Timothy A. Myers ◽

Joel R. Norris

Keyword(s):

Surface Temperature ◽

Sea Surface Temperature ◽

Cloud Fraction ◽

Sea Surface ◽

Radiative Effect ◽

Low Level ◽

Temperature Advection ◽

Cloud Radiative Effect ◽

High Level ◽

The Relationship

Abstract Climate models’ simulation of clouds over the eastern subtropical oceans contributes to large uncertainties in projected cloud feedback to global warming. Here, interannual relationships of cloud radiative effect and cloud fraction to meteorological variables are examined in observations and in models participating in phases 3 and 5 of the Coupled Model Intercomparison Project (CMIP3 and CMIP5, respectively). In observations, cooler sea surface temperature, a stronger estimated temperature inversion, and colder horizontal surface temperature advection are each associated with larger low-level cloud fraction and increased reflected shortwave radiation. A moister free troposphere and weaker subsidence are each associated with larger mid- and high-level cloud fraction and offsetting components of shortwave and longwave cloud radiative effect. It is found that a larger percentage of CMIP5 than CMIP3 models simulate the wrong sign or magnitude of the relationship of shortwave cloud radiative effect to sea surface temperature and estimated inversion strength. Furthermore, most models fail to produce the sign of the relationship between shortwave cloud radiative effect and temperature advection. These deficiencies are mostly, but not exclusively, attributable to errors in the relationship between low-level cloud fraction and meteorology. Poor model performance also arises due to errors in the response of mid- and high-level cloud fraction to variations in meteorology. Models exhibiting relationships closest to observations tend to project less solar reflection by clouds in the late twenty-first century and have higher climate sensitivities than poorer-performing models. Nevertheless, the intermodel spread of climate sensitivity is large even among these realistic models.

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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

Journal of Climate ◽

10.1175/jcli-d-18-0753.1 ◽

2019 ◽

Vol 32 (19) ◽

pp. 6197-6217 ◽

Cited By ~ 6

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.

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Modelling the relationship between liquid water content and cloud droplet number concentration observed in low clouds in the summer Arctic and its radiative effects

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-29-2020 ◽

2020 ◽

Vol 20 (1) ◽

pp. 29-43

Author(s):

Joelle Dionne ◽

Knut von Salzen ◽

Jason Cole ◽

Rashed Mahmood ◽

W. Richard Leaitch ◽

...

Keyword(s):

Linear Relationship ◽

Water Content ◽

Liquid Water ◽

Cloud Droplet ◽

Liquid Water Content ◽

Number Concentration ◽

Radiative Effect ◽

Low Clouds ◽

Cloud Radiative Effect ◽

Cloud Droplet Number Concentration

Abstract. Low clouds persist in the summer Arctic with important consequences for the radiation budget. In this study, we simulate the linear relationship between liquid water content (LWC) and cloud droplet number concentration (CDNC) observed during an aircraft campaign based out of Resolute Bay, Canada, conducted as part of the Network on Climate and Aerosols: Addressing Key Uncertainties in Remote Canadian Environments study in July 2014. Using a single-column model, we find that autoconversion can explain the observed linear relationship between LWC and CDNC. Of the three autoconversion schemes we examined, the scheme using continuous drizzle (Khairoutdinov and Kogan, 2000) appears to best reproduce the observed linearity in the tenuous cloud regime (Mauritsen et al., 2011), while a scheme with a threshold for rain (Liu and Daum, 2004) best reproduces the linearity at higher CDNC. An offline version of the radiative transfer model used in the Canadian Atmospheric Model version 4.3 is used to compare the radiative effects of the modelled and observed clouds. We find that there is no significant difference in the upward longwave cloud radiative effect at the top of the atmosphere from the three autoconversion schemes (p=0.05) but that all three schemes differ at p=0.05 from the calculations based on observations. In contrast, the downward longwave and shortwave cloud radiative effect at the surface for the Wood (2005b) and Khairoutdinov and Kogan (2000) schemes do not differ significantly (p=0.05) from the observation-based radiative calculations, while the Liu and Daum (2004) scheme differs significantly from the observation-based calculation for the downward shortwave but not the downward longwave fluxes.

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Persistent Spring Shortwave Cloud Radiative Effect and the Associated Circulations over Southeastern China

Journal of Climate ◽

10.1175/jcli-d-18-0385.1 ◽

2019 ◽

Vol 32 (11) ◽

pp. 3069-3087 ◽

Cited By ~ 3

Author(s):

Jiandong Li ◽

Wei-Chyung Wang ◽

Jiangyu Mao ◽

Ziqian Wang ◽

Gang Zeng ◽

...

Keyword(s):

Water Vapor ◽

Tibetan Plateau ◽

South China Sea ◽

South China ◽

Water Vapor Transport ◽

Radiation Balance ◽

Radiative Effect ◽

Southeastern China ◽

China Sea ◽

Cloud Radiative Effect

Abstract Clouds strongly modulate regional radiation balance and their evolution is profoundly influenced by circulations. This study uses 2001–16 satellite and reanalysis data together with regional model simulations to investigate the spring shortwave cloud radiative effect (SWCRE) and the associated circulations over southeastern China (SEC). Strong SWCRE, up to −110 W m−2, persists throughout springtime in this region and its spring mean is the largest among the same latitudes of the Northern Hemisphere. SWCRE exhibits pronounced subseasonal variation and is closely associated with persistent regional ascending motion and moisture convergence, which favor large amounts of cloud liquid water and resultant strong SWCRE. Around pentad 12 (late February), SWCRE abruptly increases and afterward remains stable between 22° and 32°N. The thermal and dynamic effects of Tibetan Plateau and westerly jet provide appropriate settings for the maintenance of ascending motion, while water vapor, as cloud water supply, stably comes from the southern flank of the Tibetan Plateau and South China Sea. During pentads 25–36 (early May to late June), SWCRE is further enhanced by the increased water vapor transport caused by the march of East Asian monsoon systems, particularly after the onset of the South China Sea monsoon. After pentad 36, these circulations quickly weaken and the SWCRE decreases accordingly. Individual years with spring strong and weak rainfall are chosen to highlight the importance of the strength of the ascending motion. The simulation broadly reproduced the observed results, although biases exist. Finally, the model biases in SWCRE–circulation associations are discussed.

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Trends in surface radiation and cloud radiative effect at four Swiss sites for the 1996–2015 period

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-13227-2019 ◽

2019 ◽

Vol 19 (20) ◽

pp. 13227-13241 ◽

Cited By ~ 3

Author(s):

Stephan Nyeki ◽

Stefan Wacker ◽

Christine Aebi ◽

Julian Gröbner ◽

Giovanni Martucci ◽

...

Keyword(s):

Longwave Radiation ◽

Ground Temperature ◽

Surface Radiation ◽

Specific Humidity ◽

Shortwave Radiation ◽

Radiative Effect ◽

Cloud Properties ◽

Cloud Radiative Effect ◽

Downward Longwave Radiation ◽

Integrated Water Vapour

Abstract. The trends of meteorological parameters and surface downward shortwave radiation (DSR) and downward longwave radiation (DLR) were analysed at four stations (between 370 and 3580 m a.s.l.) in Switzerland for the 1996–2015 period. Ground temperature, specific humidity, and atmospheric integrated water vapour (IWV) trends were positive during all-sky and cloud-free conditions. All-sky DSR and DLR trends were in the ranges of 0.6–4.3 W m−2 decade−1 and 0.9–4.3 W m−2 decade−1, respectively, while corresponding cloud-free trends were −2.9–3.3 W m−2 decade−1 and 2.9–5.4 W m−2 decade−1. Most trends were significant at the 90 % and 95 % confidence levels. The cloud radiative effect (CRE) was determined using radiative-transfer calculations for cloud-free DSR and an empirical scheme for cloud-free DLR. The CRE decreased in magnitude by 0.9–3.1 W m−2 decade−1 (only one trend significant at 90 % confidence level), which implies a change in macrophysical and/or microphysical cloud properties. Between 10 % and 70 % of the increase in DLR is explained by factors other than ground temperature and IWV. A more detailed, long-term quantification of cloud changes is crucial and will be possible in the future, as cloud cameras have been measuring reliably at two of the four stations since 2013.

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