Direct atmosphere opacity observations from CALIPSO provide new constraints on cloud‐radiation interactions

Guzman, Rodrigo; Chepfer, Hélène; Noël, Vincent; Guélis, Thibault Vaillant de; Kay, J. E.; Raberanto, Patrick; Cesana, G; Vaughan, Mark; Winker, David M.

doi:10.1002/2016jd025946

Cited by 52 publications

(117 citation statements)

References 33 publications

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“…Thincloud cover is very homogeneous over all oceans, with slight maxima in some regions, near the warm pool. These results are discussed in Guzman et al (2017).…”

Section: Introductionmentioning

confidence: 92%

“…However, this assumes the knowledge that the cloud is opaque, but cloud emissivity from passive measurements is also sensitive to hypothesis made on the clear-sky and surface property. Unlike passive measurements, lidar measurements robustly separate opaque clouds and thin clouds from the presence or absence of a surface echo (Guzman et al, 2017). × 2 • grid box PDF by the ratio of the number of opaque single columns over the number of all single columns.…”

Section: Definition and Approximations Of The Cloud Radiative Temperamentioning

confidence: 99%

“…In this paper, we summarize the vertical profiles of clouds observed by active sensors using three specific cloud levels that drive the LW CRE at the TOA and that can be accurately observed by spaceborne lidar: cloud-top altitude, cloud-base altitude, and the altitude of opacity, at which the lidar signal becomes fully attenuated within an opaque cloud. This altitude of opacity and the opaque-cloud cover are both observed by spaceborne lidar, and are strongly correlated to the LW CRE (Guzman et al, 2017), because emissions from layers located below the altitude of opacity have little influence on the outgoing LW radiation (OLR). Previous studies (Ramanathan, 1977;Wang et al, 2002) suggested that the link between the opaque-cloud temperature and the OLR is linear, which would be mathematically very convenient for the study of cloud feedbacks (derivatives), but these studies are limited to radiative transfer simulations only.…”

Section: Introductionmentioning

confidence: 99%

“…Our study builds on the work of Guzman et al (2017) by considering Z | opaque in terms of temperature rather than alti- provided in CALIOP level 1 data and also reported in GOCCP v3.0 data.…”

Section: Introductionmentioning

confidence: 99%

“…The GCM-Oriented CALIPSO Cloud Product (GOCCP)-OPAQ (GOCCP v3.0;Guzman et al, 2017) has 40 vertical levels with 480 m vertical resolution. Every CALIOP single-shot profile -including multilayer profilesis classified into one of three types (Fig.…”

Section: Introductionmentioning

confidence: 99%

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The link between outgoing longwave radiation and the altitude at which a spaceborne lidar beam is fully attenuated

et al. 2017

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Abstract. According to climate model simulations, the changing altitude of middle and high clouds is the dominant contributor to the positive global mean longwave cloud feedback. Nevertheless, the mechanisms of this longwave cloud altitude feedback and its magnitude have not yet been verified by observations. Accurate, stable, and long-term observations of a metric-characterizing cloud vertical distribution that are related to the longwave cloud radiative effect are needed to achieve a better understanding of the mechanism of longwave cloud altitude feedback. This study shows that the direct measurement of the altitude of atmospheric lidar opacity is a good candidate for the necessary observational metric. The opacity altitude is the level at which a spaceborne lidar beam is fully attenuated when probing an opaque cloud. By combining this altitude with the direct lidar measurement of the cloud-top altitude, we derive the effective radiative temperature of opaque clouds which linearly drives (as we will show) the outgoing longwave radiation. We find that, for an opaque cloud, a cloud temperature change of 1 K modifies its cloud radiative effect by 2 W m −2 . Similarly, the longwave cloud radiative effect of optically thin clouds can be derived from their top and base altitudes and an estimate of their emissivity. We show with radiative transfer simulations that these relationships hold true at single atmospheric column scale, on the scale of the Clouds and the Earth's Radiant Energy System (CERES) instantaneous footprint, and at monthly mean 2 • × 2 • scale. Opaque clouds cover 35 % of the ice-free ocean and contribute to 73 % of the global mean cloud radiative effect. Thin-cloud coverage is 36 % and contributes 27 % of the global mean cloud radiative effect. The link between outgoing longwave radiation and the altitude at which a spaceborne lidar beam is fully attenuated provides a simple formulation of the cloud radiative effect in the longwave domain and so helps us to understand the longwave cloud altitude feedback mechanism.

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“…Thincloud cover is very homogeneous over all oceans, with slight maxima in some regions, near the warm pool. These results are discussed in Guzman et al (2017).…”

Section: Introductionmentioning

confidence: 92%

Section: Definition and Approximations Of The Cloud Radiative Temperamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

The link between outgoing longwave radiation and the altitude at which a spaceborne lidar beam is fully attenuated

et al. 2017

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Using Space Lidar Observations to Decompose Longwave Cloud Radiative Effect Variations Over the Last Decade

Guélis

Chepfer

Noël

et al. 2017

Geophysical Research Letters

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Measurements of the longwave cloud radiative effect (LWCRE) at the top of the atmosphere assess the contribution of clouds to the Earth warming but do not quantify the cloud property variations that are responsible for the LWCRE variations. The CALIPSO space lidar observes directly the detailed profile of cloud, cloud opacity, and cloud cover. Here we use these observations to quantify the influence of cloud properties on the variations of the LWCRE observed between 2008 and 2015 in the tropics and at global scale. At global scale, the method proposed here gives good results except over the Southern Ocean. We find that the global LWCRE variations observed over ocean are mostly due to variations in the opaque cloud properties (82%); transparent cloud columns contributed 18%. Variation of opaque cloud cover is the first contributor to the LWCRE evolution (58%); opaque cloud temperature is the second contributor (28%).

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Isolating the Liquid Cloud Response to Recent Arctic Sea Ice Variability Using Spaceborne Lidar Observations

et al. 2018

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While the radiative influence of clouds on Arctic sea ice is known, the influence of sea ice cover on Arctic clouds is challenging to detect, separate from atmospheric circulation, and attribute to human activities. Providing observational constraints on the two‐way relationship between sea ice cover and Arctic clouds is important for predicting the rate of future sea ice loss. Here we use 8 years of CALIPSO (Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observations) spaceborne lidar observations from 2008 to 2015 to analyze Arctic cloud profiles over sea ice and over open water. Using a novel surface mask to restrict our analysis to where sea ice concentration varies, we isolate the influence of sea ice cover on Arctic Ocean clouds. The study focuses on clouds containing liquid water because liquid‐containing clouds are the most important cloud type for radiative fluxes and therefore for sea ice melt and growth. Summer is the only season with no observed cloud response to sea ice cover variability: liquid cloud profiles are nearly identical over sea ice and over open water. These results suggest that shortwave summer cloud feedbacks do not slow long‐term summer sea ice loss. In contrast, more liquid clouds are observed over open water than over sea ice in the winter, spring, and fall in the 8 year mean and in each individual year. Observed fall sea ice loss cannot be explained by natural variability alone, which suggests that observed increases in fall Arctic cloud cover over newly open water are linked to human activities.

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Direct atmosphere opacity observations from CALIPSO provide new constraints on cloud‐radiation interactions

Cited by 52 publications

References 33 publications

The link between outgoing longwave radiation and the altitude at which a spaceborne lidar beam is fully attenuated

The link between outgoing longwave radiation and the altitude at which a spaceborne lidar beam is fully attenuated

Using Space Lidar Observations to Decompose Longwave Cloud Radiative Effect Variations Over the Last Decade

Isolating the Liquid Cloud Response to Recent Arctic Sea Ice Variability Using Spaceborne Lidar Observations

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