Seasonal and interannual variations of top‐of‐atmosphere irradiance and cloud cover over polar regions derived from the CERES data set

Kato, Seiji; Loeb, Norman G.; Minnis, Patrick; Francis, Jennifer A.; Charlock, Thomas P.; Rutan, David A.; Clothiaux, Eugene E.; Sun-Mack, S.

doi:10.1029/2006gl026685

Cited by 46 publications

(50 citation statements)

References 23 publications

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“…A cloud response to changing sea ice is observed because low cloudiness tends to increase substantially during autumn following a particularly low September ice extent. Kato et al (2006) suggested that an apparent increase of cloud cover in response to reduced Arctic sea ice could diminish the ice-albedo feedback. However, their analysis considered only shortwave radiation.…”

Section: Discussionmentioning

confidence: 98%

Interannual Variations of Arctic Cloud Types in Relation to Sea Ice

2010

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Sea ice extent and thickness may be affected by cloud changes, and sea ice changes may in turn impart changes to cloud cover. Different types of clouds have different effects on sea ice. Visual cloud reports from land and ocean regions of the Arctic are analyzed here for interannual variations of total cloud cover and nine cloud types, and their relation to sea ice.Over the high Arctic, cloud cover shows a distinct seasonal cycle dominated by low stratiform clouds, which are much more common in summer than winter. Interannual variations of cloud amounts over the Arctic Ocean show significant correlations with surface air temperature, total sea ice extent, and the Arctic Oscillation. Low ice extent in September is generally preceded by a summer with decreased middle and precipitating clouds. Following a low-ice September there is enhanced low cloud cover in autumn. Total cloud cover appears to be greater throughout the year during low-ice years.Multidecadal trends from surface observations over the Arctic Ocean show increasing cloud cover, which may promote ice loss by longwave radiative forcing. Trends are positive in all seasons, but are most significant during spring and autumn, when cloud cover is positively correlated with surface air temperature. The coverage of summertime precipitating clouds has been decreasing over the Arctic Ocean, which may promote ice loss.

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Section: Discussionmentioning

confidence: 98%

Interannual Variations of Arctic Cloud Types in Relation to Sea Ice

2010

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“…Kato et al (2006) found that the peak cloud fraction in the Arctic is coincident with minimum sea ice coverage. From the MODIS mean cloud distribution in the Arctic from 2002 to 2006, a higher cloud fraction is almost always observed over open water than over sea ice.…”

Section: B Level-3 Gridded Analysismentioning

confidence: 96%

Errors in Cloud Detection over the Arctic Using a Satellite Imager and Implications for Observing Feedback Mechanisms

Liu¹,

Ackerman²,

Maddux³

et al. 2010

Journal of Climate

104

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Arctic sea ice extent has decreased dramatically over the last 30 years, and this trend is expected to continue through the twenty-first century. Changes in sea ice extent impact cloud cover, which in turn influences the surface energy budget. Understanding cloud feedback mechanisms requires an accurate determination of cloud cover over the polar regions, which must be obtained from satellite-based measurements. The accuracy of cloud detection using observations from space varies with surface type, complicating any assessment of climate trends as well as the understanding of ice-albedo and cloud-radiative feedback mechanisms. To explore the implications of this dependence on measurement capability, cloud amounts from the Moderate Resolution Imaging Spectroradiometer (MODIS) are compared with those from the CloudSat and Cloud-Aerosol Lidar and Infrared Pathfinder (CALIPSO) satellites in both daytime and nighttime during the time period from July 2006 to December 2008. MODIS is an imager that makes observations in the solar and infrared spectrum. The active sensors of CloudSat and CALIPSO, a radar and lidar, respectively, provide vertical cloud structures along a narrow curtain.Results clearly indicate that MODIS cloud mask products perform better over open water than over ice. Regional changes in cloud amount from CloudSat /CALIPSO and MODIS are categorized as a function of independent measurements of sea ice concentration (SIC) from the Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E). As SIC increases from 10% to 90%, the mean cloud amounts from MODIS and CloudSat-CALIPSO both decrease; water that is more open is associated with increased cloud amount. However, this dependency on SIC is much stronger for MODIS than for CloudSat-CALIPSO, and is likely due to a low bias in MODIS cloud amount. The implications of this on the surface radiative energy budget using historical satellite measurements are discussed. The quantified ice-water difference in MODIS cloud detection can be used to adjust estimated trends in cloud amount in the presence of changing sea ice cover from an independent dataset. It was found that cloud amount trends in the Arctic might be in error by up to 2.7% per decade. The impact of these errors on the surface net cloud radiative effect (''forcing'') of the Arctic can be significant, as high as 8.5%.

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“…Global mean energy balance is not satisfied in either ERBE (Trenberth et al 2009) or CERES (Kato et al 2006) data due to instrumental and observational errors. For this reason we define \NET TOA [, as half the difference between the integrated net radiation in the NH minus that in the SH; this definition implicitly ensures global energy balance and calculates the hemispheric asymmetry in radiative input over the two hemispheres.…”

Section: The Hemispheric Asymmetry Of Radiation At the Top Of The Atmmentioning

confidence: 99%

The ocean’s role in setting the mean position of the Inter-Tropical Convergence Zone

et al. 2013

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Through study of observations and coupled climate simulations, it is argued that the mean position of the Inter-Tropical Convergence Zone (ITCZ) north of the equator is a consequence of a northwards heat transport across the equator by ocean circulation. Observations suggest that the hemispheric net radiative forcing of climate at the top of the atmosphere is almost perfectly symmetric about the equator, and so the total (atmosphere plus ocean) heat transport across the equator is small (order 0.2 PW northwards). Due to the Atlantic ocean's meridional overturning circulation, however, the ocean carries significantly more heat northwards across the equator (order 0.4 PW) than does the coupled system. There are two primary consequences. First, atmospheric heat transport is southwards across the equator to compensate (0.2 PW southwards), resulting in the ITCZ being displaced north of the equator. Second, the atmosphere, and indeed the ocean, is slightly warmer (by perhaps 2°C) in the northern hemisphere than in the southern hemisphere. This leads to the northern hemisphere emitting slightly more outgoing longwave radiation than the southern hemisphere by virtue of its relative warmth, supporting the small northward heat transport by the coupled system across the equator. To conclude, the coupled nature of the problem is illustrated through study of atmosphere-oceanice simulations in the idealized setting of an aquaplanet, resolving the key processes at work.

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Seasonal and interannual variations of top‐of‐atmosphere irradiance and cloud cover over polar regions derived from the CERES data set

Cited by 46 publications

References 23 publications

Interannual Variations of Arctic Cloud Types in Relation to Sea Ice

Interannual Variations of Arctic Cloud Types in Relation to Sea Ice

Errors in Cloud Detection over the Arctic Using a Satellite Imager and Implications for Observing Feedback Mechanisms

The ocean’s role in setting the mean position of the Inter-Tropical Convergence Zone

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