The response of a general circulation model to cloud longwave radiative forcing. I: Introduction and initial experiments

Slingo, A.; SLINGO, JM

doi:10.1256/smsqj.48208

Cited by 18 publications

(31 citation statements)

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“…Through these various effects, clouds influence both locally and remotely the atmospheric static stability, the wind shear and the meridional gradients of temperature. In doing so they help to determine the localization and strength of large-scale dynamical features such as the tropical Hadley-Walker circulation, intraseasonal oscillations and mid-latitude jets 25,33,46,47 and influence the rate of development, the structure and the strength of smaller-scale disturbances such as tropical and extratropical cyclones, as well as the organization of convection and the occurrence of a range of mesoscale phenomena 1,42,48,49 . New opportunities now make it possible to considerably improve the understanding of these interactions (Box 2).…”

Section: Four Questionsmentioning

confidence: 99%

Clouds, circulation and climate sensitivity

Bony¹,

Stevens²,

Frierson³

et al. 2015

Nature Geosci

796

624

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NATURE GEOSCIENCE | VOL 8 | APRIL 2015 | www.nature.com/naturegeoscience 261 C louds stimulate the human spirit. Although they have been recognized for centuries as harbingers of weather, only in recent decades have scientists begun to appreciate the role of clouds in determining the general circulation of the atmosphere and its susceptibility to change.Forming mostly in the updrafts of the turbulent and chaotic airflow, clouds embody the complex and multiscale organization of the atmosphere into dynamical entities, or storms. These entities mediate the radiative transfer of energy, distribute precipitation and are often associated with extreme winds. It has long been recognized that the water and heat transfer that clouds mediate plays a fundamental role in tropical circulations, and there is increasing evidence that they also influence extratropical circulations 1 . Globally, the impact of clouds on Earth's radiation budget -and hence surface temperatures -also depends critically on how clouds interact with one another and with larger-scale circulations 2 . Far from being passive tracers of a turbulent atmosphere, clouds thus embody processes that can actively control circulation and climate (Box 1).For practical reasons, early endeavours to understand climate deployed a 'divide and conquer' strategy in which efforts to understand clouds and convective processes developed separately from efforts to understand larger-scale circulations. Over time, a gap developed between the subdisciplines. But technological progress and conceptual advances have tremendously increased our capacity to observe and simulate the climate system, such that it is now possible to study more readily how small-scale convective processes -that is, clouds -couple to large-scale circulations (Box 2). Much as a new accelerator allows physicists to explore the implication of the interactions among forces acting over different length scales, these new capabilities are transforming how atmospheric scientists think about the interplay of clouds and climate. This offers a great opportunity not only to close the gap between scientific communities, but Fundamental puzzles of climate science remain unsolved because of our limited understanding of how clouds, circulation and climate interact. One example is our inability to provide robust assessments of future global and regional climate changes. However, ongoing advances in our capacity to observe, simulate and conceptualize the climate system now make it possible to fill gaps in our knowledge. We argue that progress can be accelerated by focusing research on a handful of important scientific questions that have become tractable as a result of recent advances. We propose four such questions below; they involve understanding the role of cloud feedbacks and convective organization in climate, and the factors that control the position, the strength and the variability of the tropical rain belts and the extratropical storm tracks.also to answer some of the most pressing questions about the fate of our pl...

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Section: Four Questionsmentioning

confidence: 99%

Clouds, circulation and climate sensitivity

Bony¹,

Stevens²,

Frierson³

et al. 2015

Nature Geosci

796

624

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“…The vertical structure of Q 1 has been shown to influence the atmosphere on scales ranging from the life cycle of individual mesoscale convective systems (e.g., Houze 1982Houze , 1989Mapes and Houze 1995) and the evolution of extratropical cyclones (Weaver 1999) to the propagation speed of tropical intraseasonal oscillations (e.g., Lau and Peng 1987;Lee et al 2001) and the strength of the Hadley and Walker circulations (e.g., Slingo and Slingo 1988;1991;Hartmann et al 1984;Sherwood et al 1994;Schumacher et al 2004). The common conclusion to be drawn from these studies is the importance of feedback between clouds, precipitation, and their impact on atmospheric diabatic heating.…”

Section: Introductionmentioning

confidence: 99%

A 10-Year Climatology of Tropical Radiative Heating and Its Vertical Structure from TRMM Observations

L’Ecuyer

McGarragh

2010

Journal of Climate

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This paper outlines recent advances in estimating atmospheric radiative heating rate profiles from the sensors aboard the Tropical Rainfall Measuring Mission (TRMM). The approach employs a deterministic framework in which four distinct retrievals of clouds, precipitation, and other atmospheric and surface properties are combined to form input to a broadband radiative transfer model that simulates profiles of upwelling and downwelling longwave and shortwave radiative fluxes in the atmosphere. Monthly, 58 top of the atmosphere outgoing longwave and shortwave flux estimates agree with corresponding observations from the Clouds and the Earth's Radiant Energy System (CERES) to within 7 W m 22 and 3%, respectively, suggesting that the resulting products can be thought of as extending the eight-month CERES dataset to cover the full lifetime of TRMM.The analysis of a decade of TRMM data provides a baseline climatology of the vertical structure of atmospheric radiative heating in today's climate and an estimate of the magnitude of its response to environmental forcings on weekly to interannual time scales. In addition to illustrating the scope and properties of the dataset, the results highlight the strong influence of clouds, water vapor, and large-scale dynamics on regional radiation budgets and the vertical structure of radiative heating in the tropical and subtropical atmospheres. The combination of the radiative heating rate product described here, with profiles of latent heating that are now also being generated from TRMM sensors, provides a unique opportunity to develop large-scale estimates of vertically resolved atmospheric diabatic heating using satellite observations.

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“…The magnitude of the OLR decrease depends on the difference in temperature between the cloud top and the atmosphere and surface below, and so is largest for the high (cold) cloud in the tropical atmosphere and is smallest for the low cloud in the subarctic winter atmosphere, where the cloud top temperature is almost the same as that of the surface. Slingo and Slingo (1988) argue that a similar situation applies to the downward radiation at the surface. For cloudless skies, more than half the longwave radiant flux received at the ground from the atmosphere comes from gases in the lowest 100 m and roughly 90% from the lowest kilometre.…”

Section: Greenhouse Warming By Cloudsmentioning

confidence: 88%

“…The cloud longwave forcing, Cf(L), may be defined as (Slingo and Slingo, 1988): where OLR is the outgoing longwave radiation at the top of the atmosphere and OLR, is the value for clear skies. Since temperature generally decreases with height, the temperature of a cloud top is usually less than that of the underlying atmosphere and surface, so the longwave emission from the cloud top is smaller than the upward flux in a clear atmosphere at the same level.…”

Section: Greenhouse Warming By Cloudsmentioning

confidence: 99%

“…Therefore the warming of the surface by low clouds changes in the opposite sense to that of atmosphere water vapour, because it increases from equator to pole. Slingo and Slingo (1988) illustrated cloud longwave forcing by the simple numerical experiment of inserting high and low clouds into two extreme atmospheric profiles representing the subarctic winter and tropical conditions. They used the Meteorological Office radiation scheme (Slingo and Wilderspin, 1986) and undertook calculations first for clear skies, and then for complete cover by low and then high cloud, the latter being considerably lower in the subarctic winter profile than in the tropical profile because of the shallower troposphere.…”

Section: Greenhouse Warming By Cloudsmentioning

confidence: 99%

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Interactions between the Earth's surface, atmospheric greenhouse gases and clouds

Lockwood

1990

Progress in Physical Geography: Earth and Environment

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In its normal state, the Earth-atmosphere system absorbs solar radiation and maintains global energy balance by reradiating this energy to space as infrared or longwave radiation. The intervening atmosphere absorbs and emits the longwave radiation, but as the atmosphere is colder than the surface, it absorbs more energy than it emits upward to space (Raval and Ramanathan, 1989). The energy that escapes to space F is significantly smaller than that emitted by the surface E. The greenhouse effect G above any location is therefore given by:It is useful to divide the greenhouse effect into two components and consider it for cloudless and cloudy skies. Raval and Ramanathan (1989) have done this for the open oceans. They used the open ocean because, in the infrared, the ocean surface approximates to a black body to within 1 % , and because the diurnal surface temperature variation is small in the ocean's mixed layer (less than a few degrees K), and therefore the uncertainties in the calculated values of E are a minimum over the oceans. They estimated the emission from the surface using the Stefan-Boltzmann black body law and the observed surface temperature.Land-surface temperatures and emissions are considerably more complex, in particular large diurnal temperature variations are observed, and the longwave emission depends on both vegetation cover and soil moisture state. For example, in the temperate latitude spring many plants break dormancy and begin foliage production. The appearance of leaves triggers a rapid increase in transpiration as well as changes in albedo and alters the thermodynamic properties of the surface layer. Normally, seasonal variations in tropospheric thickness, and year-to-year variability in the green-up date, mask the impact of these effects on surface maximum temperature. Schwartz and Karl (1990) demonstrated for the agricultural inland USA at least a 3.5°C reduction in surface daily maximum temperatures over any two-week period subsequent to first leaf compared to a two-week period prior to first leaf. During extreme drought, which produces widespread plant wilt, surface maximum temperatures may be expected to increase. Changes in surface temperature change the surface longwave emission by about 6 W m-2 per degree

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The response of a general circulation model to cloud longwave radiative forcing. I: Introduction and initial experiments

Cited by 18 publications

References 0 publications

Clouds, circulation and climate sensitivity

Clouds, circulation and climate sensitivity

A 10-Year Climatology of Tropical Radiative Heating and Its Vertical Structure from TRMM Observations

Interactions between the Earth's surface, atmospheric greenhouse gases and clouds

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