The simplified exchange method revisited: An accurate, rapid method for computation of infrared cooling rates and fluxes

Schwarzkopf, Malte; Fels, Stephen B.

doi:10.1029/89jd01598

Cited by 238 publications

(141 citation statements)

References 28 publications

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“…The shortwave radiation [Freidenreich and Ramaswamy, 1999] and longwave radiation [Schwarzkopf and Fels, 1991;Schwarzkopf and Ramaswamy, 1999] schemes are similar to those in the SKYHI GCM. Convection is simulated with either a Fickian diffusion scheme [Ramaswamy and Kiehl, 1985] or a conventional convective adjustment scheme [Manabe and Wetherald, 1967].…”

Section: Model Descriptionsupporting

confidence: 50%

Sensitivity of the atmospheric lapse rate to solar cloud absorption in a radiative‐convective model

Erlick

Ramaswamy

2003

J. Geophys. Res.

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[1] Previous radiative-convective model studies of the radiative forcing due to absorbing aerosols such as soot and dust have revealed a strong dependence on the vertical distribution of the absorbers. In this study, we extend this concept to absorption in cloud layers, using a one-dimensional radiative-convective model employing high, middle, and low cloud representations to investigate the response of the surface temperature and atmospheric lapse rate to increases in visible cloud absorption. The visible singlescattering albedo (ssa) of the clouds is prescribed, ranging from 1.0 to 0.6, where 0.99 is the minimum that would be expected from the presence of absorbing aerosols within the cloud drops on the basis of recent Monterey Area Ship Track (MAST) Experiment case studies. Simulations are performed with respect to both a constant cloud optical depth and an increasing cloud optical depth and as a function of cloud height. We find that increases in solar cloud absorption tend to warm the troposphere and surface and stabilize the atmosphere, while increases in cloud optical depth cool the troposphere and surface and slightly stabilize the atmosphere between the low cloud top and surface because of the increase in surface cooling. In the absence of considerations involving microphysical or cloud-climate feedbacks, we find that two conditions are required to yield an inversion from a solar cloud absorption perturbation: (1) The solar absorption perturbation must be included throughout the tropospheric clouds column, distributing the solar heating to higher altitudes, and (2) the ssa of the clouds must be 0.6, which is an unrealistically low value. The implication is that there is very little possibility of significant stabilization of the global mean atmosphere due to perturbation of cloud properties given current ssa values.INDEX TERMS: 0345 Atmospheric Composition and Structure: Pollution-urban and regional (0305); 1620 Global Change: Climate dynamics (3309); 3359 Meteorology and Atmospheric Dynamics: Radiative processes; KEYWORDS: solar cloud forcing, radiativeconvective model, indirect aerosol effect Citation: Erlick, C., and V. Ramaswamy, Sensitivity of the atmospheric lapse rate to solar cloud absorption in a radiative-convective model,

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Section: Model Descriptionsupporting

confidence: 50%

Sensitivity of the atmospheric lapse rate to solar cloud absorption in a radiative‐convective model

Erlick

Ramaswamy

2003

J. Geophys. Res.

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“…CCAM includes a fairly comprehensive set of physical parameterizations. The GFDL parameterizations for long-wave and short-wave radiation (Schwarzkopf and Fels 1991;Lacis and Hansen 1974) are employed, with interactive cloud distributions determined by the liquid and ice-water scheme of Rotstayn (1997). The model employs a stability-dependent boundary layer scheme based on Monin-Obukhov similarity theory (McGregor et al 1993), together with the non-local treatment of Holtslag and Boville (1993).…”

Section: Data Used and Model Setupmentioning

confidence: 99%

Downscaling over Vietnam using the stretched-grid CCAM: verification of the mean and interannual variability of rainfall

2013

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Rainfall over Vietnam is highly variable from north to south, due to the interaction of the monsoonal winds with the terrain. There is high rainfall from April to September, and little rainfall from October to March (except along the central Vietnam coast). In order to study the ability of the Commonwealth Scientific and Industrial Research Organisation stretched-grid Conformal Cubic Atmospheric Model (CCAM) to capture the climatic and interannual variability of rainfall, downscaled simulations at approximately 20 km horizontal resolution over the region were produced for the period 1979-2001. A scaleselective digital filter was used to force the winds, temperature and sea-level pressure from the ERA-Interim reanalysis for length scales greater than about 700 km. For wind and temperature, the forcing is applied for pressuresigma levels above about 0.9. ERA-Interim sea surface temperatures were used over the oceans. The simulations were primarily validated against the gridded Asian Precipitation Highly Resolved Observational Data Integration Toward Evaluation of the Water Resources rainfall dataset and station observations using standard statistical methods. It was found that CCAM reproduces well the amount and spatial variability of rainfall, with an area-averaged bias for the entire study domain of less than 1 mm day -1 ; CCAM is also able to capture the rainfall pattern under different El Niño Southern Oscillation phases reasonably well for the dry season. For interannual variability, the simulation generally performed better for North and Central Vietnam than for South Vietnam, where rainfall variability was overestimated.

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“…It has been recently improved [Schwarzkopf and Ramaswamy, 1999] to account for the effects of CH4, N20, halocarbons, and the foreign-broadened H20 continuum. The longwave (LW) spectrum ranges from 4.55 gm to oo and accounts for absorption by H20, CO2, 03, CH4, N20, and four halocarbons (CFC-11, CFC-12, CFC-113, and HCFC-22).…”

Section: Radiative Transfer Algorithmsmentioning

confidence: 99%

“…The longwave radiative-transfer algorithm is described by Schwarzkopf and Fels [1991] and is based on the Simplified Exchange Approximation method. It has been recently improved [Schwarzkopf and Ramaswamy, 1999] to account for the effects of CH4, N20, halocarbons, and the foreign-broadened H20 continuum.…”

Section: Radiative Transfer Algorithmsmentioning

confidence: 99%

Radiative impact of the Mount Pinatubo volcanic eruption: Lower stratospheric response

Ramachandran¹,

Ramaswamy²,

Stenchikov³

et al. 2000

J. Geophys. Res.

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Abstract. Volcanic aerosols in the stratosphere produce significant transitory solar and infrared radiative perturbations, which warm the stratosphere, cool the surface and affect stratospheric circulation. In this study, using the Geophysical Fluid Dynamics Laboratory SKYHI general circulation model (GCM) with a high vertical resolution and a recently improved radiative transfer code, we investigate the aerosol radiative forcing and the stratospheric temperature response for the June 15, 1991, Mount Pinatubo eruption, the most well observed and largest volcanic eruption of the 20th Century. The investigation is carried out using an updated, comprehensive monthly and zonal-mean Pinatubo aerosol spectral optical properties data set. While the near-infrared solar spectral effects contribute substantially to the total stratospheric heating due to aerosols, over the entire global domain the longwave component exceeds the solar in causing a warming of the lower stratosphere (30-100 hPa). In contrast, the magnitude of the solar perturbation (increased reflection) in the overall surface-atmosphere radiative heat balance exceeds that due to the longwave (infrared trapping effect). The troposphere affects the stratospheric radiative forcing, mainly because of the dependence of the reflected solar and upward longwave radiation on cloudiness, and this adds to the uncertainty in the calculation of the stratospheric temperature response. A four-member ensemble of 2-year GCM integrations (June 1991 to May 1993) were performed using fixed sea surface temperatures and a cloud prediction scheme, one set with and another without the volcanic aerosols. The temperature of the tropical lower stratosphere increases by a statistically significant 3 K, which is almost I K less than in previous investigations that employed coarser vertical resolution in the stratosphere, but is still larger than observed. In the low latitudes the evolution of the simulated temperature response •nimics that observed only through about the first year. Thereafter, despite a significant aerosol optical depth perturbation in the tropical atmosphere, there is a lack of a signature in the temperature response that can be unambiguously attributed to the Pinatubo aerosols, suggesting other forced or unforced variations (e.g., ozone changes, quasi-biennial oscillation) occurring in the actual atmosphere which are unaccounted for in the model. In the high latitudes the large interannual variability prohibits a clear quantitative comparison between simulated and observed temperature changes and renders the aerosol-induced thermal signals statistically insignificant. In the global mean the evolution of the simulated lower stratospheric temperature response is in excellent agremnent with the observation for the entire 2-year period, in contrast to the model-observation comparison at the low latitudes. This arises because in the global mean the stratospheric response is not sensitive to dynamical adjustments within the atmosphere caused by internal variations, and dep...

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The simplified exchange method revisited: An accurate, rapid method for computation of infrared cooling rates and fluxes

Cited by 238 publications

References 28 publications

Sensitivity of the atmospheric lapse rate to solar cloud absorption in a radiative‐convective model

Sensitivity of the atmospheric lapse rate to solar cloud absorption in a radiative‐convective model

Downscaling over Vietnam using the stretched-grid CCAM: verification of the mean and interannual variability of rainfall

Radiative impact of the Mount Pinatubo volcanic eruption: Lower stratospheric response

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