Impact of an improved radiation scheme in the MAECHAM5 General Circulation Model

Abstract. In order to improve the representation of the shortwave radiative transfer in the MAECHAM5 general circulation model, the spectral resolution of the shortwave radiation parameterization used in the model has been increased and extended in the UV-B and UV-C bands. The upgraded shortwave parameterization is first validated offline with a 4 stream discrete-ordinate line-by-line model. Thereafter, two 20-years simulations with the MAECHAM5 middle atmosphere general circulation model are performed to evaluate the temperature changes and the dynamical feedbacks arising from the newly introduced parameterization. The offline clear-sky comparison of the standard and upgraded parameterizations with the discrete ordinate model shows considerable improvement for the upgraded parameterization in terms of shortwave fluxes and heating rates. In the simulation with the upgraded ratiation parameterization, we report a significant warming of almost the entire atmosphere, largest at 1 hPa at the stratopause, and stronger zonal mean zonal winds in the middle atmosphere. The warming at the summer stratopause alleviates the cold bias present in the model when the standard radiation scheme is used. The stronger zonal mean zonal winds induce a dynamical feedback that results in a dynamical warming (cooling) of the polar winter (summer) mesosphere, caused by an increased downward (upward) circulation in the winter (summer) hemisphere. In the troposphere, the changes in the spectral resolution and the associated changes in the cloud optical parameters introduce a relatively small warming and, consistenly, a moisteneing. The warming occurs mostly in the upper troposphere and can contribute to a possible improvement of the model temperature climatology.

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Impact of an improved shortwave radiation scheme in the MAECHAM5 General Circulation Model

Atmospheric Chemistry and Physics ◽

10.5194/acp-7-2503-2007 ◽

2007 ◽

Vol 7 (10) ◽

pp. 2503-2515 ◽

Cited By ~ 64

Author(s):

C. Cagnazzo ◽

E. Manzini ◽

M. A. Giorgetta ◽

P. M. De F. Forster ◽

J. J. Morcrette

Keyword(s):

Radiative Transfer ◽

General Circulation Model ◽

Spectral Resolution ◽

General Circulation ◽

Circulation Model ◽

Shortwave Radiation ◽

Transfer Model ◽

Ozone Absorption ◽

Zonal Winds ◽

Radiation Scheme

Abstract. In order to improve the representation of ozone absorption in the stratosphere of the MAECHAM5 general circulation model, the spectral resolution of the shortwave radiation parameterization used in the model has been increased from 4 to 6 bands. Two 20-years simulations with the general circulation model have been performed, one with the standard and the other with the newly introduced parameterization respectively, to evaluate the temperature and dynamical changes arising from the two different representations of the shortwave radiative transfer. In the simulation with the increased spectral resolution in the radiation parameterization, a significant warming of almost the entire model domain is reported. At the summer stratopause the temperature increase is about 6 K and alleviates the cold bias present in the model when the standard radiation scheme is used. These general circulation model results are consistent both with previous validation of the radiation scheme and with the offline clear-sky comparison performed in the current work with a discrete ordinate 4 stream scattering line by line radiative transfer model. The offline validation shows a substantial reduction of the daily averaged shortwave heating rate bias (1–2 K/day cooling) that occurs for the standard radiation parameterization in the upper stratosphere, present under a range of atmospheric conditions. Therefore, the 6 band shortwave radiation parameterization is considered to be better suited for the representation of the ozone absorption in the stratosphere than the 4 band parameterization. Concerning the dynamical response in the general circulation model, it is found that the reported warming at the summer stratopause induces stronger zonal mean zonal winds in the middle atmosphere. These stronger zonal mean zonal winds thereafter appear to produce a dynamical feedback that results in a dynamical warming (cooling) of the polar winter (summer) mesosphere, caused by an increased downward (upward) circulation in the winter (summer) hemisphere. In addition, the comparison of the two simulations performed with the general circulation model shows that the increase in the spectral resolution of the shortwave radiation and the associated changes in the cloud optical properties result in a warming (0.5–1 K) and moistening (3%–12%) of the upper tropical troposphere. By comparing these modeled differences with previous works, it appears that the reported changes in the solar radiation scheme contribute to improve the model mean temperature also in the troposphere.

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Calculating the Natural Atmospheric Radiation Using the General Circulation Model of the Earth’s Lower and Middle Atmosphere

Mathematical Models and Computer Simulations ◽

10.1134/s207004822005004x ◽

2020 ◽

Vol 12 (5) ◽

pp. 803-815

Author(s):

B. N. Chetverushkin ◽

I. V. Mingalev ◽

E. A. Fedotova ◽

K. G. Orlov ◽

V. M. Chechetkin ◽

...

Keyword(s):

General Circulation Model ◽

General Circulation ◽

Middle Atmosphere ◽

Circulation Model ◽

Atmospheric Radiation

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A new radiation infrastructure for the Modular Earth Submodel System (MESSy, based on version 2.51)

10.5194/gmd-2015-277 ◽

2016 ◽

Cited By ~ 1

Author(s):

Simone Dietmüller ◽

Patrick Jöckel ◽

Holger Tost ◽

Markus Kunze ◽

Cathrin Gellhorn ◽

...

Keyword(s):

Optical Properties ◽

Atmospheric Chemistry ◽

Radiative Forcing ◽

General Circulation ◽

Circulation Model ◽

Shortwave Radiation ◽

Aerosol Optical Properties ◽

On Line ◽

User Friendly ◽

Radiation Scheme

Abstract. The Modular Earth Submodel System (MESSy) provides an interface to couple submodels to a basemodel via a highly flexible data management facility (Jöckel et al., 2010). In the present paper we present the four new radiation related submodels RAD, AEROPT, CLOUDOPT and ORBIT. The submodel RAD (with shortwave radiation scheme RAD_FUBRAD) simulates the radiative transfer, the submodel AEROPT calculates the aerosol optical properties, the submodel CLOUDOPT calculates the cloud optical properties, and the submodel ORBIT is responsible for Earth orbit calculations. These submodels are coupled via the standard MESSy infrastructure and are largely based on the original radiation scheme of the general circulation model ECHAM5, however, expanded with additional features. These features comprise, among others, user-friendly and flexibly controllable (by namelists) on-line radiative forcing calculations by multiple diagnostic calls of the radiation routines. With this, it is now possible to calculate radiative forcing (instantaneous as well as stratosphere adjusted) of various greenhouse gases simultaneously in only one simulation, as well as the radiative forcing of cloud perturbations. Examples of on-line radiative forcing calculations in the ECHAM/MESSy Atmospheric Chemistry (EMAC) model are presented.

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Parameterization of PBL Processes in an Atmospheric General Circulation Model: Description and Preliminary Assessment

Monthly Weather Review ◽

10.1175/2008mwr2464.1 ◽

2009 ◽

Vol 137 (3) ◽

pp. 1061-1082 ◽

Cited By ~ 27

Author(s):

Celal S. Konor ◽

Gabriel Cazes Boezio ◽

Carlos R. Mechoso ◽

Akio Arakawa

Keyword(s):

General Circulation Model ◽

General Circulation ◽

Atmospheric General Circulation Model ◽

Potential Temperature ◽

Circulation Model ◽

Surface Fluxes ◽

Shortwave Radiation ◽

Model Description ◽

Atmospheric General Circulation ◽

Seasonal And Diurnal Variations

Abstract This paper presents the basic features of a newly developed planetary boundary layer (PBL) parameterization, and the performance assessment of a version of the University of California, Los Angeles (UCLA), Atmospheric General Circulation Model (AGCM) to which the parameterization is incorporated. The UCLA AGCM traditionally uses a framework in which a sigma-type vertical coordinate for the PBL shares a coordinate surface with the free atmosphere at the PBL top. This framework facilitates an explicit representation of processes concentrated near the PBL top, which is crucially important especially for predicting PBL clouds. In the new framework, multiple layers are introduced between the PBL top and earth’s surface, allowing for predictions of the vertical profiles of potential temperature, total water mixing ratio, and horizontal winds within the PBL. The vertically integrated “bulk” turbulent kinetic energy (TKE) is also predicted for the PBL. The PBL-top mass entrainment is determined through an equation including the effects of TKE and the radiative and evaporative cooling processes concentrated near the PBL top. The surface fluxes are determined from an aerodynamic formula in which the velocity scale depends both on the square root of TKE and the grid-scale PBL velocity at the lowermost model layer. The turbulent fluxes within the PBL are determined through an approach that includes the effects of both large convective and small diffusive eddies. AGCM simulations with the new formulation of PBL are analyzed with a focus on the seasonal and diurnal variations. The simulated seasonal cycle of stratocumulus over the eastern oceans is realistic, as are the diurnal cycles of the PBL depth and precipitation over land. The simulated fluxes of latent heat, momentum, and shortwave radiation at the ocean surface and baroclinic activity in the middle latitudes show significant improvements over the previous versions of the AGCM based on the single-layer PBL.

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