scholarly journals Sensitivity of Simulated Climate to Horizontal and Vertical Resolution in the ECHAM5 Atmosphere Model

2006 ◽  
Vol 19 (16) ◽  
pp. 3771-3791 ◽  
Author(s):  
E. Roeckner ◽  
R. Brokopf ◽  
M. Esch ◽  
M. Giorgetta ◽  
S. Hagemann ◽  
...  
Keyword(s):  
General Circulation ◽  
Circulation Model ◽  
Horizontal Resolution ◽  
Boreal Winter ◽  
Cold Bias ◽  
Vertical Resolution ◽  
Max Planck ◽  
Mean Climate ◽  
The Impact ◽  
Mean Square Errors

Abstract The most recent version of the Max Planck Institute for Meteorology atmospheric general circulation model, ECHAM5, is used to study the impact of changes in horizontal and vertical resolution on seasonal mean climate. In a series of Atmospheric Model Intercomparison Project (AMIP)-style experiments with resolutions ranging between T21L19 and T159L31, the systematic errors and convergence properties are assessed for two vertical resolutions. At low vertical resolution (L19) there is no evidence for convergence to a more realistic climate state for horizontal resolutions higher than T42. At higher vertical resolution (L31), on the other hand, the root-mean-square errors decrease monotonically with increasing horizontal resolution. Furthermore, except for T42, the L31 versions are superior to their L19 counterparts, and the improvements become more evident at increasingly higher horizontal resolutions. This applies, in particular, to the zonal mean climate state and to the stationary wave patterns in boreal winter. As in previous studies, increasing horizontal resolution leads to a warming of the troposphere, most prominently at midlatitudes, and to a poleward shift and intensification of the midlatitude westerlies. Increasing the vertical resolution has the opposite effect, almost independent of horizontal resolution. Whereas the atmosphere is colder at low and middle latitudes, it is warmer at high latitudes and close to the surface. In addition, increased vertical resolution results in a pronounced warming in the polar upper troposphere and lower stratosphere, where the cold bias is reduced by up to 50% compared to L19 simulations. Consistent with these temperature changes is a decrease and equatorward shift of the midlatitude westerlies. The substantial benefits in refining both horizontal and vertical resolution give some support to scaling arguments deduced from quasigeostrophic theory implying that horizontal and vertical resolution ought to be chosen consistently.

scholarly journals Impact of a simple parameterization of convective gravity-wave drag in a stratosphere-troposphere general circulation model and its sensitivity to vertical resolution

1998 ◽  
Vol 16 (2) ◽  
pp. 238-249 ◽  
Author(s):  
C. Bossuet ◽  
M. Déqué ◽  
D. Cariolle
Keyword(s):  
General Circulation ◽  
Climate Model ◽  
Positive Impact ◽  
Deep Convection ◽  
Circulation Model ◽  
Wave Drag ◽  
Horizontal Resolution ◽  
Vertical Resolution ◽  
Mean Flow ◽  
The Impact

Abstract. Systematic westerly biases in the southern hemisphere wintertime flow and easterly equatorial biases are experienced in the Météo-France climate model. These biases are found to be much reduced when a simple parameterization is introduced to take into account the vertical momentum transfer through the gravity waves excited by deep convection. These waves are quasi-stationary in the frame of reference moving with convection and they propagate vertically to higher levels in the atmosphere, where they may exert a significant deceleration of the mean flow at levels where dissipation occurs. Sixty-day experiments have been performed from a multiyear simulation with the standard 31 levels for a summer and a winter month, and with a T42 horizontal resolution. The impact of this parameterization on the integration of the model is found to be generally positive, with a significant deceleration in the westerly stratospheric jet and with a reduction of the easterly equatorial bias. The sensitivity of the Météo-France climate model to vertical resolution is also investigated by increasing the number of vertical levels, without moving the top of the model. The vertical resolution is increased up to 41 levels, using two kinds of level distribution. For the first, the increase in vertical resolution concerns especially the troposphere (with 22 levels in the troposphere), and the second treats the whole atmosphere in a homogeneous way (with 15 levels in the troposphere); the standard version of 31 levels has 10 levels in the troposphere. A comparison is made between the dynamical aspects of the simulations. The zonal wind and precipitation are presented and compared for each resolution. A positive impact is found with the finer tropospheric resolution on the precipitation in the mid-latitudes and on the westerly stratospheric jet, but the general impact on the model climate is weak, the physical parameterizations used appear to be mostly independent to the vertical resolution.Key words. Meteorology and atmospheric dynamics · Convective processes · Waves and tides

scholarly journals The Meteorological Global Model GLOBO at the ISAC-CNR of Italy Assessment of 1.5 Yr of Experimental Use for Medium-Range Weather Forecasts

2011 ◽  
Vol 26 (6) ◽  
pp. 1045-1055 ◽  
Author(s):  
Piero Malguzzi ◽  
Andrea Buzzi ◽  
Oxana Drofa
Keyword(s):  
General Circulation ◽  
Initial Conditions ◽  
Circulation Model ◽  
Daily Basis ◽  
Horizontal Resolution ◽  
Limited Area ◽  
National Council ◽  
Meteorological Model ◽  
Medium Range ◽  
Mean Square Errors

Abstract Since August 2009, the GLOBO atmospheric general circulation model has been running experimentally at the Institute of Atmospheric Sciences and Climate (ISAC) of the National Council of Research of Italy. GLOBO is derived from the Bologna Limited Area Model (BOLAM), a gridpoint limited-area meteorological model that was developed at the same institute and that has been extended to the entire earth atmosphere. The main dynamical features and physical parameterizations of GLOBO are presented. Starting from initial conditions obtained from the analysis of the NCEP Global Forecast System (GFS) model valid at 0000 UTC, 6-day forecasts with average horizontal resolution of 32 km were performed on a daily basis and in real time. The assessment of the forecast skill during the 1.5-yr period included the calculation of the monthly averaged root-mean-square errors (model prediction versus gridded analyses) of geopotential height at 500 hPa and mean sea level pressure for the northern and southern extratropics, performed accordingly to WMO Commission for Basic Systems (CBS) standards. The verification results are compared with models from other global data processing and forecasting system centers, as are available in the literature. The GLOBO skill for medium-range forecasts turns out to be comparable to that of the above models. The lack of analyses based on model forecasts and data assimilation is likely to penalize the scores for shorter-term forecasts.

A multi-model assessment of sub-monthly polar motion and the associated ocean bottom pressure variability

2020 ◽  
Author(s):  
Michael Schindelegger ◽  
Alexander Harker ◽  
David Salstein ◽  
Henryk Dobslaw
Keyword(s):  
General Circulation ◽  
Polar Motion ◽  
Circulation Model ◽  
Horizontal Resolution ◽  
Ocean Bottom ◽  
Model Assessment ◽  
Bottom Pressure ◽  
Max Planck ◽  
Ocean Bottom Pressure ◽  
Partial Representation

<p>Budgeting geophysical fluid excitations against space-geodetic observations of polar motion reveals non-negligible residuals on sub-monthly time scales, typically 1−2 cm when projected onto the Earth's surface. A possible source for these discrepancies are imperfections in the hydrodynamic models used to derive the required ocean excitation functions. To guide future model improvements, we present a systematic assessment of the oceanic component of sub-monthly polar motion based on three global time-stepping models which are forced by the same atmospheric data but considerably differ in their numerical setup and physical parameterizations. In particular, we use ocean bottom pressure output and angular momenta from (i) the finite-element 2 Dimensions Gravity Wave Model (Mog2D), (ii) the baroclinic Max-Planck-Institute Ocean Model (MPIOM) at 1° horizontal resolution, representing the current industry standard, and (iii) a more experimental, eddy-permitting setup of the MITgcm (MIT General Circulation Model). Validations of data from 2007 to 2008 are performed against observed polar motion and daily GRACE (Gravity Recovery and Climate Experiment) solutions, which resolve the broad scales of ocean bottom pressure variability relevant for angular momentum considerations. No definite quantitative results are available at the time of this writing, but a specific question we aim to answer is whether the MITgcm run outperforms the other models in our validations, given its higher resolution and partial representation of flow interactions with major topographic features.</p>

scholarly journals Vertical resolution dependence of gravity wave momentum flux simulated by an atmospheric general circulation model

2014 ◽  
Vol 7 (6) ◽  
pp. 7559-7573
Author(s):  
S. Watanabe ◽  
K. Sato ◽  
Y. Kawatani ◽  
M. Takahashi
Keyword(s):  
Gravity Wave ◽  
Momentum Flux ◽  
General Circulation ◽  
Circulation Model ◽  
General Circulation Models ◽  
Horizontal Resolution ◽  
Vertical Resolution ◽  
Time Step ◽  
Atmospheric General Circulation ◽  
Wave Momentum

Abstract. The dependence of the gravity wave spectra of energy and momentum flux on the horizontal resolution and time step of atmospheric general circulation models (AGCMs) has been thoroughly investigated in the past. In contrast, much less attention has been given to the dependence of these gravity wave parameters on models' vertical resolutions. The present study demonstrates the dependence of gravity wave momentum flux in the stratosphere and mesosphere on the model's vertical resolution, which is evaluated using an AGCM with a horizontal resolution of about 0.56°. We performed a series of sensitivity test simulations changing only the model's vertical resolution above a height of 8 km, and found that inertial gravity waves with short vertical wavelengths simulated at higher vertical resolutions likely play an important role in determining the gravity wave momentum flux in the stratosphere and mesosphere.

scholarly journals Methyl iodide production in the open ocean

2014 ◽  
Vol 11 (16) ◽  
pp. 4459-4476 ◽  
Author(s):  
I. Stemmler ◽  
I. Hense ◽  
B. Quack ◽  
E. Maier-Reimer
Keyword(s):  
Methyl Iodide ◽  
General Circulation ◽  
Circulation Model ◽  
Global Scale ◽  
Global Ocean ◽  
Phytoplankton Production ◽  
Boreal Winter ◽  
Max Planck ◽  
Data Set ◽  
Carbon Cycle Model

Abstract. Production pathways of the prominent volatile organic halogen compound methyl iodide (CH3I) are not fully understood. Based on observations, production of CH3I via photochemical degradation of organic material or via phytoplankton production has been proposed. Additional insights could not be gained from correlations between observed biological and environmental variables or from biogeochemical modeling to identify unambiguously the source of methyl iodide. In this study, we aim to address this question of source mechanisms with a three-dimensional global ocean general circulation model including biogeochemistry (MPIOM–HAMOCC (MPIOM – Max Planck Institute Ocean Model HAMOCC – HAMburg Ocean Carbon Cycle model)) by carrying out a series of sensitivity experiments. The simulated fields are compared with a newly available global data set. Simulated distribution patterns and emissions of CH3I differ largely for the two different production pathways. The evaluation of our model results with observations shows that, on the global scale, observed surface concentrations of CH3I can be best explained by the photochemical production pathway. Our results further emphasize that correlations between CH3I and abiotic or biotic factors do not necessarily provide meaningful insights concerning the source of origin. Overall, we find a net global annual CH3I air–sea flux that ranges between 70 and 260 Gg yr−1. On the global scale, the ocean acts as a net source of methyl iodide for the atmosphere, though in some regions in boreal winter, fluxes are of the opposite direction (from the atmosphere to the ocean).

scholarly journals Impacts of soil-aquifer heat and water fluxes on simulated global climate

2013 ◽  
Vol 10 (1) ◽  
pp. 1185-1212 ◽  
Author(s):  
N. Y. Krakauer ◽  
M. J. Puma ◽  
B. I. Cook
Keyword(s):  
Soil Moisture ◽  
Land Surface ◽  
General Circulation ◽  
Soil Column ◽  
Circulation Model ◽  
The Arctic ◽  
Water Fluxes ◽  
Limited Impact ◽  
Mean Climate ◽  
The Impact

Abstract. Climate models have traditionally only represented heat and water fluxes within relatively shallow soil layers, but there is increasing interest in the possible role of heat and water exchanges with the deeper subsurface. Here, we integrate an idealized 50 m deep aquifer into the land surface module of the GISS ModelE general circulation model to test the influence of aquifer-soil moisture and heat exchanges on climate variables. We evaluate the impact on the modeled climate of aquifer-soil heat and water fluxes separately, as well as in combination. The addition of the aquifer to ModelE has limited impact on annual-mean climate, with little change in global mean land temperature, precipitation, or evaporation. The seasonal amplitude of deep soil temperature is strongly damped by the soil-aquifer heat flux. This not only improves the model representation of permafrost area but propagates to the surface, resulting in an increase in the seasonal amplitude of surface air temperature of >1 K in the Arctic. The soil-aquifer water and heat fluxes both slightly decrease interannual variability in soil moisture and land-surface temperature, and decrease the soil moisture memory of the land surface on annual timescales. The results of this experiment suggest that deepening the modeled land surface, compared to modeling only a shallower soil column with a no-flux bottom boundary condition, has limited impact on mean climate but does affect seasonality and interannual persistence.

scholarly journals On the impact of recent developments of the LMDz atmospheric general circulation model on the simulation of CO<sub>2</sub> transport

2018 ◽  
Vol 11 (11) ◽  
pp. 4489-4513 ◽  
Author(s):  
Marine Remaud ◽  
Frédéric Chevallier ◽  
Anne Cozic ◽  
Xin Lin ◽  
Philippe Bousquet
Keyword(s):  
Land Surface ◽  
General Circulation ◽  
Circulation Model ◽  
Surface Model ◽  
Strong Impact ◽  
Vertical Resolution ◽  
Atmospheric General Circulation ◽  
Inverse Systems ◽  
The Impact ◽  
Physical Parameterizations

Abstract. The quality of the representation of greenhouse gas (GHG) transport in atmospheric general circulation models (GCMs) drives the potential of inverse systems to retrieve GHG surface fluxes to a large extent. In this work, the transport of CO2 is evaluated in the latest version of the Laboratoire de Météorologie Dynamique (LMDz) GCM, developed for the Climate Model Intercomparison Project 6 (CMIP6) relative to the LMDz version developed for CMIP5. Several key changes have been implemented between the two versions, which include a more elaborate radiative scheme, new subgrid-scale parameterizations of convective and boundary layer processes and a refined vertical resolution. We performed a set of simulations of LMDz with different physical parameterizations, two different horizontal resolutions and different land surface schemes, in order to test the impact of those different configurations on the overall transport simulation. By modulating the intensity of vertical mixing, the physical parameterizations control the interhemispheric gradient and the amplitude of the seasonal cycle in the Northern Hemisphere, as emphasized by the comparison with observations at surface sites. However, the effect of the new parameterizations depends on the region considered, with a strong impact over South America (Brazil, Amazonian forest) but a smaller impact over Europe, East Asia and North America. A finer horizontal resolution reduces the representation errors at observation sites near emission hotspots or along the coastlines. In comparison, the sensitivities to the land surface model and to the increased vertical resolution are marginal.

scholarly journals On the impact of recent developments of an atmospheric general circulation model on the simulation of CO<sub>2</sub> transport

2018 ◽  
Author(s):  
Marine Remaud ◽  
Frédéric Chevallier ◽  
Anne Cozic ◽  
Xin Lin ◽  
Philippe Bousquet
Keyword(s):  
Land Surface ◽  
General Circulation ◽  
Circulation Model ◽  
Surface Model ◽  
Strong Impact ◽  
Vertical Resolution ◽  
Atmospheric General Circulation ◽  
Inverse Systems ◽  
The Impact ◽  
Physical Parameterizations

Abstract. The quality of the representation of greenhouse gas (GHG) transport in atmospheric General Circulation Models (GCMs) drives the potential of inverse systems to retrieve GHG surface fluxes to a large extent. In this work, the transport of CO2 is evaluated in the latest version of the LMDz GCM, developed for the Climate Model Intercomparison Project 6 (CMIP6) relative to the LMDz version developed for CMIP4. Several key changes have been implemented between the two versions; those include a more elaborate radiative scheme, new sub-grid scale parameterizations of convective and boundary layer processes, and a refined vertical resolution. We performed a set of simulations of LMDz with the different physical parameterizations, two different horizontal resolutions and different land surface schemes, in order to test the impact of those different configurations on the overall transport simulation. By modulating the intensity of vertical mixing, the physical parameterizations control the interhemispheric gradient and the amplitude of the seasonal cycle in the summer northern hemisphere, as emphasized by the comparison with observations at surface sites. However, the effect of the new parameterizations depends on the region considered, with a strong impact over South America (Brazil, Amazonian forest) but a smaller impact over Europe, Eastern Asia and North America. A finer horizontal resolution reduces the representation errors at observation sites near emission-hot spots or along the coastlines. In comparison, the sensitivities to the land surface model and to the increased vertical resolution are marginal.

scholarly journals Impacts of soil–aquifer heat and water fluxes on simulated global climate

2013 ◽  
Vol 17 (5) ◽  
pp. 1963-1974 ◽  
Author(s):  
N. Y. Krakauer ◽  
M. J. Puma ◽  
B. I. Cook
Keyword(s):  
Soil Moisture ◽  
Land Surface ◽  
General Circulation ◽  
Soil Column ◽  
Circulation Model ◽  
The Arctic ◽  
Water Fluxes ◽  
Limited Impact ◽  
Mean Climate ◽  
The Impact

Abstract. Climate models have traditionally only represented heat and water fluxes within relatively shallow soil layers, but there is increasing interest in the possible role of heat and water exchanges with the deeper subsurface. Here, we integrate an idealized 50 m deep aquifer into the land surface module of the GISS ModelE general circulation model to test the influence of aquifer–soil moisture and heat exchanges on climate variables. We evaluate the impact on the modeled climate of aquifer–soil heat and water fluxes separately, as well as in combination. The addition of the aquifer to ModelE has limited impact on annual-mean climate, with little change in global mean land temperature, precipitation, or evaporation. The seasonal amplitude of deep soil temperature is strongly damped by the soil–aquifer heat flux. This not only improves the model representation of permafrost area but propagates to the surface, resulting in an increase in the seasonal amplitude of surface air temperature of > 1 K in the Arctic. The soil–aquifer water and heat fluxes both slightly decrease interannual variability in soil moisture and in land-surface temperature, and decrease the soil moisture memory of the land surface on seasonal to annual timescales. The results of this experiment suggest that deepening the modeled land surface, compared to modeling only a shallower soil column with a no-flux bottom boundary condition, has limited impact on mean climate but does affect seasonality and interannual persistence.

scholarly journals The Effects of a Well-Resolved Stratosphere on the Simulated Boreal Winter Circulation in a Climate Model

2019 ◽  
Vol 76 (5) ◽  
pp. 1203-1226 ◽  
Author(s):  
Yoshio Kawatani ◽  
Kevin Hamilton ◽  
Lesley J. Gray ◽  
Scott M. Osprey ◽  
Shingo Watanabe ◽  
...  
Keyword(s):  
General Circulation ◽  
Climate Model ◽  
Middle Atmosphere ◽  
Circulation Model ◽  
Boreal Winter ◽  
Quasi Biennial Oscillation ◽  
Westerly Jet ◽  
The Impact ◽  
Jet Structure ◽  
Biennial Oscillation

Abstract The impact of stratospheric representation is investigated using the Model for Interdisciplinary Research on Climate Atmospheric General Circulation Model (MIROC-AGCM) run with different model-lid heights and stratospheric vertical resolutions, but unchanged horizontal resolutions (~1.125°) and subgrid parameterizations. One-hundred-year integrations of the model were conducted using configurations with 34, 42, 72, and 168 vertical layers and model-lid heights of ~27 km (L34), 47 km (L42), 47 km (L72), and 100 km (L168). Analysis of the results focused on the Northern Hemisphere in winter. Compared with the L42 model, the L34 model produces a poorer simulation of the stratospheric Brewer–Dobson circulation (BDC) in the lower stratosphere, with weaker polar downwelling and accompanying cold-pole and westerly jet biases. The westerly bias extends into the troposphere and even to the surface. The tropospheric westerlies and zone of baroclinic wave activity shift northward; surface pressure has negative (positive) biases in the high (mid-) latitudes, with concomitant precipitation shifts. The L72 and L168 models generate a quasi-biennial oscillation (QBO) while the L34 and 42 models do not. The L168 model includes the mesosphere, and thus resolves the upper branch of the BDC. The L72 model simulates stronger polar downwelling associated with the BDC than does the L42 model. However, experiments with prescribed nudging of the tropical stratospheric winds suggest differences in the QBO representation cannot account for L72 − L42 differences in the climatological polar night jet structure. The results show that the stratospheric vertical resolution and inclusion of the full middle atmosphere significantly affect tropospheric circulations.

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