scholarly journals Development of the GEOS-5 atmospheric general circulation model: evolution from MERRA to MERRA2

2015 ◽  
Vol 8 (5) ◽  
pp. 1339-1356 ◽  
Author(s):  
A. Molod ◽  
L. Takacs ◽  
M. Suarez ◽  
J. Bacmeister
Keyword(s):  
General Circulation Model ◽  
General Circulation ◽  
Atmospheric General Circulation Model ◽  
Weather Prediction ◽  
Circulation Model ◽  
Wave Drag ◽  
Atmospheric General Circulation ◽  
Wide Range ◽  
Simulated Climate ◽  
The Impact

Abstract. The Modern-Era Retrospective Analysis for Research and Applications-2 (MERRA2) version of the Goddard Earth Observing System-5 (GEOS-5) atmospheric general circulation model (AGCM) is currently in use in the NASA Global Modeling and Assimilation Office (GMAO) at a wide range of resolutions for a variety of applications. Details of the changes in parameterizations subsequent to the version in the original MERRA reanalysis are presented here. Results of a series of atmosphere-only sensitivity studies are shown to demonstrate changes in simulated climate associated with specific changes in physical parameterizations, and the impact of the newly implemented resolution-aware behavior on simulations at different resolutions is demonstrated. The GEOS-5 AGCM presented here is the model used as part of the GMAO MERRA2 reanalysis, global mesoscale simulations at 10 km resolution through 1.5 km resolution, the real-time numerical weather prediction system, and for atmosphere-only, coupled ocean-atmosphere and coupled atmosphere-chemistry simulations. The seasonal mean climate of the MERRA2 version of the GEOS-5 AGCM represents a substantial improvement over the simulated climate of the MERRA version at all resolutions and for all applications. Fundamental improvements in simulated climate are associated with the increased re-evaporation of frozen precipitation and cloud condensate, resulting in a wetter atmosphere. Improvements in simulated climate are also shown to be attributable to changes in the background gravity wave drag, and to upgrades in the relationship between the ocean surface stress and the ocean roughness. The series of resolution-aware parameters related to the moist physics was shown to result in improvements at higher resolutions and result in AGCM simulations that exhibit seamless behavior across different resolutions and applications.

scholarly journals Development of the GEOS-5 atmospheric general circulation model: evolution from MERRA to MERRA2

2014 ◽  
Vol 7 (6) ◽  
pp. 7575-7617 ◽  
Author(s):  
A. Molod ◽  
L. Takacs ◽  
M. Suarez ◽  
J. Bacmeister
Keyword(s):  
General Circulation Model ◽  
General Circulation ◽  
Atmospheric General Circulation Model ◽  
Weather Prediction ◽  
Circulation Model ◽  
Wave Drag ◽  
Atmospheric General Circulation ◽  
Wide Range ◽  
Simulated Climate ◽  
The Impact

Abstract. The Modern-Era Retrospective Analysis for Research and Applications-2 (MERRA2) version of the GEOS-5 Atmospheric General Circulation Model (AGCM) is currently in use in the NASA Global Modeling and Assimilation Office (GMAO) at a wide range of resolutions for a variety of applications. Details of the changes in parameterizations subsequent to the version in the original MERRA reanalysis are presented here. Results of a series of atmosphere-only sensitivity studies are shown to demonstrate changes in simulated climate associated with specific changes in physical parameterizations, and the impact of the newly implemented resolution-aware behavior on simulations at different resolutions is demonstrated. The GEOS-5 AGCM presented here is the model used as part of the GMAO's MERRA2 reanalysis, the global mesoscale "nature run", the real-time numerical weather prediction system, and for atmosphere-only, coupled ocean–atmosphere and coupled atmosphere–chemistry simulations. The seasonal mean climate of the MERRA2 version of the GEOS-5 AGCM represents a substantial improvement over the simulated climate of the MERRA version at all resolutions and for all applications. Fundamental improvements in simulated climate are associated with the increased re-evaporation of frozen precipitation and cloud condensate, resulting in a wetter atmosphere. Improvements in simulated climate are also shown to be attributable to changes in the background gravity wave drag, and to upgrades in the relationship between the ocean surface stress and the ocean roughness. The series of "resolution aware" parameters related to the moist physics were shown to result in improvements at higher resolutions, and result in AGCM simulations that exhibit seamless behavior across different resolutions and applications.

scholarly journals Improved Simulation of the Antarctic Stratospheric Final Warming by Modifying the Orographic Gravity Wave Parameterization in the Beijing Climate Center Atmospheric General Circulation Model

Atmosphere ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 576
Author(s):  
Yixiong Lu ◽  
Tongwen Wu ◽  
Xin Xu ◽  
Li Zhang ◽  
Min Chu
Keyword(s):  
Gravity Wave ◽  
General Circulation Model ◽  
General Circulation ◽  
Climate Models ◽  
Atmospheric General Circulation Model ◽  
Circulation Model ◽  
Wave Drag ◽  
Atmospheric General Circulation ◽  
Stratospheric Final Warming ◽  
The Antarctic

The Antarctic stratospheric final warming (SFW) is usually simulated with a substantial delay in climate models, and the corresponding temperatures in austral spring are lower than observations, implying insufficient stratospheric wave drag. To investigate the role of orographic gravity wave drag (GWD) in modeling the Antarctic SFW, in this study the orographic GWD parameterization scheme is modified in the middle-atmosphere version of the Beijing Climate Center Atmospheric General Circulation Model. A pair of simulations are conducted to compare two orographic GWD schemes in simulating the breakdown of the stratospheric polar vortex over Antarctica. The control simulation with the default orographic GWD scheme exhibits delayed vortex breakdown and the cold-pole bias seen in most climate models. In the simulation with modified orographic GWD scheme, the simulated vortex breaks down earlier by 8 days, and the associated cold-pole bias is reduced by more than 2 K. The modified scheme provides stronger orographic GWD in the lower stratosphere, which drives an accelerated polar downwelling branch of the Brewer–Dobson circulation and, in turn, produces adiabatic warming. Our study suggests that modifying orographic GWD parameterizations in climate models would be a valid way of improving the SFW simulation over Antarctica.

Simulating the QBO in an Atmospheric General Circulation Model: Sensitivity to Resolved and Parameterized Forcing

2016 ◽  
Vol 73 (4) ◽  
pp. 1649-1665 ◽  
Author(s):  
James A. Anstey ◽  
John F. Scinocca ◽  
Martin Keller
Keyword(s):  
Gravity Wave ◽  
General Circulation Model ◽  
General Circulation ◽  
Atmospheric General Circulation Model ◽  
Circulation Model ◽  
Wave Drag ◽  
Vertical Resolution ◽  
Atmospheric General Circulation ◽  
Downward Influence ◽  
Seasonal Synchronization

Abstract The quasi-biennial oscillation (QBO) of tropical stratospheric zonal winds is simulated in an atmospheric general circulation model and its sensitivity to model parameters is explored. Vertical resolution in the lower tropical stratosphere finer than ≈1 km and sufficiently strong forcing by parameterized nonorographic gravity wave drag are both required for the model to exhibit a QBO-like oscillation. Coarser vertical resolution yields oscillations that are seasonally synchronized and driven mainly by gravity wave drag. As vertical resolution increases, wave forcing in the tropical lower stratosphere increases and seasonal synchronization is disrupted, allowing quasi-biennial periodicity to emerge. Seasonal synchronization could result from the form of wave dissipation assumed in the gravity wave parameterization, which allows downward influence by semiannual oscillation (SAO) winds, whereas dissipation of resolved waves is consistent with radiative damping and no downward influence. Parameterized wave drag is nevertheless required to generate a realistic QBO, effectively acting to amplify the relatively weaker mean-flow forcing by resolved waves.

scholarly journals Radiative impacts of cloud heterogeneity and overlap in an atmospheric General Circulation Model

2012 ◽  
Vol 12 (19) ◽  
pp. 9097-9111 ◽  
Author(s):  
L. Oreopoulos ◽  
D. Lee ◽  
Y. C. Sud ◽  
M. J. Suarez
Keyword(s):  
General Circulation Model ◽  
General Circulation ◽  
Atmospheric General Circulation Model ◽  
Circulation Model ◽  
Cloud Fraction ◽  
The Other ◽  
Atmospheric General Circulation ◽  
Radiative Impacts ◽  
The Impact ◽  
Layer Cloud

Abstract. The radiative impacts of horizontal heterogeneity of layer cloud condensate, and vertical overlap of both condensate and cloud fraction are examined with the aid of a new radiation package operating in the GEOS-5 Atmospheric General Circulation Model. The impacts are examined in terms of diagnostic top-of-the atmosphere shortwave (SW) and longwave (LW) cloud radiative effect (CRE) calculations for a range of assumptions and overlap parameter specifications. The investigation is conducted for two distinct cloud schemes, one that comes with the standard GEOS-5 distribution, and another used experimentally for its enhanced cloud microphysical capabilities. Both schemes are coupled to a cloud generator allowing arbitrary cloud overlap specification. Results show that cloud overlap radiative impacts are significantly stronger in the operational cloud scheme where a change of cloud fraction overlap from maximum-random to generalized results in global changes of SW and LW CRE of ~4 Wm−2, and zonal changes of up to ~10 Wm−2. This is an outcome of fewer occurrences (compared to the other scheme) of large layer cloud fractions and fewer multi-layer situations where large numbers of atmospheric layers are simultaneously cloudy, both conditions that make overlap details more important. The impact of the specifics of condensate distribution overlap on CRE is much weaker. Once generalized overlap is adopted, both cloud schemes are only modestly sensitive to the exact values of the overlap parameters. When one of the CRE components is overestimated and the other underestimated, both cannot be driven simoultaneously towards observed values by adjustments to cloud condensate heterogeneity and overlap specifications alone.

scholarly journals The climate in The Netherlands during the Younger Dryas and Preboreal: means and extremes obtained with an atmospheric general circulation model

2001 ◽  
Vol 80 (2) ◽  
pp. 19-30 ◽  
Author(s):  
H. Renssen
Keyword(s):  
The Netherlands ◽  
General Circulation Model ◽  
General Circulation ◽  
Atmospheric General Circulation Model ◽  
Late Quaternary ◽  
Younger Dryas ◽  
Circulation Model ◽  
Atmospheric General Circulation ◽  
The Impact ◽  
Boreal Climate

AbstractThe shift from the coldYounger Dryas phase to the relatively warm Pre-boreal at~l 1.5 thousand years BP occurred within 50 calendar years and represents a clear example of rapid climate warming. Geologists and palaeo-ecologists have extensively studied the impact of this shift on the environment in The Netherlands. The global atmospheric general circulation model of the Max-Planck-Institute for Meteorology is applied to perform simulations of the Younger Dryas and Pre-boreal climates. Here detailed results are presented for the grid-cell representing The Netherlands, providing quantified estimates of climatic means and extremes for both periods. The results suggest that the Younger Dryas climate was characterised by cold winters (temperatures regularly below -20 °C) and cool summers (13-14 °C), with a high inter-annual variability, strong fluctuations in temperature, frequent storms and snowfall from September to May. The Pre-boreal climate was a ‘continental’ version of present-day climate, with cooler winters, warmer summers (~2 °C difference) and more snowfall, but lower wind speeds. Also, the Pre-boreal climate was wetter than the present and Younger Dryas climates. The main driving factors were the low temperatures of the partly sea-ice covered N Atlantic Ocean and the insolation that was very different from today, with more incoming solar radiation during summer (+30W/m2) and less during winter (-10W/m2).The presented detailed results could be valuable for interpreting palaeo-environmental records and for modelling studies on sedimentological processes during the Late Quaternary.

scholarly journals Oceanic Forcing of Antarctic Climate Change: A Study Using a Stretched-Grid Atmospheric General Circulation Model

2014 ◽  
Vol 27 (15) ◽  
pp. 5786-5800 ◽  
Author(s):  
Gerhard Krinner ◽  
Chloé Largeron ◽  
Martin Ménégoz ◽  
Cécile Agosta ◽  
Claire Brutel-Vuilmet
Keyword(s):  
Climate Change ◽  
General Circulation Model ◽  
General Circulation ◽  
Atmospheric General Circulation Model ◽  
Surface Condition ◽  
Circulation Model ◽  
Sea Surface ◽  
Variable Resolution ◽  
Atmospheric General Circulation ◽  
Simulated Climate

Abstract A variable-resolution atmospheric general circulation model (AGCM) is used for climate change projections over the Antarctic. The present-day simulation uses prescribed observed sea surface conditions, while a set of five simulations for the end of the twenty-first century (2070–99) under the Special Report on Emissions Scenarios (SRES) A1B scenario uses sea surface condition anomalies from selected coupled ocean–atmosphere climate models from phase 3 of the Coupled Model Intercomparison Project (CMIP3). Analysis of the results shows that the prescribed sea surface condition anomalies have a very strong influence on the simulated climate change on the Antarctic continent, largely dominating the direct effect of the prescribed greenhouse gas concentration changes in the AGCM simulations. Complementary simulations with idealized forcings confirm these results. An analysis of circulation changes using self-organizing maps shows that the simulated climate change on regional scales is not principally caused by shifts of the frequencies of the dominant circulation patterns, except for precipitation changes in some coastal regions. The study illustrates that in some respects the use of bias-corrected sea surface boundary conditions in climate projections with a variable-resolution atmospheric general circulation model has some distinct advantages over the use of limited-area atmospheric circulation models directly forced by generally biased coupled climate model output.

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