scholarly journals Tropical temperature trends in Atmospheric General Circulation Model simulations and the impact of uncertainties in observed SSTs

2014 ◽  
Vol 119 (23) ◽  
pp. 13,327-13,337 ◽  
Author(s):  
T. J. Flannaghan ◽  
S. Fueglistaler ◽  
I. M. Held ◽  
S. Po-Chedley ◽  
B. Wyman ◽  
...  
Keyword(s):  
General Circulation Model ◽  
General Circulation ◽  
Atmospheric General Circulation Model ◽  
Circulation Model ◽  
Model Simulations ◽  
Temperature Trends ◽  
Atmospheric General Circulation ◽  
The Impact

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 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 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 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.

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