Atmospheric general circulation models of the Jurassic

1993 ◽  
Vol 341 (1297) ◽  
pp. 317-326 ◽  
Keyword(s):  
General Circulation ◽  
Cloud Cover ◽  
Atmospheric General Circulation Model ◽  
Circulation Model ◽  
General Circulation Models ◽  
High Latitudes ◽  
Geological Data ◽  
First Order ◽  
Atmospheric General Circulation ◽  
Atmospheric General Circulation Models

An atmospheric general circulation model (GCM) is used to simulate the climate of the Jurassic. It is found that the model gives first order agreement with geological data but that closer comparison is limited by uncertainties in the model and in the imposed boundary conditions. The model results suggest that the relative warmth of high latitudes is strongly influenced by changing sea ice and cloud cover. The implied oceanic heat transports are surprisingly small.

scholarly journals Variability of the Stratospheric Quasi-Biennial Oscillation and Its Wave Forcing Simulated in the Beijing Climate Center Atmospheric General Circulation Model

2019 ◽  
Vol 77 (1) ◽  
pp. 149-165 ◽  
Author(s):  
Yixiong Lu ◽  
Tongwen Wu ◽  
Weihua Jie ◽  
Adam A. Scaife ◽  
Martin B. Andrews ◽  
...  
Keyword(s):  
General Circulation Model ◽  
General Circulation ◽  
Atmospheric General Circulation Model ◽  
Circulation Model ◽  
General Circulation Models ◽  
Kelvin Waves ◽  
Quasi Biennial Oscillation ◽  
Wave Forcing ◽  
Atmospheric General Circulation ◽  
Biennial Oscillation

Abstract It is well known that the stratospheric quasi-biennial oscillation (QBO) is forced by equatorial waves with different horizontal/vertical scales, including Kelvin waves, mixed Rossby–gravity (MRG) waves, inertial gravity waves (GWs), and mesoscale GWs, but the relative contribution of each wave is currently not very clear. Proper representation of these waves is critical to the simulation of the QBO in general circulation models (GCMs). In this study, the vertical resolution in the Beijing Climate Center Atmospheric General Circulation Model (BCC-AGCM) is increased to better represent large-scale waves, and a mesoscale GW parameterization scheme, which is coupled to the convective sources, is implemented to provide unresolved wave forcing of the QBO. Results show that BCC-AGCM can spontaneously generate the QBO with realistic periods, amplitudes, and asymmetric features between westerly and easterly phases. There are significant spatiotemporal variations of parameterized convective GWs, largely contributing to a great degree of variability in the simulated QBO. In the eastward wind shear of the QBO at 20 hPa, forcing provided by resolved waves is 0.1–0.2 m s−1 day−1 and forcing provided by parameterized GWs is ~0.15 m s−1 day−1. On the other hand, westward forcings by resolved waves and parameterized GWs are ~0.1 and 0.4–0.5 m s−1 day−1, respectively. It is inferred that the eastward forcing of the QBO is provided by both Kelvin waves and mesoscale convective GWs, whereas the westward forcing is largely provided by mesoscale GWs. MRG waves barely contribute to the formation of the QBO in the model.

scholarly journals Set-up and preliminary results of mid-Pliocene climate simulations with CAM3.1

2011 ◽  
Vol 4 (4) ◽  
pp. 3339-3361 ◽  
Author(s):  
Q. Yan ◽  
Z. Zhang ◽  
H. Wang ◽  
Y. Gao ◽  
W. Zheng
Keyword(s):  
Global Warming ◽  
General Circulation ◽  
Atmospheric General Circulation Model ◽  
Surface Air Temperature ◽  
Circulation Model ◽  
High Latitudes ◽  
Atmospheric General Circulation ◽  
Climate Simulations ◽  
Low Latitudes ◽  
Set Up

Abstract. The mid-Pliocene warm period (~3.3 to 3.0 Ma BP) is a potential analogue for future climate under global warming. In this study, we use an atmospheric general circulation model (AGCM) called CAM3.1 to simulate the mid-Pliocene climate with the PRISM3D boundary conditions. The simulations show that the global annual mean surface air temperature (SAT) increases by 2.0 °C in the mid-Pliocene compared with the pre-industrial temperature. The greatest warming mainly occurs in the high latitudes of both hemispheres, with little change in SAT at low latitudes. The equator-to-pole SAT gradient is reduced in the mid-Pliocene simulation. The annual mean precipitation is enhanced by 3.6% of the pre-industrial value. However, the changes in precipitation are greater in low latitudes than high latitudes.

scholarly journals Set-up and preliminary results of mid-Pliocene climate simulations with CAM3.1

2012 ◽  
Vol 5 (2) ◽  
pp. 289-297 ◽  
Author(s):  
Q. Yan ◽  
Z. S. Zhang ◽  
H. J. Wang ◽  
Y. Q. Gao ◽  
W. P. Zheng
Keyword(s):  
Global Warming ◽  
General Circulation ◽  
Atmospheric General Circulation Model ◽  
Surface Air Temperature ◽  
Circulation Model ◽  
High Latitudes ◽  
Atmospheric General Circulation ◽  
Climate Simulations ◽  
Low Latitudes ◽  
Set Up

Abstract. The mid-Pliocene warm period ~3.264 to 3.025 Ma) is a potential analogue for future climate under global warming. In this study, we use an atmospheric general circulation model (AGCM) called CAM3.1 to simulate the mid-Pliocene climate with the PRISM3D boundary conditions. The simulations show that the global annual mean surface air temperature (SAT) increases by 2.0 °C in the mid-Pliocene compared with the pre-industrial temperature. The greatest warming occurs at high latitudes of both hemispheres, with little change in SAT at low latitudes. The equator-to-pole SAT gradient is reduced in the mid-Pliocene simulation. The annual mean precipitation is enhanced by 3.6% of the pre-industrial value. However, the changes in precipitation are greater at low latitudes than at high latitudes.

scholarly journals Optimizing Parameters in an Atmospheric General Circulation Model

2005 ◽  
Vol 18 (17) ◽  
pp. 3527-3535 ◽  
Author(s):  
C. A. Severijns ◽  
W. Hazeleger
Keyword(s):  
Cost Function ◽  
General Circulation Model ◽  
General Circulation ◽  
Atmospheric General Circulation Model ◽  
Circulation Model ◽  
General Circulation Models ◽  
Radiation Budget ◽  
Nonlinear Dependence ◽  
Atmospheric General Circulation ◽  
The Cost

Abstract An efficient method to optimize the parameter values of the subgrid parameterizations of an atmospheric general circulation model is described. The method is based on the downhill simplex minimization of a cost function computed from the difference between simulated and observed fields. It is used to find optimal values of the radiation and cloud-related parameters. The model error is reduced significantly within a limited number of iterations (about 250) of short integrations (5 yr). The method appears to be robust and finds the global minimum of the cost function. The radiation budget of the model improves considerably without violating the already well simulated general circulation. Different aspects of the general circulation, such as the Hadley and Walker cells improve, although they are not incorporated into the cost function. It is concluded that the method can be used to efficiently determine optimal parameters for general circulation models even when the model behavior has a strong nonlinear dependence on these parameters.

The Last Interglaciation in Northeast Siberia

1995 ◽  
Vol 43 (2) ◽  
pp. 147-158 ◽  
Author(s):  
Anatoly V. Lozhkin ◽  
Patricia M. Anderson
Keyword(s):  
General Circulation ◽  
General Circulation Models ◽  
The Arctic ◽  
The North ◽  
River Terraces ◽  
Atmospheric General Circulation ◽  
Winter Temperatures ◽  
Atmospheric General Circulation Models ◽  
Arctic Coast ◽  
Organic Deposits

AbstractAlluvial, fluvial, and organic deposits of the last interglaciation are exposed along numerous river terraces in northeast Siberia. Although chronological control is often poor, the paleobotanical data suggest range extensions of up to 1000 km for the primary tree species. These data also indicate that boreal communities of the last interglaciation were similar to modern ones in composition, but their distributions were displaced significantly to the north-northwest. Inferences about climate of this period suggest that mean July temperatures were warmer by 4 to 8°C, and seasonal precipitation was slightly greater. Mean January temperatures may have been severely cooler than today (up to 12°C) along the Arctic coast, but similar or slightly warmer than present in other areas. The direction and magnitude of change in July temperatures agree with Atmospheric General Circulation Models, but the 126,000-year-B.P. model results also suggest trends opposite to the paleobotanical data, with simulated cooler winter temperatures and drier conditions than present during the climatic optimum.

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