Beyond Thermal Interaction between Ocean and Atmosphere: On the Extratropical Climate Variability due to the Wind-Induced SST*

2008 ◽  
Vol 21 (10) ◽  
pp. 2001-2018 ◽  
Author(s):  
Dong Eun Lee ◽  
Zhengyu Liu ◽  
Yun Liu
Keyword(s):  
Heat Flux ◽  
Air Temperature ◽  
General Circulation ◽  
Initial Conditions ◽  
Stochastic Perturbation ◽  
General Circulation Models ◽  
Ocean Dynamics ◽  
Extended Model ◽  
Zonal Wind Anomaly ◽  
Temperature Variance

Abstract Prescribing sea surface temperature (SST) for the atmospheric general circulation models (GCM) may not lead to underestimation of the coupled variability. In this study, a set of SST-driven atmospheric GCM experiments, starting from slightly different multiple initial conditions, is performed. The SST used here is prepared by a coupled GCM, which has the same atmospheric GCM component as the AGCM used in the experiment with the prescribed SST. The results indicate that prescribing SST leads to underestimation of the coupled air temperature variance only in subtropics. Meanwhile, in midlatitudes, prescribing SST may result in the overestimation of the coupled air temperature variance, where the major role of ocean–atmosphere contrast is to provide damping for SST. The simple stochastically driven coupled model is revisited with an extension to the direct wind-driven forcing for SST. In addition to the previous setup relying exclusively on the stochastic perturbation for air temperature, the ocean temperature is also forced by the pure random wind. By this extended model, it is speculated that the coupled air temperature variance can be overestimated by prescribing SST, depending on the sensitivity of SST to the wind-driven heat flux. The midlatitude is the most probable place for the overestimation since the wind-driven ocean dynamics can enhance the wind-driven surface heat flux due to the dominant zonal wind anomaly.

scholarly journals Contributors to linkage between Arctic warming and East Asian winter climate

2021 ◽  
Author(s):  
Xinping Xu ◽  
Shengping He ◽  
Yongqi Gao ◽  
Botao Zhou ◽  
Huijun Wang
Keyword(s):  
Sea Ice ◽  
General Circulation ◽  
Initial Conditions ◽  
Wave Train ◽  
East Asian ◽  
Surface Air Temperature ◽  
General Circulation Models ◽  
The Arctic ◽  
Winter Climate ◽  
Arctic Warming

AbstractPrevious modelling and observational studies have shown discrepancies in the interannual relationship of winter surface air temperature (SAT) between Arctic and East Asia, stimulating the debate about whether Arctic change can influence midlatitude climate. This study uses two sets of coordinated experiments (EXP1 and EXP2) from six different atmospheric general circulation models. Both EXP1 and EXP2 consist of 130 ensemble members, each of which in EXP1 (EXP2) was forced by the same observed daily varying sea ice and daily varying (daily climatological) sea surface temperature (SST) for 1982–2014 but with different atmospheric initial conditions. Large spread exists among ensemble members in simulating the Arctic–East Asian SAT relationship. Only a fraction of ensemble members can reproduce the observed deep Arctic warming–cold continent pattern which extends from surface to upper troposphere, implying the important role of atmospheric internal variability. The mechanisms of deep Arctic warming and shallow Arctic warming are further distinguished. Arctic warming aloft is caused primarily by poleward moisture transport, which in conjunction with the surface warming coupled with sea ice melting constitutes the surface-amplified deep Arctic warming throughout the troposphere. These processes associated with the deep Arctic warming may be related to the forcing of remote SST when there is favorable atmospheric circulation such as Rossby wave train propagating from the North Atlantic into the Arctic.

scholarly journals Seasonal Surface Air Temperature and Precipitation in the FSU Climate Model Coupled to the CLM2

2005 ◽  
Vol 18 (16) ◽  
pp. 3217-3228 ◽  
Author(s):  
D. W. Shin ◽  
S. Cocke ◽  
T. E. LaRow ◽  
James J. O’Brien
Keyword(s):  
Heat Flux ◽  
Air Temperature ◽  
Climate Model ◽  
Initial Conditions ◽  
Sensible Heat Flux ◽  
Surface Air Temperature ◽  
Community Land Model ◽  
Temperature And Precipitation ◽  
The Impact ◽  
Convective Scheme

Abstract The current Florida State University (FSU) climate model is upgraded by coupling the National Center for Atmospheric Research (NCAR) Community Land Model Version 2 (CLM2) as its land component in order to make a better simulation of surface air temperature and precipitation on the seasonal time scale, which is important for crop model application. Climatological and seasonal simulations with the FSU climate model coupled to the CLM2 (hereafter FSUCLM) are compared to those of the control (the FSU model with the original simple land surface treatment). The current version of the FSU model is known to have a cold bias in the temperature field and a wet bias in precipitation. The implementation of FSUCLM has reduced or eliminated this bias due to reduced latent heat flux and increased sensible heat flux. The role of the land model in seasonal simulations is shown to be more important during summertime than wintertime. An additional experiment that assimilates atmospheric forcings produces improved land-model initial conditions, which in turn reduces the biases further. The impact of various deep convective parameterizations is examined as well to further assess model performance. The land scheme plays a more important role than the convective scheme in simulations of surface air temperature. However, each convective scheme shows its own advantage over different geophysical locations in precipitation simulations.

On the use of idealised test cases for ocean model development

2021 ◽  
Author(s):  
Julie Deshayes
Keyword(s):  
Boundary Conditions ◽  
General Circulation ◽  
Model Development ◽  
General Circulation Models ◽  
Ocean Model ◽  
Ocean Dynamics ◽  
Test Cases ◽  
Training Tool ◽  
Research Activities ◽  
Historical Progress

<p>When comparing realistic simulations produced by two ocean general circulation models, differences may emerge from alternative choices in boundary conditions and forcings, which alters our capacity to identify the actual differences between the two models (in the equations solved, the discretization schemes employed and/or the parameterizations introduced). The use of idealised test cases (idealized configurations with analytical boundary conditions and forcings, resolving a given set of equations) has proven efficient to reveal numerical bugs, determine advantages and pitfalls of certain numerical choices, and highlight remaining challenges. I propose to review historical progress enabled by the use of idealised test cases, and promote their utilization when assessing ocean dynamics as represented by an ocean model. For the latter, I would illustrate my talk using illustrations from my own research activities using NEMO in various contexts. I also see idealised test cases as a promising training tool for inexperienced ocean modellers, and an efficient solution to enlarge collaboration with experts in adjacent disciplines, such as mathematics, fluid dynamics and computer sciences.</p>

Forecast skill of autumn snow for European winter climate during the 20th century: A multi member seasonal prediction experiment

2021 ◽  
Author(s):  
Martin Wegmann ◽  
Yvan Orsolini ◽  
Antje Weisheimer ◽  
Bart van den Hurk ◽  
Gerrit Lohmann
Keyword(s):  
Snow Cover ◽  
General Circulation ◽  
Initial Conditions ◽  
Internal Variability ◽  
Seasonal Prediction ◽  
General Circulation Models ◽  
Reanalysis Data ◽  
Winter Climate ◽  
European Continent ◽  
Near Surface

<p>As the leading climate mode to explain wintertime climate variability over Europe, the North Atlantic Oscillation (NAO) has been extensively studied over the last decades. Recently, studies highlighted the state of the Northern Hemispheric cryosphere as possible predictor for the wintertime NAO (Cohen et al. 2014). Although several studies could find seasonal prediction skill in reanalysis data (Orsolini et al. 2016, Duville et al. 2017,Han & Sun 2018), experiments with ocean-atmosphere general circulation models (AOGCMs) still show conflicting results (Furtado et al. 2015, Handorf et al. 2015, Francis 2017, Gastineau et al. 2017). </p><p>Here we use two kinds ECMWF seasonal prediction ensembles starting with November initial conditions taken from the long-term reanalysis ERA-20C and forecasting the following three winter months. Besides the 110-year ensemble of 50 members representing internal variability of the atmosphere, we investigate a second ensemble of 20 members where initial conditions are split between low and high snow cover years for the Northern Hemisphere. We compare two recently used Eurasian snow cover indices for their skill in predicting winter climate for the European continent. Analyzing the two forecast experiments, we found that prediction runs starting with high snow index values in November result in significantly more negative NAO states in the following winter (DJF), which in turn modulates near surface temperatures. We track the atmospheric anomalies triggered by the high snow index through the tropo- and stratosphere as well as for the individual winter months to provide a physical explanation for the formation of this particular climate state.</p><p> </p>

scholarly journals Mathematics applied to the climate system: outstanding challenges and recent progress

2013 ◽  
Vol 371 (1991) ◽  
pp. 20120518 ◽  
Author(s):  
Paul D. Williams ◽  
Michael J. P. Cullen ◽  
Michael K. Davey ◽  
John M. Huthnance
Keyword(s):  
General Circulation ◽  
Recent Progress ◽  
Initial Conditions ◽  
Global Climate ◽  
Climate Science ◽  
General Circulation Models ◽  
Climate System ◽  
Future Research ◽  
Theme Issue ◽  
Physically Based

The societal need for reliable climate predictions and a proper assessment of their uncertainties is pressing. Uncertainties arise not only from initial conditions and forcing scenarios, but also from model formulation. Here, we identify and document three broad classes of problems, each representing what we regard to be an outstanding challenge in the area of mathematics applied to the climate system. First, there is the problem of the development and evaluation of simple physically based models of the global climate. Second, there is the problem of the development and evaluation of the components of complex models such as general circulation models. Third, there is the problem of the development and evaluation of appropriate statistical frameworks. We discuss these problems in turn, emphasizing the recent progress made by the papers presented in this Theme Issue. Many pressing challenges in climate science require closer collaboration between climate scientists, mathematicians and statisticians. We hope the papers contained in this Theme Issue will act as inspiration for such collaborations and for setting future research directions.

scholarly journals Numerically Converged Solutions of the Global Primitive Equations for Testing the Dynamical Core of Atmospheric GCMs

2004 ◽  
Vol 132 (11) ◽  
pp. 2539-2552 ◽  
Author(s):  
L. M. Polvani ◽  
R. K. Scott ◽  
S. J. Thomas
Keyword(s):  
Cross Sections ◽  
General Circulation ◽  
Initial Conditions ◽  
General Circulation Models ◽  
Primitive Equations ◽  
Test Case ◽  
Dynamical Core ◽  
Temporal Averaging ◽  
Atmospheric General Circulation Models ◽  
Short Time

Abstract Solutions of the dry, adiabatic, primitive equations are computed, for the first time, to numerical convergence. These solutions consist of the short-time evolution of a slightly perturbed, baroclinically unstable, midlatitude jet, initially similar to the archetypal LC1 case of Thorncroft et al. The solutions are computed with two distinct numerical schemes to demonstrate that they are not dependent on the method used to obtain them. These solutions are used to propose a new test case for dynamical cores of atmospheric general circulation models. Instantaneous horizontal and vertical cross sections of vorticity and vertical velocity after 12 days, together with tables of key diagnostic quantities derived from the new solutions, are offered as reproducible benchmarks. Unlike the Held and Suarez benchmark, the partial differential equations and the initial conditions are here completely specified, and the new test case requires only 12 days of integration, involves no spatial or temporal averaging, and does not call for physical parameterizations to be added to the dynamical core itself.

Using a Forest Stand Simulation Model to Examine the Ecological and Climatic Significance of the Late-Quaternary Pine-Spruce Pollen Zone in Eastern Virginia, U.S.A.

1990 ◽  
Vol 33 (2) ◽  
pp. 204-218 ◽  
Author(s):  
Gordon B. Bonan ◽  
Bruce P. Hayden
Keyword(s):  
Simulation Model ◽  
Air Temperature ◽  
General Circulation ◽  
Late Quaternary ◽  
General Circulation Models ◽  
Annual Precipitation ◽  
Forest Composition ◽  
Pollen Record ◽  
Composition And Structure ◽  
Atmospheric General Circulation Models

AbstractFull-glacial pollen records from southeastern United States are composed primarily of pine and spruce, with lesser amounts of fir, birch, and oak. A simulation model of forest dynamics was used to reconstruct the composition and structure of these forests on the Delmarva Peninsula of Virginia, where pollen data were available to test the model, and climate and soils data were available to drive the model. Reconstructed annual precipitation and summer air temperature were consistent with modern analog estimates from the pollen record. Annual precipitation was also consistent with climates simulated by atmospheric general circulation models, but summers were colder. Correcting these simulated climates for possible errors resulted in summer air temperature consistent with our estimate. However, two alternative parameter sets relating simulated tree growth to air temperature sums precluded robust forest reconstructions. With one parameter set, the species dominating the simulated forests were not consistent with the pollen record. The other parameter set produced forests more consistent with paleoecological data, indicating that the climate was correct. These differences in simulated forest composition reflected inadequacies in the parameterization of air temperature effects in forest models.

scholarly journals A One-Dimensional Mixed Layer Ocean Model for Use in Three-Dimensional Climate Simulations: Control Simulation Compared to Observations

2005 ◽  
Vol 18 (13) ◽  
pp. 2199-2221 ◽  
Author(s):  
Monica Y. Stephens ◽  
Robert J. Oglesby ◽  
Martin Maxey
Keyword(s):  
Heat Flux ◽  
Mixed Layer ◽  
General Circulation ◽  
Climate Model ◽  
Mixed Layer Depth ◽  
Circulation Model ◽  
Ocean Model ◽  
Ocean Dynamics ◽  
One Dimensional ◽  
Mixed Layer Ocean

Abstract A study has been made of the dynamic interactions between the surface layer of the ocean and the atmosphere using a climate model that contains a new approach to predicting the sea surface temperature (SST). The atmospheric conditions are simulated numerically with the NCAR Community Climate Model (CCM3). The SST is determined by a modified Kraus–Turner-type one-dimensional mixed layer ocean model (MLOM) for the upper ocean that has been coupled to CCM3. The MLOM simulates vertical ocean dynamics and demonstrates the effects of the seasonal variation of mixed layer depth and convective instability on the SST. A purely thermodynamic slab ocean model (SOM) is currently available for use with CCM3 to predict the SST. A large-scale ocean general circulation model (OGCM) may also be coupled to CCM3; however, the OGCM is computationally intensive and is therefore not a good tool for conducting multiple sensitivity studies. The MLOM provides an alternative to the SOM that contains seasonally and spatially specified mixed layer depths. The SOM also contains a heat flux correction called Q-flux that crudely accounts for ocean heat transport by artificially specifying a heat flux that forces the SOM to replicate the observed SST. The results of the coupled MLOM–CCM3 reveal that the MLOM may be used on a global scale and can therefore replace the standard coupled SOM–CCM3 that contains no explicit ocean dynamics. Additionally, stand-alone experiments of the MLOM that are forced with realistic winds, heat, and moisture fluxes show that the MLOM closely approximates the observed seasonal cycle of SST.

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