scholarly journals Diagnostic and prognostic model studies of the Adriatic Sea general circulation: Seasonal variability

2002 ◽  
Vol 107 (C1) ◽  
Author(s):  
M. Zavatarelli
Keyword(s):  
Seasonal Variability ◽  
General Circulation ◽  
Prognostic Model ◽  
Adriatic Sea ◽  
Model Studies

scholarly journals The Adriatic Sea modelling system: a nested approach

2003 ◽  
Vol 21 (1) ◽  
pp. 345-364 ◽  
Author(s):  
M. Zavatarelli ◽  
N. Pinardi
Keyword(s):  
General Circulation ◽  
Adriatic Sea ◽  
Numerical Models ◽  
Pilot Project ◽  
Northern Adriatic ◽  
Dense Water Formation ◽  
Main Circulation ◽  
Forecasting System ◽  
Modelling System ◽  
Circulation Characteristics

Abstract. A modelling system for the Adriatic Sea has been built within the framework of the Mediterranean Forecasting System Pilot Project. The modelling system consists of a hierarchy of three numerical models (whole Mediterranean Sea, whole Adriatic Sea, Northern Adriatic Basin) coupled among each other by simple one-way, off-line nesting techniques, to downscale the larger scale flow field to highly resolved coastal scale fields. Numerical simulations have been carried out under climatological surface forcing. Simulations were aimed to assess the effectiveness of the nesting techniques and the skill of the system to reproduce known features of the Adriatic Sea circulation phenomenology (main circulation features, dense water formation,flow at the Otranto Strait and coastal circulation characteristics over the northern Adriatic shelf), in view of the pre-operational use of the modelling system. This paper describes the modelling system setup, and discusses the simulation results for the whole Adriatic Sea and its northern basin, comparing the simulations with the observed climatological circulation characteristics. Results obtained with the northern Adriatic model are also compared with the corresponding simulations obtained with the coarser resolution Adriatic model. Key words. Oceanography: general (continental shelf processes; numerical modelling) – Oceanography: physical (general circulation)

scholarly journals Predictions of Indian Ocean SST Indices with a Simple Statistical Model: A Null Hypothesis

2009 ◽  
Vol 22 (18) ◽  
pp. 4930-4938 ◽  
Author(s):  
Dietmar Dommenget ◽  
Malte Jansen
Keyword(s):  
Indian Ocean ◽  
Statistical Model ◽  
General Circulation Model ◽  
Null Hypothesis ◽  
General Circulation ◽  
Circulation Model ◽  
Tropical Indian Ocean ◽  
Model Studies ◽  
Sst Variability ◽  
The Indian Ocean

Abstract Several recent general circulation model studies discuss the predictability of the Indian Ocean dipole (IOD) mode, suggesting that it is predictable because of coupled ocean–atmosphere interactions in the Indian Ocean. However, it is not clear from these studies how much of the predictability is due to the response to El Niño. It is shown in this note that a simple statistical model that treats the Indian Ocean as a red noise process forced by tropical Pacific SST shows forecast skills comparable to those of recent general circulation model studies. The results also indicate that some of the eastern tropical Indian Ocean SST predictability in recent studies may indeed be beyond the skill of the simple model proposed in this note, indicating that dynamics in the Indian Ocean may have caused this improved predictability in this region. The model further indicates that the IOD index may be the least predictable index of Indian Ocean SST variability. The model is proposed as a null hypothesis for Indian Ocean SST predictions.

scholarly journals Towards Direct Simulation of Future Tropical Cyclone Statistics in a High-Resolution Global Atmospheric Model

2010 ◽  
Vol 2010 ◽  
pp. 1-13 ◽  
Author(s):  
Michael F. Wehner ◽  
G. Bala ◽  
Phillip Duffy ◽  
Arthur A. Mirin ◽  
Raquel Romano
Keyword(s):  
High Resolution ◽  
Radiative Forcing ◽  
General Circulation ◽  
Circulation Model ◽  
Atmospheric Model ◽  
Tropical Storm ◽  
Model Studies ◽  
The North ◽  
Resolution Model ◽  
High Resolution Model

We present a set of high-resolution global atmospheric general circulation model (AGCM) simulations focusing on the model's ability to represent tropical storms and their statistics. We find that the model produces storms of hurricane strength with realistic dynamical features. We also find that tropical storm statistics are reasonable, both globally and in the north Atlantic, when compared to recent observations. The sensitivity of simulated tropical storm statistics to increases in sea surface temperature (SST) is also investigated, revealing that a credible late 21st century SST increase produced increases in simulated tropical storm numbers and intensities in all ocean basins. While this paper supports previous high-resolution model and theoretical findings that the frequency of very intense storms will increase in a warmer climate, it differs notably from previous medium and high-resolution model studies that show a global reduction in total tropical storm frequency. However, we are quick to point out that this particular model finding remains speculative due to a lack of radiative forcing changes in our time-slice experiments as well as a focus on the Northern hemisphere tropical storm seasons.

scholarly journals Differing responses of the QBO to SO<sub>2</sub> injections in two global models

2020 ◽  
Author(s):  
Ulrike Niemeier ◽  
Jadwiga H. Richter ◽  
Simone Tilmes
Keyword(s):  
General Circulation ◽  
Climate Model ◽  
Numerical Models ◽  
General Circulation Models ◽  
Injection Rate ◽  
Equatorial Region ◽  
Quasi Biennial Oscillation ◽  
Vertical Advection ◽  
Model Studies ◽  
The Impact

Abstract. Artificial injections of sulfur dioxide (SO2) into the stratosphere show in several model studies an impact on stratospheric dynamics. The quasi-biennial oscillation (QBO) has been shown to slow down or even vanish, under higher SO2 injections in the equatorial region. But the impact is only qualitatively, but not quantitatively consistent across the different studies using different numerical models. The aim of this study is to understand the reasons behind the differences in the QBO response to SO2 injections between two general circulation models, the Whole Atmosphere Community Climate Model (WACCM-110L) and MAECHAM5-HAM. We show that the response of the QBO to injections with the same SO2 injection rate is very different in the two models, but similar when a similar stratospheric heating rate is induced by SO2 injections of different amounts. The reason for the different response of the QBO corresponding to the same injection rate is very different vertical advection in the two models, even in the control simulation. The stronger vertical advection in WACCM results in a higher aerosol burden and stronger heating of the aerosols, and, consequently in a vanishing QBO at lower injection rate than in simulations with MAECHAM5-HAM.

The Influence of Meridional Gradients in Insolation and Longwave Optical Depth on the Climate of a Gray Radiation GCM

2018 ◽  
Vol 31 (19) ◽  
pp. 7803-7822
Author(s):  
Nicholas J. Lutsko ◽  
Max Popp
Keyword(s):  
Surface Temperature ◽  
Optical Depth ◽  
General Circulation ◽  
Prognostic Model ◽  
Circulation Model ◽  
Lapse Rate ◽  
The Earth ◽  
Global Mean Surface Temperature ◽  
Earth’S Climate ◽  
Global Mean

The relative contributions of the meridional gradients in insolation and in longwave optical depth (caused by gradients in water vapor) to the equator-to-pole temperature difference, and to Earth’s climate in general, have not been quantified before. As a first step to understanding these contributions, this study investigates simulations with an idealized general circulation model in which the gradients are eliminated individually or jointly, while keeping the global means fixed. The insolation gradient has a larger influence on the model’s climate than the gradient in optical depth, but both make sizeable contributions and the changes are largest when the gradients are reduced simultaneously. Removing either gradient increases global-mean surface temperature due to an increase in the tropospheric lapse rate, while the meridional surface temperature gradients are reduced. “Global warming” experiments with these configurations suggest similar climate sensitivities; however, the warming patterns and feedbacks are quite different. Changes in the meridional energy fluxes lead to polar amplification of the response in all but the setup in which both gradients are removed. The lapse-rate feedback acts to polar amplify the responses in the Earth-like setup, but is uniformly negative in the other setups. Simple models are used to interpret the results, including a prognostic model that can accurately predict regional surface temperatures, given the meridional distributions of insolation and longwave optical depths.

Interpreting Stationary Wave Nonlinearity in Barotropic Dynamics

2010 ◽  
Vol 67 (7) ◽  
pp. 2240-2250 ◽  
Author(s):  
Lei Wang ◽  
Paul J. Kushner
Keyword(s):  
General Circulation ◽  
Wave Model ◽  
Stationary Wave ◽  
Stationary Waves ◽  
Mean Flow ◽  
Model Studies ◽  
The Difference ◽  
Wave Models ◽  
Wave Nonlinearity ◽  
Basic Features

Abstract Stationary wave nonlinearity describes the self-interaction of stationary waves and is important in maintaining the zonally asymmetric atmospheric general circulation. However, the dynamics of stationary wave nonlinearity, which is often calculated explicitly in stationary wave models, is not well understood. Stationary wave nonlinearity is examined here in the simplified setting of the response to localized topographic forcing in quasigeostrophic barotropic dynamics in the presence and absence of transient eddies. It is shown that stationary wave nonlinearity accounts for most of the difference between the linear and full nonlinear response, particularly if the adjustment of the zonal-mean flow to the stationary waves is taken into account. The separate impact of transient eddy forcing is also quantified. Wave activity analysis shows that stationary wave nonlinearity in this setting is associated with Rossby wave critical layer reflection. A nonlinear stationary wave model, similar to those used in baroclinic stationary wave model studies, is also tested and is shown to capture the basic features of the full nonlinear stationary wave solution.

Model simulations of Cretaceous climates: the role of geography and carbon dioxide

1993 ◽  
Vol 341 (1297) ◽  
pp. 307-316 ◽  
Keyword(s):  
Carbon Dioxide ◽  
General Circulation ◽  
Atmospheric Carbon Dioxide ◽  
Circulation Model ◽  
Accurate Estimate ◽  
Early Model ◽  
Solar Insolation ◽  
Model Studies ◽  
Geologic Record

A general circulation model (GENESIS) with seasonally varying solar insolation and a mixed layer ocean is applied to assess the role of continental geometry and increased levels of carbon dioxide to explain the warmth of the Cretaceous period. Model experiments suggest that the role of geography is negligible, in contrast to early model studies with mean annual solar insolation and a simple energy balance ocean. Higher atmospheric carbon dioxide (4 times present) resulted in a 5.5°C globally averaged surface temperature increase, close to the lower limit required to explain the geologic record. Mid-Cretaceous carbon dioxide concentrations of 4-6 times the present day concentrations are a reasonable explanation of Cretaceous warmth if the GENESIS model provides an accurate estimate of climate sensitivity to geography and carbon dioxide.

scholarly journals A Study of Coupling Parameter Estimation Implemented by 4D-Var and EnKF with a Simple Coupled System

2015 ◽  
Vol 2015 ◽  
pp. 1-16 ◽  
Author(s):  
Guijun Han ◽  
Xinrong Wu ◽  
Shaoqing Zhang ◽  
Zhengyu Liu ◽  
Ionel Michael Navon ◽  
...  
Keyword(s):  
Parameter Estimation ◽  
General Circulation ◽  
Coupling Parameter ◽  
Coupled Model ◽  
Circulation Model ◽  
Coupled System ◽  
Model Studies ◽  
Error Covariance ◽  
Estimated Parameters ◽  
Observing System Simulation Experiment

Coupling parameter estimation (CPE) that uses observations to estimate the parameters in a coupled model through error covariance between variables residing in different media may increase the consistency of estimated parameters in an air-sea coupled system. However, it is very challenging to accurately evaluate the error covariance between such variables due to the different characteristic time scales at which flows vary in different media. With a simple Lorenz-atmosphere and slab ocean coupled system that characterizes the interaction of two-timescale media in a coupled “climate” system, this study explores feasibility of the CPE with four-dimensional variational analysis and ensemble Kalman filter within a perfect observing system simulation experiment framework. It is found that both algorithms can improve the representation of air-sea coupling processes through CPE compared to state estimation only. These simple model studies provide some insights when parameter estimation is implemented with a coupled general circulation model for improving climate estimation and prediction initialization.

scholarly journals Long-Term Maximum and Minimum Temperature Projections Over Metro Vancouver, Canada

2021 ◽  
Vol 9 ◽  
Author(s):  
Chuyin Tian ◽  
Guohe Huang ◽  
Yanli Liu ◽  
Denghua Yan ◽  
Feng Wang ◽  
...  
Keyword(s):  
Seasonal Variability ◽  
Minimum Temperature ◽  
General Circulation ◽  
Energy Requirement ◽  
General Circulation Models ◽  
Maximum Temperature ◽  
Daily Maximum Temperature ◽  
Daily Maximum ◽  
Climate Projections ◽  
Metro Vancouver

Evident climate change has been observed and projected in observation records and General Circulation Models (GCMs), respectively. This change is expected to reshape current seasonal variability; the degree varies between regions. High-resolution climate projections are thereby necessary to support further regional impact assessment. In this study, a gated recurrent unit-based recurrent neural network statistical downscaling model is developed to project future temperature change (both daily maximum temperature and minimum temperature) over Metro Vancouver, Canada. Three indexes (i.e., coefficient of determinant, root mean square error, and correlation coefficient) are estimated for model validation, indicating the developed model’s competitive ability to simulate the regional climatology of Metro Vancouver. Monthly comparisons between simulation and observation also highlight the effectiveness of the proposed downscaling method. The projected results (under one model set-up, WRF-MPI-ESM-LR, RCP 8.5) show that both maximum and minimum temperature will consistently increase between 2,035 and 2,100 over the 12 selected meteorological stations. By the end of this century, the daily maximum temperature and minimum temperature are expected to increase by an average of 2.91°C and 2.98°C. Nevertheless, with trivial increases in summer and significant rises in winter and spring, the seasonal variability will be reduced substantially, which indicates less energy requirement over Metro Vancouver. This is quite favorable for Metro Vancouver to switch from fossil fuel-based energy sources to renewable and clean forms of energy. Further, the cold extremes’ frequency of minimum temperature will be reduced as expected; however, despite evident warming trend, the hot extremes of maximum temperature will become less frequent.

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