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Impact of the surface temperature and vertical shear of zonal wind on the dynamics of a simple two-layer model of the atmosphere

Brojewski R., Jakubiak B., Jasiński J.

Acta Geophysica

2007

Vol. 55, no. 2

231-252

The paper presents and analyzes, from the point of view of smooth dynamic systems theory, a two-layer baroclinic model of the troposphere in geostrophic approximation. The model describes airflow in β-channel within the tropospheric part of the main Hadley circulation cell. It enables to obtain, after application of the Galerkin method, a fairly simple low-parametric dynamic system describing the phenomena of nonlinear interactions, bifurcations and blocking in the atmosphere. This enables to take into consideration such basic factors influencing the atmospheric dynamics like the heat exchange within the surface, orography, vertical variability of zonal wind and hydrostatic stability. Impact of zonal thermal variability of the surface and vertical shear of zonal wind in the troposphere on the orographic bifurcation was investigated and the oscillation character in the dynamic system after Hopf bifurcation of the second kind was analyzed. Additionally, the model dynamics was investigated in conditions in-cluding momentum forcing in the upper and lower parts of the troposphere and excluding orographic interaction, as well as in the conditions of thermal interaction between the troposphere and the surface for the vertical shear of zonal wind in both tropospheric layers. Impact of the mean zonal wind in the troposphere on the prop-erties of model dynamics was assessed. It was proved that zonally varied surface temperature and layered mean zonal wind in the atmosphere are the parameters that have basic influence on the model dynamics. They cause numerous bifurcations and strongly influence the periods of oscillations of the model variables. They are often Hopf bifurcations of the second kind during which tropospheric states fairly distant from the ones before the bifurcations are generated. This significantly influences the model predictability.

Dynamics of a 2L-baroclinic model of the troposphere. Part 1: Thermal bifurcation and blocking

Brojewski R., Jakubiak B., Jasiński J.

Journal of Technical Physics

2005

Vol. 46, no 3

131-147

The paper analyzes, from the point of view of the theory of smooth dynamic systems, a simple two-layer model of baroclinic atmosphere applied within the main Hadley cell of circulation. The dynamics of the model was investigated in conditions excluding orographic influence but including momentum forcing in the upper and lower layers of the troposphere and thermal interaction between the troposphere and the surface for various vertical differentiations of the zonal drift in two tropospheric layers. The obtained results contribute to a profound view onto the applicability of classical weather forecasting models based on the hydrodynamic attitude.