Thermal wind relation

Application of the Thermal Wind Relation The mean temperature in the layer between 65 and 60 kPa decreases in the eastward direction by 4 C per 100 km. If the geoslrophic wind at 65kPa is from the southeast at 20ms 1, what are the geo-strophic windspeed and direction at 60kPa. Assume/ = 10 4s 1. 

Now the thermal wind relation will allow us to calculate the change in geostrophic wind over this layer. The only temperature gradient is in the eastward (x) direction. From (21.22), there is no change ug with altitude. From (21.22), we can express... 

Fig. 9.2.2 Mars zonal mean thermal winds derived from the temperature cross section of Fig. 9.2.1. The thermal wind relation was used to calculate the vertical shear of the zonal wind, and the wind speeds shown were then obtained assuming zero velocity at the planetary surface as a boundary condition (Smith et al., 2001).

This alternative formulation of geostrophic equilibrium is known as the thermal wind equation it relates the vertical shear of the zonal-mean zonal wind to the horizontal gradient of the zonal-mean temperature. If the temperature decreases toward the poles (as observed in the wintertime stratosphere), then a positive vertical shear will develop so that the zonal-mean zonal wind becomes increasingly eastward with altimde. On the other hand, if the pole-ward temperature gradient is positive (as is the case in the summer stratosphere), then the zonal wind will become more westward with altitude. This is precisely what is observed, as may be ascertained by comparing the mean temperature distributions of Fig. 5 with the zonal-mean zonal wind distributions of Fig. 6. 

The thermal wind equation relates the appearance of the summer westward and winter eastward jets in the stratosphere to the temperatiue distribution, which is in turn a result of the latitudinal variation of heating due to absorption of ultraviolet radiation by ozone and large-scale motion of air parcels. 

We concentrate on the information obtained from infrared spectroscopy and radiometry, both directly and in conjunction with other data sets, such as those from visible imaging. To provide the necessary background for the subjects of this section, we first review the equations of fluid motion and the succession of approximations leading to a tractable set of equations that can be used to describe the motion of a planetary atmosphere. Eor most of the cases considered, geostrophic balance and the associated thermal wind equations play major diagnostic roles in the inference of atmospheric motions from remotely sensed temperatures. For this reason, the derivation of these relations will be discussed in some detail. Other... 

The geostrophic relations and the associated thermal wind equations can provide significant insight into the behavior of rotating atmospheres they are the lowest order approximation in a systematic development of large-scale atmospheric dynamics. In addition, these equations have been used to obtain information on atmospheric winds from remotely sensed measurements for many of the planetary atmospheres considered here. Therefore, we examine the geostrophic... 

We now relate the measured temperatures to the mean zonal wind. In this case it is not possible to use the geostrophic thermal wind equation (9.2.29) as an examination of Eq. (9.2.21) shows. The ratio of the second term to the first term in the brackets on the left side of the equation is of the order of the ratio of the 243-day planetary rotation period to the four-day atmospheric rotation period or 60 hence, the second term dominates. This suggests a first approximation ... 

Externally impo.seddisplacements. Externally caused movement of restraints wiU impose displacements on the piping in addition to those related to thermal effects. Such movements may result from causes such as wind sway or temperature changes in connected equipment. 

Thermal turbulence is turbulence induced by the stability of the atmosphere. When the Earth s surface is heated by the sun s radiation, the lower layer of the atmosphere tends to rise and thermal turbulence becomes greater, especially under conditions of light wind. On clear nights with wind, heat is radiated from the Earth s surface, resulting in the cooling of the ground and the air adjacent to it. This results in extreme stabihty of the atmosphere near the Earth s surface. Under these conditions, turbulence is at a minimum. Attempts to relate different measures of turbulence of the wind (or stability of the atmosphere) to atmospheric diffusion have been made for some time. The measurement of atmospheric stabihty by temperature-difference measurements on a tower is frequently ntihzed as an indirect measure of turbulence, particularly when climatological estimates of turbulence are desired. 

Oilfields in the North Sea provide some of the harshest environments for polymers, coupled with a requirement for reliability. Many environmental tests have therefore been performed to demonstrate the fitness-for-purpose of the materials and the products before they are put into service. Of recent examples [33-35], a complete test rig has been set up to test 250-300 mm diameter pipes, made of steel with a polypropylene jacket for thermal insulation and corrosion protection, with a design temperature of 140 °C, internal pressures of up to 50 MPa (500 bar) and a water depth of 350 m (external pressure 3.5 MPa or 35 bar). In the test rig the oil filled pipes are maintained at 140 °C in constantly renewed sea water at a pressure of 30 bar. Tests last for 3 years and after 2 years there have been no significant changes in melt flow index or mechanical properties. A separate programme was established for the selection of materials for the internal sheath of pipelines, whose purpose is to contain the oil and protect the main steel armour windings. Environmental ageing was performed first (immersion in oil, sea water and acid) and followed by mechanical tests as well as specialised tests (rapid gas decompression, methane permeability) related to the application. Creep was measured separately. 

Thermophysical Properties. Several investigators have focused their work on evaluation of the thermophysical properties of clothing assemblies and either related the results to mannequins or wear trials or discounted the need for such trials and elaborate models. Total thermal resistance of a clothed body to heat transfer from the body to surrounding air was considered to be the sum of three properties thermal resistance of the textile, thermal resistance to heat transfer at the textile surface, and thermal resistance of the air interlayer. Relationships between thermal resistance of clothing assemblies, air permeability, wind speed, and assembly thickness were also explored (5J). A method for calculating the effects of wind speed on thermal resistance of clothing claims to be as reliable as tests that use mannequins (58). 

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