Gradient wind

Fig. 17 12. Balance of forces resulting in gradient wind around low pressure.

Fig. 17-13. Balance of forces resulting in gradient wind around high pressure. Note that the wind speed is greater for a given pressure gradient force than that around low pressure.

In the friction layer where the isobars are curved, the effect of frictional drag is added to the forces discussed under gradient wind. The balance of the pressure gradient force, the coriolis deviating force, the centrifugal force, and the frictional drag in the vicinity of the curved isobars results in wind flow around low pressure and high pressure in the Northern Hemisphere, as shown in Fig. 17-16. 

Fig. 17-16. Effect of friction upon gradient wind around low (left) and high (right) pres-...

This specific coastal wind system develops in dependence on the temperature difference between water and land, and the gradient wind between the highs and lows at the ground (Loth, 1988). 

On an average, the land and sea breeze system of the Baltic Sea is up to 200 m high, extends about 300 m toward the Baltic Sea and about 500 m into the hinterland. During the high pressure weather periods in May and June, when the Baltic Sea water is still relatively cold, the sea breeze system of the Baltic Sea is formed most intensively. If in such cases onshore gradient wind exists under certain weather conditions, it is significantly... 

Another sea breeze feature is that an existing weak and coast-parallel gradient wind is strengthened by the sea breeze during the day in the direct coastal seam only, and occasionally turns somewhat toward the Baltic Sea. Over the open Baltic Sea, however, the weak wind situation persists. 

Certain high pressure weather conditions with strong offshore breeze suppress the sea breeze formation. So it happens if, for example, at the southern Baltic Sea coast with southeast weather conditions, a strong gradient wind overcompensates the local sea breeze system. A strong directional gustiness and a change of the coastal wind speed results frequently from the counteraction of the two wind systems. 

At the Warnemiinde coast, this strengthened northwest wind arises preferably if at cyclonic northwest weather conditions the gradient wind is blowing continuously strongly and from northwest for a longer period of time. At the Warnemunde coast it is often particularly strongly pronounced because it receives an additional thermal wind reinforcement there under certain convective weather conditions due to ascending air over the inhabited cities (thermal lift). 

Gradient wind Horizontal wind in which the Coriolis... 

ATMOSPHERIC MESOSCALE SYSTEMS are identified as those in which the instantaneous pressure field can be determined accurately by the temperature field, but the winds, even in the absence of surface frictional effects, are out of balance with the horizontal pressure gradient force. The pressure field under this situation is said to be hydrostatic. Larger scale atmospherie features, in eontrast, have a wind field that is close to a balance with the horizontal pressure gradient force. These large-scale winds are said to be near gradient wind balance. ... 

Gradient wind Wind resulting from a balance between the horizontal components of the pressure gradient, Coriolis, and centrifugal forces. 

The gradient wind can be obtained if these equations are rewritten in polar coordinates (r, (p), where r = and (p = tan (y/x). Defining tangential and radial velocities Ur and Wp, respectively, the polar coordinate form of Eq. (54) is... 

The wind Fgr satisfying this equation is called the gradient wind. Although the flow is steady, it is curved and hence there is a centripetal acceleratioa This acceleration is measured by the term V /r and may be considered to define a centrifugal force per unit mass. Therefore, the gradient wind may be seen as a balance between centrifugal, Coriolis, and pressure gradierrt forces. 

Thus, the geostrophic wind overestimates the gradient wind for cyclones (where there is cerrtral low pressure and Fgr > 0) arrd underestirrrates it for anticyclones (where there is cerrtral high pressure arrd < 0). 

As with the thermal wind, the gradient wind has many apphcations. One application is an explanation of why the pressure gradient is generally weaker near the center of an anticyclone than near the center of a cyclone. This can... 

For physically meaningM solutions the quantity under the square root must be positive. Now for anticyclones dp I dr < 0 so that for a realizable gradient wind... 

For cyclones, dp/dr > 0,andthe quantity underthe square root is always positive, so that gradient wind balance places no restriction on the pressure gradient at the center of a cyclone. 

Coherence evolution in the presence of a field gradient winds the transverse magnetization up along the gradient direction in the form of a helix of pitch 2nl yG5). The periodicity imphed in this helix may be characterized... 

---