Atmospheric Pressure Changes: The Importance of Deviations from the Balanced (Gradient) Wind

1948 ◽  
Vol 1 (1) ◽  
pp. 41
Author(s):  
CHB Priestley
Keyword(s):  
Surface Pressure ◽  
Pressure Rise ◽  
Vertical Motion ◽  
Surface Friction ◽  
Pressure System ◽  
Gradient Wind ◽  
Horizontal Acceleration ◽  
Cold Pools ◽  
Pressure Changes ◽  
Effect Of Surface

The paper comprises a discussion of the effect of deviations from the instantaneously balanced, or gradient, wind on the translation and development of the surface pressure field. The deviation is shown to consist primarily of two components, which are associated respectively with vertical motion and horizontal acceleration in the air trajectory. With certain types of pressure system, the first of the above components makes a contribution towards translation of the system. But its major role is in maintenance of the system against the dissipating effect of surface friction. The part played by this component in the intensification of anticyclones, end the formation of secondary depressions and cold pools is discussed : in particular, these common types of development are linked with vertical motion at the tropopause and in the stratosphere. The level just below the tropopause is shown to be crucial in the study of anticyclogenesis. The collapse of an anticyclone under excessive surface heating, the formation of "heat lows", and the pressure rise associated with convectional squalls are also attributed to this deviation. By means of the deviation associated with horizontal acceleration, the changes in pressure force experienced by a moving element give rise to compensating flows which restrict any rapid local changes in surface pressure. In conjunction with the control exercised by the balanced wind(l), this accounts for the remarkable conservatism of surface pressure in face of the large convergence or divergence which atmospheriic motion appears to imply. Apart from its controlling influence, the contribution from the horizontal acceleration increases with increasing asymmetry of the system. The eastward thrust of sharp ridges of high pressure is attributable to this deviation.

The Relation of Isallobaric Wind Components to the Change of Pressure over a Given Locality*

1941 ◽  
Vol 22 (3) ◽  
pp. 117-120
Author(s):  
I. Gringorten
Keyword(s):  
Practical Importance ◽  
Surface Friction ◽  
Pressure Change ◽  
Theoretical Treatment ◽  
Wind Component ◽  
Small Departure ◽  
Gradient Wind ◽  
The Right ◽  
Pressure Changes ◽  
Good Agreement

Non-Technical Summary Why cyclones deepen and fill up is one of the fundamental problems in meteorology that still largely resists theoretical treatment; but it is a matter of great practical importance because it does not seem that our daily forecasts will improve greatly until we find quantitative expressions for the factors leading to development as well as mere translation of pressure systems. Mr. Gringorten in this paper follows up a line of attack already laid down by several European investigators to see how well it may agree with reality. While he does not offer us a new principle the result is very interesting because he shows that the familiar conception of the isallobaric wind component, i.e. the small departure of the wind from the “gradient wind” which follows the isobars (except with surface friction), must play an important role in the pressure changes observed on the weather maps or the barograms every day. Qualitatively we have believed this for some time but Mr. Gringorten has computed the expected pressure change, from formulae proposed by Bjerknes and by Sutcliffe, for a particular time and place. This case was for the layers between 2000 and 8000 feet above Detroit between 7:30 p.m. Feb. 2 and 7:30 p.m. Feb. 3, 1940. The computed pressure change at 2000 feet was at the rate of 22.8 millibars in 12 hours but the observed change was only 5 mb. The practical meteorologist will not regard this as very good agreement but in view of the great difficulties in the theoretical treatment of such a problem the theoretician finds some consolation in that at least the computation gives results in the right direction. Of course, as Mr. Gringorten points out, it was obvious on Feb. 3 from the A. M. weather map that the pressure would fall at Detroit by that evening, and no one would suggest that the theory be used for forecasting.—R. G. S.

Full 3-D Unsteady Numerical Simulation of Control Stage in Partial Admission Turbine

2015 ◽  
Vol 741 ◽  
pp. 509-512
Author(s):  
Guo Ping Li ◽  
Ke Ke Gao ◽  
Ke Yang ◽  
Yong Hui Xie
Keyword(s):  
Numerical Simulation ◽  
Surface Pressure ◽  
Flow Parameters ◽  
Control Stage ◽  
Air Turbine ◽  
Unsteady Surface Pressure ◽  
Partial Admission ◽  
Unsteady Numerical Simulation ◽  
Pressure Changes ◽  
Mixing Losses

The unsteady flow parameters in control stage of partial admission are analyzed in details with full 3-D numerical simulation. The full annulus structure of air turbine in partial admission is modeled due to the unsymmetrical geometry. The partial admission is accomplished through the inlet blocked using segmental arc. The unsteady surface pressure changes of eight blades in the transition regions which demonstrate the power output ability are presented. That the entropy rise associated with the losses at different cross mainly caused by mixing losses and flow separation in partial admission is analyzed to estimate the efficiency distribution.

Pressure Changes And “Tornadoes” (Squalls) On the West Coast Of Africa*

1943 ◽  
Vol 24 (8) ◽  
pp. 311-317 ◽  
Author(s):  
H. Regula
Keyword(s):  
West Coast ◽  
Pressure Rise ◽  
The Other ◽  
The West ◽  
Minimum Pressure ◽  
First Case ◽  
Pressure Changes ◽  
Pressure Fall

SYNOPSIS Forecasting the weather on the west coast of Africa is made difficult by the inaccurate pressure reports of ships at sea and of land stations whose elevation are not definitely known. However, from reliable reports of coastal stations a relation between pressure changes and wind variations is demonstrated, (see fig. 2–4). In each example a 24–48 hour pressure fall with onshore winds all along the coast was followed by a 24–48 hour pressure rise with off-shore winds. Two examples of pressure variations on a ship's barogram when a “tornado” occurred are given in fig. 5–6. Each diagram shows a falling pressure tendency followed by a rising tendency, with the “tornado” at the minimum pressure in the first case and 10 hours after the minimum in the second case. Evidently whenever these tendencies are observed together thunderstorms should be forecasted. This is born out for the statistics July to October 1934 which show 15 thunderstorms on the 22 days when the pressure was rapidly rising, and only 10 thunderstorms for the other 61 days!

S1304-1-6 Effect of surface friction on wedging characteristics of polycarbonatesheets

2009 ◽  
Vol 2009.4 (0) ◽  
pp. 299-300
Author(s):  
Takuya TAKAHASHI ◽  
Shigeru NAGASAWA ◽  
Yasushi FUKUZAWA
Keyword(s):  
Surface Friction ◽  
Effect Of Surface
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