For a mass of air, the geostrophic pressure gradient is given by: dP/dr = 2 omeg

Question

For a mass of air, the geostrophic pressure gradient is given by: dP/dr = 2 omega v rho sin beta Define the symbols in the equation above. Vanuatu is a collection of small islands surrounded by the ocean. Cyclone Pam was forecast to hit Port Vila in Vanuatu (17.75 degree S, 168.3 degree E) on 13 March 2015. The forecast pressure changes were from 895 hPa at the centre of the cyclone to 921 hPa over a distance of 700 km. Calculate the forecast geostrophic wind speed in kilometres per hour. How would the forecast geostropic wind velocity differ if the same pressure gradient was located at 48 degree S?

Explanation / Answer

a) here w= angular velocity of spinning system .

In sin B , B is latitude

v is horizontal velocity

And p is air density

and do/Dr is pressure gradient, which is change in pressure with distance.

(b) here change in pressure= 921-895=26 h Pa

Distance =700km

Hence dp/dr =26/700 hpa/km

Here B = 17.75°

Putting the value of air density and w,

Putting all values in the equation of part(a) we will get the wind speed.

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