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How to Calculate Geostrophic Current

Geostrophic currents are flows of sea water that run along the gradient lines in a high pressure system. It is the result of the balance between the Coriolis force and the force of the pressure gradient. Most of the planet's major ocean currents are in fact geostrophic in nature. These currents can be considered flows that bend around hills or mountains. When the geostrophic current is calculated, it is assumed that you are calculating the speed and direction of the current.

Things You'll Need

Calculator
Latitude
Relative sea level
Distance between sea level measurements

Instructions

- 1
  Determine the Coriolis parameter for the latitude of the current. This is calculated using the equation f = 2*O*sin(phi) where O is a constant equal to 7.29 * 10 ^ -5 s ^ -1. For example, the Coriolis parameter for Boston, Massachusetts at latitude 42° N, is 2 * 7.29 * 10 ^-5 * sin(42) = -0.000133628842.
- 2
  Calculate the slope between the two sea level measurements. This is the difference in height divided by the horizontal distance between the two points. For example, the slope for two points with a height difference of 3 cm 1 km apart would be 0.03/1,000 = 0.00003.
- 3
  Divide the force of gravity by the Coriolis parameter, then multiply by the slope between the two points. So the geostrophic current at the two Boston points is therefore (9.8 / -0.0001336) * 0.00003 = 2.20 meters per second. The negative sign in front means the force is in the "downward" direction since it is in the northern hemisphere.

Nature