PHYS OCE- Geostrophic Motion- Lecture 11

what is geostrophic currents

steady state flow when coriolis term is balanced by pressure gradient term

what are the assumptions for geostrophic currents

earth’s rotation is important (small Ro), friction is not important, steady state solution (neglect time dependent terms)

what is the formula for rossby number

nonlinear terms/ coriolis terms = U/fL

what is geostrophic balance

coriolis force and pressure gradients are in balance, steady solutions (no change with time), solutions can only be found if pressure is known

what are assumptions for geostrophic flow

ocean currents are horizontal only, small rossby number, neglect wind stress and friction

what are the two types of pressure gradients

sea level difference and density difference (or both)

what is cyclonic circulation

anti-clockwise around low pressure

what is anticyclonic circulation

clockwise around high pressure

what is an example of cyclonic circulation in atlantic, pacific, and indian ocean

hurricane in atl, typhoon in pacific, and cyclone in indian

where does high pressure flow in northern hemisphere

to the right

where does high pressure flow in southern hemisphere

to the left

what can be used to estimate surface currents

ocean surface topography from models and satellite altimetry

what is the equation for surface velocity

v = g/f(dh/dx)

what does baroclinic flow depend on

velocity changes with depth

what is the equatorial undercurrent

trapped currents near equator caused by coriolis

what is barotropic flow

flow where pressure depends on density only, horizontal

what is baroclinic flow

flow when surfaces of constant pressure (isobars) and surfaces of constant density (isopycnal) intersect or are misaligned

formula for barotropic flow

fv = 1/density (∂p/∂x)

formula for baroclinic flow

fu = -1/density (∂p/∂x)

what is g’

reduced gravity parameter, for stratified fluid

what is the formula for the isopycnal slope

i2 = - (density1)/(density2-density1)x i1

what is barotropic fluid

lines of constant density are paralle to lines of constant pressure

how to calculate geostrophic currents from observation

ctd measure S, T profiles at 2 points, calculate density at both, calculate pressure at each depth, get geostrofic velocity

what extra steps do you need to calculate geostrophic currents from observations if it is baroclinic

level of no motion, measure surface slope, measure currents at some depth

what is the formula for geopotential distance

dΦ = -1/density (dp)

what is geopotential distance

distance between two isobaric surfaces