NOAA Ocean Service Education banner



" "

Currents

 

How Are Currents Measured? 1 2 3 4 5 6

arrow back to previous page arrow forward to next page

High frequency radar antenna used to measure direction and speed of ocean surface currents.
 
This antenna uses high frequency radar to measure the direction and speed of ocean surface currents. Click on the image for a larger view.
image bar
 
HF Radar plot of ocean surface currents.
 
This plot of ocean surface currents was created using shore-based high frequency Radar. Click on the image for a larger view.
image bar

Shore-based Current Meters

Shore-based current meters employ radio antennas and high frequency (HF) Radio Detecting and Ranging systems (radar) to measure surface ocean currents. Following the same premise of the ADCP, these shore-based instruments use the Doppler effect to determine when currents are moving toward or away from the shore. If a wind-driven current is moving toward the shore, the return signal is at a high frequency. If the wind-driven current is moving away from shore, the return signal is at a low frequency. Scientists also use these measurements to determine the velocity of the current. When two or more radar antennas are used, a scientist can calculate an entire field of surface current velocities for thousands of points. Using this data, the scientist can produce a “map” of surface currents for a large coastal area.

 

 

 

 

 

 

 

Back to 1 2 3 4 5

arrow back to previous page  (top)  arrow forward to next page



 

" "