COMPARISON OF COASTAL CURRENTS FROM HF RADAR AND ADCP DATA OC3570 LCDR Kim, KC ROKN 16 SEP 2003

PURPOSE to examine the Horizontal Pattern of Shear observed on 1600-2400 July 21 to examine the Relationship of CODAR data with ADCP data to describe the Surface Current Circulation in Monterey Bay

Fundamental Issues on Naval OPS Littoral Ocean complicated coastline and complex bathymetry winds, waves, and currents interact with the boundaries on much smaller space and time scales Conventional measurement techniques are limited military operations in Littoral Ocean Mine OPS Amphibious OPS LOTS(Logistics over the Shore) OPS

HF RD Introduction Usage Measuring Currents to measure sfc current Vel fields near the coast to provide a higher resolution in space Measuring Currents Resonant Bragg Scattering: amplifies the scattered signal directed toward the reciever

Doppler Shift: how to calculate the surface currents When electromagnetic waves interact with a mobile surface, the surface velocity induces a shift  = 2 u/ c Simple situation: a current constant with depth travelling in the direction of wave propagation cw = cpw + U under the assumption U<<cpw cw = cpw + cw(k) : original frequency u: vel of the TGT c: speed of light c: wave’s apparent speed cp: wave’s phase speed U (z): horizontal current vel profile

Sample HF Doppler spectrum showing Bragg resonant peaks from approaching and receding waves.

DATA Collection *

DATA Collection(Cont’) B Time series on A and B A B

DATA Collection(Cont’) Data for Time series on A and B Total Data Points Missing Data Points Mean STD Time Gap U Vel. At HF RD 52 9 -0.57 cm/s 9.68 60 min V Vel. At HF RD -0.56 cm/s 9.5 U Vel. At 15m 104 0.57 cm/s 4.62 30 min U Vel. At 23m 1.22 cm/s 5.08 U Vel. At 31m 2.14 cm/s 4.81 V Vel. At 15m 1.56 cm/s 6.78 V Vel. At 23m 2.41 cm/s 5.61 V Vel. At 31m 2.91 cm/s 4.36

Bathymetry of the Canyon

LEG I

Depth: 15m Depth: 25m Depth: 75m Depth: 125m

Depth: 175m Depth: 225m Depth: 275m Depth: 325m

Time Series at the Head of Canyon

HF RD ADCP Depth: 15m ADCP Depth: 23m ADCP Depth: 31m

Total U Vel at 15m Total V Vel at 15m Corr.: 0.29 Corr.: 0.8163 Total U Vel at 23m Total V Vel at 23m Corr.: 0.2298 Corr.: 0.8215 Total U Vel at 31m Total V Vel at 31m Corr.: 0.0059 Corr.: 0.6770

UA Vel at 15m VA Vel at 15m Corr.: -0.2037 Corr.: 0.5853 UA Vel at 23m VA Vel at 23m Corr.: -0.3137 Corr.: 0.5750 UA Vel at 31m VA Vel at 31m Corr.: -0.5567 Corr.: 0.3816

UB Vel at 15m VB Vel at 15m Corr.: 0.9966 Corr.: 0.8351 UB Vel at 23m VB Vel at 23m Corr.: 0.8474 Corr.: 0.9069 UB Vel at 31m VB Vel at 31m Corr.: 0.6941 Corr.: 0.8164

260400

261800

270400

Possible Reason?

SFC Current Circulation In MTRY Bay(260300-270400)

SFC Current Circulation In MTRY Bay(270500-280600)

Conclusion U Velocity has Low correlation but V has High. More correlation on location B(Further off the coast) than A in both U and V component. Further experiment with a Longer Time series and more stations needed for the better understanding this process.

REFERENCES Special Issue on High Frequency Radars for Coastal Oceanography, Oceanography, Vol. 10, No.2 1997 Lorell A. Meadows, High Frequency Radar Measurements of Friction Velocity in the Marine Boundary Layer http://www.oc.nps.navy.mil/~icon/frames/hfradar_frame.html

QUESTION?