The plots below were created using 10 km grid and show a zoomed OUT view of the currents between Point Arena and Point Reyes. See high resolution plots for a zoomed IN view of currents from the Sonoma coast to Point Reyes.

Click on a thumbnail to view full sized plots:

Note:

• A white background in a CHL or SST plot indicates that no satellite data was available at the time the plot was generated.
• Due to satellite data latency, CHL plots are 3 days behind real time, SST plots 1 day behind.

Sea Surface Temperature data from NESDIS, Chlorophyll data from MODIS/Aqua, courtesy NOAA Coastwatch.

The plots below were created using 2 km grid and show a zoomed IN view of the currents between Point Reyes and the Sonoma coast. See low resolution plots for a zoomed OUT view of currents from Point Reyes to Point Arena.

Click on a thumbnail to view full sized plots:

 

Wind and current analysis reveal the timing and duration of upwelling events. The section plots below represent daily averaged offshore current conditions. Alongshore and cross-shore wind speed is displayed in the top of the plot. The cross-shore and alongshore surface current velocity and distance offshore over time are plotted in color.

Click on a thumbnail to view full sized plots:

SECTION PLOT DESCRIPTION

A “section plot” is a distance vs. time colored contour plot of the currents along a line extending seaward from the coast. The origin (zero kilometers) is at the coast, with increasing distance farther offshore.  Currents are rotated into “alongshore” and “cross-shore” directions (please refer to the image “key”, below, on this page).

The locations of the three lines used to generate the section plots are shown below. The “Bodega Line” is a line along which measurements are currently being made once a month. The “Point Reyes” line is shown here for convenience, to allow easy investigation of northward flow past the point.

The “alongshore” directions are defined as follows: 

CODE Line, 320 degrees
Bodega Line, 320 degrees
Point Reyes Line, 20 degrees

The choice of 20 degrees for the Point Reyes line is an effort to look at alongshore nearshore currents in more detail. It does not represent a true index of flow past the point for the far offshore currents. The plots tend to be similar regardless of minor changes in the specified rotation.

The winds from NDBC 46013 are rotated into along-coast and cross-coast as well, using 320 degrees.

KEY TO THE PLOTS

1. wind speed (m/s) in a given direction
2. dashed line = cross-shore (E+W-) wind direction
3. bold line = alongshore (N+S-) wind direction
4. cross-shore current velocity (cm/s)
5. alongshore current velocity (cm/s)
6. distance offshore (km)

High Frequency Radar: Sea Surface Current and Wave Sensors

Instrument Type: CODAR Ocean Sensors SeaSonde HF Radar System

Description: High-frequency (HF) radar uses radio-wave backscatter to map surface currents over wide swaths of the coastal ocean. These sensors are commonly referred to by the trade name "CODAR" (Coastal Ocean Dynamics Applications Radar) and take advantage of the propagation of radio waves over large distances out and back across the surface of the conducting sea water, and they have resonant interactions with ocean surface waves (i.e., the ones that can make people seasick). Back at the shoreline, a measurement of the frequency offset (i.e., Doppler shift) of the reflected radio waves provides a remotely sensed measurement of the speed of the ocean waves and surface currents.

Locations:

5 MHz - Bodega Marine Laboratory: 38° 19' 10.1" N 123° 4' 25.0" W - Installed: 2 February 2007
5 MHz - Point Arena: 38° 55' 42.4" N 123° 43' 40.0" W - Installed: 16 June 2007
12 MHz - Bodega Marine Laboratory: 38° 19' 2.3" N 123° 4' 20.9" W - Installed: May 2001
12 MHz - Point Reyes: 38° 2' 49.7" N 122° 59' 20.9" W - Installed: June 2001
12 MHz - Salt Point State Park: 38° 34' 0.5" N 123° 19' 53.7" W - Installed: 2002

12 MHz Specifications - Surface currents: Map spatial resolution: 2 x 2 km
Map temporal interval: hourly; currents averaged over one hour
Map area coverage: 65 km along shore x 30 km offshore, variable
Map vector accuracies: speed < 7 cm/s, direction < 10°

Specifications - Waves:

Target range: 3 km from coast around each radar
Significant wave height accuracy: 7 to 15%
Dominant on-shore direction accuracy: 5° to 12°
Dominant wave period accuracy: 0.6 s
Minimum detectable significant wave height: 1 m
Wave temporal interval: hourly; waves averaged over one hour

Specifications - Radiated signal:

Output radiated power: 80 watts peak, 40 watts average
Operating frequency range: 12-14 MHz

Matlab/HFR Progs Compatible QA/QC Scripts

BML HFR Progs Supplement: Matlab routines to calculate temporal and spatial statistics for HF radar data, and perform QA/QC on the data.

The statistics are described in the following paper: Quality Control of HF Radar Measurements: Temporal and “Nearest Neighbor” Spatial Statistics, by Chris Halle, submitted August 2008. Please reference the paper and/or acknowledge this website if using these routines or statistics.

TO DOWNLOAD: PC: right click on file name > save target as…
Mac: option click on file name to download…

SampleStatsScripts.zip: Scripts that calculate the statistics and qa/qc the radials and totals.  Script names generally follow the naming convention:  (1) scripts starting with “Get” – calculate the statistics, (2) script starting with “Clean” – qa/qc the radials or totals using the previously calculated statistics and user-specified totals, and (3) scripts starting with “Inv” – use the previously calculates stats and allow the user to interactively investigate the effects of setting different screening levels for the statistics.

SampleDrivingScripts.zip: Samples of scripts that call the stats routines in the folder SampleStatsScripts.

SampleUsefulScripts.zip: Miscellaneous useful scripts.

Current Rose Routines for HFR Data (HFRosePlotRoutines.zip): Prompt driven routines that allow the user to specify the date search range, etc, and generate plots similar to this sample plot.

Driving routines to begin with:

Radial QA/QC:

• GenericGetRadialStats  (can run GenericPlotRadialStats to plot the stats up)
• GenericFirstOrderCleanRadials
• GenericSecOrderRadialStatsClean

Totals QA/QC:

• GenericLRTotalsPartA(unfinished)
• Subsequent routines to be included

Stats Summaries:

• SummaryOfRadialCleaning.m contains parameters to clean radials
• SummaryOfTotalCleaning.m contains parameters to clean totals

Questions, comments or suggestions can be directed to the author, Chris Halle.

HFR_Progs Matlab Toolbox

High Frequency Radar Sea Surface Current Data

• For data requests please contact bmldata@ucdavis.edu, and see the data disclaimer and terms of use.
• Oceanography, Surface Currents, Matlab Scripts: Chris Halle, John Largier
• Radar Operation, Maintenance, Website: Deedee Shideler
• Radar Operation, Maintenance, Progamming: Marcel Losekoot