Mapping Coastal Surface Winds in Monterey Bay Using High Frequency Radar
Mapping Coastal Surface Winds in Monterey Bay Using High Frequency Radar

Author: Raymond R. Delgado, III

Publisher:

Published: 1999-03-01

Total Pages: 134

ISBN-13: 9781423545019

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Over-water wind directions derived from high frequency (HF) radar - the new Multi-frequency Coastal Radar (MCR) - are compared to in-situ observations to determine the skill of the radar measurements. Conventional beam processing of data collected from two MCR sites located around Monterey Bay during summer 1997 is used to create wind directions based on the relative strength of the positive and negative Bragg-resonant peaks, which correspond to the wind-driven waves approaching and receding from the radar, respectively. Based on a selected functional relationship that converts the radar signal to wind direction, radar-derived wind directions are created using a new wind- retrieval algorithm and are compared to mooring observations under a variety of wind conditions. Analysis indicates that the signal not only follows wind direction, but also strongly correlates to the wind speed measured at the mooring. Results show that many of the Bragg peaks are close to the noise level, and consequently, low signal-to-noise ratios restrict the statistical confidence of the measurements. Nonetheless, maps of radar-derived wind directions show good agreement with in situ observations, especially when the wind speed is relatively strong and is sustained for long duration.

Mapping Coastal Surface Winds in Monterey Bay Using High Frequency Radar
Mapping Coastal Surface Winds in Monterey Bay Using High Frequency Radar

Author: Raymond R. Delgado

Publisher:

Published: 1999

Total Pages: 134

ISBN-13:

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Over-water wind directions derived from high frequency (HF) radar - the new Multi-frequency Coastal Radar (MCR) - are compared to in-situ observations to determine the skill of the radar measurements. Conventional beam processing of data collected from two MCR sites located around Monterey Bay during summer 1997 is used to create wind directions based on the relative strength of the positive and negative Bragg-resonant peaks, which correspond to the wind-driven waves approaching and receding from the radar, respectively. Based on a selected functional relationship that converts the radar signal to wind direction, radar-derived wind directions are created using a new wind-retrieval algorithm and are compared to mooring observations under a variety of wind conditions. Analysis indicates that the signal not only follows wind direction, but also strongly correlates to the wind speed measured at the mooring. Results show that many of the Bragg peaks are close to the noise level, and consequently, low signal-to-noise ratios restrict the statistical confidence of the measurements. Nonetheless, maps of radar-derived wind directions show good agreement with in situ observations, especially when the wind speed is relatively strong and is sustained for long duration.

An Investigation of Surface Current Patterns Related to Upwelling in Monterey Bay, Using High Frequency Radar
An Investigation of Surface Current Patterns Related to Upwelling in Monterey Bay, Using High Frequency Radar

Author: Andres Enriquez

Publisher:

Published: 2004-06-01

Total Pages: 101

ISBN-13: 9781423518105

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High Frequency (HF) radar backscatter instruments are under development and testing in the marine science and defense science communities for their abilities to remotely sense surface parameters in the coastal ocean over large areas. In the Navy context, the systems provide real-time mapping of ocean surface currents and waves critical to characterization and forecasting of the battlespace environment. In this study, HF radar, aircraft and satellite information were used to investigate and describe surface current in Monterey Bay, California, for a period of ten months, from June 1, 2003 to March 31, 2004. A network of five CODAR-type HF radar instruments measured hourly surface currents over the bay. The measurements were averaged over one-hour intervals and total surface velocities were mapped on a grid in the Monterey Bay. Major upwelling events were observed during the period of June 14 to June 27, July 4 to July 19, August 8 to August 18 and other upwelling events were observed until late October. These periods of upwelling favorable winds are common during summer with durations of 10 to 20 days. Cyclonic circulation cells are developed on shore during upwelling conditions and an anticyclonic circulation in the middle of the bay is observed when the wind shifts to the southwest producing a strong flow out of the bay close to the coastline off Point Pi os. Downwelling conditions are much less common than upwelling, with occurrences during winter and early fall storms with events lasting between two to five days. When the wind blows to the northeast with an intensity of 4 m/s or more for more than 12 hours, a well developed anticyclonic gyre forms in the middle of the bay. This is associated with a strong current, 35 to 40 cm/s, which flushes out in the southern part of the bay close to the coast off Point Pi os. This flow reverses when the winds veer to the southwest and enter into the Bay with less intensity.

Evolution of Diurnal Surface Winds and Surface Currents for Monterey Bay
Evolution of Diurnal Surface Winds and Surface Currents for Monterey Bay

Author: Michael D. Foster

Publisher:

Published: 1993

Total Pages: 114

ISBN-13:

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The diurnal-period fluctuations of winds and surface currents are analyzed for September 1992 in and around Monterey Bay. Wind records are compared for three coastal stations and two mooring sites. Remotely-sensed surface current observations from two CODAR (HF radar) sites are used to explore the ocean's response to diurnal-period forcing. An average diurnal cycle is formed at each wind station and at all CODAR bins. The earliest sea breeze response is seen at the coastal wind stations where morning winds accelerate toward the coastal mountain ranges. A few hours later, the coastal winds accelerate to the southeast down the Salinas Valley. Offshore afternoon winds rotate from their normal alongshore orientation to also become aligned with the valley. The CODAR-derived surface currents respond in less than the two-hour sampling rate to the onset of the diurnal onshore winds. Currents accelerate in the direction of the Salinas Valley. As the day progresses, the more offshore currents rotate clockwise out from under the winds in a possible Ekman or inertial adjustment that continues throughout the night and spreads onshore. In the afternoon, a complicated eddy pattern develops near shore in a possible response to the coastal boundary.

Oceanography - High Frequency Radar and Ocean Thin Layers, Volume 10
Oceanography - High Frequency Radar and Ocean Thin Layers, Volume 10

Author: Larry Atkinson

Publisher:

Published: 1999

Total Pages: 77

ISBN-13:

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Partial contents include: (1) HF Radar Instruments, Past to Present; (2) Mapping Surface Currents in Monterey Bay with CODAR-type HF Radar; (3) The Coastal Jet: Observations of Surface Currents over the Oregon Continental Shelf from HF Radar; (4) Tidal and Wind-driven Currents from OSCR; (5) Larval Transport and Coastal Upwelling: an Application of HF Radar in Ecological Research; (6) Evolution of Bearing Determination in HF Current Mapping Radars; (7) Shipboard Deployment of a VHF OSCR System for Measuring Offshore Currents; and (8) Experience with Shipborne Measurements of Surface Current Fields by Radar.

Characterization of OSCR HF Radar Data in Monterey Bay
Characterization of OSCR HF Radar Data in Monterey Bay

Author: Kimberley F. Boyer

Publisher:

Published: 1997

Total Pages: 108

ISBN-13:

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A 53-hour long record of surface current data from the OSCR HF radar system was gathered over Monterey Bay on 6-8 May, 1995. In this study, OSCR data is evaluated with regard to semi-diurnal (M2) and diurnal (K1) tidal period fluctuations, the seabreeze, seabreeze influenced flow, and both standard and cannonical-day mean flow patterns. The OSCR data is considered on its own and in comparison to similar data types previously gathered by CODAR, a previously established Monterey Bay HF radar system. Two of three CODAR sites were co- located with the two OSCR sites. Internal wave influence is observed in the M2 tidal constituent analysis and the seabreeze greatly influences fluctuations of the K1 tidal period. Results from analysis of OSCR data replicated or reinforced data and results from the CODAR system. Initial OSCR data appears not to have been significantly affected by possible distortion of the phased-array beam patterns. However, contamination of OSCR returns by simultaneous activation of the CODAR systems is apparent in the data.

Using Multifrequency HF Radar to Estimate Ocean Wind Fields
Using Multifrequency HF Radar to Estimate Ocean Wind Fields

Author:

Publisher:

Published: 2005

Total Pages: 5

ISBN-13:

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As indicated by growing deployments world wide, HF radar is an increasingly important tool for mapping coastal surface currents. It has been used to determine wind direction. We report further on the ability of multifrequency HF radar to measure the vector wind field and the impact that such measurements have on the measurement of wind fields over coastal land and sea. In this study, we use a year-long 2000-2001 data set collected over Monterey Bay, California. Our Multifrequency Coastal Radars (MCRs) operated at 4.8, 6.8, 13.4 and 21.8 MHz, measuring currents at effective depths of about 2.5, 1.8, 0.9 and 0.6 m respectively. For training and validation we use the M-1 buoy deployed by Francisco Chavez at the Monterey Bay Aquarium Research Institute. Validation results over the year time span indicate standard errors of prediction of 1.7 m/s for wind speed and 25 for direction with biases of 0.1 m/s and 0.3 respectively. We discuss limitations of this technique at low wind speeds. Finally, we present a regional wind field assimilating HF radar estimates and demonstrate the beneficial impact of multifrequency HF radar, wind field measurements, on estimation of the coastal wind field over both land and sea.

Climatology and Analysis of the Monterey Bay Sea Breeze
Climatology and Analysis of the Monterey Bay Sea Breeze

Author: Robert D. Round

Publisher:

Published: 1993

Total Pages: 126

ISBN-13:

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Sea breeze events on the Monterey Bay are examined from a single station at the mouth of the Salinas Valley. Data analyzed are continuous, two- minute meteorological samples of windspeed, wind direction, temperature, dew point, incoming shortwave irradiance, and incoming longwave irradiance. A speed index is defined using the average hourly maximum and minimum windspeeds oriented in the cross-shore direction thereby reflecting the thermally induced diurnal windspeed enhancement. Large-scale effects on this mesoscale circulation are presented through evaluation of changes in boundary layer depth with changes in speed index. Changes in boundary layer depth as reflected in trends of inland stratus penetration and offshore flow provide insight for anticipating sea breeze intensity.

Validation of High Frequency Radar Used in Ocean Surface Current Mapping Via In-situ Drifting Buoys
Validation of High Frequency Radar Used in Ocean Surface Current Mapping Via In-situ Drifting Buoys

Author:

Publisher:

Published: 2008

Total Pages: 110

ISBN-13:

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High frequency (HF) radar and its application to mapping ocean surface currents is a relatively new field of study in oceanography. Nevertheless, this scientific field produces real, tangible, accurate real-time results readily available to the military operational planner. The information gained through this process aids in the planning and execution of littoral operations via the development of the battle-space environment. Additionally, commercial use of this information can aide in the containment of coastal oil spills, efforts in search and rescue, and the execution of coastal engineering projects. Indeed, the utilization of High Frequency radar in the ocean environment has many beneficial qualities used by a wide variety of organizations. This study focuses on the validation aspects of High Frequency radar through the use of four drifters placed in-situ from 23-27 January 2008 on the Central California Coast from Monterey to San Francisco. A second experiment was conducted from 01-10 April 2008 involving 32 drifters placed west of the San Francisco Bay. Various statistical comparisons of radial current velocity data from 12 CODAR (Coastal Ocean Dynamics Application Radar) stations to the radial velocity data of each of the drifters will be analyzed.

Synoptic-scale Influence on the Monterey Bay Sea-breeze
Synoptic-scale Influence on the Monterey Bay Sea-breeze

Author: Michael Charles Knapp

Publisher:

Published: 1994

Total Pages: 112

ISBN-13:

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The diurnal fluctuations of the surface ambient wind associated with the sea-breeze are analyzed for the period May 01 through September 30, 1993 from a single station, Monterey airport, located on the southern Monterey Bay coast. Data analyzed included time series of wind speed, wind direction, clouds, precipitation and locally generated 3 hourly surface pressure analyses of California and the Pacific northwest. The characteristics of the sea-breeze circulation under varying synoptic-scale patterns are evaluated to determine the modifying roles of boundary layer stability, surface inversion strength, and low-level cloud amount on the resultant time of onset and peak intensity of the Monterey Bay sea-breeze. The primary modifying factor under all synoptic-scale pressure patterns was the boundary layer depth and stability with the differential heating taking longer to destabilize the boundary layer during the Trough regime.