Investigation of First Order Line Settings for MARACOOS High Frequency Radars

Investigation of First Order Line Settings for MARAC OOS High Frequency Radars Investigation of First Order Line Settings for MARAC OOS High Frequency Radars Erick Rivera Erick Rivera 1 , Hugh Roarty , Hugh Roarty 1 , John Kerfoot , John Kerfoot 1 , Josh Kohut , Josh Kohut 1 , Mike Smith , Mike Smith 1 , Ethan Handel , Ethan Handel 1 , Colin Evans , Colin Evans 1 , Scott Glenn , Scott Glenn 1 , Belinda Lipa , Belinda Lipa 2 , Bruce Nyden , Bruce Nyden 2 , Hector Aguilar , Hector Aguilar 2 , Bill Rector , Bill Rector 2 1 Rutgers University Instit ute of Marine and Coastal Sciences, Rutgers University Instit ute of Marine and Coastal Sciences, 2 Codar Ocean Sensors, Inc. Codar Ocean Sensors, Inc. An An impor tant important requirement requi reme nt of of the the SeaSonde SeaSonde data data proce ssing processing softwa re sof twa re is is the the corre ct corr ect deline ation del ineati on of of the the fir st fir st ord er ord er Bra gg Bra gg reg ion region. Eff ect ive Effective first first order orde r delineation delineation can ca n be be ach iev ed ach iev ed usi ng u si ng a a combination combination of of CODAR CODAR recommendations reco mme ndati ons and and ca reful care ful exa minat ion ex aminatio n of of the the loca l loc al condit ions conditions influencing influe ncin g the the rela tive rela tive posit ions pos iti ons of of fi rst fir st and and second second orde r or der sea se a echo echo. . Using Using cross cross spec tra spec tra maps maps and and powe r powe r plots plots (Rang e (Rang e Slice s), Slices), appropriate appropriate boundaries bounda ries can ca n be be set, set, resul ting res ult ing in in th e the bes t best ove rall ove rall qualit y qualit y data data. . Th e The following following is is a a disc ussio n disc ussio n of of st eps , ste ps, examples examples and and recomme ndations recomme ndations to to help helpachieve achie ve the the proper proper First irst Order rder Line ine (FOL FOL) ) sett ings settings. 5 mHz systemshowing Second Order features 13 m Hz systemshowing Second Order features X(PEAK POWER) X/ FNULL x X/ FNULL The The MARACOOS MARACOOS regio n reg ion con sis ts consists of of fourteen fo urteen long lo ng range ra nge syst ems syst ems that that measure measure sea sea surf ac e surfa ce curre nts cur rents alo ng along the theMid Mid- -Atlantic Atlantic coast coast. In In thi s this post er post er we we have have ident ified ident ified four four doma ins doma ins that that show show different diff ere nt chara cter istic cha racteris tic in in first fi rst or der order region region. The The set tings settings were wereset set acco rding according to to visua l visua l inspe ctio ns inspe ctio ns in in Ran ge Range cell ce ll 3 3, 6 and and 11 11 and an d by by chan ging chan ging time time with with each each cross cross spectra spec tra file file Findings Findings It is critical to understand factors It is critical to understand factors affecting flow in the area sensed by each affecting flow in the area sensed by each individual radar when determing first order individual radar when determing first order line settings line settings The settings of FOL for each site differs The settings of FOL for each site differs along the Mid along the Mid- -Atlantic from north to south. Atlantic from north to south. We identified four different current We identified four different current regimes. For large networks, we found it regimes. For large networks, we found it helpful to analyze each site in dependently helpful to analyze each site in dependently to get high quality radials to get high quality radials Careful inspection of both power plots Careful inspection of both power plots and cross spectra maps significantly and cross spectra maps significantly increase the accuracy of Bragg peak increase the accuracy of Bragg peak delineation delineation Accurat e Bragg peak delineation is Accurat e Bragg peak delineation is achieve on 5 MHz systems without achieve on 5 MHz systems without looking for second order features (nulls) looking for second order features (nulls) Recognizing First and Second Order Features Determining First Order Line Settings Type of Site 5 MHz 13 MHz 25 MHz = Decide not to look for Null (Nsec= 0) = Decide to Look for Null (Nsec= 1) ± FromPeak Power down by Peak Drop off 20 ±25 dB 5 MHz 13 MHz 25 MHz ± FromPeak Power down to Peak Drop off 20 ±25 dB From peak Power down to Peak Null ~6 dB Sets the boundaries Finds the Null Sets the boundaries Dominant Features: Fast curre nts Strong tidal influence Dominant Features: Coastal shelf environme nt Some tidal influen ce SITE Signal Above Noise (Factor) Max Velocity (cm/s) Peak Dropp off (dB) Peak Drop off (Factor) NAUS 6 dB (3.98) 150 21 125.89 NANT 6 dB (3.98) 150 21 125.89 MVCO 6 dB (3.98) 150 21 125.89 BLCK 6 dB (3.98) 150 21 125.89 MRCH 6 dB (3.98) 150 20 100.0 HOOK 6 dB (3.98) 150 20 100.0 LOVE 6 dB (3.98) 150 20 100.0 BRIG 6 dB (3.98) 150 20 100.0 ASSA 7 dB (5.01) 150 21.8 151.36 CEDR 7 dB (5.01) 150 21.8 151.36 LISL 7 dB (5.01) 150 21.8 151.36 DUCK SITE DOWN HATY 7 dB (5.01) 250 26 398.11 Dominant Features: Coastal environment Fresh water discharge from two estuaries Dominant Features: Shelf/Coasta l environment Strong Western Boun dary Current Introduction Identify Ide ntif y the the typ e type of of frequency fre quenc y that tha t radar radar will wil l be be oper ating oper atingat at Decide Decide to to lo ok lo ok or or not not to to look look for for null nullto to set set the the bounda rie s boundaries surrounding su rr ou n di ng Fi rs t First Order Orde r Lines Lines Figu re sho ws the boundaries between Fir st Ord er (shaded dar k) and Seco nd Or der (shaded li ght). Our pr imary object ive is to ide nt if y t he bo unda ri es surr ou nd in g th e fi rst or de r re gi on (dar k blue ) fo r ea ch spec tr a. The se boundaries ar e based on the inter action of the ra dar withthe oce an wav es. Since Since the the lower lower freque ncy freque ncy syste ms systems hav e have grea ter greate r separa tion separa tion between between the the fir st fir st and and second second order order peaks peaks (abov e), (abov e), settin gs set tings for fo ra 5 MHz MHz system system DO DO NOT NOT look lookfor for nul ls nulls. The The bound aries bound aries are are identif ied identif ied with wit h the the Pea k Pea k Drop Drop off of f (F (F DOWN DOWN ) ) fro m fromthe thepeak peak power power. Since Si nce the the hi gher higher freq uency freq uency systems systems typica lly typica lly have have less less separation separation between bet wee n the the fir st fir st and and sec ond secon d order order region s, region s, setting s set ting s for fo r a 13 13 & & 25 25 MHz MHz system system DO DO look look for for null s nulls. The The algor ithm algor ithm looks looks for for nul ls nul ls from fro m the the Peak Peak Power Power down down by by the the Pea k Pea k Nul l Null (F (F NULL NULL ) to to constr ain const rain the the bounda ries bounda ries of of th e the first first order order regi on region. If If no no null s nul ls are are found, found, it it will will go go down down by by Pea k Pea k Drop Drop off off (F (F DOWN DOWN ) When When lookin g lookin g for for nul ls nul ls it itis is IMPORTANT IMPORTANT , that that Peak PeakNull Nul l (F (F NULL NULL ) < < Peak Peak Drop Drop off of f (F (F DOWN DOWN )

Investigation of First Order Line Settings for MARACOOS High Frequency Radars

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