In Situ Measurements of Surface Gravity Waves in Typhoon Conditions
1
IN SITU MEASUREMENTS OF SURFACE GRAVITY WAVES IN TYPHOON CONDITIONS Clarence O. Collins III 1 , Hans C. Graber 1 , William M. Drennan 1 , Neil J. Williams 1 , Rafael J. Ramos 1 , Bjoern Lund 1 , and Eric J. Terrill 2 1)Rosenstiel School of Marine and Atmospheric Science (RSMAS), University of Miami 2) Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Drive, La Jolla CA, 92093 INTRODUCTION The Impact of Typhoons on the Ocean in the Pacific (ITOP) field campaign took place in late 2010 within the Philippine Sea approximately 740 km east of southern Taiwan. ITOP included the measurements made by moored buoys, drifters, gliders, air craft, satellite, and research vessels. Directional wave spectra and integral wave parameters were derived from data recorded by several of these platforms. The platforms include 3 drifting miniature wave buoys (MWB), the X-band nautical radar (WaMoS) on the R/V Roger Revelle, Jason-1 (Ku and C band) and Jason-2 (Ku band) satellite altimeters, and two mooring sites. Each mooring site included a buoy with a 6m NOMAD type hull called EASI (Extreme Air Sea Interaction) [Drennan and Williams 2008] which was moored to the bottom, and an ASIS (Air-Sea Interaction Spar) buoy [Graber et al. 2000] tethered to the EASI by a 60 m cable. The moorings operated continuously for approximately 4 months and endured the relatively close passages of 4 major tropical cyclones: Typhoon Dianmu (~ year day 220), Typhoon Fanapi (~ year day 260), Super Typhoon Megi (~year day 290), and Typhoon Chaba (~year day 300). Clarence O. Collins III, RSMAS-AMP, 4600 Rickenbacker Cswy, Miami FL 33149 USA Phone: +1 305 421 4282, Fax: +1 305 421 4701, E-Mail: [email protected] This work has been funded by the U.S. Office of Naval Research under grant N00014-08-1- 0581 REFERENCES • Drennan, W. M. and Williams, N. J. (2008): An Air Sea Interaction Buoy for High Winds, NSF Report NSF-OCE-0526442, p. 8. • Graber, H. C., Terray, E. A., Donelan, M. A., Drennan, W. M., Van Leer, J. C., and Peters, D. B. (2000): ASIS – A New Air-Sea Interaction Spar Buoy: Design and Performance at Sea, Journal of Atmospheric and Oceanic Technology, 17, pp. 708-720. • Longuet-Higgins, M. S., Cartwright, D. E., & Smith, N. D. (1963): Observations of the directional spectrum of sea waves using the motions of a floating buoy. Ocean Wave Spectra, pp. 111-136 FOR MORE INFO PLEASE SEE THE FOLLOWING POSTERS: •Williams et al -AIR-SEA MEASUREMENTS FROM MOORED SURFACE BUOYS IN THE PACIFIC DURING THE 2010 TYPHOON SEASON (session 091, PosterID: B1904 20 Feb 2012 1700-1800) •Ramos et al – WIND MEASUREMENTS FROM ASIS AND EASI BUOYS DURING THE ITOP EXPERIMENT (session 022, PosterID: B1819 23 Feb 2012 17:00-18:00) •Potter et al – UPPER OCEAN RESPONSE TO TYPHOONS DURING THE 2010 SEASON (session 022, PosterID: B1820 23 Feb 2012 17:00-18:00) •Lund et al – WIND AND WAVE RETRIEVAL FROM MARINE X-BAND RADAR DATA UNDER TYPHOON CONDITIONS (session 022, PosterID: B1821 23 Feb 2012 17:00-18:00) •Romeiser et al – AN EMPIRICAL ALGORITHM FOR OCEAN WAVE RETRIEVALS FROM SCANSAR IMAGES UNDER TYPHOON CONDITIONS (session 175, PosterID: B1494 23 Feb 2012 17:00-18:00) SPATIAL SEPERATION The northern mooring (EASI N and ASIS N) was located at 21.23 o N, 126.96 o E at a depth of 5,608 m, and the southern mooring (EASI S and ASIS S) was located at 19.63 o N, 127.25 o E at a depth of 5,512m. The distance between moorings was approximately 180 km. For this study, the area is split into 2 zones, referred to as North Zone (NZ) and South Zone (SZ), formed by 100km radii centered at each EASI buoy. The two zones are plotted below with the MWBs’ drift track, the R.V. Roger Revelle’s ship track, and the satellite altimeters’ points of closest approach associated with different passes. This is a relatively large zone for wave comparisons, but preliminary NORTH ZONE TIME SERIES SOUTH ZONE TIME SERIES Wave Sensors Mean Distance [km] EASI N – ASIS N < .1 EASI N – MWB 42 49 EASI N – MWB 43 57 EASI N – WaMoS 20 EASI N – Jason-1 79 EASI N – Jason-2 55 EASI S – ASIS S < .1 EASI S – MWB 41 60 EASI S – MWB 42 51 EASI S – MWB 43 23 EASI S – WaMoS 48 EASI S – Jason-1 67 EASI S – Jason-2 40 CONCLUSION Wave spectra, directional distributions, and integral wave parameters are reported from the 2010 ITOP experiment. The measurements of the 2 EASI buoys were compared and validated against other sensors within 100km, including 2 ASIS buoys, 3 MWBs, the WaMoS, and Jason-1 (Ku and C band) and Jason-2 (Ku band) satellite altimeters. The comparisons were very good for Hs and WD with few exceptions. The exceptions may be due to high spatial variability or the presence of multi-modal seas. The comparisons for Tp were not as good, but the poor agreement can be attributed to the innate sampling variability of the parameter and some (perhaps spurious) isolated points. The measurements are generally consistent and provide a unique look at surface gravity waves in Typhoon conditions. This work provides many avenues for future research. STATISTICAL COMPARISON AND VALIDATION II PEAK PERIOD Platform/Stat # pts slope int. [m] R bias [m] std [m] COV CI% CI%/b EASI N/ASIS N 2662 1.028 0.067 0.989 0.106 0.0952 0.06 66.8 92.4 EASI N/MWB 42 179 1.170 -0.038 0.968 0.121 0.1003 0.06 35.8 71.5 EASI N/MWB 43 197 1.032 0.134 0.918 0.166 0.0956 0.06 30.5 74.1 EASI N/Jason1 Ku 18 0.982 0.181 0.956 0.144 0.3855 NA NA NA EASI N/Jason1 C 18 1.064 0.120 0.955 0.251 0.3811 NA NA NA EASI N/Jason2 Ku 22 1.094 -0.030 0.978 0.131 0.1679 NA NA NA EASI S/ASIS S 5073 0.939 0.101 0.986 0.007 0.1214 0.06 88.7 89.3 EASI S/MWB 41 56 0.997 0.110 0.966 0.107 0.2006 0.06 41.1 67.9 EASI S/MWB 42 125 1.016 0.116 0.900 0.130 0.0811 0.06 32.8 76 EASI S/MWB 43 59 0.851 0.948 0.364 0.439 0.4020 0.06 44.1 69.5 EASI S/Jason1 Ku 9 1.175 -0.094 0.974 0.215 0.2960 NA NA NA EASI S/Jason1 C 9 1.240 -0.621 0.884 -1.117 0.5459 NA NA NA EASI S/Jason2 Ku 22 0.845 0.258 0.757 0.003 0.5280 NA NA NA Platform/Stat # pts slope int. [s] R bias [s] std [s] COV CI% CI%/b EASI N/ASIS N 1779 1.097 -0.981 0.539 -0.218 1.399 0.1 78.9 80.2 EASI N/MWB 42 179 0.765 1.932 0.537 -0.103 1.185 0.1 84.4 84.4 EASI N/MWB 43 197 0.801 1.076 0.450 -0.504 2.111 0.1 56.3 61.4 EASI N/WaMoS 150 2.284 -10.730 0.271 0.547 1.579 0.1 86.7 95.3 EASI S/ASIS S 3383 0.941 0.349 0.754 -0.137 1.338 0.1 80.8 81.1 EASI S/MWB 41 56 0.085 8.216 0.203 -0.458 2.336 0.1 91.1 91.1 EASI S/MWB 42 125 0.597 2.765 0.580 -0.241 1.466 0.1 64.8 60.8 EASI S/MWB 43 59 0.303 6.219 0.196 -0.085 0.487 0.1 100 100 EASI S/WaMoS 353 1.089 -0. 686 0.694 -0.094 1.830 0.1 73.4 74.8 Platform/Stat # pts slope int. [°] R bias [°] std [°] EASI N/MWB 42 179 0.894 23.97 0.655 -1.71 47.57 EASI N/MWB 43 197 0.805 10.74 0.943 5.76 19.43 EASI N/WaMoS 150 1.106 -9.431 0.919 -0.70 23.15 EASI S/MWB 41 56 0.275 89.38 0.895 -12.08 26.32 EASI S/MWB 42 125 1.179 -1.62 0.976 -14.00 12.62 EASI S/MWB 43 59 3.601 -529.7 0.970 9.22 13.90 EASI S/WaMoS 353 1.085 7.45 0.818 -11.33 34.62 STATISTICAL COMPARISON AND VALIDATION I In contrast to other platforms, the EASI buoys operated continuously throughout the entire experiment including the passage of the 4 Typhoons. Therefore, comparisons focus on validating EASI’s measurements. Comparisons were divided for the NZ and SZ. The integral wave parameters of significant wave height (Hs), peak period (Tp), and wave direction at the spectral peak (WD) were compared. EASI was treated as a Heave-Pitch-Roll buoy [MS Longuet-Higgins et al 1963]. Although NOAA’s NDBC has routinely used 6m NOMAD buoys for non-directional wave measurements, to the authors’ knowledge, this is the first presentation of directional wave measurements from such a buoy. Being as such, validation of the directional measuring capabilities was an important aspect of these comparisons. SIGNIFICANT WAVE HEIGHT WAVE DIRECTION AT THE PEAK Peak period, although a common parameter, is not a vary stable measure of period. This lack of stability is reflected in the low correlation coefficients and high standard differences. There are also isolated points (suspected to spurious) which throw off the comparative results. Even so, it is estimated that most of variability can be explained by the inherent sampling variability of the parameter. Future work will explore more stable period parameters. The table above shows the number of points, the fit parameters for a maximum likelihood regression, a directional association measure, directional bias, and directional standard difference. The direction at the peak is also an unstable parameter. Directionally multi-modal seas (which the buoys cannot resolve) with similar energies in each mode are a possibility. The multi-modality causes the peak direction to jump back and forth between peaks. The jumping causes comparisons to be poor and muddles the interpretation of results. It is suspected that multi-modal seas occur throughout the experiment, but this is speculation until it can be further investigated with the superior directional resolution of the WaMoS. Considering this, the wave directions compare surprisingly well with very high associations. Future work will include comparisons of more stable measures of mean direction, comparison of directional spread, investigation of higher-order methods to calculate directional spectra from EASI, and investigation of directional modality. The tables show the # of points, fit parameters for a maximum likelihood regression, the correlation coefficient, bias, standard difference, estimated coefficient of variance, and the percentage of points that fall within a 90% confidence interval with and without bias. The comparisons are very good in general with most R values ≥ .90. The notable exception is EASI S vs MWB 43. The comparison was during Tropical Cyclone Diamnu. It is suspected that there was unusually strong spatial variability in Hs at the time, and is a matter for future investigation. MWB WaMoS ASI S EAS I Photo Credit: Dr. Hans C. Graber analysis shows similar results with comparisons made within smaller radii (i.e. 25km, 50km). The mean distance to the mobile platforms is actually much less than 100km. The criterion is slightly relaxed for measurements made during a particular pass of Jason- 1. 126 126. 127 127.5 128 19 19.5 20 20.5 21 21.5 22 Longitude [ E] Latitude [ N] C om parison Area W aM oS (S hip) M W B 43 M W B 42 M W B 41 E AS I/A S IS N E AS I/A S IS S N orth Zone S outh Zone Jason-1 Jason-2 F req [H z] 0.05 0.15 0.25 0.35 0.45 D ir [ ] N E S W 2 4 6 8 10 H s [m ] 5 10 15 20 25 T p [s] 220 240 260 280 300 320 N E S W YearD ay 2010 W D [ ] -2 0 2 4 -0.1 0 0.1 0.2 EASI S ASIS S MW B 41 MW B 42 MW B 43 W aM oS Jason-1 Ku Jason-1 C Jason-2 Ku -2 0 2 4 -0.1 0 0.1 0.2 F req [H z] 0.05 0.15 0.25 0.35 0.45 D ir [ ] N E S W 2 4 6 8 10 H s [m ] 5 10 15 20 25 T p [s] 220 240 260 280 300 320 N E S W YearD ay 2010 W D [ ] EASI N ASIS N MW B 42 MW B 43 W aM oS Jason-1 Ku Jason-1 C Jason-2 Ku ACKNOWLEDGEMENTS This work would not have been possible without the technical support of Mike Rebozo (RSMAS). Thanks to Henry Potter (RSMAS), Michele Gierach (RSMAS), Ian Brooks (Leeds), Dominic Salisbury (Leeds), Sara Norris (Leeds), Sharein E-Tourky (RSMAS) and Anibal Herrera (RSMAS) who were cruise participants. Thanks to Mike Ohmart and Avery Snyder (UW-APL) for help with ASIS recoveries. Thanks to the captains and crew of the R/V Roger Revelle, and the WHOI mooring operations team. Funding provided by the U.S. Office of Naval research. Dianmu Fanap i Megi Chaba Malaka s Dianmu Fanap i Megi Chaba Malaka s a ) b ) c ) d ) e ) a ) b ) c ) d ) e )
description
In Situ Measurements of Surface Gravity Waves in Typhoon Conditions. Clarence O. Collins III 1 , Hans C. Graber 1 , William M. Drennan 1 , Neil J. Williams 1 , Rafael J. Ramos 1 , Bjoern Lund 1 , and Eric J. Terrill 2 - PowerPoint PPT Presentation
Transcript of In Situ Measurements of Surface Gravity Waves in Typhoon Conditions
IN SITU MEASUREMENTS OF SURFACE GRAVITY WAVES IN TYPHOON CONDITIONS
Clarence O. Collins III1, Hans C. Graber1, William M. Drennan1, Neil J. Williams1, Rafael J. Ramos1, Bjoern Lund1, and Eric J. Terrill2 1)Rosenstiel School of Marine and Atmospheric Science (RSMAS), University of Miami
2) Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Drive, La Jolla CA, 92093
INTRODUCTIONThe Impact of Typhoons on the Ocean in the Pacific (ITOP) field campaign took place in late 2010 within the Philippine Sea approximately 740 km east of southern Taiwan. ITOP included the measurements made by moored buoys, drifters, gliders, air craft, satellite, and research vessels. Directional wave spectra and integral wave parameters were derived from data recorded by several of these platforms. The platforms include 3 drifting miniature wave buoys (MWB), the X-band nautical radar (WaMoS) on the R/V Roger Revelle, Jason-1 (Ku and C band) and Jason-2 (Ku band) satellite altimeters, and two mooring sites. Each mooring site included a buoy with a 6m NOMAD type hull called EASI (Extreme Air Sea Interaction) [Drennan and Williams 2008] which was moored to the bottom, and an ASIS (Air-Sea Interaction Spar) buoy [Graber et al. 2000] tethered to the EASI by a 60 m cable. The moorings operated continuously for approximately 4 months and endured the relatively close passages of 4 major tropical cyclones: Typhoon Dianmu (~ year day 220), Typhoon Fanapi (~ year day 260), Super Typhoon Megi (~year day 290), and Typhoon Chaba (~year day 300).
Clarence O. Collins III, RSMAS-AMP, 4600 Rickenbacker Cswy, Miami FL 33149 USAPhone: +1 305 421 4282, Fax: +1 305 421 4701, E-Mail: [email protected]
This work has been funded by the U.S. Office ofNaval Research under grant N00014-08-1-0581
REFERENCES• Drennan, W. M. and Williams, N. J. (2008): An Air Sea Interaction Buoy for High
Winds, NSF Report NSF-OCE-0526442, p. 8.• Graber, H. C., Terray, E. A., Donelan, M. A., Drennan, W. M., Van Leer, J. C., and
Peters, D. B. (2000): ASIS – A New Air-Sea Interaction Spar Buoy: Design and Performance at Sea, Journal of Atmospheric and Oceanic Technology, 17, pp. 708-720.
• Longuet-Higgins, M. S., Cartwright, D. E., & Smith, N. D. (1963): Observations of the directional spectrum of sea waves using the motions of a floating buoy. Ocean Wave Spectra, pp. 111-136
FOR MORE INFO PLEASE SEE THE FOLLOWING POSTERS:•Williams et al -AIR-SEA MEASUREMENTS FROM MOORED SURFACE BUOYS IN THE PACIFIC DURING THE 2010 TYPHOON SEASON (session 091, PosterID: B1904 20 Feb 2012 1700-1800)•Ramos et al – WIND MEASUREMENTS FROM ASIS AND EASI BUOYS DURING THE ITOP EXPERIMENT (session 022, PosterID: B1819 23 Feb 2012 17:00-18:00)•Potter et al – UPPER OCEAN RESPONSE TO TYPHOONS DURING THE 2010 SEASON (session 022, PosterID: B1820 23 Feb 2012 17:00-18:00)•Lund et al – WIND AND WAVE RETRIEVAL FROM MARINE X-BAND RADAR DATA UNDER TYPHOON CONDITIONS (session 022, PosterID: B1821 23 Feb 2012 17:00-18:00)•Romeiser et al – AN EMPIRICAL ALGORITHM FOR OCEAN WAVE RETRIEVALS FROM SCANSAR IMAGES UNDER TYPHOON CONDITIONS (session 175, PosterID: B1494 23 Feb 2012 17:00-18:00)
SPATIAL SEPERATIONThe northern mooring (EASI N and ASIS N) was located at 21.23oN, 126.96oE at a depth of 5,608 m, and the southern mooring (EASI S and ASIS S) was located at 19.63oN, 127.25oE at a depth of 5,512m. The distance between moorings was approximately 180 km. For this study, the area is split into 2 zones, referred to as North Zone (NZ) and South Zone (SZ), formed by 100km radii centered at each EASI buoy. The two zones are plotted below with the MWBs’ drift track, the R.V. Roger Revelle’s ship track, and the satellite altimeters’ points of closest approach associated with different passes. This is a relatively large zone for wave comparisons, but preliminary
NORTH ZONE TIME SERIES SOUTH ZONE TIME SERIES
Wave Sensors Mean Distance [km]EASI N – ASIS N < .1EASI N – MWB 42 49EASI N – MWB 43 57EASI N – WaMoS 20EASI N – Jason-1 79EASI N – Jason-2 55EASI S – ASIS S < .1EASI S – MWB 41 60EASI S – MWB 42 51EASI S – MWB 43 23EASI S – WaMoS 48EASI S – Jason-1 67EASI S – Jason-2 40
CONCLUSIONWave spectra, directional distributions, and integral wave parameters are reported from the 2010 ITOP experiment. The measurements of the 2 EASI buoys were compared and validated against other sensors within 100km, including 2 ASIS buoys, 3 MWBs, the WaMoS, and Jason-1 (Ku and C band) and Jason-2 (Ku band) satellite altimeters. The comparisons were very good for Hs and WD with few exceptions. The exceptions may be due to high spatial variability or the presence of multi-modal seas. The comparisons for Tp were not as good, but the poor agreement can be attributed to the innate sampling variability of the parameter and some (perhaps spurious) isolated points. The measurements are generally consistent and provide a unique look at surface gravity waves in Typhoon conditions. This work provides many avenues for future research.
STATISTICAL COMPARISON AND VALIDATION IIPEAK PERIOD
Platform/Stat # pts slopeint. [m]
Rbias [m]
std [m]
COV CI% CI%/b
EASI N/ASIS N 2662 1.028 0.067 0.989 0.106 0.0952 0.06 66.8 92.4EASI N/MWB 42 179 1.170 -0.038 0.968 0.121 0.1003 0.06 35.8 71.5EASI N/MWB 43 197 1.032 0.134 0.918 0.166 0.0956 0.06 30.5 74.1EASI N/Jason1 Ku
18 0.982 0.181 0.956 0.1440.3855
NA NA NA
EASI N/Jason1 C 18 1.064 0.120 0.955 0.251 0.3811 NA NA NAEASI N/Jason2 Ku
22 1.094 -0.030 0.978 0.131 0.1679 NA NA NA
EASI S/ASIS S 5073 0.939 0.101 0.986 0.007 0.1214 0.06 88.7 89.3EASI S/MWB 41 56 0.997 0.110 0.966 0.107 0.2006 0.06 41.1 67.9EASI S/MWB 42 125 1.016 0.116 0.900 0.130 0.0811 0.06 32.8 76EASI S/MWB 43 59 0.851 0.948 0.364 0.439 0.4020 0.06 44.1 69.5EASI S/Jason1 Ku
9 1.175 -0.094 0.974 0.215 0.2960 NA NA NA
EASI S/Jason1 C 9 1.240 -0.621 0.884 -1.117 0.5459 NA NA NAEASI S/Jason2 Ku
22 0.845 0.258 0.757 0.003 0.5280 NA NA NA
Platform/Stat#
ptsslope int. [s] R
bias [s]
std [s]
COV CI% CI%/b
EASI N/ASIS N 1779 1.097 -0.981 0.539 -0.218 1.399 0.1 78.9 80.2EASI N/MWB 42
179 0.765 1.932 0.537 -0.103 1.185 0.1 84.4 84.4
EASI N/MWB 43
197 0.801 1.076 0.450 -0.504 2.111 0.1 56.3 61.4
EASI N/WaMoS
150 2.284 -10.730 0.271 0.547 1.579 0.1 86.7 95.3
EASI S/ASIS S 3383 0.941 0.349 0.754 -0.137 1.338 0.1 80.8 81.1EASI S/MWB 41
56 0.085 8.216 0.203 -0.458 2.336 0.1 91.1 91.1
EASI S/MWB 42
125 0.597 2.765 0.580 -0.241 1.466 0.1 64.8 60.8
EASI S/MWB 43
59 0.303 6.219 0.196 -0.085 0.487 0.1 100 100
EASI S/WaMoS
353 1.089 -0. 686 0.694 -0.094 1.830 0.1 73.4 74.8Platform/Stat # pts slope int. [°] R bias [°] std [°]
EASI N/MWB 42 179 0.894 23.97 0.655 -1.71 47.57
EASI N/MWB 43 197 0.805 10.74 0.943 5.76 19.43
EASI N/WaMoS 150 1.106 -9.431 0.919 -0.70 23.15
EASI S/MWB 41 56 0.275 89.38 0.895 -12.08 26.32
EASI S/MWB 42 125 1.179 -1.62 0.976 -14.00 12.62
EASI S/MWB 43 59 3.601 -529.7 0.970 9.22 13.90
EASI S/WaMoS 353 1.085 7.45 0.818 -11.33 34.62
STATISTICAL COMPARISON AND VALIDATION IIn contrast to other platforms, the EASI buoys operated continuously throughout the entire experiment including the passage of the 4 Typhoons. Therefore, comparisons focus on validating EASI’s measurements. Comparisons were divided for the NZ and SZ. The integral wave parameters of significant wave height (Hs), peak period (Tp), and wave direction at the spectral peak (WD) were compared. EASI was treated as a Heave-Pitch-Roll buoy [MS Longuet-Higgins et al 1963]. Although NOAA’s NDBC has routinely used 6m NOMAD buoys for non-directional wave measurements, to the authors’ knowledge, this is the first presentation of directional wave measurements from such a buoy. Being as such, validation of the directional measuring capabilities was an important aspect of these comparisons. SIGNIFICANT WAVE HEIGHT
WAVE DIRECTION AT THE PEAK
Peak period, although a common parameter, is not a vary stable measure of period. This lack of stability is reflected in the low correlation coefficients and high standard differences. There are also isolated points (suspected to spurious) which throw off the comparative results. Even so, it is estimated that most of variability can be explained by the inherent sampling variability of the parameter. Future work will explore more stable period parameters.
The table above shows the number of points, the fit parameters for a maximum likelihood regression, a directional association measure, directional bias, and directional standard difference. The direction at the peak is also an unstable parameter. Directionally multi-modal seas (which the buoys cannot resolve) with similar energies in each mode are a possibility. The multi-modality causes the peak direction to jump back and forth between peaks. The jumping causes comparisons to be poor and muddles the interpretation of results. It is suspected that multi-modal seas occur throughout the experiment, but this is speculation until it can be further investigated with the superior directional resolution of the WaMoS. Considering this, the wave directions compare surprisingly well with very high associations. Future work will include comparisons of more stable measures of mean direction, comparison of directional spread, investigation of higher-order methods to calculate directional spectra from EASI, and investigation of directional modality.
The tables show the # of points, fit parameters for a maximum likelihood regression, the correlation coefficient, bias, standard difference, estimated coefficient of variance, and the percentage of points that fall within a 90% confidence interval with and without bias. The comparisons are very good in general with most R values ≥ .90. The notable exception is EASI S vs MWB 43. The comparison was during Tropical Cyclone Diamnu. It is suspected that there was unusually strong spatial variability in Hs at the time, and is a matter for future investigation.
MWB WaMo
S
ASIS
EASI
Photo Credit: Dr. Hans C. Graber
analysis shows similar results with comparisons made within smaller radii (i.e. 25km, 50km). The mean distance to the mobile platforms is actually much less than 100km. The criterion is slightly relaxed for measurements made during a particular pass of Jason-1.
126 126. 127 127.5 128
19
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Longitude [E]
La
titu
de
[ N]
Comparison Area
WaMoS (Ship)MWB 43MWB 42MWB 41EASI/ASIS NEASI/ASIS SNorth ZoneSouth ZoneJason-1Jason-2
Fre
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Hz]
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[s]
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W
Year Day 2010
WD
[]
-2
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-0.100.10.2
EASI SASIS SMWB 41MWB 42MWB 43WaMoSJason-1 KuJason-1 CJason-2 Ku
-2
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-0.100.10.2
Fre
q [
Hz]
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m]
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Year Day 2010W
D [
]
EASI NASIS NMWB 42MWB 43WaMoSJason-1 KuJason-1 CJason-2 Ku
ACKNOWLEDGEMENTSThis work would not have been possible without the technical support of Mike Rebozo (RSMAS). Thanks to Henry Potter (RSMAS), Michele Gierach (RSMAS), Ian Brooks (Leeds), Dominic Salisbury (Leeds), Sara Norris (Leeds), Sharein E-Tourky (RSMAS) and Anibal Herrera (RSMAS) who were cruise participants. Thanks to Mike Ohmart and Avery Snyder (UW-APL) for help with ASIS recoveries. Thanks to the captains and crew of the R/V Roger Revelle, and the WHOI mooring operations team. Funding provided by the U.S. Office of Naval research.
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