45

Improved Meteorological Measurements from

Buoys and Ships for the World

Ocean Circulation Experiment

Robert A. WELLER and David S. HOSOM

Woods Hole Oceanographic Institution,Woods Hole, MA 02543 - U.SA.

ABSTRACf

The World Ocean Circulation Experiment (WOCE) is directed at understanding ocean circulationand its interrelation to climate. During WOCE, moored buoys and ships will provide attractive platformsfrom which to make accurate in-situ measurements of the basic observables- sea surface temperature, airtemperature, wind velocity, barometric pressure, solar and longwave radiation, humidity and precipitation.From these measurements accurate estimates of the air-sea fluxes can be made. Drifting or moored air-seainteraction buoys will also be needed in WOCE for the verification of the surface data collected by remotesensing.

The overall goal of the "Improved Meteorological Measurements from Ships and Buoys" (IMET)effort is to develop accurate and reliable means of making meteorological measurements from ships andbuoys during WOCE. Work being done at the University of Southern California concentrates onimproving longwave radiation sensors. Scripps Institution of Oceanography is evaluating the effect ofplatform motions on radiometers, anemometers, and heading sensors. The work at the Woods HoleOceanographic Institution includes development and evaluation of improved sensors, testing to quantifyerrors associated with present sensors, development of prototype data loggers capable of supportingintelligent data acquisition algorithms that reduce measurement error, and testing of sensors and dataloggers on local moorings and on research ships.

Prototype buoy and ship data loggers are complete. Prototypes of some of the sensor modules arealso complete. An optical WORM (Write Once, Read Many times) disc for storage has been working welleven during rough weather testing on OCEANUS (Prada,1988) .Test buoy deployments began in January1989 and test ship installations will be in operation later in 1989. Sensors for all variables are under teston land. Testing of the most promising of these will be continued on the test buoy and ship installationsbeginning in 1989.

1. Introduction.

Vertical exchange across the air-sea interface of horizontal momentum and ofbuoyancy, including heat and freshwater, couples the ocean and atmosphere. Observingthis coupling is a fundamental need if WOCE is to understand ocean circulation and itsinterrelation to climate. During WOCE moored buoys and ships will provide especiallyattractive platforms from which to make accurate in-situ measurements of the basicobservables -- sea surface temperature, air temperature, wind velocity, barometricpressure, solar and longwave radiation, humidity and precipitation -- and from which tomake accurate estimates of the air-sea fluxes. They are attractive because they providethe means to make a direct measurement in situ and because sensors and electronics are

_ returned periodically for calibration. The pre- and post-calibration procedure, along withan understanding of sensor performance in the field, provide the methodology to

46

maintain and quantify the accuracy of the measurements. To obtain such high qualitymeasurements in support of objectives of the Core 1 (the global description), Core 2 (theSouthern Ocean), and Core 3 (ocean process studies) projects, the plan during WOCE isto deploy moored buoys equipped with meteorological instrumentation and to similarlyequip a subset of the ships involved in WOCE.

The overall goal of the "Improved Meteorological Measurements from Ships andBuoys" (IMET) effort is to develop accurate and reliable means of makingmeteorological measurements from ships and buoys during WOCE. Work being done atthe University of Southern California concentrates on improving longwave radiationsensors and determining the accuracy of net longwave flux estimates. Scripps Institutionof Oceanography is evaluating the effect of platform motion on radiometers,anemometers, and heading sensors and investigating methods of reducing that error. Thework at the Woods Hole Oceanographic Institution includes development and evaluationof improved humidity sensors; testing to quantify errors associated with present sensorsfor precipitation, sea and air temperature, and barometric pressure; participation withScripps in the work on platform motion effects; development of prototype data loggerscapable of supporting intelligent data acquisition algorithms that reduce measurementerror; and testing of sensors and data loggers on local moorings and on research ships.Testing will include a variety of sensors (spanning various measurement techniques anda range of costs) in order to be able to quantify the trade-offs between accuracy,reliability, and initial expense.

2. Required measurements.

The basic meteorological quantities that need to be measured include sea surfacetemperature (SST), air temperature, wind speed and direction, barometric pressure,humidity (which may be obtained through wet bulb depression), incoming solar andlongwave radiation, and precipitation. Stress, sensible heat flux, latent heat flux andevaporation are determined from these basic data using bulk formulae. Net shortwaveradiation and net longwave radiation are also calculated. Accuracies of 10 watts persquare meter are sought in the estimates of the mean values (averaged over monthly andlonger time scales) of each of the four components of heat flux (sensible, latent,shortwave, longwave); accuracies of approximately 1 millimeter per day are sought inevaporation and precipitation; and an accuracy of 10% or 0.01 Pa is sought in stress.

..

Table of Desired Measurements.variable llni.t.s MinWind Speed mls 0.7Wind Direction deg 0Air Temp. degC -40Sea Surface Temp. degC -5Solar Insolation W1m2 0Barometric Press. mb 850Relative Humidity %RH 0Longwave Radiation W1m2 0Precipitation mm/hr 0

Mu50

3604545

14001050

120600600

Res0.10.70.0010.0010.10.10.10.10.1

The majority of conventional surface meteorological data are provided byobservations from the Volunteer Observing Ships (VOS). These data contain randomerrors due to inadequate sampling, poor instrument calibrations, ship air flowdisturbance, etc. Effects such as heat contamination from the ship and salt contamination

47

of wet bulbs result in systematic biases. Random errors can be reduced by averaging butsystematic biases must be identified by comparison of the VOS data with higher qualitydata from meteorological buoys. research ships. or an improved subset of the VOS.Drifting or moored air-sea interaction buoys will also be needed in WOCE for theverification of the surface fluxes of heat and momentum which have been determinedfrom remote sensing or from atmospheric general circulation models and to obtain datafrom regions away from regular ship tracks. Data at the original sampling rate will bestored in the buoys for later recovery; averaged data will be telemetered via ARGOS forimmediate use.

Net short wave radiation is estimated by measuring downwelling short waveradiation with a pyranometer and multiplying by (l-alpha), where alpha is the albedo (asfrom Payne 1972 for example). Instruments must be carefully calibrated and gimbalmounted to compensate for ship and buoy motion. Downward long wave radiation ismeasured by a similar sensor fitted with an opaque dome. Errors due to the radiativeheating from parts of the ship in the field of view can be large and are additional to errordue to motion and sensor deficiencies. Upwelling long-wave radiation must be inferredas the graybody emission of the sea surface plus the reflection of downwelling long waveradiation by the sea surface and by modelling dependence on air temperature andhumidity (Siegel and Dickey 1986 ). Errors in measuring SST will enter in the graybodyformula and are thus potentially large. but there are also uncertainties in the sea surfaceemissivity. sea surface reflectance. and the empirical model dependence on airtemperature and humidity. However. it is difficult to make a good measurement of thesea surface temperature of the ocean. With diurnal heating. SST may be up to 3 degreesC warmer than the temperature at a depth of 1 meter, and. during a shower. relativelyfresh water can be found at the surface that is cooler than the water below. Further.sensors placed on a ship or buoy hull may be affected by the thermal mass of the hulland. if not shielded. may be directly heated by the penetrating radiation. Such radiativeheating is also the primary problem with air temperature measurements althoughaspirated air temperature sensor shields can be used to attempt to bring the error in airtemperature down to approximately 0.2 degrees C. Humidity measurements of thedesired accuracy will require the development of new sensors. Errors in the buoyancyflux will be associated with errors in both total heat flux and precipitation estimates.

3. Meteorological instrumentation.

Meteorological packages and sensor sets for use on both ships and buoys duringWOCE are now under development. Air-sea fluxes will be computed using stabilitydependent algorithms for momentum. sensible heat. and latent heat (Large and Pond1981.1982) and computing net shortwave using an albedo look-up table. and netlongwave by estimating outgoing longwave with an improved graybody algorithm nowbeing developed. Raw data and original sampling rate (as fast as every minute for oneyear) fluxes will be stored: several-hour averaged surface variables and fluxes will betelemetered via ARGOS. ARGOS data will be monitored (and quality checked so it willqualify for distribution via GTS) and archived at an accessible (dial-up and/or Ethemet)data base.

Prototype buoy and ship data loggers are complete. Prototypes of some of thesensor modules are also complete. An optical WORM (Write Once. Read Many times)disc for storage has been working well even during rough weather in a test installation onOCEANUS (Prada and Baggeroer 1988). Test buoy deployments began in January 1989.and test ship installations will be in operation later in 1989. Sensors for all variables.including precipitation. are under test on land. Testing of the most promising of thesewill be continued on the test buoy and ship installations beginning in 1989. Special

48

efforts are being made to develop relative humidity and precipitation sensors, to reduceerrors in sea surface and air temperatures, to reduce errors in short and longwaveradiation measurements associated with platform motion, to develop an improved wind/vane! compass sensor, and to establish a reliable system configuration for use on shipsand buoys.

4. Shipboard system.

286/386Primary Computer

DataLink

286/386Auxiliary Computer

FIG.I. Shipboard system block diagram

The ship data logger/controller is an NEC APC-IV personal computer, as shownin Figure 1. Software development is carried out using standard MS-DOS compatibleprograms. The primary computer collects the data from the various sensors via a digitalinterface built into each sensor. It then stores the raw data on the optical disk, displaysthe data on a real time operator display, performs calculations and transmits longer termaverage data and calculated data via ARGOS. There is a color printer for hard copy datain a strip chart form and a keyboard for operator interaction. There are two basic sensorgroupings, one that collects one minute averages and one that is capable of high speed

49

sampling of motion and radiation if desired. There is an auxiliary computer that iscapable of accessing the primary optical disk and doing data analysis and evaluationwithout disturbing the primary data collection.

S.Buoy system.

: DissipationI

LOPACSComputer System

FIG.2. Buoy system block diagram

The buoy data logger/controller is based on a low-powered processor unit calledLOPACS as shown in Figure 2. This controller is a CMOS based. IBM compatible.commercially available unit that is described in Reference 6. The software developmentis carried out using standard MS-DOS compatible programs that would be similar butnot the same as the ship system. The system functions in the same way as a ship systemexcept there is no operator display or interaction. The electronics is housed in awatertight area on the buoy and can be controlled via a watertight connector to a remoteterminal.

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6. Sensor modules.

The sensor set will provide measurement of wind velocity, air temperature, seatemperature, barometric pressure, relative humidity, incoming shortwave radiation,incoming longwave radiation and precipitation. Various alternate sensors for eachvariable are being tested to establish reliabililty, accuracy. and cost versus performanceinformation for each type of measurement. The sensor modules being designed and builtto work with the system are the current choice for sensors to satisfy the measurementsrequired and are referred to as the "strawman" sensor set. The following figures andparagraphs describe the strawman sensor configurations.

Each sensor will be mated to a microprocessor based module that will performsome sampling tasks, convert the raw sensor output to engineering units, and send thedata digitally over RS-485 (ship) or RS-232 (CMOS open drain) (buoy) link to the datalogger/controller. Refer to Figure 3. for the configuration of the Digital Data Module.Each digital module is housed in a plastic, watertight 4.5" diameter housing with a 4 wireunderwater connector providing power and data. In the development modules, there aretwo aluminum chassis. one of which contains one or more custom front end interfaceprinted circuit cards while the other contains at least three cards, including a power andcommunications board, a digital module processor (DMP) card (currently a Basicon 2iunit) and an integrating 15 bit plus sign, analog to digital converter,parallel and counterI/O card. The (DMP) is typically programmed in BASIC 52 with 'C' as an alternative.This modular approach permits development of future sensor modules by investigators inother laboratories that will be compatible with the data collection system.

Digital Data Module

III III PRT Temperature Probe

1111 Radiation Shield

~tumng Tube4·pln UW Connectors.

Digital ModuleEnd CapFrolll End Chassis

Quad AOIplMulliplexerPRTlMultiplexerDual '·bil Gray DecoderCoil/llall Willd Speed

Digital Chassisl'ower/ColIIOlunlcallonsDill· Processor (DASICONjAIDCon.erler, lS·bil

~~~~~ Rubber Shock Pad~ End Cap

r------,I II I Sensor

FIG.3. Digital data module FIG.4. Air temperature module

The air temperature module uses a PRT (platinum Resistance Thermometer)inside of an R. M. Young radiation shield shown in Figure 4. An autoranging, ratiometricmeasurement will be made to provide as high an accuracy as possible. The PRT offers a

51

linear, ultra low drift sensor. Close coupling of the sensor and the shielded front endelectronics will provide a stable, low noise analog section and the DMP will beprogrammed to provide corrections based on stored calibration data.

Sea Surface Temperature is electronically very similar to the Air Temperaturemodule but will be housed in an aluminum underwater housing for mounting under thebuoy and is shown in Figure 5. The ship mounting is being evaluated but will probablybe custom for each ship that the system is installed on.

PRT Temperature Probe

Pressure Housing

Digital Data Module

FIG.5. Sea surface temperature module

Wind MonitorCoil/Ma&ne! orHallElTectlMa&ne.

9·blt Gray Vane Encoder9-bit Gray Compass

Digital Data Module

FIG.6. Wind speed and direction module

The wind speed and direction module is shown in Figure 6. An R. M. YoungWind Monitor has been selected since it has a proven record and uses a propeller tomeasure speed. The potentiometer is removed and the vane shaft extended down into thetop of the data module housing addition. A commercially available 9 bit Gray Code shaftencoder is coupled to the vane. A Digicourse Model 226 gimbaled compass with a 9 bitGray Code output is in the same housing. The wind speed will be measured with eitherthe standard coil and magnet or with a Hall Effect unit and magnet. The front endelectronics include a dual 9 bit Gray code to binary decoder and electronics to processeither of the speed signals. The DMP will be programmed to sample, store and processthe standard vector averaged wind data over a one minute time period.

The Short Wave Radiation module will consist of an Eppley PSP (PrecisionSpectral Pyranometer) mounted on an aluminum housing which provides a referencemass for the PSP. This is fastened to a standard digital module and the combination ismounted in a 2 axis gimbal as shown in Figure 7. This gimbal has low corrosion, sealedbearings that are filled with a lubricant. This provides extended life and some damping.The sensor can be adjusted in the gimbal to minimize acceleration sensitivity. The lowlevel signal from the sensor is amplified by a low noise amplifier and sampled by theAID card under DMP control.

Long Wave Radiation is measured by a Foot thermopile (Foot 1986) and has twocompensating thermistors. The low level signals are amplified, multiplexed and storedby the DMP, where the compensation is accomplished by software rather than analogelectronics. The long wave sensor also has a two axis gimbal as shown in Figure 8.

.-

Dllltal Data Module

2 nil Glmbul

52

r--;

II

Long Wave SensorAlumlnulII Housing

Dlgllal Data Module

2 axis Ghnbal

FIG.7. Short wave radiation module FIG.8. Long wave radiation module

The Barometric Pressure and Relative Humidity module shown in Figure 9 uses acommon digital data module. The barometric pressure gage is an AIR (AtmosphericInstrumentation Research Inc.) Model DB-lA with a parallel digital output that goesdirectly to the DMP. The relative humidity unit is a Rotronics Model MP-lOO-F that hasanalog outputs for both relative humidity and local temperature. These are multiplexedinto the NO card and controlled by the DMP.

Radiation Shield

Relative Humldlly

Gill Pressure Pori

Barometric Pressure Gale

Weatber-tlllht Houllnll

Dlllllal Data Module

, ,\ r'\ ,/'-'

Preclpllalion Gage ..

':.... 1 M I~- ounl ng Clampu,---r'r---+--I

Dlllltal Data Module

FIG. IO. Precipitation moduleFIG.9. Barometric pressure andrelative humidity module

The Precipitation sensor is an R. M. Young Model 50102 Rain Gage with a 0 to50 millimeter capacity unit that automatically empties and repeats the measurement andis shown in Figure 10. The unit has a 0 to 5 volt output that is converted in the NOboard. The DMP makes measurements and keeps track of the emptying cycles. There is aheater for cold weather use but this would only be used on ships for power reasons. Thedigital data module will be mounted beside the rain gage.

53

7. Deployments during WOCE.

Potential deployments of the IMET systems in moored arrays and on ships inWOCE are discussed below. The primary goal of these deployments would be to providedata needed for the validation of the air-sea flux and meteorological data fields to beproduced during WOCE. Detailed reasons for the deployments are given elsewhere; butbriefly, these deployments would:

• Provide, at the site of a moored array embedded in a Core 3 or Core 1 or 2 data field,a point with time series of the surface variables and air-sea fluxes of the highestpossible accuracy, both for examining response to local forcing and for reducing theerror in the larger scale field.

• Validate routine products of atmospheric models, serving as a diagnostic point tocheck the performance of coupled atmosphere-ocean models.

• Provide very accurate input data or provide a means to validate/estimate the error inthe air-sea flux fields used to force ocean or atmosphere models.

• Provide, at selected sites, accurate time series of surface variables and air-sea fluxesto assess the accuracy of existing climatologies (such as the Levitus data) and, if notassimilated, of the data fields being produced during WOCE.

• Validate satellite products and methodology, including wind, SST, rainfall (during theTropical Rainfall Measurement Mission, TRMM), the use of microwave radiometers(SSM/I) to measure total water content in the atmospheric column and infer surfacehumidity, and radiation products from polar orbiting satellites.

• Provide the means to assess systematic errors in the data fields collected by theVolunteer Observing Ships (VOS).

• Lay the groundwork for a methodology and network of moored buoys that willreplace the weather ships and for a method of maintaining a near real-time watch onoceanic locations where good surface data would, because of teleconnections, be adiagnostic to change in global circulation/climate.

Moored BuoyThe buoy deployments would be as follows:

• 1991-1993: Eight moored surface buoys, in the Ekman/Subduction process study inthe Azores-Canary area.

• 1993-1997: Up to ten moorings at special locations and in arrays with a minimum of 3elements for the purpose of calibration and validation of the WOCE air-sea fluxfields. These arrays would be maintained at their sites for two years.

The large scale air-sea flux fields that might be provided by satellites and models willnot be sufficient to address the needs of the planned Ekman Subduction experiment inthe eastern North Atlantic in 1991 -1993. Accurate, in situ measurements are needed toprovide the most accurate estimates of the wind stress and buoyancy forcing of the upperocean. An array of eight surface moorings, each with meteorological instrumentationand each supporting current meters is under discussion.

For WOCE the plan is to build 10 surface meteorological mooring hardware sets by1993 and thus to be able to maintain (with back to back one year deployments equipmentat 2-3 sites in any year. Coordination will be sought with other investigators to addcurrent meters to each mooring to examine local ocean response to atmospheric forcing,

54

to quantify the division between geostrophic and ageostrophic wind-driven flows, and toadd data points with details of the vertical structure to the fields of ocean circulationbeing constructed during WOCE.

Ship DeploymentsThe ship deployments would be of three types:

• Research Ship System (RSS): Research Vessels participating in the WOCE Core 1,2,and Core 3 activities with science parties seeking high quality meteorologicalobservations.

• WOCE Hydrographic Program Ship System (WHPSS): Research Vesselsparticipating on the WOCE Hydrographic Program.

• Ship of Opportunity System (SOS): Volunteer Observing hips (VOS) makingrepeated XBT and/or ADCP sections.

The RSS installation on U.S.Research Vessels would include three sensorinstallations (port, starboard, and bow mast) and a sensor suite designed to provide thebest possible measurements of the surface variables and best possible estimates of theair-sea fluxes at reasonable cost (thus excluding as standard items an infraredhygrometer, optical rain gauge, and sonic anemometer). Two NEC APC-IV's would beused to provide redundancy and real-time access for the science party to themeteorological data. One APC-IV would carry on ARGOS telemetry and data logging atthe standard rate and in the format to be provided by the other ships and buoys; thesecond APC-IV would be menu-driven and available to the science party and/or residenttechnician. This underway sampling would be coordinated with other underwaysampling efforts. The optical disks would be returned after one or more legs to bequality-checked and read into the data base. Five RSS would be built in order to maintainfour at sea. Targeted are the research ships where collection of meteorological data willbe of direct scientific interest. Also, it is planned that one RSS be installed temporarilyon a U.K. ship involved in WOCE for purposes of intercomparison. It is hoped that thefive RSS will remain in operation following WOCE and that their data will continue tobe distributed via GTS and archived.

The research ships involved in the WHP are the second focus of attention becausethey will provide platforms that will provide ship velocity data (via GPS), permittingtrue wind to be determined, and because the installation of a semi-permanentmeteorological package (WHPSS) would benefit from the attention of the residenttechnician/science party on board. Port and starboard installation would be done and asingle APC-IV would be installed. This would support ARGOS telemetry ofseveral-hour averaged surface variables and fluxes, recording of raw data and rawsampling rate fluxes on optical disk, and simple strip-Chart display (on video terminaland/or printer) of the data. Prime candidates are those ships in the WHP making sectionsin data sparse regions and/or sections that pass thru regions in particular need ofcalibration/validation.

The VOS making the repeat XBT sections would be the third choice. This SOSpackage will be a self-contained , unit similar to the package used on buoys. A singlesensor set will be installed on a temporary mast. When possible, one sensor module willbe used to link to ship's navigation, permitting determination of absolute wind andmomentum flux. Internal logging on optical disk of raw data and raw sampling ratefluxes and ARGOS telemetry of several-hour averaged data will be supported. Primarytargets for the planned installations will be ships equipped for WOCE to collect XBTand/or ADCP data, especially those transiting regions with otherwise sparse coverage of

55

surface meteorology and air-sea fluxes and/or locations where the modelling and remotesensing efforts need validation data. Four SOS will be built and used in a cooperativeeffort involving the investigators collecting the XBT/ADCP data.

Acknowledgments. This work was supported by the Ocean Sciences Division of theNational Science Foundation. Grant No. OCE-8709614. Cooperating investigators areRob Pinkel at Scripps Institution of Oceanography and Tom Dickey at the University ofSouthern California.

REFERENCES

Foot. 1.S.•1986: A New Pyrgeometer. J. Atmos. Oceanic Tech .• 3. 363-370 .Large. W.G. and S.• Pond. 1981: Open Ocean Momentum Flux Measurements in

Moderate to Strong Winds. 1. Phys, Oceanogr.• Ll, 324 -336.Large. W.G. and S.• Pond. 1982: Sensible and Latent Heat Flux Measurements Over

the Ocean. J. Phys. Oceanogr.• 12. 464 -482.Payne, R.E.• 1972: Albedo of the Sea Surface. 1. Atmospheric Sciences. 29. 959-970.Prada, K.E.. 1988: Optical Disk Use and Evaluation in Harsh Field Environments.

WHOI Contribution No. 6908. EOS December 8.1988.Prada, K.E. and A.B.• Baggeroer, 1988: An Artic Remote Autonomous Measurement

Platform. WHOI Contribution No. 6608. January 1988. Proceedings of a Workshopon Instrumentation and Measurements in the Polar Regions; also Oceans 87 with thesame title.

Siegel, D.A. and T.D.• Dickey. 1986: Variability of Net Longwave Radiation of theEastern North Pacific. J. Geophys. Res.• 91. 7657 -7666.

WESTERN PACIFIC INTERNATIONAL MEETING

AND WORKSHOP ON TOGA COARE

Noumea, New Caledonia

May 24-30, 1989

edited by

Joel Picaut *Roger Lukas **

Thierry Delcroix *

* ORSTOM, Noumea, New Caledonia** JIMAR, University of Hawaii, U.S.A.

INSTITUT FRANCAIS DE RECHERCHE SCIENTIFIQUEPOUR LE DtVELOPPEMENT EN COOPtRATlON

Centre de Noumea

vii

TABLE OF CONTENTS

ABSTRACT i

RESUME iii

ACKNOWLEDGMENTS vi

INTRODUCTION

1. Motivation 12. Structure ..... .......................... ... ... .......... ............. ......... .... ...... .. ...... . .. 2

LIST OF PARTICIPANTS 5

AGENDA 7

WORKSHOP REPORT

1. Introduction ............................... ............. .. .......... .. ....... ...... .... ... ...... .. 192. Working group discussions, recommendations, and plans 20

a. Air-Sea Fluxes and Boundary Layer Processes 20b. Regional Scale Atmospheric Circulation and Waves 24c. Regional Scale Oceanic Circulation and Waves 30

3. Related prograDlS ................. ......... ......... ............ .......... ...... .... . ........ . . 35a. NASA Ocean Processes and Satellite Missions .. . .. .. . 35b. Tropical Rainfall Measuring Mission .. . .. . . 37c. Typhoon Motion Program 39d. World Ocean Circulation Experiment .. . .. .. . 39

4. Presentations on related technology ....... ............ .. .. ..... ... ..... ... .. ...... .. . 405. National reports 406. Meeting of the International Ad Hoc Committee on TOGA COARE 40

APPENDIX: WORKSHOP RELATED PAPERS

Robert A. WeUer and David S. Hosom: Improved MeteorologicalMeasurements from Buoys and Ships for the World OceanCirculation Experiment ............. .. .... ............. .......... .. ........ ....... .... . ....... .... 45Peter H. Hildebrand: Flux Measurement using Aircraftand Radars 57-Waiter F. Dabberdt, Hale Cole, K. Gage, W. Ecklund and W.L. Smith:Determination of Boundary-Layer Fluxes with an IntegratedSounding System 81·

viii

MEETING COLLECTED PAPERS

WATER MASSES. SEA SURFACE TOPOGRAPHY. AND CIRCULATION

KJaus Wyrtki: Some Thoughts about the West Pacific Warm Pool.................. 99Jean Rene Donguy, Gary Meyers, and Eric Lindstrom: Comparison ofthe Results of two West Pacific Oceanographic Expeditions FOC (l971)and WEPOCS (1985-86) 111Dunxin Hu, and Maochang Cui: The Western Boundary Current in theFar Western Pacific Ocean 123Peter Hacker, Eric Firing, Roger Lukas, Philipp L. Richardson. andCurtis A. Collins: Observations of the Low-latitude Western BoundaryCirculation in the Pacific during WEPOCS ill ................ .. . . .. .. .. 135Stephen P. Murray, John Kindle, Dharma Arief, and Harley Hurlburt:Comparison of Observations and Numerical Model Results in the IndonesianThroughflow Region 145Christian Henin: Thermohaline Structure Variability along 165eEin the Western Tropical Pacific Ocean (January 1984 - January 1989) 155David J. Webb. and Brian A. King: Preliminary Results fromCharles Darwin Cruise 34A in the Western Equatorial Pacific 165Warren B. White, Nicholas Graham. and Chang-Kou Tai: Reflection ofAnnual Rossby Waves at The Maritime Western Boundary of the TropicalPacific ..... .......... ... .. .. .... .... ... .............................. ............ ........ ... .... .... .... 173William S. Kessler: Observations ofLong Rossby Waves in the NorthernTropical Pacific .......................... ..... .. .. ... . .. ... . ........... .. .. ......... .... . .. .. ... ... .. 185Eric Firing, and Jiang Songnian: Variable Currents in the WesternPacific Measured During the US/PRC Bilateral Air-Sea Interaction Programand WEPOCS 205John S. Godfrey, and A. Weaver: Why are there Such StrongSteric Height Gradients off Western Australia? 215John M. Toole, R.C. Millard, Z. Wang, and S. Po: Observationsof the Pacific North Equatorial Current Bifurcation at the Philippine Coast 223

EL NINO/SOUTHERN OSCILLATION 1986-87

Gary Meyers, Rick Bailey, Eric Lindstrom, and Helen PhiUips:Air/Sea Interaction in the Western Tropical Pacific Ocean during1982/83 and 1986/87 229Laury Miller, and Robert Cheney: GEOSAT Observations of SeaLevel in the Tropical Pacific and Indian Oceans during the 1986-87El Nino Event 247Thierry Delcroix, Gerard Elmn, and Joel Picaut: GEOSAT SeaLevel Anomalies in the Western Equatorial Pacific duringthe 1986-87 El Nino. Elucidated as Equatorial Kelvinand Rossby Waves 259Gerard Eldin. and Thierry Delcroix: Vertical Thermal StructureVariability along 165eE during the 1986-87 ENSO Event 269Michael J. McPhaden: On the Relationship between Winds andUpper Ocean Temperature Variability in the Western EquatorialPacific ..... ..... ...... ... .. .... ... ........................................... ..... .. .. .... .. .... ........ 283

i"'{

John S. Godfrey, K. Ridgway, Gary Meyers, and Rick Bailey:Sea Level and Thennal Response to the 1986-87 ENSO Event in theFar Western Pacific 291Joel Picaut, Bruno Camusat, Thierry Delcroix, MichaelJ. McPhaden, and Antonio J. Busalacchi: Surface Equatorial FlowAnomalies in the Pacific Ocean during the 1986-87 ENSO using GEOSATAltimeter Data 301

TIlEORETICAL AND MODELING STUDIES OF ENSOAND RELATED PROCESSES

Julian P. McCreary, Jr.: An Overview of Coupled Ocean-AtmosphereModels of El Nino and the Southern Oscillation 313Kensuke Takeuchi: On Wann RossbyWaves and their Relationsto ENSO Events 329Yves du Penhoat, and Mark A. Cane: Effect of Low Latitude WesternBoundary Gaps on the Reflection of Equatorial Motions 335Harley Hurlburt, John Kindle, E. Joseph Metzger, and Alan Wallcraft:Results from a Global Ocean Model in the Western Tropical Pacific 343John C. Kindle, Harley E. Hurlburt, and E. Joseph Metzger: On theSeasonal and Interannual Variability of the Pacific to Indian OceanThroughflow 355Antonio J. Busalacchi, Michael J. McPhaden, Joel Picaut, and ScottSpringer: Uncertainties in Tropical Pacific Ocean Simulations: TheSeasonal and Interannual Sea Level Response to Three Analyses of theSurface Wind Field 367Stephen E. Zebiak: Intraseasonal Variability - A Critical Componentof ENSO? 379Akimasa Sumi: Behavior of Convective Activity over the "Jovian-type"Aqua-Planet Experiments 389Ka-Ming Lau: Dynamics of Multi-Scale Interactions Relevant to ENSO 397Pecheng C. Chu and Roland W. Garwood, Jr.: Hydrological Effectson the Air-Ocean Coupled System 407Sam F. Iacobellis, and Richard CJ. Somerville: A one DimensionalCoupled Air-Sea Model for Diagnostic Studies during TOGA-COARE 419AlIan J. Clarke: On the Reflection and Transmission of Low FrequencyEnergy at the Irregular Western Pacific Ocean Boundary - a PreliminaryReport 423Roland W. Garwood, Jr., Pecheng C. Chu, Peter Muller, and NiklasSchneider: Equatorial Entrainment Zone: the Diurnal Cycle 435Peter R. Gent: A New Ocean GCM for Tropical Ocean and ENSO Studies 445Wasito Hadi, and Nuraini: The Steady State Response of IndonesianSea to a Steady Wind Field .......................................................... ............ 451Pedro Ripa: Instability Conditions and Energetics in the Equatorial Pacific 457Lewis M. Rothstein: Mixed Layer Modelling in the Western EquatorialPacific Ocean 465Neville R. Smith: An Oceanic Subsurface Thermal Analysis Scheme withObjective Quality Control 475Duane E. Stevens, Qi Hu, Graeme Stephens, and David Randall: Thehydrological Cycle of the Intraseasonal Oscillation , 485Peter J. Webster, Hai-Ru Chang, and Chidong Zhang: TransmissionCharacteristics of the Dynamic Response to Episodic Forcing in the WannPool Regions of the Tropical Oceans .. _ 493

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MOMENWM, REAT, AND MOISlURE FLUXES BETWEENATMOSPHERE AND OCEAN

W. Timothy Liu: An Overview of Bulk Parametrization and RemoteSensing of Latent Heat Flux in the Tropical Ocean ...................................... 513E. Frank Bradley, Peter A. Coppin, and John S. Godfrey: Measurementsof Heat and Moisture Fluxes from the Western Tropical Pacific Ocean 523Richard W. Reynolds, and Ants Leetmaa: Evaluation of NMC'sOperational Surface Fluxes in the Tropical Pacific 535Stanley P. Hayes, Michael J. McPhaden, John M. Wallace, and JailPicaut: The Influence of Sea-Surface Temperature on Surface Wind in theEquatorial Pacific Ocean 543T.D. Keenan, and Richard E. Carbone: A Preliminary Morphology ofPrecipitation Systems In Tropical Northern Australia 549Phillip A. Arkin: Estimation of Large-Scale Oceanic Rainfall for TOOA 561Catherine Gautier, and Robert Frouin: Surface Radiation Processes inthe Tropical Pacific 571Thierry Delcroix, and Christian Henin: Mechanisms of SubsurfaceThermal Structure and Sea Surface Thermo-Haline Variabilities in the SouthWestern Tropical Pacific during 1979-85 - A Preliminary Report 581Greg. J. Holland, T.D. Keenan, and MJ. Manton: Observations from theMaritime Continent: Darwin, Australia 591Roger Lukas: Observations of Air-Sea Interactions in the Western PacificWarm Pool during WEPOCS 599M. Nunez, and K. Michael: Satellite Derivation of Ocean-Atmosphere HeatFluxes in a Tropical Environment ............................................................. 611

EMPIRICAL SlUDIES OF ENSO AND SHORT-TERM CLIMATE VARIABILITY

Klaus M. Weickmann: Convection and Circulation Anomalies over theOceanic Warm Pool during 1981-1982 623Claire Perigaud: Instability Waves in the Tropical Pacific Observed withGEOSAT 637Ryuichi Kawamura: Intraseasonal and Interannual Modes of Atmosphere;.Ocean System Over the Tropical Western Pacific 649David Gutzler, and Tamara M. Wood: Observed Structure of ConvectiveAnomalies 659Siri Jodha Khalsa: Remote Sensing of Atmospheric Thermodynamics inthe Tropics 665Bingrong Xu: Some Features of the Western Tropical Pacific: Surface WindField and its Influence on the Upper Ocean Thermal Structure 677,Bret A. Mullan: Influence of Southern Oscillation on New ZealandWeather 687Kenneth S. Gage, Ben Basley, Warner Ecklund, D.A. Carter, andJohn R.McAfee: Wind Profiler Related Research in the Tropical Pacific 699John Joseph Bates: Signature of a West Wind Convective Event inSSM/I Data 711David S. Gutzler: Seasonal and Interannual Variability of the Madden-Iulian Oscillation 723Marie-H~lene Radenac: Fine Structure Variability in the Equatorial WesternPacific Ocean 735George C. Reid, Kenneth S. Gage, and John R. McAfee: The Oimatologyof the Western Tropical Pacific: Analysis of the Radiosonde Data Base 741

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Chung-Hsiung Sui, and Ka-Ming Lau: Multi-Scale Processes in theEquatorial Western Pacific , 747Stephen E. Zebiak: Diagnostic Studies of Pacific Surface Winds 757

MISCELLANEOUS

Rick J. Bailey, Helene E. Phillips, and Gary Meyers: Relevance to TOGAof Systematic XBT Errors 775Jean Blanchot, Robert Le Borgne, Aubert Le Bouteiller, and MartineRodier: ENSO Events and Consequences on Nutrient, Planktonic Biomass,and Production in the Western Tropical Pacific Ocean 785Yves Dandonneau: Abnonnal Bloom of Phytoplankton around weN in theWestern Pacific during the 1982-83 ENSO 791Ceclle Dupouy: Sea Surface Chlorophyll Concentration in the South WesternTropical Pacific, as seen from NIMBUS Coastal Zone Color Scanner from1979 to 1984 (New Caledonia and Vanuatu) 803Michael Szabados, and Darren Wright: Field Evaluationof Real-Time XBT Systems 811Pierre Rual: For a Better XBT Bathy-Message: Onboard Quality Control,plus a New Data Reduction Method 823