145

Comparison of Observations and Numerical Model

Results in the Indonesian Throughflow Region

Stephen P. MURRAy(l), John KINDLE(2),Dhanna ARIEF(l) and Harley HURLBURT(2)

(l)Coastal Studies Institute and Department ofGeologyand Geophysics, Louisiana State University,

Baton Rouge, Louisiana 70803 - U.SA.(2Waval Oceanographic Research and Development Activity,

Code 323, Bay St. Louis, Mississippi 39529 - U.SA.

ABSTRACT

Observations of currents, transport, sea level, and sea level slope in Lombok Strait and west Flores Sea in1985 and 1986 have been compared to a simulation of the NORDA global ocean model in the Indonesianthroughflow region. Despite the relatively coarse grid scale of the model compared to topographic lengthscales in the region, the model appears to be realistically reproducing many of the observed features. Thepredicted transport through the Lombok Strait, for example, agrees with detailed observations of phase andmagnitude, especially when corrected for grid size limitations. The sea surface fluctuations and sea surfaceslopes predicted by the model agree within less than a factor of 1.5 with sea level changes and slopes observedon tide gauges. There do appear to be several cases of phase difference of several months between model andobservations that require further investigation.

I. Introduction

The importance of a net transport of mass, heat, and salt from the Pacific Ocean to theIndian Ocean through the Indonesian archipelago is now well recognized. Present estimatesof the magnitude of the net transport (popularly referred to as the Indonesian throughflow)by various indirect methods vary greatly, from 1.5 to 20 Sv (l Sv = 1()6 m3.s-1) (Cox, 1982;Fine, 1985; Fu, 1986; Godfrey, 1981; Piola, and Gonion, 1984; Wyrtki, 1961). For ageneral review, see Gordon and Golding (1986). It has been generally assumed that thethroughflow is concentrated in the wide, deep passages bracketing Timor. The first directobservations of the throughflow, however, were taken in the Lombok Strait, presumably ofsecondary importance to the Timor passages on the basis of cross-sectional area. Theseobservations (Murray and Dhanna Arief, 1986) showed a net Indian Ocean-directedtransport reaching 4 Sv in August 1985 with a 1985 annual average of 1.7 Sv. Extrapolatingthese results solely on the basis of cross-sectional area above the 200-m depth levelsuggests a total throughflow of 10-12 Sv. There could, however, be considerabledifferences between the pressure gradients driving the flows in the Lombok and Timorareas.

Recently Wyrtki (1987), using sea level data from Davao and Darwin and dynamicheight data from the areas south of Mindanao and south of Java, showed that the strongpressure gradient between the Pacific and Indian oceans is concentrated in the upper 200 m.Interannual variations of the sea level differences agree well with the throughflow transport

predicted by the NORDA wind-driven numerical model (Kindle et al., 1987).The initial NORDA numerical model (Kindle et al., 1987) did not include the Lombok

Strait, but the results in (Murray and Dhanna Arief, 1986) instigated its inclusion in theupdated version discussed here. The objective of this paper is a comparison and evaluationbetween current and sea-level observations made in the Lombok Strait and west Flores Seain 1985-1986 and the model results.

146

2. Observational program

In order to understand the processes controlling circulation in the Lombok Strait andadjacent sectors of the Java and Flores Seas (see Fig. I), field work and data collection wereconducted from January 1985 to March 1986. Seven current moorings were deployed, fivein the Lombok Strait and two in the bathymetric trough (in the western Flores Sea) linkingthe Makassar Strait outflow to the Lombok Strait. More than 120 current meter months ofdata were collected. A total of 234 CID casts were taken in the Lombok Strait, its IndianOcean approaches, and the western Flores Sea extending as far north as the Makassar Straitand east into the Flores Sea to 119°E. Thirty-four meter months of sea level (pressuregauge) data were taken in the Strait and at the Makassar trough mooring site. Data on theregional sea level during our observations were collected from tide gauges in thePhilippines and northwest Australia courtesy of Klaus Wyrtki, University of Hawaii, andthe Hinders Tidal Observatory, Australia.

The annual cycle of current velocity in the Lombok Strait is best shown from the dataobtained at the 35-m depth level at site 2 (Fig. 2). The period January 10 through February15, 1985, was characterized by persistent strong southerly flows reaching 60 cm.s-1 inlate January. Large flow reversals to the north through most of February and again in lateApril appear closely controlled by tropical cyclone activity in the Timor Sea (Murray andDharma Arief, 1986). Southward currents increase in magnitude from May through July,reaching peaks of 90 cm.s-1 in August and September at the height of the SoutheasternMonsoon. Late October through December 1985 is a period of weak flow with distinctnorthward flow reversals in early December 1985 and a strong reversal in January 1986.Monthly block average values from all the current meter data at sites 1 and 2 are used inreference (Murray and Dharma Arief, 1988) to compute the annual transport cyclediscussed earlier.

FIG.I. Map of theIndo-Pacific convergencezone with an insetshowing mooring sites inthe LombokStrait

N

~I d= 3SM

147

d =300M"''' 111.'" \lIP .. ,;p' 4'" ;..,-. "»iF wc W-

d=aOOM

-- ...," .... -- st.'", 'e "'d *.., pcrt'd •• ,:» ;0 ••", liP ,M,

JAN I FEB ! MAR I APR I MAY

10 20 3'0 4'0 s'o a'o 7'0 a'o 90 100 110 120 13'0 140

DAYS

FIG.2. Fifteen-month timeseries of currentvectors from the 35-mlevelat site2, Lombok Strait

3. The numerical model

To examine the mean, seasonal, and interannual variability of the Pacific to Indian Oceanthroughflow and the forcing mechanisms responsible for the variability, we use the mostrecent version of the NORDA Global Model, forced by the European Center forMedium-Range Weather Forecasts (ECMWF) 1000 mb winds from 1980 through 1987.

The NORDA Global Model is a multi-layer, primitive equation formulation thatincorporates a free surface, arbitrary coastline geometry, full-scale bottom topography inthe lowest layer, and a semi-implicit time scheme. The numerical simulation utilizes aone-active-layer, reduced-gravity version of the model, which includes the effects of mixingand mean thermodynamics. Hence all transport is concentrated in the upper layer. Themodel grid resolution is 0.50 in latitude and 0.70 in longitude. For further details of themodel, see accompanying papers by Kindle et al., and Hurlburt et al., in this volume.a. Observations and ModelResults

The annual mean wind stress in the western equatorial Pacific Ocean, especially thesearising from the steady westerly directed trade winds, create a persistent elevated watersurface south of the Philippines, clearly illustrated in both the model simulation (not shown)and the GDEM dynamic height climatology of the same area (0/1000 db), which shows a21-24-cm drop in sea level from south of the Philippines to the Indian Ocean south of Java.A persistent southward flow down the Makassar Strait results throughout the year, as shownin both the ship drift observations and our model results. Figure 3 illustrates the model

148

FIG.3. The model velocity field in thestudy area on May 28, 1985.Representative current speeds (cm/sec)are shown at a few locations.

T =0.64 e·032 v

results for the upper layer velocity field in the throughflow region on May 28, 1985. Thestrong southward flow in the Makassar Strait (30-60 cm.s·l ) , fed from the SulawesiSea, bifurcates at the archipelago, one branch entering directly into the Indian Oceanthrough the Lombok Strait and the other branch flowing east through the Flores and Bandaseas. The time series of transport predicted by the model for 1985-1986 is compared to ourobservations in Figure 4.

The computations of observed transport through the Lombok Strait presented in (Murrayand Dharma Arief, 1988) are based on monthly block averages of current meter data, whichallowed for temporal variation in the vertical current profile. In order to increase temporalresolution for a comparison to the model output, the carefully determined monthly averagetransports were regressed against monthly average velocity components from variouscurrent meters. A best-fit relation (R2 =0.79) determined over the range of the monthlyaverages (5 s v s 55 cm.s'J):

where T is transport in Sv and v is the monthly average north-south component of currentspeed at the 35-m level (V35) at the site 2 mooring, gave best results. Utilizing thisrelationship, the v time series from this current meter was passed through a 30-day low-passfilter (v (LP» and used to compute transport. For the limited amount of data outside therange of the monthly averages where v (LP) < 5 cm.s· l , we let T ~ 0 linearly with v (LP).Correspondingly, when v (LP) > 55 cm.s-', an algorithm where v =constant =v35 in theupper 100 m and decreases parabolically to 0 at 200 m gave good results.

Figure 4 shows a comparison between transport through the Lombok Strait calculatedfrom the observations in this manner and from the numerical model. In all figures,eastward- and northward-directed flows are positive; westward- and southward-directedflows are negative. Owing to restrictions on the model grid size, the Lombok opening inthe model for the upper active layer is about 2.2 times the actual cross section of the straitabove the 200-m depth level, where the net transport is calculated. Note a transport scaleadjusted for this discrepancy on the figure. We note the general agreement in phase

149

? ? ? ?.: -.. :: OBSERVED TRANSPORT : ~ jl. \

0.0

> -1.0Ill·

\j...a:0la. -3.III FlG.4. The transport through thezc -4. Lombok Strait predicted by the modela:...

-5.0 compared to the transport observed in

-e. the north strait, The right side of theMODEL TRANSPORT c lower panel is a scale corrected for

11/

excess cross-sectional area mandated-2.0 Cl:> CCD Cl by modellimitations... -".0 11/Cl: ..0 u... 11/

CD -S.O-3.

Cl:z Cl:c 0Cl: -s.e u.. -... >

CD

-10.00 120 3S0 .. SO

between the major pulse in southward transport and the good agreement in magnitudebetween the model adjusted transport and the observations. The distinct pulse of lowsouthward transport in February because of intense cyclonic activity in the Timor Sea ispresent in both the observations and the model despite the fact that the model is driven bymonthly averaged winds. The period of low transport in the observations from November1985 to February 1986 appears to be well modeled also.

In Figure 5 the observed transport in Lombok is compared to the observed sea leveldifference between Davao and Darwin. While the period of largest southerly transportcertainly occurs in the months of the northern summer, when the sea level difference ishigh, there does appear to be a 2-month lag of maximum Lombok transport with thegreatest sea level difference. This suggests Darwin, with its location on the inside of theextremely wide Sahul shelf, is not the best index for the sea level in the Timor Sea. Despitethis disagreement in phase, the long temporal drop in sea level slope from September 1985to February 1986 is accompanied by decreasing transport.

0.0

> -1.0III...a:0la. -3.IIIzc -4.a:...

-5.0

-e.

? ?... ... :; OBSERVED TRANSPORT

? ?1\

FlG.5. The observed transport in thestrait compared to the Darwin minusDavao sea level difference. January1985-March 1986.

SEA LEVEL Dlff DAVAO-DARWIN 18S5

15.02u...; -5.01&1:le

3eo120 240TIME IN DAYS

-25.0~-....,--.....,....----.--~-....----~:-----r­o

150

The surface dynamic height field (0/500 db) determined during the first week of June1985 is shown in Figure 6, and the model simulation of the free surface elevation is given inFigure 7. The general agreement in the overlap area, the west Flores Sea-Makassar Straitjunction, is encouraging. A bulge of the sea surface south of Sulawesi and a drop in sealevel of 8-10 cm from the Flores Sea south of Sulawesi to the Java shelf is present in bothmodel and data.

SO JAVA SEA

FIG.6. Dynamic height (dyn. cm) as observed onour cruisein the flrst weekof 11Dle 1985.

FIG.7. Deviation of the free surfacepredicted by the model for 28 May1985. Compare the overlapping areas inFigures 6 and7.

151

With a certain degree of confidence now established in the model, it is interesting at thispoint to investigate the model results relating the Lombok Strait transport to the totalIndonesian throughflow. In Figure 8 the total throughflow (PACIO) computed across114.75°E in the Indian ocean between Java and Australia reaches maximums of 17.5, 14,and 10 Sv in 1984, 1985, and 1986, respectively. Lombok (LBK) is predicted to carryroughly half the flow during maximum transport phases and the entire southwardthroughflow during low transport phases, there arising a back flow into the Banda Seaduring these periods. The transport southward down the Makassar Strait predicted duringthese three years (Fig. 8, lower panel) suggests Makassar is carrying -70% of thethroughflow during peak periods. At certain times, however, as in the first quarter of 1986,the southward transport in the Makassar Strait exceeds the throughflow, indicating storagewithin the archipelago or a recirculation back into the Pacific through the passages betweenIrian Jaya and northeastern Sulawesi.

Or---t+------------;-----"lrr------:-:----:-:---=-=-=--::--::~:_:_:=--__i

-2.5

: -5.0=»a:Q -7.5a:w~ -10.0

-12.5

-15.0

-17.5

-2.5

: -5.0=»a:Q -7.5a:w> -10.0(/)

-12.5

PACIO(1 1 4.0 5 E. 2 2.00 S)T 0 (1 1 4.0 5 E • 9 . 0 0 S)

MAKASSARSTRAIT

(118.27E. Ea) TO (119.67E. Ea) NOROA 323 5 -MAY-59

FIG.8. Transport through the Lombok Strait (LBK), the total Pacific-Indian throughflow (PACIO) across114.75°E, and southward transport in the MakassarStrait across the equator, 1984-1987. Negative values offlow for Lombokand Makassarare southwarddirected,but westwardfor the PACIOflow.

152

b. Sea LevelDifferencesThe observed Davao-Darwin sea-level difference and the observed zonal wind stress in

the Indian Ocean south of the archipelago during our observation period are compared tothe model transport through the Lombok Strait in Figure 9. The interrelationship betweenthe three signals is clear. The westward zonal wind stress in the Indian Ocean appears to bea key factor in depressing the Timor Sea water level and in pulling water southward throughthe Lombok Strait

SEA LEVEL DIFF DAVAO-DARWIN 1885

1886-1888 WIND-STRESS IN THE INDIAN OCEAN-ECMWF WINDS

16:I0

...J:Cl -6wJ:

-26I

\.10

C\I .06:I...z 0)(

I;:)

-.06-e...-.10

-.16,

-2.0>Ul

... -4.0er0e,

-8.0Ulz-eer -8.0...

-10.00 120 240

TIME IN DAYS

380

cCW

-1.0 ~

ow...ower

-3.0 eroo

-4.0 ~

480

FIG.9. The model transport through the Lombok Strait compared to theaverageECMWF wind stress in theTimorSeaand Davao-Darwin sea leveldifference for theperiodJanuary 1985-April1986.

The change in the free surface elevation in the model at 126°E, 6°N (off the Philippines) iscompared to the observed Davao sea level in Figure 10. The 15-20 cm range in bothsignals and the sharp rise in the first 4-5 months of 1985, followed by a gradual 8-monthdrop, also in both signals, are all encouraging. The sea level difference between thePhilippine grid point and the Lombok grid point compared to the observed Davao minusDarwin signal (Fig. 11) is considerably less satisfactory. We suspect Darwin is not a goodrepresentative point for sea level in the Timor Sea, a point that needs to be explored further.The ranges of sea level differences at 20-30 cm and the occurrence of the maximum

relative slope in mid-summer in both cases, however, supports the general validity of themodel.

153

30

i~.. 10 FIG. 10. Observed sea level at Davao:z:Cl compared to sea level at the model gridjjj:z: point off the southern Philippines at l260E,

06ON.

0:0/01/01188-10

80 120 180 240 300 380 420TIME IN DAYS

30

20

i~ 10 FIG.lt. The Davao-Darwin sea levelwo

differences, January 1985-March 1986,zw 0er compared to the sea level differencew...... between the model grid points off the0- 10

southern Philippines and the Lombok-20 Strait.

0 80 120 180 240 300 380 420TIME IN DAYS

4. Summary

Observations of currents, transport, sea level, and sea level slope in Lombok Strait andwest Flores Sea in 1985 and 1986 have been compared to a simulation of the NORDAglobal ocean model in the Indonesian throughflow region. Despite the relatively coarsegrid scale of the model compared to topographic length scales in the region, the modelappears to be realistically reproducing many of the observed features. The predictedtransport through the Lombok Strait, for example, agrees with detailed observations ofphase and magnitude, especially when corrected for grid size limitations. The sea surfacefluctuations and sea surface slopes predicted by the model agree within less than a factor of1.5 with sea level changes and slopes observed on tide gauges. There do appear to beseveral cases of phase difference of several months between model and observations thatrequire further investigation.

REFERENCES

Cox, M., 1982: Numerical Models of Ocean Circulation. National Academy of SciencePress, Washington, D.C.

Fine, R. A., 1985: Direct evidence using tritium data for throughflow from the Pacific intothe Indian Ocean, Nature, 315, 478-480.

Fu, L., 1986: Mass, heat and freshwater fluxes in the south Indian Ocean, J. Phys.Oceanogr., 16, 1683-1693.

Godfrey, J. S., and T. 1. Golding, 1981: The Sverdrup relation in the Indian Ocean, and theeffect of Pacific-Indian Ocean through flow on Indian Ocean circulation and on theEast Australian Current, J. Phys. Oceanogr., 11, 771-779.

Gordon, A. L., 1986: Interocean exchange of thermocline water, J. Geophys. Res.; 91,5037-5046.

154

Hurlburt, H. E., J. C. Kindle, and E. J. Metzger, Results from a global ocean model in thewestern tropical Pacific, 1989.

Kindle, J. C., G. Heburn, and R. Rhodes, 1987: An estimate of the Pacific to IndianOceanthroughflow froma global numerical model, Interannual variability of the Pacific toIndianthroughflow, I : Furtherprogress in equatorial oceanography (E. Katz andJ.Wine, 008.), Nova University. In: Furtherprogress in equatorial oceanography (E.Katz and1. Wine, eds.), Nova University Press, Ft. Lauderdale, FL, 317-321.

Kindle, J. C., H. E. Hurlburt, andE. J. Metzger, On the seasonal and interannual variabilityof the Pacificto Indian Ocean throughflow, 1989.

Murray, S. P., and Dharma Arief, 1986: Effect of Indian Ocean cyclones on net flowthrough the Lombok Strait. Indonesia (abs.), E05, 67, 1017, AGUFallMeeting,December 1986.

Murray. S. P., and Dharma Arief, 1988: Throughflow into the Indian Ocean through theLombok Strait, January 1985-January 1986, Nature, 333, 444-447.

Piola, A. R., and A. L. Gonion, 1984: Pacificand Indian Oceanupper-layer salinity budget,J. Phys. Oceanogr., 14,747-753.

Wyrtki, K., 1961: Physical oceanography of the Southeast Asian waters, Scientific Resultsof Maritime Investigations of the South ChinaSea and Gulfof Thailand 1959-1961,NAGA Rep., 2, 195 pp., Scripps Inst.Oceanogr., La Jolla, California, U.S.A.

Wyrtki, K., 1987: Indonesia throughflow and the associated pressure gradient, J. Geophys.Res., 92, 12941-12946.

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

x

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

xi

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