407

Hydrological Effects on the Air-Ocean Coupled System

PechengC.mu and Roland W. GARWOOD, Jr

Department ofOceanography, Naval Postgraduate SchoolMonterey, CA 93943 - V.SA.

ABSTRACT

The ocean and atmosphere are driven by the Iluxes of momentum, heat, andwater mass. The importance of the Iluxcs of momentum and heat is well recog-nized by both meteorologists and oceanographers. The hydrological cycle is,however, only given considerable attention in atmospheric models since the latentheat release is an important source of the atmospheric general circulation. Thehydrological cycle is given less attention in ocean models although it is realizedthat evaporation and precipitation are contributors to the surface buoyancy fluxwhich determines the depth of mixing and drives the thcrmohalinc circulation.

The cloud and the ocean mixed layer are highly coupled by both the heat andmoisture fluxcs across the air-ocean interface. Two time scales are found in thispaper: a sea surface temperature (SST) time scale, TT' that is virtually controlledby the oceanic planetary boundary layer (OPBL), and a cloud-SST coupling timescale, T", T' These two time scales depend on the stability of the marine atmo-spheric boundary layer (MA BL).

An air-ocean model is developed in this paper for the coupled system of anunstable atmosphere overlying a stable ocean. The model results demonstratethat the exchanges of heat and water lluxcs across the sea surface leads to bothgrowing and decaying modes of oscillation on 3-6 day and 20-30 day time scales.These oscillatory solutions are entirely thermodynamic and do not require wavedynamics for their existence.

1. Introduction

Since 1970 significant progress has been made both in our ability to carry outair-sea interaction field work and in our understanding of many of the processesfound on both sides of the air-sea interface. Many studies, both observational andtheoretical, have shown that the surface wind and the SST are two important el-ements in the air-sea coupled system (Chu, 19R9). Since clouds have significanteffects on the large-scale atmospheric circulation through the transfer of heat andmoisture, and on the OPBL through the attenuation of the solar radiation at theocean surface, there may he strong feedback between the clouds and the OPBL.Fig.l shows the main physical processes (heat, mass, and momentum fluxcs) atthe two adjacent boundary layers: the OPBL and the marine atmosphericboundary layer (MABL). Fig.2 illustrates the feedback pathways between theclouds and the ocean mixed layer.

408

b_.1._-

Fig.! Main physical processes at the two adja~ent. ~oulldary layers.

Surface SalinityFlux

fig.2 Feedback paths between OPBL and clouds.

The feedback mechanism between clouds and ocean mixed layer in the buoy-ant forcing regime (upward buoyancy nux at the ocean surface) was illustratedby Chu rind Garwood (1989). However, the TOGA (Tropical Ocean Global At-mosphere Program) observations have shown the warm pool regions of the west-ern Pacific to be in the buoyant damping regime (downward buoyancy nux) forthe OPBL due to fresh water influx caused by an excess of precipitation overevaporation. The OPBL is usually stable, and the MABL is generally unstable.Therefore, the feedback mechanism in this coupled system (unstable MABL -stable OPBL) should have different form from the buoyant forcing case.

Although our coupled model is one-dimensional, we are aware of the impor-tance of the horizontal advection and the limitation of one-dimensional models.However, the intent of this work is to develop a formalism to examinethermodynamic feedback between the two fluids. Because we wish to concentrateon the thcrrnodyna mic intcraction, horizontaI advection is ignored initially,

409

2. Similarity Functions in the MAUL

According to the similarity theory it is assumed that if a variable (wind, tem-perature, or moisture, etc.) is appropriately scaled, then its profile follows a uni-versal function whose form, in general, is determined empirically. For thebarotropic atmosphere the appropriate scales for wind and height are

(I )

where U, is the geostrophic wind speed, which is assumed here to be 10mls , 1.10

•

is the atmospheric friction velocity. The geostrophic drag coefficient CR is definedby Yamada (1976) as

e = ua* = K{[ In(~) - Ai + B2}- 1/2 (2)g IUgl Zn

where K is the von Karman constant, 0.4. The roughness parameter, Zo, is ap-proximately 1.5 x 10"m. The ratio ""Izo is 0.6 x H)7 for an MABL height,ha = Ikm. The heat and moisture transfer coefficients are determined hy

w'aO' In IV'aq' 10ell = - A , CH = - A (3)

ua*[O - O(zo)] , ua*[q - q(zn)]

where W, 0, q are the vertical velocity, potential temperature, and specific humid-ity, respectively. The supcrscript 11 , 11 means the disturbanee, and 11 1\ 11 indicatesthe values being taken at the top of the MABL. The heat transfer coefficient isfurther computed by Yarnada (1976) as

c, = = _K_ [In( 11.-) - C]-I (4)Pr,,· Zo

where Pro is the turbulent Prandtl numbcr for neutral stability, having a value of0.74 according to Busingcr et al. (1971). Based on thc Wangara data, thc simi-larity functions A, B, e are experimentally determined by Yamada (1976) for t.hestable atmosphere:

A = 1.855 - 0.38hal La (0 s h(JI L(J s 35),

A = -2.94(hal La - 19.94)1/2 (35 < ha/l.J(J);

B = 3.02 + 0.3holLa (0 ~ "alLa S 35),

B = 2.R5(hal La - 12.47) I /2 (35 < halLa);

C = 3.665 -0.829halLa (0 :::;; hatLa s IR),

e = -4.23(lzalLa - 11.21 )1/2 (18 < halLa)

and for the unstable atmosphere (/'"IL" < 0)

A = 10.0 - 8.145(1 - 0.008376IzaILa)- 1/3,

B = 3.02(1 - 3.29haILa)- 1/3,

(Sa)

410

C= 12.0-8.335(1 -0.03106haILar-I /3 (5b)where L" is the atmospheric Obukhov length scale. The computation for themoisture transfer coefficient is not very clear yet. In this paper we assume that

(6)

Substitution of (5 a.b) into (2) and (4) leads to the apparently strong dependenceof Cg, Cll , Cr: on the atmospheric stability parameter hl1lL", as shown in Fig.3.These parameters have much larger values for the unstable lIH1n for the stableatmosphere, i.c.,

Cg rv 0.0316, Cfl ' C,;; rv 0.063 (IInlLfl < 0)

eg rv 0.003, Cfl , Cl: rv 0.004 (lIalLfl > 0)o

10 r ,

'CII , CF.-'_-~ .~

10 2

10 I-j-----,--.,----r------r__....--_--.-600.0-iOO.0 -200.0 0.0 200.0 iOO.O 600.0

h..L..

Fig.3 Dependence of Cg , CII , C,,. 011 the atmospheric stabilityparameter (h,,1 L,,).

(7)

3. Time Rate of Change of the Cloud Cover

The time rate of change of cloud cover is assumed to be proportional to themoisture supply divided by the amount of water vapor necessary to produce themodel cloud. The main processes causing the cloud dissolution are precipitationand mixing with the environmental air. The cloud evaporation due to mixing withambient air is a complicated problem, and is neglected for the sake of simplicityhere. Thus the equation for cloud cover is

anat -

(AltO + E - Pr)hr.

(R)

where he is the total amount of water vapor needed to create the cloud over a unitarea. From mean distrlbutions of temperature and mixing ratio in the environ-mental air outside the cloud and inside a deep cumulus cloud (Kuo, 1965), weestimate that he rv .'5 cm. The large-scale horizontal moisture convergence in thecolumn of atmosphere per unit area is denoted MtO•

411

4. Relationship between Precipitation Rate and Cloud Cover

By linear regression of hourly rain amounts and satellite IR brightness dataobtained during Phases I, 11, and Ifl of GATE, Alhright et al. (1985) presenteda linear relationship between average precipitation rate P,. in boxes 1.5" (168 km)on a side and cloud cover n of the boxes by clouds wit.h tors coklcr than -36" C:

P,(ms- I ) = (0.472 + 8.33311) x 10-7 (9)

This result confirms Arkin's (1979) earlier analysis for the GATE Bvscalc array.

( 10)

5. Ocean Mixed Layer

Much of the one-dimensional theory for the OPBL or mixed layer is depend-ent upon the validity of two crucial hypotheses. The first of these is that verticalmixing within the turbulent boundary layer and entraiment mixing at its baseoccur in response to the local atmospheric forcing - the surface wind stress andthe buoyancy flux at the sea surface. The second hypothesis is that the mechan-ical energy budget is the key to the understanding and prediction of mixed layerdynamics (Garwood, 1977, 1979).

The buoyancy flux is attributable to heat nux, evaporation, and precipitation.The shear production of turbulence is attributable to surface wind stress. In thewestern Pacific warm pool regions, the excess precipitation effect prevails over thebuoyancy effect of heat lost at the ocean surface, causing the net buoyant nux tobe downward. The mixed layer depth equals the Obukhov length scale:

32uw•

hw = LW=-B-

where L; is the oceanic Obukhov length scale. The oceanic friction velocity is

and B is the downward surface buoyancy flux

ClgFB =flgS(P, - E) - Pwc

pw(11 )

(12)- AT

where Pa, Pw are the air and sea water densities, Cl is the sea water thermal ex-pansion coefficient, and fI is the salinity contraction coefficient. Because theOPBL is in the buoyant damping regime, the mixed layer heat and salinitybudgets include no entrainment:

er; Fif! = - (w),

PwCp 11'.'

(13)as (E - P,)S-=+ -Asat hI'.'

where c;lt') is the specific heat under constant pressure. The parameters AT and Asare the horizontal advcction for temperature and salinity, respectively.

412

The effects of clouds on the buoyancy nux at the ocean surface arc two-fold:(I) decreasing 80 through the increase in the net heat loss at the ocean surface, F, by reducing the incoming solar radiation, and (2) increasing 80 due to prccipi-tation. The net heat loss from the ocean surface is given by

where q,(T) is the saturated mixing ratio. The incoming solar radiation absorbedby the ocean surface is R" and RI. is the net energy loss from the ocean surfaceby longwavc radiation, L is the latent heat of vaporization of water, and H, is thesensible heat nux to the air. The standard bulk formulae arc used to calculate thesurface cvapora tion:

(15)

6. Cloud Effects on the Net Radiation at the Ocean Surface

Clouds reduce the solar radiation incident at the ocean surface by scatteringand absorption, which is computed by Budykn's (J978) formula

R, = [I - aslIll - (l.~1l(1 - I1)JRJII (16)

Here R.o (340 W I1l 2) is the solar radiation absorbed by the ocean surface layerunder a clear sky. The parameters IX.," and a..o represent albedos of the earth-atmosphere system with complete cloud cover ancl a cloudless sky, respectively,and have the following values:

a.m = 0.46, a.11I = 0.2

Thc ocean surface emits longwavc radiation to the atmosphere and to space.However, clouds, as well as dry air, partially absorb the radiation and re-emitiongwavc radiation back to the OCC:ln surface. Thus the net upward energy lossby longwavc radiation at t.he ocean surface, RII, is corrected for the downwardradiation by the clouds and the air. From longwavc radiation data, Budyko(1978) derived a scrni-crnprical formula:

R,,=a-f-hT-(al +"1)11 (17)

The dimensional coefficients a, h, a l , and b,

413

redly related to the exchange at the air-ocean interface. From the basic equationsof the coupled system (R), (10), (12), and (13), the pcrturbations satisfy the fol-lowing equations:

an' = ~ ( aE T'IV _ ar, 11')at h er; anc

- -, hw , hw exg aF - aE r

h IV = - -=- B = -=- [( f' (' -aT + fJgS -;-1' )1' IVB B IV -pw IV 0 IV

- - -, exg aF - ap, ,- flgS(P, - E)S + ( fJ c -~- - figS -a-)n ]

wpw Oil n

aT' I - - Fh'w I ( aF n' +~ 1" + w )~ = - I) c(w)Ti an aTw w hwp w w

as' (E - P ) s (P - E)S--=--.....;.'- S' + --=- (E' - P',) + ' -'\ h' wjjf= I I I'Llw 111' 111'8. Three Basic Time Scales

Three time scales are found from (IR)-(21):

Cloud time scale

_I lap,T ----

11 --- he an

Using (9) and taking he = Scm, we have

TIl '" 0.6 day

SST variation time scale

(1 R)

(19)

(20)

(21 )

(22)

(23)

(24)

. 11

The net heat loss from the ocean surface is computed by (14). Assuming that 0and qare determined by the large-scale atmospheric motion, we have

2aF L ~ CE~ = Pacpal/g( I + 2 C )Cgell

w cpaRvTw '11

therefore

(25)

Cloud and SST coupling time scale

414

(26)

(27)

Using (16) and (17) we have

ofon =

o(RI - R) 2) S -15 11/ . -~ . r nl011

I

Among these three time scales, L" is the shortest. The other two, L.,. and L",,,,,largely depend on the parameters CR, ell' and CF. , which arc functions of the at-mospheric stability. FigA shows the dependence of LT and L",,,, on the atmosphericstability. For the unstable atmosphere (It,,/ L(I < 0), L",.,. '" 3 - 6 days, andL.,. - 20 - 30 days. For the stable atmosphere (h) L" > 0), L",,,, - 0.3 - 1 years,and LT IV I - 3 years.

Ill'

10

---------'t'\'»>:' 't «r: _.--:

/,J

'-'--'----SOO.O-iOO.O -200.0

o -j-----,---.----y----.---r-----.I0.0

IIaLa

rig.4 Dependence of r, and t",r on the atmospheric stabilityparameter ha/ L,,).

9. Solutions

Since the time scale for cloud feedback is so much shorter than that for SSTfeedback, i.e., LIt~LTt the cloud cover perturbation, n', almost instantaneously fol-lows the SST for the temperature feedback:

oetet;11' = 1"IV (2R)

i)P,/on

Eq.(9) shows that

t1P, -7 -I-:"1- - H.3.1 x to I1lS ,

till

(30)

415

and for Till = 25"C, U(I' = 0.1m]s,

ee C dq,r(zo) 463 10-7 -IK-IaT = EUa• dT "".) x ms .w . w

Therefore, a I"C change in SST implies a 0.56 change in cloud cover.

Neglecting the small terms in the prognostic equations for T'III and S' andeliminating three among the four variables n', T'III' S' , and h' HI from (19), (20),(21), (28), we obtain the second order differential equation,

a21/J 2p - l' -I -I at/I W/ -I -I 2-- - [r 'I' + T7' ) - + (T 'I' + T7' ) I11 = 0 (29)at2 l' - It n, at (l' _ p)2 n.

where t/I represents n', T' w' S'/ , and h'lV' There are two nondimcnsional parame-ters,

4a.gF/pwcpw 4pg(P, - 1tl"sIt - l'-- -- I I' - -- I I

{JghwS(T;'r -I- TT ) {JghwS(T;'r + TT )that indicate the relative importance of mean heat and mean salinity fluxcs in themean surface buoyancy nux (11). The general solutions of (29) have the form:

I/J = Cl exp«(1l t) -I- C2exp«(12t) (31)

where Cl and C2 are integral constants, and (11 and (12 are the cigcnvalucs whichare the roots of the second-order algebraic equation

22 21t - l' ( -I -I) Pl' ( -I -1)2 () (32)(1 - l' _ p Tn.T+ TT (1 + ( )2 T",T+ TT =

l'-p

10. Instability and Oscillation Criteria

The instability criteria for the thermodynamically coupled air-ocean systemare

0 growing (33)

where G is (11 or (12' the root of the second-order equation (32). The oscillatia cri-terion for the coupled system are

Im(a)1

= 0 nonoscillatory

t-= 0 oscillatory (34)

The roots (1. and (12 are

(2p - l') _I -1 ~ 2 2(112= 2(- ) (T" T + TT )[1 ± (I - Ill' /(2/1 - l'). l' - It • (35)

416

The condition for the generation or growing/decaying modes, which can he de-duced from (38), is:

0 growing (36)

and the condition for oscillatory/nonoscillatory modes is:

> /1 nonoscillatory

< Il oscillatory (37)

Separation or different modes in the y - l' plane is shown in Fig.5. For thebuoyant damping regime (B > 0, i.c., Y > 11> 0) which corresponds to the westernPacific warm pool regime, the relative importance or the mean surface heat andsalinity fluxes in the mean buoyancy nux B is a key factor controling the modesor the coupled air-ocean system. The mean surface salinity flux, measured hy )I,makes the upper ocean more buoyant (stabilizing factor), however, the mean up-ward heat flux, measured by /1, makes the upper ocean less buoyant (dcstabilizingfactor). The larger the parameter Y (/1) , the stronger the negative (positive)feedback mechanism. Combining (36) and (37) leads to the same results:

2J.lY > -e-Nonoscittatory Damping, - JP

2/1---- > Y > 2/l =>O.w:illalory DampingI-j;

2J.l2Jl > Y > =>o.fj(~illalory Growing

I +f;

2/1---->Y>/II +j;

-e-Nonoscillatory Growins; (38)

417

\.0

!!;c.:::;s~s

0.0 ~~,....§~::::\,;

Ll.G· ~~....

418

REFERENCES

Albright, M.D., E.E. Recker, R.J. Reed, and R.Q. Dang, 1985: The diurnalvariation of deep convection and inferred precipitation in the central tropicalPacific during January- February 1979. Mon. Wea. Rev., t 13, 1663-16RO.

Arkin, P.A., 1979: The relationship between fractional coverage of high cloudand rainfall accumulations during GATE over the Bvscalc array. Mon. Wea.Rev., 107, 13R2-13R7.

Budyko, M.I., 197R: The heat balance of the earth. Climatic Change (cd. J.Gribbin), Carnbgidgc Univ. Press, R5-113.

Chu , P.C., 19R9: Relationship between thermally forced surface wind and seasurface temperature gradient. Pure & App!. Geophys., 130, 31-45.

Chu, P.c., and R.W. Garwood, Jr., 19RR: Comment on "A coupled dynamic-thermodynamic model of an ice-ocean in the marginal ice zone" by SirpaHakkincn. J. Geophys. Res., 93, 5155-5156.

Chu, P.c., and R.W. Garwood, .lr., 19&9: Cloud - ocean mixed layer feedback.AMS Symposium on the Role of Clouds in Atmospheric Chemistry and GlobalClimate, 39-44.

Garwood, R.W. Jr., 1977: An oceanic mixed layer capable of simulating cyclicstates. J. Phys. Oceanogr., 7, 455-46R.

Garwood, R.W. Jr., 1979: Air-sea interaction and dynamics of the surface mixedlayer. Rev. Geophys. Space Phys., 17, 1507-1524.

Kuo, I-LL., 1965: On formation and intensification of tropical cyclones throughlatent heat release by cumulus convection. J. Atmos. ScL, 22,40-63.

Yamada, T., 1976: On the similarity functions A, 13, and C of the planetaryboundary layer. J. Atmos. ScL, 33, 7R 1-793.

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