Diurnal variation over the tropical monsoon regions during northern summer 1991

188 Pages·1.8 MB·English

by  Jiminez, Greg M

NPS ARCHIVE
1997
e 0^>
JIMINEZ, G.
NAVAL POSTGRADUATE SCHOOL
Monterey, California
THESIS
DIURNAL VARIATION OVER THE TROPICAL
MONSOON REGIONS DURING NORTHERN
SUMMER
1991
by
Greg M. Jimenez
March 1997
Thesis Advisor: Chih-Pei Chang
Co-Advisor: Peter C. Chu
Thesis
J503 Approved for public release; distribution is unlimited.
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1. AGENCYUSEONLY (Leaveblank) REPORTDATE 3. REPORTTYPEANDDATESCOVERED
March 1997 Master's Thesis
4. TITLEAND SUBTITLE DIURNALVARIATION OVERTHE TROPICAL FUNDINGNUMBERS
MONSOON REGIONS DURINGNORTHERN SUMMER 1991
6. AUTHOR(S)Jimenez, Greg M.
PERFORMINGORGANIZATIONNAME(S)ANDADDRESS(ES) PERFORMING
7.
Naval Postgraduate School ORGANIZATION
Monterey CA 93943-5000 REPORTNUMBER
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AGENCYREPORTNUMBER
11. SUPPLEMENTARYNOTES Theviews expressedinthis thesis arethose ofthe authoranddonotreflectthe
officialpolicyorpositionofthe DepartmentofDefense ortheU.S. Government.
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13. ABSTRACT (maximum 200words)
Thisstudyexaminesdiurnal variationofconvectionoverwesternIndia,theBayofBengal,IndochinaandthenorthernSouth
ChinaSeaduringthe 1991 northernsummermonsoonusingcombinedJapanese(GMS)andIndian(TNSAT)geostationarysatellite
data,ECMWF 850hPawinddata, andNCEPseasurfacetemperatureanalyses.
Thediurnalcycleisexaminedintermsofspatialandtemporalstructurepriortoonsetandduringthemonsoon. Thenorthern
SouthChinaSeaisexaminedtodeterminehowdifferentperiodsofsynopticinfluencesresultedinananomalouslystrongdiurnal
signalduringJune. ThewindandSSTdataareusedtoexaminetherelationshipbetweenthediurnalvariationofconvectionandboth
low-levelconvergenceandvertical latentheatfluxes.
ConvectionoverwestIndiaismostcommonduringMayandJuneandstartsasadiurnal systemoverlandthatbecomes
organizedandpropagateswestwardovertheeastArabianSea. TheBayofBengal followstheclassicland-seabreezemodeland
convection ismodulatedbyconvergencebetweenthelandbreezeandlarge-scalemonsoonflow. Thediurnalcycleisgenerally
enhancedovertheoceanduringactivephasesofconvectiveactivity. Themaximumlatentheatfluxesgenerallyoccurspriorto
maximumconvectionduetostrongmonsoonflowenhancingevaporation.
14. SUBJECTTERMS 15. NUMBEROF
DIURNAL VARIATION, WEST INDIA, ONSET OFNORTHERN SUMMER PAGES 175
MONSOON OVERINDIA, MONSOON CONVECTION 16. PRICECODE
17. SECURITYCLASSIFICA- 18. SECURITYCLASSIFI- 19. SECURITYCLASSIFICA- 20. LIMITATIONOF
TIONOFREPORT CATIONOFTHIS PAGE TIONOFABSTRACT ABSTRACT
UL
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Approved for public release; distribution is unlimited.
DIURNAL VARIATION OVER THE TROPICAL MONSOON REGIONS
DURING NORTHERN SUMMER
1991
Greg M. Jimenez
//
Lieutenant, United States Navy
B.S., Colorado School ofMines, 1986
Submitted in partial fulfillment
ofthe requirements for the degrees of
MASTER OF SCIENCE IN METEOROLOGY
MASTER OF SCIENCE IN PHYSICAL OCEANOGRAPHY
from the
NAVAL POSTGRADUATE SCHOOL
March 1997

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ABSTRACT
This study examines diurnal variation ofconvection over western India, the
Bay ofBengal, Indochina and the northern South China Sea during the 1991 northern
summer monsoon using combined Japanese (GMS) and Indian (INSAT) geostationary
satellite data, ECMWF 850 hPa wind data, and NCEP sea surface temperature
analyses.
The diurnal cycle is examined in terms ofspatial and temporal structure prior
to onset and during the monsoon. The northern South China Sea is examined to
determine how different periods of synoptic influences resulted in an anomalously
strong diurnal signal during June. The wind and SST data are used to examine the
relationship between the diurnal variation of convection and both low-level
convergence and vertical latent heat fluxes.
Convection over west India is most common during May and June and starts
as a diurnal system over land that becomes organized and propagates westward over
the east Arabian Sea. The Bay ofBengal follows the classic land-sea breeze model
and convection is modulated by convergence between the land breeze and large-scale
monsoon flow. The diurnal cycle is generally enhanced over the ocean during active
phases ofconvective activity. The maximum latent heat fluxes generally occurs prior
to maximum convection due to strong monsoon flow enhancing evaporation.
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VI
TABLE OF CONTENTS
INTRODUCTION
I.
DATA AND METHODOLOGY
II. 9
A. SATELLITE IMAGERY 9
WIND DATA
B. 11
OCEANOGRAPHIC DATA
C. 12
REMARKS
D. 17
m. WESTERN INDIA AND EASTERN ARABIAN SEA 21
MAY
A. 1991 21
B. JUNE 1991 30
C. JULY 1991 34
IV. BAY OF BENGAL 39
A MAY
1991 39
B. JUNE 1991 42
C. JULY 1991 45
D. AUGUST 1991 48
Vll
INDOCHINA
V. 51
MAY
A. 1991 51
B. JUNE 1991 53
C. JULY 1991 55
AUGUST
D. 1991 57
NORTHERN SOUTH CHINA SEA
VI. 61
A. JUNE 6-11, 1991 62
B. JUNE 19-26, 1991 63
SUMMARY AND CONCLUSIONS
VII. 153
LIST OF REFERENCES 161
INITIAL DISTRIBUTION LIST 165
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