Simulation of atmospheric frontogenesis with a semi-Lagrangian numerical model. PDF
Preview Simulation of atmospheric frontogenesis with a semi-Lagrangian numerical model.
NAVAL POSTGRADUATE SCHOOL Monterey, California THESIS SIMULATION OF ATMOSPHERIC FRONTOGENESIS WITH A SEMI-LAGRANGIAN NUMERICAL MODEL by Ricardo Carvalho de Almeida September 1991 Thesis Advisor: RogerTerry Williams Approved for public release; distribution is unlimited T256904 Unclassified SECURITYCLASSIFICATIONOFTHISPAGE REPORT DOCUMENTATION PAGE la REPORTSECURITYCLASSIFICATION 1b RESTRICTIVE MARKINGS Unclassified 2a SECURITYCLASSIFICATIONAUTHORITY 3 DISTRIBUTION/AVAILABILITYOF REPORT Approvedtor publicrelease;distribution isunlimited 2b DECLASSIFICATION/DOWNGRADINGSCHEDULE 4 PERFORMINGORGANIZATION REPORTNUMBER(S) 5 MONITORINGORGANIZATION REPORT NUMBER(S) 6a NAME OF PERFORMINGORGANIZATION 6b OFFICESYMBOL 7a NAMEOF MONITORINGORGANIZATION Naval PostgraduateSchool (Ifapplicable) NavalPostgraduateSchool 55 6c ADDRESS(City,State,andZIPCode) 7b ADDRESS(City, State, andZIPCode) Monterey,CA 93943 5000 Monterey,CA 93943 5000 8a NAME OF FUNDING/SPONSORING 8b OFFICESYMBOL 9 PROCUREMENTINSTRUMENTIDENTIFICATION NUM8ER ORGANIZATION (Ifapplicable) 8c ADDRESS(City, State,andZIPCode) 10 SOURCEOFFUNDING NUMBERS ProgramElementNo ProjectNo WorkunitActev>ion Number 11 TITLE (IncludeSecurityClassification) SIMULATIONOFATMOSPHERIC FRONTOGENESISWITHASEMI LAGRANGIAN NUMERICALMODEL 12 PERSONALAUTHOR(S) RicardoCarvalhodeAlmeida 13a TYPEOFREPORT 13b TIME COVERED 14 DATEOFREPORT(year, month,day) 15 PAGE COUNT Master'sThesis From To September 1991 70 16 SUPPLEMENTARYNOTATION TheviewsexpressedinthisthesisarethoseoftheauthoranddonotreflecttheofficialpolicyorpositionoftheDepartmentofDefenseorthe U.S. Government. 17 COSATICODES 18 SUBJECTTERMS(continueonreverseifnecessaryandidentifybyblocknumber) FIELD GROUP SUBGROUP Meteorology,NumericalWeatherPrediction,Semi-Lagrangian,Frontogenesis 19 ABSTRACT(continueonreverseifnecessaryandidentifybyblocknumber) InthisstudyanumericalmodelbasedonthehydrostaticBoussinesqequationsisusedtosimulateatmosphericfrontogenesisdrivenby an irrotationalnon-divergentdeformationwindfield. Theequationsarenumericallyintegratedbyusingthesemi-Lagrangiantechniqueassociated withtwodifferenttimeschemes:explicitandsemi-implicit. Bothschemesproducerealisticfrontsafterapproximately 40hoursofmodel integration. Thesemi- Lagrangiansemi-implicitschemeismoresuccessfulinhandlingthesharpgradientsassociated withthefront. Also,the semi-Lagrangiansemi implicitequationsareintegratedwithtimestepsaslongas3600sec.producingsolutionswithrelativelysmallerrors. Thisindicatesthatthisnumericalschemeisappropriateforuseinmesoscaleregionalmodels. 20 DISTRIBUTION/AVAILABILITYOFABSTRACT 21 ABSTRACTSECURITYCLASSIFICATION PI UNCLASSIFIED/UNLIMITED J SAMEASREPORT Unclassified 22a NAMEOF RESPONSIBLE INDIVIDUAL 22b TELEPHONE (IncludeAreacode) 22c OFFiCE SYMBOL MR/Wu RogerT.Williams (408)646 2296 DD FORM 1473.84 MAR 83 APReditionmaybeused untilexhausted SECURITYCLASSIFICATIONOF this PAGE Allothereditionsareobsolete Unclassified by Almeida RicardoCarvalhode Ricaraov. Navy Brazilian »>»«;. ™t«d !»,.*.! s„b degree of irements for the oftherequii OCEANOGRAPHY METEOnRRnOTLO0GQYY AANND PHYSICAL MASTEROFSCIENCEfN from the SCHOOL HAVALPOSTGRADUATE 1991 September ABSTRACT In this study a numerical model based on the hydrostatic Boussinesq equations is used to simulate atmospheric frontogenesis driven by an irrotational non-divergent deformation wind field The equations are numerically mtegrated by using the serru- Lagrangian technique associated with two different time schemes: explicit and senii- implicit Both schemes produce realistic fronts after approximately 40 hours ofmodel integration. Thesemi-Lagrangian semi-implicit scheme ismore successful in handling the sharpgradients associated with the front. Also, the semi-Lagrangian semi-implicit equations are mtegrated with time steps as long as 3600 sec. producing solutions with relatively smallerrors. This indicates that this numerical scheme isappropriate for use in mesoscale regional models. in TABLE OF CONTENTS INTRODUCTION I. 1 THE SEMI-LAGRANGIAN SCHEME II. 3 III. BASIC EQUATIONS 6 IV NUMERICAL SOLUTION 17 A. INITIAL CONDITIONS 17 B. THE SPATIAL GRID 20 FORMULATION OF THE MODELS C. 20 1. Semi-Lagrangian Explicit Scheme 20 2. Semi-Lagrangian Semi-Implicit Scheme 22 V EXPERIMENTS AND RESULTS 31 A. PARAMETERS USED IN THE EXPERIMENTS 31 B. DESCRIPTION OF THE EXPERIMENTS 34 SUMMARY AND CONCLUSIONS VI. 58 LIST OF REFERENCES 60 IV
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