Intraseasonal relationships between tropical heating and extratropical jets.

118 Pages·1.4 MB·English

by  Neith, Michael T.;Murphree, James Thomas.

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Intraseasonal RelationshipsBetweenTropical Heating
and ExtratropicalJets
by
MichaelT. Neith
Lieutenant United States Navy
,
B.S., Allentown College of
St. Francisde Sales, 1986
Submittedin partial fulfillment
ofthe requirementsforthe degree of
MASTER OF SCIENCE IN METEOROLOGY AND
PHYSICAL OCEANOGRAPHY
from the
NAVAL POSTGRADUATE SCHOOL
DECEMBER1992 /
l_iinjunuoiriijjj
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« PERFORMINGORGANIZATIONREPORTNUMBER(S) 5 MONITORINGORGANIZATIONREPORTNUMBER(S)
6a.NAMEOFPERFORMINGORGANIZATION 6b OFFICESYMBOL 7a NAMEOFMONITORINGORGANIZATION
NavalPostgraduateSchool (Ifapplicable) NavalPostgraduateSchool
55
6c.ADDRESS(City,State,andZIPCode) 7b.ADDRESS(Crty,State,andZIPCode)
Monterey,CA 93943-5000 Monterey,CA 93943-5000
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ORGANIZATION (Ifapplicable)
8c ADDRESS(Crty,State,andZIPCode) 10.SOURCEOFFUNDINGNUMBERS
ProgramElementNo ProjectNo TaskNo WorkUnitAccession
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11 TITLE(IncludeSecurityGasification)
INTRASEASONALRELATIONSHIPSBETWEENTROPICALHEATINGANDEXTRATROPICALJETS
12 PERSONALAUTHOR(S) MichaelT.Neith
13a.TYPEOFREPORT 13b TIMECOVERED 14 DATEOFREPORT(year,month,day) 15 PAGECOUNT
Master'sThesis From To 1992,December,14 109
16.SUPPLEMENTARYNOTATION
TheviewsexpressedinthisthesisarethoseoftheauthoranddonotreflecttheofficialpolicyorpositionoftheDepartmentofDefenseortheU.S.
Government.
17 COSATICODES 18 SUBJECTTERMS(continueonreverseifnecessaryandidentifybyblocknumber)
FIELD GROUP SUBGROUP Teleconnections;lntraseasonalOscillations;TropicalHeating;ExtratropicalJets
19.ABSTRACT(continueonreverseifnecessaryandidentifybyblocknumber)
lntraseasonalvariationsofthenorthernmidlatitudecirculationandtheirrelationshipswiththeglobaltropicalheatingfieldareinvestigated
usingclimatemodelfields. Thegreatestintraseasonalvarianceinthemidlatitudeflowisfoundinthevicinityofthetimemeanjets,andinthe
areasimmediatelydownstreamofthesejetexits. Themodelkineticenergyfieldassociatedwiththesejetsshowsaclear30-60dayvariationand
eastwardpropagationwithinandbetweenthedifferentjetregions. Thisintraseasonalbehavoirisfoundtobe wellcorrelatedwithheating
anomaliesinspecificpartsoftheglobaltropics.
Foreachofthesejetregions,weuseasimplecompositeanalysistoidentifytheglobalheatingpatternsassociatedwithperiodsofstrongandweak
flow. FortheNorthPacificjet,strongflowoccursduringandafterperiodsofpositiveheatinganomaliesinthetropicalwesternandcentral
Pacific,andnegativeheatinganomaliesintheIndianOcean. Conversely,TheNorthPacificflowisweakwhentheseheatinganomaliesare
reversed. TheNorthAtlanticjetshowscomparablerelationships,withpositiveheatinganomaliesinthetropicalwesternandeasternPacific,and
negativeheatinganomaliesinthetropicalIndianandAtlanticOceans,beforeandduringperiodsofstrongflow.
TheseintraseasonalteleconnectionsbetweenindividualjetsandtheglobaltropicalheatingfieldareespeciallyclearfortheNorthPacificand
NorthAtlanticjets. Inadditiontorelativelydirectforcingfromnearbytropicalheatsources,thejetsmaybeinfluencedbyrelativelyremote
tropicalheatsources,whosesignalspropagatethroughupstreamjets. Theseintraseasonalteleconnectionsbetweentheglobaltropicalheating
fieldandtheNorthPacificandNorthAtlanticjetsmayhaveimportantimplicationsforextendedrangeforecastingforNorthAmericaand
Europe.
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JamesThomasMurphree [phone] MR/Me
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ABSTRACT
Intraseasonal variations of the northern midlatitude
circulation and their relationships with the global tropical
heating field are investigated using climate model fields.
The greatest intraseasonal variance in the midlatitude flow is
found in the vicinity of the time mean jets, and in the areas
immediately downstream of these jet exits. The model kinetic
energy field associated with these jets shows a clear 30-60
day variation and eastward propagation within and between the
different jet regions. This intraseasonal behavior is found
to be well correlated with heating anomalies in specific parts
of the global tropics.
For each of the jet regions, we use a simple composite
analysis to identify the global heating patterns associated
with periods of strong and weak flow. For the North Pacific
jet, strong flow occurs during and after periods of positive
heating anomalies in the tropical western and central Pacific,
and negative heating anomalies in the Indian Ocean.
Conversely, the North Pacific flow is weak when these heating
anomalies are reversed. The North Atlantic jet shows
comparable relationships, with positive heating anomalies in
the tropical western and eastern Pacific, and negative heating
anomalies in the tropical Indian and Atlantic Oceans, before
and during periods of strong flow.
111
L.I
These intraseasonal teleconnections between individual
jets and the global tropical heating field are especially
clear for the North Pacific and North Atlantic jets. In
addition to relatively direct forcing from nearby tropical
heat sources, the jets may be influenced by relatively remote
tropical heat sources, whose signals propagate through
upstream jets. These intraseasonal teleconnections between
the global tropical heating field and the North Pacific and
North Atlantic jets may have important implications for
extended range forecasting in North America and Europe.
IV
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LIST OF SYMBOLS AND ACRONYMS
AF Africa
-
AT Atlantic Ocean
-
C - positive POLR (cooling) anomalies
CHT cumulus heating
-
CP central Pacific Ocean
-
DERF dynamical extended range forecasting
-
EA East Asia
-
ECMWF European Center for Medium Range Forecasts
-
EP eastern Pacific Ocean
-
EU Eurasia
-
FFT Fast Fourier Transform
-
FNOC Fleet Numerical Oceanography Center
-
GCM general circulation model
-
GMT Greenwich Mean Time
-
H negative POLR (heating) anomalies
-
10 Indian Ocean
-
ITCZ Inter-Tropical Convergence Zone
-
KE kinetic energy
-
m meter
-
mb millibar
-
MJO Madden-Julian Oscillation
-
NA North America
-
NAT North Atlantic Ocean
-
NOGAPS Navy Operational Global Atmospheric Prediction System
-
NP North Pacific Ocean
-
OLR outgoing longwave radiation
-
PKE processed kinetic energy
-
POLR processed outgoing longwave radiation
-
s - second
SACZ South Atlantic Convergence Zone
-
SPCZ South Pacific Convergence Zone
-
T transition between tropical heating and cooling
-
T49 triangular 49 truncation
-
U200 200mb zonal wind
-
U250 250mb zonal wind
-
V200 200mb meridional wind
-
VHT vertically- integrated heating
-
W Watts
-
WESTPAC - western Pacific Ocean (5°N - 25°N)
WP - western Pacific Ocean (30°S - 30°N)
velocity potential
X -
^ streamfunction
-
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