Geoscience Reference
In-Depth Information
a
nalysis
of
mbpa
Results.of.the.MBPA.analysis.were,.in.some.ways,.more.revealing.than.those.from.
the.simple.correlation.analysis..As.previously.noted,.MBPA.is.a.technique.both.for.
classifying. a. data. set. and. for. determining. the. most. important. variables. for. class.
membership..When.interpreting.these.results,.however,.it.is.important.to.remember.
that. Spearman. rank. values. are. used. as. classiication. variables. regardless. of. their.
signiicance..Thus,.circulations.that.were.not.signiicant.according.to.univariate.cor-
relation.may.be.signiicant.contributors.to.the.multivariate.regionalization.process.
Classiication. and. regionalization. of. the. climate. mode. correlations. (Figure 9.3).
show.a.complex.pattern.across.North.America,.which.can.roughly.be.divided.into.
four.regions,.each.determined.by.a.different.pattern.of.dominant.indices..The.most.
spatially.extensive.of.these.categories.is.the.area.dominated.by.correlation.between.
precipitation.and.the.SOI..This.class.occurs.in.two.large.regions:.one.generally.in.the.
northern.latitudes.and.extending.into.the.Great.Lakes.region,.and.the.other.extending.
from.central.Mexico.into.the.United.States.along.the.cordillera..These.two.regions.
correspond.to.areas.known.to.be.affected.by.ENSO.events.(Hoerling.et.al..1997).and.
also.match.areas.of.positive.SOI.correlation.(Figure 9.2).
The. next. largest. class. consists. of. areas. dominated. by. the. combined. effects. of.
the.PDO.and.SOI,.with.the.PDO.being.the.more.signiicant.of.the.two..This.class.is.
found.mainly.in.one.large,.roughly.contiguous.region.dominating.the.Atlantic.coast,.
Midwest,. and. the. northern. Great. Plains. in. the. United. States. and. extending. north.
onto.the.Canadian.Shield..A.second.region.lies.along.the.Paciic.Coast.of.Oregon,.
Washington,.and.British.Columbia..A.few.smaller,.outlying.regions.occur.through-
out.the.interior.of.Alaska.and.the.northern.Canadian.provinces.
The.third.region.is.determined.by.correlation.with.three.circulation.modes:.the.
PDO,.PNA,.and.SOI..This.region.is.found.along.the.Gulf.Coast,.extending.northward.
into. Texas,. the. southern.Great. Plains,. and. the. Mississippi.River. valley..A. second,.
smaller.contiguous.area.dominates.the.Columbian.plateau..Like.the.third.class,.the.
fourth.circulation.class.is.also.determined.by.correlation.with.three.climate.modes,.
but.the.effects.of.the.NAO.replace.the.PDO.as.the.most.important.determinant..This.
class.is.found.almost.exclusively.in.the.subtropics,.dominating.the.Caribbean.islands.
and.the.Gulf.Coast.of.Mexico,.but.with.an.extension.into.the.Paciic.coast.and.Baja.
areas,.as.well..Numerous.other.grid.cells.were.classiied.based.on.other.combina-
tions. of. circulation. indices,. but. the. four. classes. summarized. here. were. the. most.
important.and.spatially.extensive.results.of.the.regionalization.
The.results.of.MBPA.classiication.of.the.station.data.are.summarized.in.Table 9.3,.
along.with.the.classiication.for.the.precipitation.grid.containing.each.of.the.LTER.
sites.used.in.this.study.(extracted.from.Figure 9.3)..Presentation.of.both.results.side.
by.side.facilitates.comparison.of.the.two.results.and.determination.of.whether.the.
relationship.between.circulation.indices.and.precipitation.for.the.station.data.resem-
bles.that.of.the.region.in.which.the.station.is.embedded.
Examination.of.the.results.presented.in.Table 9.3.shows.that,.in.general,.the.domi-
nant.climate.indices.for.precipitation.at.the.LTER.stations.are.similar.to.those.of.the.
surrounding.areas,.but.often.with.a.smaller.set.of.signiicant.correlates..Several.of.the.
sites.among.the.ARC,.CDR,.HBR,.and.NTL.sites.are.dominated.exclusively.by.the.
