Geoscience Reference
In-Depth Information
which.is.much.larger.than.the.area.associated.with.any.of.the.LTER.sites..The.value.
for.each.grid.cell.is.determined.by.interpolation.from.among.several.measurement.
stations,.each.of.which.is.essentially.a.point.measurement..In.many.cases,.the.LTER.
or.its.surrogate.station.was.used.in.the.gridding.process,.along.with.other.irst-.or.
second-order. observation. stations.. Measurements. of. climate. variables,. including.
precipitation,.are.often.spatially.variable;.even.nearby.stations.can.be.quite.different.
in.the.magnitude.of.their.measurements..This.is.often.due.to.gauge.location,.local-
ized.topography,.urban.effects,.presence.of.water.bodies,.or.other.factors.not.directly.
linked.to.large-scale.atmospheric.circulation.(McHugh.and.Goodin.2003)..For.pre-
cipitation.the.nature.of.the.causal.mechanisms.themselves.must.also.be.considered,.
especially.in.areas.where.convectional.processes.dominate.and.precipitation.events.
tend.to.be.intense,.short-lived,.and.limited.in.their.geographical.extent..Selecting.one.
gauge.from.within.a.region.(which.is.essentially.what.is.done.when.a.single.station.is.
used).may.therefore.not.be.entirely.representative.of.the.entire.grid.cell.
One.noteworthy.conclusion.that.can.be.drawn.from.the.results.shown.here.is.that.
the.pattern.of.inluence.by.teleconnection.patterns.with.circulation.modes.is.much.
more.geographically.heterogeneous.than.expected..The.broad.patterns.discussed.in.
Results.are.largely.consistent.with.previous.understanding.of.the.spatial.effects.of.
various.teleconnection.patterns..For.example,.the.pattern.of.response.of.precipitation.
to. the. SOI. is. consistent. with. previous. research. showing. the. inluence. of. ENSO. at.
LTER.sites.(Greenland.1999)..The.inluence.of.the.Paciic.North.American.pattern.
interior.continental.sites.is.also.consistent.with.previously.observed.effects.of.this.
pattern,.which.indexes.the.position.and.direction.of.the.upper.air.westerlies.and.is.
therefore.closely.tied.to.the.formation.and.movement.of.precipitation-producing.low.
pressure.systems..However,.the.mapped.relationships.between.circulation.modes.and.
precipitation.patterns.often.show.small.areas.that.deviate.from.the.broad.patterns..
An.example.of.this.can.be.seen.in.the.Alaskan.interior,.where.a.small.region.of.inlu-
ence.by.multiple.circulation.modes.lies.within.an.area.that.is.dominated.by.the.SOI..
It.is.unclear.why.this.particular.region.occurs,.because.it.seems.not.to.be.associated.
with.large-scale.topography.or.other.factors.that.might.inluence.precipitation.pat-
terns..Because.this.region.contains.the.Bonanza.Creek.LTER,.it.also.illustrates.how.
temporal.patterns.in.ecological.response.at.the.BNZ.site.might.not.be.entirely.repre-
sentative.of.the.surrounding.region..Of.course,.it.might.also.represent.some.anomaly.
in.the.data.gridding.process.(see.previous.discussion)—a.possibility.that.should.be.
considered.when.evaluating.any.of.the.results.presented.here.
The.results.presented.in.this.chapter.also.highlight.some.of.the.dificulties.with.
point-.or.station-based.climatic.research..The.LTER.network.was.established.to.
understand. the. long-term. ecology. at. sites. that. were. representative. of. a. variety.
of. ecosystems.. The. sites. were. never. intended. to. be. an. exhaustive. sampling. of.
regions.or.biomes,.however,.and.the.nonsystematic.selection.of.sites.is.apparent.
in. their. spatial. distribution. (Figure  9.1).. The. pattern. of. sampling. favors. coastal.
and. western. sites,. leaving. a. noticeable. “gap”. in. the. central. plains. east. of. the.
Mississippi,.where.few.sites.are.located..This.undersampling.makes.understand-
ing. coherent. climate. patterns. using. LTER. data. dificult,. at. best.. However,. the.
eficacy.of.this.current.study.lies.not.in.producing.information.about.the.spatial.
distribution. of. climate,. but. in. providing. a. better. framework. for. understanding.
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