大氣科學專業(yè) 專業(yè)英語3-new

Unit

III:MeteorologicalForecasts第三課：氣象預報New

Wordswarning警報GMT(Greenwich

Mean

Time)格林威治時間upper-air高空的sounding探測WWW(World

Weather

Watch)世界天氣監(jiān)視網(wǎng)code電碼GTS(Global

Telecommunication

System)全球電傳通信系統(tǒng)operationally業(yè)務上strip長帶belt

bandNOAA(National

Oceanic

and

AtmosphericAdministration)諾阿衛(wèi)星（美國國家海洋大氣管理局）TIROS(Television

and

InfRared

Observing

Satellite)泰羅斯衛(wèi)星（電視紅外業(yè)務衛(wèi)星）geosynchronous地球同步的geostationary相對于地球靜止的GOES(Geostationary

Operational

EnvironmentSatellite)地球靜止業(yè)務環(huán)境衛(wèi)星multi-channel多通道的relay中繼buoy浮標站assemble組裝，匯編集合barometric氣壓的short-range短期的long-range長期的extended

range延伸期的·

nowcasting現(xiàn)時預報，臨近預報interpolation內(nèi)插prognostic預報的

filter濾波extrapolation外推forecaster預報員conservation保守divergence輻散prognosis預測smooth平滑geopotential位勢的prediction預報spectral譜的integrate積分nest嵌套several-fold翻幾番MSL(Mean

Sea

Level)平均海平面MOS(Model

Output

Statistics)模式輸出統(tǒng)計regression回歸predictor預報因子thunderstorm

雷暴 hurricane

typhoonparameterize參數(shù)化次級結(jié)構(gòu)·

subgrid

次網(wǎng)格

substructuresub+…

亞；次級；下級

（構(gòu)詞法）subtropic

副熱帶，亞熱帶unpredictable不可預報的predictable可預報的

predictability可預報性framework框架topographic

地形的

orographicsite-specific

定點的gust陣風tornado

（陸）龍卷freezing凍結(jié)的Doppler(radar)多譜勒雷達index(indices)指數(shù)shear切變downburst下?lián)舯┝鱊ational

Meteorological

Services

perform

avariety

of

activities

in

order

to

provide

weatherforecasts.The

principal

ones

are

data

collection,

thepreparation

of

basic

analyses

and

prognosticcharts

of

short-and

long-term

forecasts

for

thepublic

as

well

as

special

services

for

aviation,shipping

,

agricultural

and

other

commercial

andindustrial

users,

and

the

issuance

of

severeweather

warnings.Data

sourcesThe

data

required

for

forecasting

and

otherservices

are

provided

by

worldwide

standardsynoptic

reports

at

00,

06,

12,

and

18

GMT,similar

observations

made

hourly,

particularly

insupport

of

national

aviation

requirements,

upper-air

soundings

(at

00

and

12

GMT),

satellite

dataand

other

specialized

networks

such

as

radarstations

for

severe

weather.Under

the

World

Weather

Watch

(WWW)program,

synoptic

reports

are

made

at

some4,000

land

stations

and

by

7,000

ships.There

are

about

700

stations

making

upper-airsoundings

(temperature,

pressure,

humidity,

and,wind).These

data

are

transmitted

in

code

via

teletypeand

radio

links

in

regional

or

national

centersand

into

the

high-speed

GlobalTelecommunications

System

(GTS)

connectingWorld

Weather

Centers

in

Melbourne,

Moscowand

Washington

and

eleven

RegionalMeteorological

Centers

for

redistribution.Some

157

states

and

territories

cooperate

in

thisactivity

under

the

aegis

of

the

WorldMeteorological

Organization

(WMO).Meteorological

information

has

been

collectedoperationally

by

satellites

of

the

United

Statesand

USSR

since

1965

and,

more

recently,

by

theEuropean

Space

Agency,

India

and

Japan.There

are

two

general

categories

of

weathersatellite:

polar

orbiters

providing

global

coveragtwice

per

24

hours

in

orbital

strips

over

the

poles(such

as

the

Unites

States

NOAA

and

TIROSseries,

and

the

USSR’s

Meteor)

andgeosynchronous

satellites(such

as

theGeostationary

Operational

EnvironmentalSatellites

(GOES)

and

Metosat

),

givingrepetitive(30-minute)

coverage

of

almost

onethird

of

the

earth’s

surface

in

low

middlelatitudes.Information

on

the

atmosphere

is

collected

asdigital

data

or

direct

readout

visible

and

infraredimages

of

cloud

cover

and

sea-surfacetemperature,

but

also

includes

globaltemperature

and

moisture

profiles

through

theatmosphere

obtained

from

multi-channel

infraredand

microwave

sensors

which

receive

radiationemitted

from

particular

levels

in

the

atmosphere.Additionally,

satellites

have

a

data

collectionsystem

(DCS)

that

relays

data

on

numerousenvironmental

variations

from

ground

platformsor

ocean

buoys

to

processing

centers;·

GOES

can

also

transmit

processed

satelliteimages

in

facsimile

and

the

NOAA

polar

orbitershave

an

automatic

picture

transmission

(APT)system

that

is

utilized

at

900

stations

worldwide.ForecastingModern

forecasting

did

not

become

possible

untilweather

information

could

be

rapidly

collected,assembled

and

processed.The

first

development

came

in

the

middle

of

thelast

century

with

the

invention

of

telegraphy,which

permitted

immediate

analysis

of

weatherdata

by

the

drawing

of

synoptic

charts.These

were

first

displayed

in

Britain

at

the

GreatExhibition

of

1851.Sequences

of

weather

change

were

correlatedwith

barometric

pressure

patterns

both

in

spaceand

time

by

such

workers

as

Fitzroy

andAbereroleby,

but

it

was

not

until

later

thattheoretical

models

of

weather

system

weredevised——notably

the

Bjerknes

depressionmodel.Forecasts

are

usually

referred

to

as

short-range,medium

(or

extended)

range

and

long-range.The

first

two

can

for

present

purposes

beconsidered

together.Short-range

forecastingForecasting

procedures

developed

up

to

the1950s

were

based

on

synoptic

principles

but,since

the

1960s,

practices

have

beenrevolutionized

by

numerical

forecasting

modelsand

the

adoption

of

“nowcasting”

techniques.During

the

first

half

of

the

century,

short-rangeforecasts

were

based

on

synoptic

principles,empirical

rules

and

extrapolation

of

pressurechanges.Since

1955

routine

forecasts

have

been

basedon

numerical

models.

These

predict

the

evolutionof

physical

processes

in

the

atmosphere

bydeterminations

of

the

conservation

of

mass,energy

and

momentum.The

basic

principle

is

that

the

rise

or

fall

ofsurface

pressure

is

related

to

mass

convergenceor

divergence,

respectively,

in

the

overlying

aircolumn.Forecast

practices

in

the

major

national

centersare

basically

similar.The

forecasts

are

essentially

derived

from

twice-daily

(00

and

12

GMT)

prognoses

ofatmospheric

circulation.Since

most

techniques

are

now

largelyautomated,

the

analyses

of

synoptic

fields

arebased

on

the

previous

12-hour

forecast

maps

asa

first

guess.Three

different

interpolation

methods

are

usedto

obtain

smoothed,

gridded

data

ontemperature,

moisture,

wind

and

geopotentialheight

for

the

surface

at

standard

pressurelevels

(850,700,

500,

400,

300,

250,

200

and100

mb)

over

the

globe.The

NMC

currently

has

two

basic

predictionmodels:

a

special

model

with

(6

or)

12

layers(from

the

boundary

layer

into

the

upperstratosphere),

which

is

integrated

for

up

to

10days,

and

a

regionally

applicable

nested

gridmodel

with

finer

horizontal

resolution.It

should

be

noted

that

typically

the

computertime

required

increases

several-fold

when

thegrid

spacing

is

halved.The

essential

forecast

products

are

MSLpressure,

temperature

and

wind

velocity

forstandard

pressure

levels,

1000-500mb

thickness,vertical

motion

and

moisture

content

in

the

lowertroposphere,

and

precipitation

amounts.Actual

weather

conditions

are

now

commonlypredicted

using

the

Model

Output

Statistics(MOS)technique

developed

by

the

US

NationalWeather

Service.Rather

than

relating

weather

variable

to

thepredicted

pressure/height

patterns

and

takingaccount

of

frontal

models,

for

example,

a

seriesof

regression

equations

are

developed

forspecific

locations

between

the

variable

of

interestand

up

to

10

predictors

calculated

by

thenumerical

models.Weather

elements

so

predicted

for

numerouslocations

include

daily

maximum/minimumtemperature,

12-hour

probability

of

precipitationoccurrence,

and

precipitation

amount,

probabilityof

frozen

precipitation,

thunderstorm

occurrence,cloud

cover

and

surface

winds.These

forecasts

are

distributed

as

facsimilemaps

and

tables

to

weather

offices

for

local

use.Errors

in

numerical

forecast

arise

from

severalsources.

One

of

the

most

serious

is

the

limitedaccuracy

of

the

initial

analyses

due

to

datadeficiencies.The

average

over

the

oceans

is

sparse

and

onlya

quarter

of

the

possible

ship

reports

may

bereceived

within

12

hours;

even

over

the

landmore

than

one-third

of

the

synoptic

reports

maybe

delayed

beyond

6

hours.However,

satellites-derived

information

andaircraft

reports

can

help

fill

some

gaps

for

theupper

air.Another

limitation

is

imposed

by

the

horizontaland

vertical

resolution

of

the

models

and

theneed

to

parameterize

subgrid

processes

such

ascumulus

convection.The

small-scale

nature

of

the

turbulent

motion

ofthe

atmosphere

means

that

some

weatherphenomena

are

basically

unpredictable,

forexample,

the

specific

locations

of

shower

cells

inan

unstable

air

mass.Greater

precision

that

the

“showers

and

brightperiods”

or

“scattered

showers”

of

theforecast

language

is

impossible

with

presenttechniques.The

procedure

for

preparing

a

forecasting

isbecoming

much

less

subjective,

although

incomplex

weather

situations

the

skill

of

theexperienced

forecaster

still

makes

the

techniquealmost

as

much

as

art

as

a

science.Detailed

regional

or

local

predictions

can

only

bemade

within

the

framework

of

the

generalforecast

situation

for

the

country

and

demandthorough

knowledge

of

possible

topographic

orother

local

effects

by

the

forecaster.NowcastingSevere

weather

is

typically

short-lived(<2

hr

)

and,due

to

its

mesoscale

character(<100km),

it

affectslocal/regional

areas

necessitating

site-specificforecasts.Include

in

this

category

are

thunderstorms,

gustfronts,

tornadoes,

high

winds

especially

alongcoasts,

over

lakes

and

mountains,

heavy

snowand

freezing

precipitation.The

development

of

radar

networks,

nowinstruments

and

high-speed

communication

linkshas

provided

a

means

of

issuing

warnings

of

suchphenomena.Several

countries

have

recently

developedintegrated

satellite

and

radar

systems

to

provideinformation

on

the

horizontal

and

vertical

extend

ofthunderstorms,

for

example.Such

data

are

supplemented

by

networks

ofautomatic

weather

stations

(including

buoys)

thatmeasure

wind,

temperature

and

humidity.In

addition,

for

detailed

boundary

layer

and

lowertroposphere

data,

there

is

now

an

array

of

verticalsounders——acoustic

sounders

(measuring

windspeed

and

direction

from

echoes

created

by

thermal

eddies),

specialized

(Doppler)

radarmeasuring

winds

in

clear

air

by

returns

either

frominsects(3.5

cm

wavelength

radar)

or

fromvariations

in

the

air’s

refractive

index(10

cmwavelength

radar).Nowcasting

techniques

use

highly

automatedcomputers

and

image

analysis

systems

tointegrate

data

from

a

variety

of

sources

rapidly.Interpretation

of

the

data

displays

requires

skillepersonnel

and/or

extensive

software

to

provideappropriate

information.The

prompt

forecasting

of

wind

shear

and

down-burst

hazards

at

airports

is

one

example

of

theimportance

of

nowcasting

procedures.Overall,

the

greatest

benefits

from

improvedforecasting

can

be

expected

in

aviation,construction

and

the

electric

power

industry

forforecast

less

than

6

hours

ahead,

in

transpiration,construction

and

manufacturing

for

12-24

hourforecasts

and

in

agriculture

for

2-5

day

forecasts.In

terms

of

economic

losses,

the

last

categorycould

benefit

the

most

from

more

reliable

andprecise

forecasts.Long-range

forecastingThe

methods

discussed

above

are

unsuitable

forpredicting

the

probable

trend

of

the

weather

fo