HEMISPHERIC WATER VAPOR EALANCE WRING 1958
by
B.S.,
ALFRED RENATO CRISI
Aeronautical Engineering 0 New tork Univer
(1941)
MS., Meteorology, New York University
(1942)
SUEMIMTED IN PARTIAL FULFILLMENT OF THE
REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE
at the
ASSACHUSETI'S INSTITUTE OF TECHNOLOGY
August 1961
Signature of Author
.....
t..nt
of
et--C,-Au
-
-
armnt of Meteorolkf
Certified b3
w
-2
-
t
- -
Thesis Supervisor
Accepted by
.hairm
, Departmental Comaittee on Graduate
Students
1
21 August 1961
--1,SP1IERIC WATER VAPM BALANCE DURING 1958
Alfred Renato Cris
Sureitted to the Department of Meteorology on August 21, 1961
in Patlal Fultillment of the Requirements for the
Degree of Master of Science
ABSTRACT
A study of the ataospheric water vapor over the northern heaiephere during the Interntlonal Geophysical Year (107) covering the
mean conditions for the calendar year 1988 Is presented. The study
includes analyses of precipitable water vapor, water vapor transport
and divergenoe of water vapor transport for the entire northern
hemalphere. The water vapor balance equation and the relation of
the divergence of water vapor transport to the field of evaporation
Finally, the
and precipitation at the earth's surface is reviewed.
field of divergence of water vapor transport as related to the earth' s
water balance is
briefly discussed.
Thesis Supervisort Victor P. Starr
Professor of Meteorology
Titles
6
2.
DAMA
3e
AS MUIONS, DZWINITIONS, DATA
AND FRn
4.
ANALYIS Of
8.
DIVER4ZNM 0F VIER VA"O
So
WATER VAPO
3ANA)
34
7,
CONCLUDI4G IMARIS
42
O.
AIKOWIU-M15Wf
40
rigev, 2
48
71gm 3
49
r~ue 4
50
ftgure 5
81
DUMIGRA
MSU8$NG
SI=MD IWtA
12
22
ERANU1'CT
29
eca1
1. fIMDOUCITUN
The ;1atew balanc
at tk
has bcen the Mbject
during the past 50 y*a
cf ~.i Inwt~:t~t,~i
1930'
eaWhe 6 erfasf
.
Until the aid-
ost of the investIgations ceeonsidered only the (lan-ocsan)
esrtr-bound branch of the water cycle.
Over land surfaces the
brwance of precipitatione evapotnspiration, run-off above and be ?ov
t
ground0 gnd the change In graind-water stoae
:or investigation.
formed the bass
ThIs type of investigatloa often produced
m*lt
which were not widely septed and which, at best, were representr*
tive of the vater budget of only limited aeas or wateratd regIonn.
Over the
aocma
the situation was made even moe difficult by the
lack of baste
qatiwttative
tion and precipitation.
sa
atwnte or computed values of evapora-
Sverdrup (1951)
bility of obserations of evaporation fre
caepared to the attual evaporation at the
discussed (1)
the un1iella
pns on board ships as
Pom
a murface, (2) the 11a-
tations .ot computations of evaporation over the oceans band upon
energy considerations
and (3) the widely divergent results obtaired
by computing evaporation rates and the vertical flux of water vapor
from the sea surftce based upn theoretical considerations involvirg
hLaracter of the eddy ditffusion and transfer
asmptions as to th
proceeses near the sea surfa ce
Jiacobs (1951) found that data on
precipitation amounts over the oceans were very scarcs end unreliable.
be was able to prepare a noe
chart of the anuaal precipitation over
available published regional precipitation data.
the oceans based upo
to this date, actual precipitation values omer the oceans
However,
rat er scarce and difficult to interpret.
are still
In view of the difficulties involved in stutding the water balonce
by oasiderlng the earthbound branm
face
eaarth
at the
cycle,
hydrologl
a nmber of studies in recent years have approached
the probles by evalating the atmospherle branch of the
e
This approach rls
cycle.
of the
o
hydrologle
the piaoliples of continu ty and mass
coservation in the atmosphere rather than at the earth ea srace.
Such aan
pproach was not feasible until reent
and quality of
tity
erological observation
years, when the quanbecame smo
nearly ade-
quate to the task of making reliable comptations of the atmospheric
branch of the hydrologic cycle and its
the earth'
part in the water balane
at
surfae
Beton, Blackbumrn
and Snead (1950)
dlswe.ed
the role of the
atmosphere In the hydrologic cycle and clarified the relation of this
cycle
to air
assees over the UMisiSeippi River watered.
serological data they deterained the total fluz of msoltture
From
n maritime
al
and conti.
air ov
the watershed and then prepared a complete
balance of the hydrologic cycle for the watershed.
showed that, aithough only a small percentage of the
sources.
from
Laritime aoieture
dp-tasdq most of the precipitation
advected over the continent i.e6
occurring is
Their study
aritime air and Is derived directly from ocemnlc
This result contradicted earlier views vhich minimized the
of water vapor in the atmoaphere to and free the oceans and held
flu
almost exclusively to a concept of land-deried sources of precipitetion.
Benton and Estoque (1954)
computed the transfer of water vapor by
the atuosphere over the North American continent for the year 1949.
They ueed all available aerological data and geostrophic winds scaled
from copies of constant prerssum
charts for 850, 700, and 500 ab and
corresponding mixing ratio humidity data to compute the water vapor
transfer and divergence field of atmospberlc water vapor transfer in
the layer ftrm the earth's surfadt
to 400 ab.
One conclusion of this
study was that there need not be a high correlation between monthly
water-vapor trw~sfer and precipitation; precipitation is more directly
associted with the not convergene -rather than with the transfer of
atmospherict
oleture.
Another conclusion was that
tasmpherie
vinds
and sixing ratios have a definite place in hydrologio research and that
the diverence field of atmospheric water vapor transfer can be used to
evaluate accurately the monthly or seasonal water balance of large
cont inental areas
The modern approach of Starr (1951)
to studies of the general
of
circulation of the atmosphere resulted in several investigations
northern hbassphere water vapor and its
culation:
relation to the general cir-
Starr, Pexzoto, and Livadas (1957); Starr and White (1955)
Starr and Peixoto (1958); and PoIxoto (1958).
the most complete.
comprehensiee
Peixoto (198M)
provided
and extensive observational study of
atmospheric water vapor ever attempted up to this date.
Lufkin (1989)
carried on in great detail the discussion of the field of divergence
of atmospherie water vapor flux which was first
Peixoto (198).
preseated by Starr and
All of the above-sentioned studies were based upon
aerological data for the year 1950 and tncluded various evaluations
of daily data for some 90 upper-air sounding stations at
up to 800 ab over the entire northern hemisphere.
the
erit
several levels
These studies proved
of treating problems assocLated with the terrestrial hydro-
logic cycle on a hemispheric basisl they made posslble the averaging
of various properties of atmospherlo molistme over particular areas
of interest or over the entire hemisphere for comparison with hydrologle and oceanographic seasreents,
such as run-off, evaporation,
precipitation, ground storage, and salinlty.
Encouraged by the results of the atmospheric water vapor studies
for the year 1950s and by the tontinuing growth of the healaphezic
network of upper-str sounding stations, the author of this paper
has extended the water vapor studies to InClude the year 198 (a
part of the 10Y)
This paper will review briefly the procedures and
some of the sore Isportant results of the new study for 1985; an
extensive and complete report will be published at a later date
the meantime,
In
the quantity (over Soo stations) and excellent quality
of the IGY data over the northern buMeaphere suggests an imediate
disaassion of the results, especially as they apply to the water
balance of the oceans and nae of the desert areas of the northern
hemisphere and aplity the comsent made by Starr and Pexoto (1906).
I
--h
2.
DATA
The basic data used in this study were serological obervations
taken during the calendar year 198. the last 1
IGY.
An extensive coverage of
months of the recent
07 selected weather stations provided
a
representative date over the entire northern hD~aephere; where
choice was possible, the most rellable and meteorologleally signifisparse,
cant stations were selected; in aras where observations were
all available data were used.
The quantity and quality of the IOY
data used In this study were aperlor to those used in any other
northern hemisphere study for a similar time period.
Figre 1 shows
the index numbers and locations of all the stations.
obserThe primary stations used in this study were 288 rawlasonde
viUn
stationes these stations are identified by ~IO index numbers and
(CPR) and
by national index numbers for the Chinese Peoples' Republic
Figure 1I
are indicated by aall station circles on the locator map in
Full, five-dgit,
block and .station numbers are used -except for Blocks
TO. 726 and 74. Alaska, United States and Canadas
respectively, where
on
only the three-digit station numbers are used to avoid overcrowding
is
the locator nap; the bleck number (99) for ocean vessel stations
omitted, but letter designators are used in addition to the three-digit
station neabere.
The upper*-alr data for thesm primary stations were
on IB1 pwuncd cards or magnetic tape; all these data were checked
and processed by electronic computer.
for
All rawlnsonde data available
each primary station were used: rarinsonde data for most stations
were available at least once each day; a majority of stations provided
two soundings each day, some thIee and evxn tour.
Statistical coa-
putations were based upon all the data avalleble at each station.
This data was made available to the M.I.T. (eral
Circulation Pro-
ject under Contract Number AF 19(804)8-6108 sih the Air Porwe Cams
bridge Research Laboratories, Offie
States Air Force at Laurence G.
of Aerospe Research, United
anseom Fielde ltdford, Massachusetts.
The data handlins and Machine pCroeesing were aeeOaplibd in a
superior manner by the Department of the Air Forces Air Weather Service
Climatic Center, Data Control Division, at Adseville, North Carolina.
The 22 secondary stations used in this study were ritepally those
in critleal arema
not covered by the primary station nfa~ ork and also
a few stations chosen to fil1 n gaps at the equatorie .
data ftro
*.rder. The
these stations were obtained with either rac ioso.
radlowind,
pilot balloon, rawinsonde or a combiation of these methode: o*L one
station, Bellinakon (WMO Number 18718), used the pilot balloon (thalp.
lite) method for observing upper winds.
The secondary stations are
identified by WSO index numbers and are indicated by mall dots on the
-8
locator map in Figure 1.
l
In gerar
the data from these stations
were not so reliable or numerous as those from the primary stations.
Statistical compttations were basd upon the 000~T data available
at each sueondary station except at Douala (84910) and Legos (85201),
where the 0600 OUT data wewe used.
These data were tabulated from
of
the IGY alcrocards and were proesed by the very capable staff
the M.,.T. General Circulation Project.
Although this study was made for the northern healsphere, a number
of stations in the southern bemasphere were included to ISprove the
equatorial boundary conditions,
Most of these stations ee within 10
degrees of latitude of the equator
all ae within 20 degrees
The
in this
southern hemisphere stations (both primary and secondary) used
in
study awre shown in their approxusiate locations beyond the equator
the border of the locator map (Figurs
1).
In spite of generally excellent coverage of data over the northern
hemisphere and near the equatorial border in the southern h ealphere,
the
there were some rather disappointing areas of little or no data:
Amazon River Basin in South Amerlea; the east-central Pacific Ocean
Hwalan
from Panmsa to Christmas Island and from Central America to the
Islands; the Indian Ocean; and Equatorial Fast Africa.
some rather prominent stations
~uch as
aHbbealy
Unfortunately
((Baghdad) and NMirobi
at M.I.T.
were completely missing from the IGY sicrocard file available
-9-
Figure 1.
Index numbers and locations of stations
-10That such interesting and critical areas were deficient in mateorological data coverage represeats a serious dborteeing in the value
of the IYf data for basic research of the general c1rculation of the
earth' s aatmosphere.
Nevertheless
the over-all coverage of reliable data over the
arctic and siddle latitudes in the northern hemisphere was excellent.
The data from aretle stations were fairly complete north to 80 degrees
latitude.
The coverage over North America was complete and espeilally
dense over the United Statees all stations in this area were used
except a few superfluous ones.
The coverage over Chinas Mongolia,
and especially the Tibetian plateau was most helpful, and, perhaps
the first daPA~of its kind to be ued in a hemispheric r
It
search study.
mnght be interesting to note some fasts on the anuber of
observations used in the computation of data from the primary set of
stations.
Michigan (Wl)
Bnlna
The esisem was 142? observations frem bault Ste. Marie,
Number 72734), the minimum was 48 observations from
Libya (MD
Number
20853).
Most stations had somewhere between
200 and 700 observations for the year 1988
a large number of stations
had between 800 and 700 observations, representing Just about two
rawinsonde observations per day during the year,
had less than 100 observations:
Nunchiang (CPR Number
Tura,. USSR (UW
Only four stations
Number 24507) had 94;
0557) had 96; Tinchwean (CPR Number 53614) had 97;
and Benina, Libya (W)M Number 62053) had 48.
over 1000 observations:
Twelve stations had
Thule, Greenland (WAD Number 04202) had
1346; Lages Field, Azores (WD Number 08509) had 1400; Oenn Air Base,
Korea (WOD Number 47122) had 181; Eglin Air Force Base
Florida
(WMCD Number 72221) had 1422; Laughlin Air Force Base. Texas (W0
Number 72261) had 1356; Oklahom City, Oklahoma
(WW1
Number 72383
had 1254; Sault Ste Marie, Michigan (WD Number 72734) had 1427;
Stephenville Air Force Bass,
Newfoundland (WM
Number 72818)
had
1374; Goose 8ay Air Base, Labrador (1CW Number 72816) had 1285l
Resolute Baey, NW
Base,
(WD Number 75O64) had 1148; Kindley Air Force
Besnds (UD Number 78016) and 1347; and Wake Island (3U0 Num-
bar 91248) bad 1008.
Complete details on station anaesindex numberS,
exact geographioal locatones, heights above sea level, periods of
record, number of observations, and all the processed data pa.ameters used in this study will be published later in a eoaprehenm
sive report.
-lo-
3.
DATA PUOCE8SING AND 1POIILE
IOHNS4 WFINITIONS,
ASET40
parameters treated i
The particular steorologil
tthis study
were the specific humidity, q, and the eoaponets of the aetual wind,
u and vi thse pearasters were derived from the basic apperra
meteorological measermeonts of presaue, tempoertueo
humidity, and
wind made at the stations showa on the chart in Pigure 1 with rlin-
sondo, radiosonde, radlowinds or pilot bslloo,
or combinations of
themr types of equipments.
The parameters u and v are the horlsontal, omponents of the wind
veotor,
, ~h
that
l
+ j v, where I Is the unit vector
in the west-to-east direction and J is the unit vector in the southb
to-north diroetion.
takeln in
Thus, u is the sonal (eaS-woest) wind cmpontt
) with **est wind positivel and v
eters per second (a ase
is the merldional (north-south) wind oeponent taken in maters per
second (a sec
) with south wind positive.
The parameter q Is the speoifle humidity in grams per kilogrem;
the simplified eXpression
q .02
(e/p) given in Baurwits (1941)
Brunt (1944) was used to compute q free the values of toepersatur
relative hutidlty at each of four standard p assure levelse
850 ab, 700 ab, and 500 ab.
iven the temperature.
and
and
1000 rab
Tr, at any
the relation
actual water vapov presea
U
a WUU
or
e/e
each station and for each papate
specific huadit
q,
,
e
e
can be obtained from
the satura
where e
Thus
at the given air temperaturea TT.
tion water vapor presr
at
Then knowleg the relative
TI
uniquely defied at that temperaturet
humidityo Ueth
BM, 1
p. the saturation 'eater vapor pes
atospheric pLressur,
uppmr
can be-. obsataed ealy
and the acemopanytg wind opi enat,
r obsOeMa-on. the
for ea
re level,
..psw
ned for
a~and ve ~en hbe ob,
each corresponding pressure level.
Since this is a research study on th general cieaRIgQion of the
northern heisphee, time aver
covered ~smmr
o year and the
periods of
Speeifically, the periods
through Decmber 198,
es of the meteorological perarmters
ikar
zed were (1)
u
r
later and easw
the
hole ye,
easons.
January
(2) the six winter mcaths, January. thrugh
March and October through Deoember 198~ and (3) the six sa
April through September 1958.
the annual period for 19598
er months,
This particular paper deals only with
the other perlods wll
be treated in a
ecplete report to be published later.
The followiNg quantities wee computed
f
tarely
the 1000,
tw
when
850, 700. and 800 ab standard pressure levels at each station
available
1.
Ustad
a.
Ima
b.
Mean ve
-
2.
q and v as besie pauamter
e*
q
q
V
q
ean q x 9,
do, Standad Deviation of q
0q)
e. Standar Deviation of v,
O(v)
d(q x v)
4 x v,
t.
Standard Deviation o
'.
Cos elaton of q ad v.
he
Covaasneo
r(qv)
qv'
of q and v,
Uslg q and a as basei
a*.
an q
q
b.
Mean a.
a
eo
as
Mesa
as
Meat wo
q z u.
$qu
peaetere.
d. Standard Deviation of q,
0(q)
Deviation of as
(u)
e.
Standar
2.
Standard Deviation of
g.
Comelation of q and a,
h.
Covrlane of q and a,
The usual
aq a. a(q a a)
r(qeu)
Wtatiteal definitioo are Implied In the above quantitte
with the "bar (
)" denoting a time avraeo over the period s-
Iarised, in this case, one year.
In computiag the tima aver
es ove
the year for each of the 2$8
18-obsered values of
ary stations, a running aveLge of all t1h
prg~
each paramter was taean.
secondary stations the
For eah of the 2
of tbO
yearly time averages were computed siaply by taking the as
mnuer sesoa
inter
and
eason aveorages
balanced distribution
an
only a very mall error even whern t
in the anmber of observationt
inaturoaes
this proed1
to the other.
sa a
o
Oe
Although siverl statistioal qMantities were computed for each
of four standard pressure levels, the only oaes to be treated In this
estdy will be the sesanspeitle bhuaidity, q, and the ee poents of
(or water Vper) transport,
the aan lasttre
o aWnd qw.
At each stan
tion the mean specifle huldity, q, for the year at any given preesure level is simply a seasare of the mean mount of water vapor at
that level and station for the yearly period.
At each station the
values, qu and qv, represent the components of the uesa horisontal
trasport of water vapor,
level. where U
helorsontal wid
for the year at any
iven pressure
is defned as given in
vector /
aI
the second paragraph of this sentions
+ 3 v.
Using the
gegrsphctal (sphersial) coordinate system (X0 O, p. t) where X is
longitude
eassured positive to the east C
tude massuned positive to the orth C
unit vector).
iS lat
unit vector), p is the pres-
sre tin ab (posetive and inceasing dowward through the atmosphere)
and t I s thetime
the respective t~al (A) and erldional ()
-10-'
transport of water vapor at any
copoents of the mean horiatal
station are the represented by the quantitles, qu and qvo for any
given pressure level and for the yearly period.
The fields of msan
pecific hmteidty and water vapor transport
for all the stations at each of the four standard presu
levels
sake for Interesting studies n themselves and exhibit vertical covalstency from level to level.
This study will treat only the ver*-
ticallya-1ntegrated values of the quatities q. qu, and qv
for the year 198 at each station bowh
in Figure 1.
omputed
The develop-
sent of the vertleal Integration technique follows that ease
The tol tal
PeiNoto (19).
a
by*
horiontal trnsport of water vapor
above a point am the earth's sarfaee for a time Interval defined by
the bar "
"
(in
this case, one year) may be sepresented by a two-
diensional vsector field,
B(As)
1
fPO
/
d
0
where g il the aeeleration of gravity, asomed constant and equal to
.2
2
9.8 x 10e
in abi q and
and
see
* and p0 is the
n
value of the
have been defted in preceding
erace pressu
sparara
The Liaai
eridional components of the vector field, Q, are given by
ab156m
4r dp
S_
aqV*
Units ofS
go a S
or
= 10 go
m
a
see
dp
0
defied as the san preespitable water .apor
Blallarly, if Wa
content In a coolUM of air of unit (on
eabove a given point
emo')
his study, then
on the earth's surtfs oer the yearly period taken In tn
o
Unit of
dp
(1)
em
auts
a
or e~ of water
o
All tmese fosmulae iacorporat
the hydrostatic equation
Op a a~g 6e
(whsre
Is the density and a the geometrie height) bease
a state ot hydrostatie
aomphere is i
most of the tIsm
qmiilibri
e.
B
variable, as, M
coordinate
, or very nearly so,
this is a valid 8assmption and certatly can be used
with extremely anal error in a study of te
as this
the at -
general elolation s ch
smos of the hydrostatic equation, the gemttlc helght
been replaced by the pr.
an the vertlcal
Actually, in p
tgg
* p, as the vertical
is used in this study.
orming the vertical IntegSStions of th yearly mean
-1--
Pa a
quantities 4, qu, and qv, it is not feasible to integrate
e pe to the
truly representative mean value ot the surtae p"r sur.
top of the atophere (p = 0) at each stations it Is rtesible and
sum s
to &
1e*ptablo
genermally
which saesaOtable.
reasonable boundary conditions
Following PIesoto (1988)
econtributions to the
b
vertical i~ntegla above the 0ewb level and between the 1000level and the eurfae
a diegarded
have
The values of speeific humidity mme very anall above 800 ab,iand
genrally high, the total water vapor
although the wind spsods s'
tranmsport reealn
sel&tively real.
Therefore, it is reasonable to
asme that the errors lntrodamd by setta
th
upper boamduy of
the vertical integrals at 800 ab ae saill these. errors are likely
to be greater in the equatorial regions and over extemsive areas of
high tormin moch as the Rocky Mountains (western United States) and
the 3 malapan Mountains and plateaus (Tibet and central Asia); an
a
estimate of the error in thes cases will probably be attampted in
later study.
In the meantbom
the
Wpper bounda y of the vertical
lntegrals has been set at 500 ab In this stdy.
The lover boundlw of the vertical Integrals has been set at the
standard 1000 ab pressu
level.
In cases where the sean surface
pressure, p0g for the yearly period is greater ttao 1000 ab, this pros
Caedure underestimates the total vetically integrated vales,
Poiioto
-B19*
found thate with the exeption of tropical arHas, the contri-
(198)
bution of the thin layer between 1000 ab and the surface was of
relative eigificance for the total Inteagted values.
little
over the trade wind reglons, where loi-
largest errors pobably ocCa
level hsidities are high winds a
presne
is
exceed
1000 ab.
strong, and the mean 8rface
ie
In eases where the
ean surface proes
less than 1000 mb or whbre the surface topography nor
&bne
The
lly e
mnds
values of hwtidity and
the 1000 ab level, the actual arfaces
wind have been used and eubstitted for the 2000 ab level; hence, no
fictiious values have been Intdauced into the vertical Integrals
for thems cams.
As a res lt of the foregolxg ~
coaditions for the vertical
mptlons in setting the boundary
ntegls, the magnitudes of the mean
horinoatal transport of water vapor and the mean precipitable water
vapor content above. the earths surface for the year 1986 bave probably
been slightly undeestinatedl however
probably been ooaftisd chiefly to extnlve
th3
dersiton
as very
aemas of high terrain
and to the trade winad reglons.
aemputed
The vertical Integrations of q, qu, and qv have been
ntmrecally, applying the trapewidal rule to the yearly man values
of these quantities at the
700, and 800 mb
our standard prNeOMr
levels of 1000, 850.
nd using the boudazy conditions at 1000 ab and 500 mb.
-20A general e2ample of this techniqte to compute W for a station wh ro
re level is reported may be illustrated a
the 1000 ab p~
lO00ab
"isoo.
follows:
qdp
Units. csek:
1-2
1000 goC
LOdynes a
ab .
p
-2 -2
Thus, the units ofW ocheck to be ga e
-2a
csm
or simply cm of water.
urOmiMal 8t2n IntStration
Integration
Step and
Layers dp
1
1000-850
dpal=50
-*
-"so'
dpaISO0
1
Lm
(Noe so
-n/u
z
-for lae
1
ia
1860
V at
100
o,eXa
200
19.for
dp=200
following$
q1
.4
above nausriCal step Integationse gives the
Adding each of t
(05
~leow dos
0+
2. 6o
3,0 1s50*5
2.0 loo
1.8
)amd
Sinilar anweical step integrations using qu and qv instad of q poand Merdlional (Q ) components of the total een
vide the onal ()
a given point on the earhrhs
horiwontal transport of water vapor
In
surface.
aayama the vertieal integrals to obtain W. X and
pasputed, dependent on station elevation as follows:
have been
Station e vation between sea level and 2500 feet.
1.
S se.
2.
Station elevation between
oo(,S~C)
L
1.6
=
3.
1000(SIC)
Station elevation above
w- 19.6
Val
a of
and
so
700
801 and
f eet.
.
,0M
.o
s0
2.0
3.5
000 feet.
.o qo
aosc
.O
S 00(S2C)
500
have been computed exactly as W us ag qu and qv
respectively instead of q in the above expMessios.
In all
when 1000 mb, 850 abe or 700 ab data were
autions,
aiesing de to station elevation, curface data were substituted for
the missing level.
The following elevation limits were used in
selecting levels for the verteal integrals,
Sea level to 2500 tfst
2501 to 6900 test
Above 8900
eet
1000, 850, 700. and 500 mb with surface
uabstituted i 1000 ab alasing
860, 700, and 500 ab with smfacme substituted If 880 ab a issing
700 and 500 abswthcsurace vibstituted
it 700 ab essiag
4*
ANALYBIS Or IOMBSD DATA
Before actual analysis of processd data, a survey was made to
determine the time and spatial distribution of this data respectively
for the yearly period and over the northern hmisphere.
Where the
desired
priary stations originally available did not afford the
e of data, SeCoSday stations were chosen to fill in
spatial covergm
the data gapsl this procudure did not present a serious problem and
was discassed earlier in the secnd seotion of this paper.
The time
distribution of the processed data from 34 of the primary stations
indicated that
ome of the computed yearly mesa values slght not
be representative due to signiftlant imbalane between the nuber of
ob~ion
the ummer
ummer and winter seasons.
A siple method of averaging
an and winter mean values was used to obtain a more
representative yearly mean value frei
frm seasomal blas.
The co-
rections to the orginally eomputed yearly mean values of We
Q
were mall at aost of the 34 stations involved
but a few cor-
rections, notably in India, wese sigtificantly large,
this fact was due t
o and
Undoubtedly
he strong seasonal monsoon associated with a
marked ohane in the climate of India from winter to somer; under
such clr
stances, an imbalance between the amuber of observations
in summer and winter seasons produces a rather strong bias in the
Moreover
yearly running sawn values.
the ICY rawinsonde upper-&ir
observing program apparently did not get under way until after the
early winter months of 1958 at Allahabad, Calcutta, and Bombay; no
observations were available for the first three months of 1988. and
thus the yearly mean values of processed data were rather biased
toward the
nmer values.
seasonal blas, sall
In all 84 primary stations affected, the
was removed and a more representative
or laMge
yearly mean value was then used for analysis.
not occur with the data fro
This blas problem did
the S secondary stations, because the
yearly asa values were talen originally as averages of the sumer
mean and winter mean values.
A complete listing of the originally
be
computed values and corrected values of all processed data will
published later.
The representative yearly mean values of W,
station were plotted on three separate charts.
used was a polar stereographi
and Q for each
The plotting chart
.projection, scale approxmastely l:40
million, of the northern bemisphere as shorn in Figure 1.
were analysed for the best posasible
The data
t; all values werse carefully
studied in relation to terrain and geographical features before the
final analysis was completed.
At one station, Miamit
namber of observations for the year was sall
Florida, the
compared with those at
A-S4
sUrrounding stations; and, sines the values at
several closely
MilSa
did not agree well with those from the nearby stations, the
values of processed data at Miaia were not used in the analysis,
The analysis of the mean precipitable water vapor content, W,
for the year 1958 was carried out first (Figure 2).
No major diff-
cultles were encountered; the data were quite eufficient for the
task, and the patterns relatively amooths Isolines were diwn for
every 0.85 a an
(or ca) of water vapor content.
The analysed
field shovs, perhaps better than any other, the essence of signifcant water vapor distribution in the atmosphere.
the analysis
bshows a continuous doesease of precipitable water vapor
cotent from the equator to the north pole.
influences and continentality are evident.
areas of the Middle
The effects of maritime
The Saharao the desert
ast south of the Casplan Sea. and the desert
region north of Tibet are dry.
rai
With few exceptionse
In additiono the effects of high ter-
on loistume distribution are illustrated by the vevy dry areas
(less than 1.0 ga ems)
and over the
over the Rockies In the western United States
ltmalayan Mountains and plateaus of Tibet and central
Asia; the possibility that the values of W over the high terrain areas
have been underesti ated was dismaed in Section 3 of this study.
Until this possibility can be fully explored and checkeds it
reasonable to bsse that the underestimation,
aould seen
if any, is mallo and
that thee areas axe, in faot,
relatively dry.
portions of the sub-tropical oceman
Over the western
asnticyclones the water vapor
content is generally higher than over the eastern portiona
this fWct
Is eqsecially evident in the Pacific and agrees with the concept of
general convergence and divergence, respectively- in the western and
eastern portions of these semma-permanent,
general circlation.
large-scale featuves of the
eas of highest water vapor content
o
The mist
are the equatorial region of South America, the equatorial westera
Pacific Ocean, the Indian Ocean (especially south and east of India),
and equatorial west Africa.
The driest aea is in the Artto where
the yearly sean pmaelpitable water vapor content is less than 0.5 gm
cm
north of 80Qm.
The 1.0 go am
isoline enclosing the Arctic
regions Is found generally at or near the latitude of
bs
south of GOaN over the regions of
ONi it dlps
outbreaks of cold,
ft
dry polar continental air in eastern Siberia and the Bering Sea and
eastern Canada and Budson Bay
it extends north of GO
and even
slightly north of TON over Jan MaynQ and northeast of Iceland, very
probably showing the effects of the wa
and wam r
olst airmasmes
North Atlantic Drift current
frequently carried northeastward across the
North Atlantic Ocean toward the Acttoi
Ocean.
The 0.8 go c
-a
isoline
encloses the area between 80ON and the North Pole and also dips slightly
southward toward eastern Siberla, over Ellemanee Island, and over Greenland.
-26is obvious from the analysis and Importait
As a concluding reark it
to note that the mean water vapor storage in the ataosphere is
very
mall.
and seridlonal (Q ) components of
The analyses of the ~soaal)
the mean horisontal transport of water vapor for the year 1958 were
completed as shown in FIgures 3 and 4.
plex
data covrage.
lacking,
d
o the
of
h th the alys
These
vers more can -
alyse
expeclally over areas of spard
In areas where data coverage was sparse or copletely
such as the equatorial eastern Pacific Ocean,
arful
atten-
tion was given to the analysed V field together with the mean wind
field (Minte, 1984; Mints and Dean
1952; Wiederanders,
1961) In preo
paring the final analyses.
The analysis of the field of sonal (k) transport of water
vapor (Figue 3) shows consistency with the mean sonal wind field.
Isoldies ae
drawn for every 5x
transport with
om
10
-1
-1
2 gia Sm
values of the sonal
ae
2 ga ca-1 se -1
areas tilled In with every 2.5 x 102
to show significant details.
Large positive (west-to east) centers
of sonal transport are found in the aid-latitudes where westerly winds
are predominant,
Oceans between
especially oter the North Pacific and North Atlantic
ON and 50ON.
Large negative (east-to-wmemt)
centers
of zonal transport are found In low latitudes where strong, persistent
easterly winds prevail
the two centers of largest
onal transport are
found in these low latitudes, one between lO
and
5IN over the
central North Pacific Ocean near the Marshall Islands and one over
the Carlbbean Sea between the northern coast of South Arisa
Puerto Rico.
A sries
and
of four amall centers of negative zonal traa&-
port are found along the southern fringes of the Arctic regions; two
very small negative centers
one over the Sae
of Okhotsk and one near
tao
the Golf of Ob in north central Siberia may be questionablee but
fairly laBg and deginite negative area
are evIdent over western
Alaska and over the Arctic Archipelago of Canada and over portions of
Greenland,
values of
North of th3se negative areas are fatnd =all positive
onal transport girdling the Arctic Ocean around 70ON to
80aNO
The analysis of the field of
eridional (W ) transport of water
vapor (Figure 4) is somewhat more complex than the field of zonal
transport of water vapor.
cm
use
I solines ar drawn for every 2
10
g
values of the seridional transport with some areas filled in
with every 1 x 10 ga ca
see
to shows gnificant details.
Large
the
centers of positive (northward) tvnsport are found generally over
regions of aid-lattude storms
especially in the vicInity of the mean
positions of the Pacific and Atlantic Polar Fronts,
Large centers of
negative (southwrd) transport are found generally over low latittudes
Atlantic
especially near 200N over the eastern North Pacific and North
Oceans where trade winds prevail.
Other centers of nortward and
southward transports are scattered throughout the northern healsphere.
Around the Aretle regions there ar both northward and southward
tra sport a but a rall southward (negative) transport is suggested
over the North Pole Itself.
An interesting strong poeltive (north
ward) transport amea, found over the lower Rio Orande Valley, extends
northward in a narrow band over the "tornado alley" of Texa o Oklahamak
and Kansse
this rather striting feature and other generally north-
south oriented bands in the feld of seridlosal water-vapor transport
over the United States (where the
are detailed data) a
resinioent
of the moist and dry tongues found on meen ilantropie sherts by
Nasias (1940).
Along the equator there seems to be roe poitive areas
than negative, but, since the analysis of lrge oquatorial regions of
sparse data relied heavily on tho mean wind feld, these results may not
.b repreentativeS Peixoto (1906) tound positive and negative areas
balaneain
each other over the equator and onelded that the net
moistare flow across the equator was practieally asro. This conclusion may certainly be
ustified ito the loag*eriod &verage s bot it
may not be valid for any particular oneuyere
period.
-29-*
S,
PAN8iORT
DIVRGNCE C0 WrAIR VAPCOR '
A-s-0Ig that the analymed t-elds of sonal and meridional conpoents of transport of water vapor abown on Figures 3 and 4 are
repxresetative of the total mean horisontal transport of water vapor
above the earth'a surface for the year 196, the ditvogence of the
oixto (1988)
water vapor transport can be oaleolated.
fosnla for the horisontal divergence
gives the
of the total (vertically-
integrated) yearly meen transprt of water vapor in the O,.p)
coordinate qmystem as
where R is the radius of the earth, taken as a constant, 0.6871 x 108 cm,
and the othew quantities are the
ame as given in preeding meotlons.
Looking at the water vapoorbalance equation for the ataospheve used
by Peixoto (f198)
and later by Luaftn (19860)
horiontal divergence
vapor above the earth's
the signiticance of the
V aQ.,s) ] of the total tmreasport of water
urface beomes am apparent
vapor balance equation will be outlined l
This water
the following paragraphs.
s
Considering a column of air of one ma arosesection extending
from the earths mrface (premsae, po) at Sach point to the top of
the atmoephere (presm re. p a 0)
the balac
equation anm be written
suah that
OW
-am
*
at
I
t.o
where
w
'
and
q d.'
Q
1 1,
fo
qVdp
o
o
W is the qMantity of Preiptable watesr vapor in the atmospberic
is6 the i-omponent of the vector represnting the total
colu= and
flw, or taaupout, of water vapor vertically Integrated above each
point on the earth e
bas
at te
T
uface.
of the ataoseaowi
is the i-cwe
Is the mom
coltan,
of water s.Ibstan
q is the specffite hmidity,
eo p is pressure,
up#nt of the Vind vector, t is ti
etd S is the acceleration of gravity am peviously defined.
In gosgvapMhial (spherical) ecordinates (A,p,t),
the equation
for temoaheIe water vapor balance takes the follow Ig tem
W
1
8t
R co
wae
iRs te
8Q
se
Q
tn
R 8O
R
1
ap
earth's radius as previously defined and 4Qtoa
Qp
ae the mnaal, sswldional, and vertical cqopilata of the total water
vapor transport vector reospectively.
tlal
coordnsate
uw
ay be defined as u,
Sw
C'p
p
dp/dt.
as the voar
Then
dp
0
(,po)
O and (O0)= 0 and
a
since at the limits of integration
q(500 ab)
With pressure, p
0.
In additione
sW/t, the rate of Ob
of water in
'in stora
the atmospheree is very saall #uech
maller, for example, than the
rate of hage of storage of gr
water, and my thus be also set
waterd
equal to aero.
rather
This reasomting becomes even mose apparent ft.
the
all amounts of preolpitaeble water vapor contained in a repre-
sentative column of air (Fiurae 2).
Therefore. asmlng negligible
storage effects, the water vapor lost in regions of positive diver
gene* sast be rsupplied; and the water vapor concentrated in regions
of negative divergence (convergence) must he rmoved.
It is also
snainabls to assume that the main souroes and sinks of satspheric
water vapor are due respectively to evaporation, o
P.
and precipitateion
Furthermore, since the horiental tr asport of water In the solid
or liqUid phase
tsvery small compared with that of water vapor in
the atmosphare, for all practifal purposa
E and P nay be equated
respectively with the evaporation and precipitation at the earth's
surfac
below the atmosphewic colwm under conslderatio~.
The exace-
of evaporation over precipitation (E - P) sust then be eqmal to the
ivciergence.
r
ateri
atmospherice
amnts into account and xrgrouping teuas
Taking these a1
water vor obalanoe beoomae
asmophier
equation tfo
Q
1
-
R Gas 0
A
the
+
(Q
cos
(E-
P)
50
The loft-band aide of this eqltion, when the values of
amr taken as yearly mean valuel
and Q
. to equivalent to the horizontal diver-
genes of the total (verticaly-integated) yearly mean twi ansport of
r vapO
water
in the atmosphere, V * Q (
cralculated te
).
Starr and Pe ioto (1968)
latitademlongitude
sean (E - P). field for a tenaegreeo
for the year 1950 uasig finite dif-
grid over the nothern helsphea
feoence methods to compute the hobrlsotal divergence of thb
mean wter vpr
transport.
total yearly
A emlar finite difference procedure was
used in this study to compute the borlaetal divergence of the total
yearly sean water vapor transport for 19 8; bhoveor,
n view of the
greater amout of data available for this 1908 study a beaste fIvedetree, l tittude-logitude grid was used
tude, where. a ten-'d
ree grid uas
semd.
eazept north of.
igmure
lsti1O
shows the distri-
buaton of the hori ental dirvestnce of the total (vertically-integrated)
-33war
s 1988.
vpor transport for the yea1
water vapor di~vrgen
Positive vals
of
show areas whre the earth's aw~face acts
as a aouwce of water vapor or where the total evapotranspiwation
Negative vale of water vapor dove-at
exeeds the peIpitation.
gence (convergence)
aow
areas where the earth's
wntace acts as
is
a sInk of water vapor or where the total evapotranspiratiao
exceeded by the precipItation.
A discusesIo
of the major ftates
vapor balance of
of Figue 5 and of their relation to the water
the staomp
e and the water balaes. at the eaths
follou ln the neat section.
ea~urfsoe wll
W TIE VAf'C
0,
As shown in
SACWZE
8 the analysis of tWim Iwriontal divergence
igoas
vpor transport for
of the total (vertically-i ntegwated) mean waterl
the year 198
W
computed
was prperd usinf the valuea of divergee, V * Q C,0),
grid area of latitude and
d plotted for evesy ftiv-~er
logitude in tim northern hemtisphere
north latitudeO
rm thm eqwator to 80 dogr
es
the area tfr SO degrees narth latitude to the north
area of latipole was oomputed Sad plotted toer every tead gree grid
tde and logitude.
The analysis ahows the existence of divergence
centers alternatng with
detail and e arater.
oerrgne
centers and exhibits considerable
In the areas of dense and Wpreentative data
11verage the detal obta
d in the
iveMdepree grid computations is
some
undobtedly JustfitledI hoever, It areas of sperse data coverage
of the detall
from
ay not be Justified because the weight of the data
reporting station can produme a demiant value of tih
ole
gence in a mall area.
of a tfe
n efSeot could be notieed in the vicinity
reporting statlones station ~anber 46747 Tugh ng, TaIwan;
station number 7886.
Hlo, Baai.
were a
Such
di-ver
Quantamo Bay, Cubal and station number 9128,
In these areas and in a te
otrbo
where
ch ettffects
opp the analysis ws maoothed slightly; otherwse th
computed
-3Svalues of diverenoe were
naly ed exactly and to Uhe best possible
fit.
legions .b the Atlantc and Pacifie oces s show
Tm equatorial
a general convaprne
of water vapor trancpott indicating an excess
of precipitationover
vaporamtIin in the areas where there is a
both hemispheres,
mean convergene of the trede winds tr
nce ae
centers of strog cone
m~
found just
Merked
of Paama and off
thse areas
the east coast of South America near the equatorl both of
are known to have exMcessve prOelpitation.
the rather stroea
America is
arHes,
Although the data supporting
divegence south of the Gulf of Marmalbo In South
this area does have rather oEanty precipitation
to the
erpared with the Amaon River basin and watershed farther
south and east.
Another interesting are
is found over the Arabian Sea.
of very strong divergence
Even though te
data supporting the
the
water vapor transport analys s in this area were spars. and
analysis raeled heavily on mean windae this divergence
can be
ca
Seal this
associated with the well known high alinity of the Arabian
high sali Sty, .of course,
evaporatc
tscaused to a great extent by the excesve
or strong diveaorgdeie of atmosphearl
Arabian 1ea (E-P lV
and positive).
~ater vapc
over the
Lufkin (1959) and Jacobs (1948)
empirical
both have derived sepwaately, in slightly different ways,
relations between the
sa-surface salinity and the field o: (E-P) for
Zeus
of the oceans where the effects of horisontal t rnaort of
urface water salinity ero negligible.
Two areas of strong convewgence borderiag
the equatorl and
mb-tuopical regins awe worthy of special note.
On. Is in the
and Ethiopia in Afrioa end the other is over
victIaty of EritreI
north cntral India etending eastw
luding Asae and Bhutan.
The first
to northeasrn India inr emquatorial east Africa
ea
contains the beadwaters of the Blue Nile and several tribataries of
the White Nile; there ame alsoseverwa riv~ flowing
this ar
ro
Soaliland and
enya.
The heavy rain
areas roaerred to In India ae well known.
coverage
fr t'
ta
over the
With more detailed datas
lose to and within the flmalayan mountains the amalysis wcald
undoubtedly contain more detail and more aeoumetely locate the center,
or possibly two centers, of comvewgenoe,
along the mountan
otne further north and elo ngated
oass and one further east over Ass.
very likely that even greater detail could At obtained I
It seenm
the dIverence
analysis over India if there were a high density of reporting stations
located so as to delineate clesaly the treeandous convergnee of water
vapor transport assooiated with the well-known aLmer monsoon.
theles, the analysis shown on FPi
ppars to be comn
8 a5
the known faets of the earth's water balace over India.
Never-
stent with
It
is ilter-
eating to note the eatension of thse prominet convergence northward
through e ao.
to.the Pairs and Ala Mountains west of SinklAg
where rain md sanow provide the
ead waters of the. Indus River and
several other aller rivers flowing into the Tari
where they disppea.
Its
Basin of Sinklang
hould also be noted that this entire large
area of convergence over India eaovers the vicinity of the headwaters
of severl extensive river aisteaI
s Indus, Ganges, Bra heaptra, Sawen,
Mekong, and Yangtwa.
The sub-tropleal regions of the Atlantic and Pacific Oceans from
15I
to 3ss
rather strong and extensive eeas of diw
b
sho
gence. In
the Atlantio the divergence pattern is elongated in an east-west direction and geneally uninterrupted.
extends
of
In the Pacific am the divergence
o Marcs Island
estward from Mexico to
it shows several centers
amrked divergence interrupted by areas of weak converence or lesa-
aerlad divergenoe.
This feate" of the analysis may be due to a cellular
structure in the Pacific antieOlcone
Over the western portion of the
Pacifie anticyolonie belt the divergence pattern is soewhat confued, bul
in generale
cnavesrgene predominatesg the ave
south and west of Japan
shows rather strong convergenee as might be epected fras
front whose mean position is
in this region.
the polar
Closely associated with
the strong divergence of the mb-tropical oceanic anticyclones are three
other interesting areas of divergences one over the central Medit rranean
Sea, another over ran, and the. third off the coast of Mauritania in
west Africa.
The central bediterranean divergence extends southeard
-so-
joino to
over the doG rt areas of Libya and Aleria and acvtaPl
the e..ast tho
Imrn; this
the Syrian Desert with the diverwgane awne
whole area is known for its drytes
and is
emn to
em
as an Imamian
is
knmen for its high salinity, wh$bh can be seadily associated
i th
portant source of atsmospherlo
oitaweg also the Medite
?hae diver-
high positive mean values of (E-P) or strong diverence.
of west Africa can be asotated with scanty pre-
gence near the coati
CIpltatlon over the region and with the cold Canary or North African
Current.
YJrde
The very mall amounts of precipitation over t
slands are well known and have plg~
thesm islnds for aony years.
subtropieal cean
d the inhabItants of
Is not difficult to prove that the
reas, which biow strong divergence of water vapor
transport, asewn -fact te a
but it
It
Cape
Jr
sources of atmospheric moisture;
it more difficult to c-eonive of
ertain dry, desert areas in
Africa$ Arabia, the Middle Easto and Iran as contributing sources of
ie
atmosphe
amoisture,
Nevertheless, tbh
divergen~c
water vapor trsport shows this to be the eaw
(1950)
of &tmospheric
8taw and Pelioto
have already emsented on this point, since the study of 1950 data
by Poxoto (1980)
deserts.
hmowed simla
r an1ars of diveigence over
No further coment will be made at this tie,
these eame
but this present
study indicates that these particular desert aras ae worthy of ses
further study from a hydrologie viewpoint.
The
id-latituadese
smaly
so
rcwand the nortlern hiatphewr
sions
mall aea elf divegence and congence., The most prgoainet m
nesC
a~as of conva
apparently asciated with the esta~-t~opical
stnu tracks acose tWihe North Atlantic and North Pacific emeans.
soE
~
coenve~rnce between loland and Greenland,
The stron
particular stas
trck
hbe due to
strong and
in 1988, but the other rther
marked aras of cvergenee In the North Atlantic region a e clearly
related to polar fvmrt stormaa
eastern United Stat8
this s e@@p4ally evident over the
and over the Gulf Stream and also in the vecinity
of the western and coastal regions of Norway and Sweden,
of tonvergence extends from the East China Sea nortb-
extensive aes
eard
A long and
over the Japk eo island
and Sakalin then eastwar
the entire northvn Pacific Ocan to the west
aeros
ast of North Ameriesa.
Here, in the vicinity of the QEAn Charlotte Ilands off the coast of
British Columbia, is found a gstrg area of convergence extending nortba
ward and southeard along the co
is known to have
area of weak
divergene
al moutan ranges.
This very area
s and regular precipitation year after year,
Wopioe
An
eonvewgence Is found inland of the coastal amontains, and
is actually shown over the deset area
of Nevada and vouthern
California ineluding Death Valley and the Salton Sea; furter inland
over the Rocy
convergence.
eouantains Ito m
another ama of soderately atrong
Within this geneal ame
of convergence are the
eadwaters
Rio Gi ndes
and dlve
Columbia, Missoa,
e rivelr systema~
of se~veral
details of other
Tek
npe
Colorado, and
l1 areas of weak convergence
4sppoed
over the United States and Canada can be
and more
by excellent data coverage and. eally merit a separate
There are two rather
cceplete study than is possible at this time
strong and m rked regions of dive
ence in the ild-latitudet
should be wnticued, although the- oer-all picture is ofe
convergence. On
~Ues
area is found just mouth of New
ard into the Atlantic; the other areas
that
of general
uondlamd and extending
$tfound over the
northern portion of the Yellow Boa# northern Korea, and the western
port on of the lea of Japan.
The divergene
over northewn Zorea was
by Lufkin (1989); it can
also found by Pelxoto (1956) and eaomnted oe
be associated with the Iong winter sonsoon carrying cold, dry air across
this region and
ertainly ireasI
its smolstur
at the
pense of
It
abould be
the underlying asrfaces, especially the Sea of Japan,
the western shores of the Japanese islands.
The rather strer
near Newfoundland Is more difficult to justify as a amefeature
of the general circulattion
ce along
to one of convyg
acge
noted that the pattern abruptly
it
divergence
pemanent
is possible that the outbreaks
of cold, dry Canadian air masss o.ver this region and into the central
North Atlantic were espectally a rked in the year 1958.
The Arctic regions north of SOON show a patchwork of small areas
and d1ivq'oene.
M
-of wvak convogno
ge
ge~aa
e
It is ditt
aml
conclusians that might be 8nSifica1
oireaImn.
lt to dr
any
t with espect to the
Nevertwhelss, the data coveage north to 80ON
was very good, ad at least the divrgenoe pattern. complex as it may
be, shabld repream
t ceondtions in 1988.
The implied divergence at
the North Pole Itaeif is close to aerol at least it is very Hsall and
camnnot be deteialned by the mthods used In this study.
-42-
7.
Whethe
CCUSI DING PEMAMS
patterns aown in Pigw*
r not the dlve9genc
are
repesentative of the mean conditions tom year to year is subject
to som
question.
Certainly the analyses 8hon
hent
and S are bad upon ufi
data of high quality to represent the
It is also quite likely that the analyses
year 198O quite ftaithlly.
in the equatorial and uab-twopical
of a true men tfor ore
regions are ganerally vepresentative
n Jst th. one year studled, bea ue in
of the
alampeun~
antiqoleones
these rWsegis a"e found the large, e
s
sub-twepies and thegenerally steady trad winds converging
eass,
3, 4,
n Pigaes 2
n the
trom both bohispheres into the man equatorial trogkh.
AlthoWh
there ay be canges in these mas-pemanent erculation systems fros
year to year, th major ftestres of thesersptes do not vary enotgh
to upset the grMal pictwe+
It
ould also be noted that in these
mum reeims the ajor teatuves of the divrgenwc
1958
pattern for the year
agreed with those tound by Pexoto (1988) for the yeaw 1950,
The situation in the aid-latitudec and Arctio regions, hcwere leaves
'sow doubt that ay e
yea
is spresentative of a ture mean.
It is
known that atram tracks vary fti year to year as does the regularity
and strength of oabeeaks of po2,w and arctic airasses into the
fwcts in thenlv
es would certainly intr
aidlatitude regions.
Thes
fluence the divegnce
of water vapor trunport in aid-%latitude and
legions, so that the
eartio
gnitude and the location of divergenco
and convergence centers could be different frem one year to the next,
Nevertheless. certain regular featwes of the aid-latitude circulation
can stand out in any one ySua
veqpence associated with the
a ea
in point is the strong con-
sptous and regular precipitation in t~e
northwestern United States and seufthestern Canada; this particular
teature showed up in both the 1980 study ad by Peizoto (198) and
in this present study for the year 1988.
It
has been
should also be noted, that, unlss spselfto mentieo
sade to the coarr,
the mejoS
features of the diverene analysis
in this study agree quite 1all with siMilar
study made of the hBmispheric
Seatures in the only other
water vapor balesee,
iee., the one by
P xoto (191).
The blesg ntroduced *by using the pilot-balloon technique to measurz winds is almost
ompletely absent in this study - as
entioned
earlier, only one secondary station used this technique to obsrve
the wVinds.
The limitations snd difftrences of various types of
sesing in
pperl-air
uns used during the lOT have probably been milnimsed by
the cont kfing efforts of the WM
Instramts on a global baiwi
to standardise techni qse and
Hoever, dtfferances in th
aents of various Countries still
Instru-
main, and, to some extent, these
differences could affect the analysis especially in regions along
the borders of two adjacent countries uniug different types of insttumento.
Finally, a
tance mst be sentioned: of
osat unfortunate eirwo.mn
ons seleted
the 22 secondary stations
.to fill in the gaps in primay
station coverage, the computing
£ of the M.I.T. General Cirou-
lation Project was not able to complete the fl8al data procesing for
20 of these stations before the deadline for completion of this thea s.
However, the data coverage of priary end secondary stations was conplete from the north pole south to 40N; In fact, it was very coam
plete south to the equatorial regions except for the lak of a few
secondary stations in the vicinity of India.
The reoaaning data pra-
cessnag for secondary stations Is now being completed; therm additional
data will be used to revise the preent atudy and will be Included in
a complete report to be published later, as already mentioned.
A more complete study of the water vapor balance for the IGY, at
least for 1986,
should now be carried on.
the work of Polxoto (1988)
and include
Such a study s~ould parallel
careful analyses of the s
er
-4-
and winter seeas ir keept g with the yearly
pleted in this pewasut study.
At
nalyees already om-
ther Inavstigation of the effect
oft hgh terrain on water vapor distribution and transport and an ezx
tensaon of the entir
be andertaken.
stdy throughout the southern hebiephere
hould
-a-4
8,
ACIDLoWEDOEMENTS
Much help bs- been received from many people and sourcs durnt
this long and ewtenelv
undertaking.
The a"thor first wishes to
express his Dsincere appreciation for the encouregement, -advice, and
assistance of Professor Victor P. Starrw whom keen and enthusiastic
interest in this study was a constant source of inapiration to carry
Th
on in spite of unexpected difficultie.
expert counsel and direct
assistance of Dr. Jose P. Peixoto was most helpful and Is greatly
appreciated.
bhe cooperation and assistance of many individuals
assooiated with the United States Air Force in procuring and machine
processing the biasl
IGY data used In this study was
peri
in making awch an extensives bemslp
those chiefly responsible for
A vital factor
research undertaking possible;
useres in this lportant aspect of this
study lncalue Major David J. Eddlaa,
Staff Meteorologist, Electronic
Systeas Divisione Air Force Systeas Commind s Mr. R. H. IPerrll and
s
Lt. Col. G. W.e M on
Deputy
irector and Diirector respectively of the
Air Weather Service Climattic Center; Dr. Adam Xochansk
and Mr. Wi111am
OSpen, of the Air Weather Servi e Climatic Center; Dr. Ralph Shapiro
of the Air Force Cambridge Research Laboratorsy
and mJbers of the staff
of the Air Weathlr Bervice Data Control Division at Asheville. N. C.
and of the M.I.T. General Citoulation Project.
The author must also
sention otber individuals adhelated with M.I.T. who helped in various
ways with typliag
hand coputatio
Mrs. Jane ?Nabb
Mri.
and plotting of data and draftinge:
Henry Cocaran; Mises Ellen C. Fetter, Ruth
Birtwell, Isabolle Kole, and Bawbara Stieglits; and Mrs. Barbara
Goodwin.
-48-
,~,~ILII~.~LU-iY~
DrY'UP491YLa~a$YI-r~-n~ I-y--liCYLY-L~UYW-
Figure 2.
Mean precipitable water vapor content, W,
for 1958.
Isoline spacing every 0.5 gm cm-
2
l?..I
~_~.
j3m
,~--
u~ai-1~e~8dEmC~i~~;;A:
Figure 3. Zonal component of the mean horizontal transport of water vapor, QX, for 1958. Isoline
l
spacing, full curves, every 5 x 102 gm c4-lsec
-
Figure 4.
Meridional component of the mean horizontal traneport of water vapor, Q , for 1958. Isoline spacing,
1
sec1.
full curves, every 2 x 102 gm am
Figure 5.
Divergence of the mean horizontal (verticalyintegrated) transport of water vapor, V * Q (Xk,),
Isoline spacing every 40 x 10"7 gm cm2sec- 1
for 1958.
(full curves for divergence and dashed curves for convergence).
a.
.i'.
-stoi,
'?.
0. 6. sod 16s Aa Esaqw
Z~ata
Vapor tT@Aft,
Oer
1
/.vcwcntnnt
the tlit
pp.
1054:
os
Iwnao,1
the atmompawo LU the Hydrologic cycles
/ftnt
The VDIM O~f
ad V* 0. SneOzi; 1950:
flazwb
82W
land 'Ed*
scrl
ea
and
Brunt. David, 1944:' H2a
~~piad1944)v Cmbuidge University PzeMv 4= pp.
(19,
London.
7JiDL~~w~Z,
~e
D 141:
Haurits
Mdhmp-11 Book CoOM*
1948
4eocobmg W. C.,I~
iwat Ed1tIon, 1941,
X*..o Nw York and L~dav 3W pp.
eeIrIfl
rlates
vans
asa
beon
of CEm.P) "ad wwrtac. salIvaltee Ovr the Niorm Atlantie.
Jawob
Woodmo
Cs,, 1961s
tioU ovOP the Oeeanm.
leam Use
""Lufk1I. go,
of Snaftm. Twesforw
scts
Lieae
32MM41Jm.
kt1 ZBa
oB4n
logical Sacletyq 1234 pps p. 1057-1070,s
lgo sa Ataophewlo Water Vapor DIvesgence and The Water
at te Sawth'sa 8ertaes.
Ogl,
Rut.
.
:1
UM~ *.eT., (VictorP. Starr, Diructo), 44p.
.6
ea
Circ41AM
The obwaw4ve
Mit,,*9 1954:
$ia388of
ftaopleves
5 ~C.o
Me
_~~~iinii
t~I ?ass
E
1952s The obwm
Mits, To, and Dam, 0,
of the
soal aivrnulatlem of tb-amsb~.
El.02
160
6,
i35*1g,
so= fleld of rcttion
17ijJ AIr
ioa1
Force C~brIftet r&wach Ceitewo CmbridaO, 1IHMO
Nalas Jeroama 1940s:M
PeIxoto, J.e IO85s
19508.usez.
Ad
l~~cje
~
A1so
Sispherlo acIdIty Conditions DiwIng the TOMw
N.- as. 0,q12M.-C
WcnEIgg Pro1ent NI .T.
(Victor Ps Stavro Director)* 142 pp.
Pelzotog J,
1989: 0. Cmapo ft DivewgencIa Do Twe*sporte Do, Vapor
Doegm No Atmoaftra,
J& Ct"Lftft
&gf
jveDa~~d
LIWO~
2A, 9wesaSoB VoIl. V119 pp 28-34
Star, V. P., 1951s
tar the acri*n1 citonation.
Th.i physical uis
1334 pp. pp 641-50.
v'Starr, V. P., md J* Pe ixoto, 1985:
On the global beleftee of water
vapor and the bydrology at deserts.
IStang, fo Pot J.
Peluftog
10, pp. 189.194.
and 0. Co LIdone#1957t
On the er-
diona fiwi of water vapor In the marwn healephe.*
Raw-ut 11, 0mUwa
iclati
Cm~d
bolect, Mt
*
Vp
14-
UZJ~JA
lStan,
V.
P. e and hiHte, ft. M4 to8s
Disect asuS
ywladfl ux of ntnr Vnpor,
Iptic
-
&MR
nt of the
.. ]AlEM
l 14, pp. 217-22,
Bvwrdrup,
. V., 10518
og,
Evaporation trom te
loaton, Asweres
oceans.
boteoroica1 Sooisy, 1334 pp.
pp 1071-1C01.
Wiederaners, C, J., 1261t
Anlyzs
of Monthly Jian Remaltamt Winds
for Standard Pnsmre Jless over the Pacific.
0
-
f
It Institte