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Mctcorol Atmos Phys 3g 215-227 (1988)

Meteorologisches Institut Universitat Bonn Bonn Federal Republic of Germany

Recent Fluctuations of Tropospheric Temperature and Water Vapour Content in the Tropics

k33

Meteorologyand Atmospheric

Physics () by Springer-Verlag 1985

551583 I (2137)

A Hense P Krahe and H Flohn

With 7 Figures

Received December 18 1986 Revised May 25 1987

Summary

During the last decades the average temperature of the tropshyical troposphere (200850 hPa layer) has steadily increased between 1965 and 1984 by about 08C in the whole equashytorial belt Data series from a section of individual stations verify this trcnd as seasonally constant but decreasing from the equator towards both hemispheres Further evidence is presented by selected mountain stations and glacier retreat in all equatorial mountains

Above the equatorial Pacific the same stations indicate an increase of moisture content in the middle troposphere (500700 hPa layer) expressed in precipitable water as well as in relative humidity This coincides with increasing sea surface temperature in the area around Indonesia and northern Ausshytralia AbovcAfrica the trend is (if real) quite patchy Due to the short residence time ofwater vapour in the atmosphere the horizontal (zonal) distances between its sources and sinks remain near 2000 km which may explain in addition to instrumental differences large regional deviations

1 Introduction

In contrast to the excessive anomalies of tempershyature water vapour cloudiness and rainfall during the recent ENSO (E1 Nino Southern Oscillation) event of 1982-1983 the slow changes before this event have aroused only marginal attention Sevshyeral area-averaged time series of tropospheric temshyperature in the Tropics (Newell and Hsiung 1984 Parker 1985 Angell and Korshover 1983) most

representing the layer 200850 hPa indicate an upshyward trend at least since the weak ENSO event of 1976 this trend had not been discussed by the authors It has been indicated by Wigley etal (1985) as a steady equatorial warming of the 300850 hPa layer Since 19745 no large negative temperature anomaly has been observed - even the recent cooling (19845) above the equatorial Pacific did not reach the intensity of the cold phases (van Loon and Shea 1985) before

Together with the problem of the unusual inshytensity of the 1983 event surpassing all other ENSO anomalies since (perhaps) 1877 these facts have motivated us to investigate time sequences of aerological data in the tropical belt We have included the water vapour content which is of primary importance not only for the greenhouse effect (Dickinson 1983) but also for static stashybility deep convection and effective release of lashytent heat (Ramanathan 1981) Indeed the phase changes of the water vapour provide one of the largest heat sources and sinks modulating the large-scale circulation patterns of the atmosphere A pilot study limited to one station in the equashytorial West Pacific (Majuro) gave positive results (Flohn 1986) A short review of the results has been given by Weber et al (1986)

110 liS ISO I)S 120 IllS to 15 IIIJ CS lG IS u

10 I I I I I ] C6~ ~l I I I r III

H

lsi I 0 1 1 1 I~I~ 1 II I I - JI III

Atbull 1

( I

-0 I BO 165 1$0 ilS (10 ~

Fig I Spatial distribution of the radiosonde network utilized in this study The symbols at each station indicate the observed linear trend in the annual mean precipitable water between 500 and 700 hPa A question mark signifies possible inhomogeneities

216 A Hense et al

2 Data All station data are taken rrom the joint WMOshyThe radiosonde network utilized in this study NOAA publication Monthly Climatic Dataor the (Fig I Tables 1 and 2) is essentially identical with World (MCD) supplemented ir available by data that orAngell and Korshover (1983) between 20middot S rrom the archive or the Meteorological Institute and 20middot N except in the Pacific Here several adshy or the University or Bonn For most stations the ditional stations have been introduced to enhance monthly mean 1200 GMT ascent is recorded in the coverage in this critical area the MCD but some report the 0000 GMT or the

-I ]1 -S -so ll $0 -lOS middot120 middotus -110 I~ JO I I t i I middotuo 1tO

bull lisl)NI ~ t f I I) ~ 11 EB I I

bull tv

I I 1 toex 1 1

J ~ ilV middotmiddot1 1 1

EB

1f I~~ f 0 -IS -)0 middots -so middot15 middot11 middot01 1111 -m -ISO middots middot110

_ II

rot ~(_ I

1middot~~tts$ Imiddot

~ ow -O2mmOo b~tween -02 and O2mmllOa

between O2and 1Ommll0a

bull above bull 10 mml0a

1 1 -

in the humidity record

217

Table I Trend of Annual Mean Tropospheric Temperature (2008S0 hPa layer) Apove the Indomiddot Pacific Ocean

Station Latitude Period Trend Longitude (CIa)


Table 2 Trend of Annual Mean Tropospheric Temperature (2008S0hPa layer) Above the Americas and Africa

Station Latitudel Pcriod Trend Longitude (CIa)

Brownsville 26deg N 97W I 96S-84 + 0032 S Juan 18degN66degW I 96S-84 + OOSO

Puerto Rico Bogota (E) SON 74degW 1965-84i + 0016 1

Rio de Janeiro Antofagasta

23degS 43degW 23degS700W

1968-84 1965-84

+ 0OS3 + 0OS3

Dakar I5NI7W 1965-84i - 0011 Niamey 13degN 2degE J965-84i - 0006 Khartoum 16degN33degE 1965-84i + 0030 Abidjan (E) SON 4degW I 96S-82 + OOSO Nairobi (E) JOS37E 1965-84i - 00292

Bulawayo 200 S 29deg E 1 96S-84 + 00143

i Minor gaps (E) = Equatorial belt I 200700 hPa December-August + 0033 2 = 200700 hPa 3 = December-May + 0035 = Trend significantly different from zero at the 9S

level

ees = eo exp [L RHbull (T- 1 - To- 1)]

so = 6105 hPa To 2731 K (3)

where R and R are the gas constants for dry air and water vapour respectively e the saturation vapour pressure [Eq (3)] and L the specific heat of condensation

We will refer to m and r as the monthly means of mixing ratio and relative humidity although this is not strictly true

Visual inspection of the plotted time series reshyvealed obviously erroneous values These have been excluded from the subsequent analysis The overall data coverage for all stations for the years after 1965 is about 95

All statistics over a certain record length have been computed only if 23 of that record length contained valid data eg seasonal means with at least 2 months annual means with at least 9 months etc

3 Homogeneity and Quality

Visual inspection of the time series provides a subshyjective way for assessing the homogeneity and quality of the data with respect to abrupt changes in the measured quantity The gradual changes are discussed below in details

Equatorial Zone 10deg N-O S

Singapore ION104degE Yap 9deg N 1380 E Truk 7NIS2degE Majuro 7degN171degE Atuona 9degS139degW

10--22degN

Hongkong 22degN114degE Guam 14degN145E Wake WN167degE

200N 15SoW rIO

10-22degS

Cocos lsI 12middotS 97 E Port Hedland 200S 119deg E Townsville WS147E Nandi 18deg S 177deg E Tahiti 18middotSISOoW

1 96S-82 1965-84i 1965-84i 1 96S-82 1967-84i

I 96S-84 1965-84 1 96S-84 I96S-84

1965-84i I 96S-84 1965-84i 1965-84i I 96S-84

+ 0067 + OOSS + 0043 + 0039 + 0046

+ 0009 1

+ 0043 + 0030 + 0042

+ 0009 + 000S2 - 0006 + 0064 + 00313

i = Minor gaps I = June-August + 0022 2 = December-February + 0020 3= December-May + 0OS6 = Trend significantly different from zero at the 9S

level

average of 1200 and 0000 GMT ascents This ( might lead to biases in a single record due to posshy

sible insolation errors (Ruprecht 1975 or Gray aI 1975) but as long as the time of ascent does Jt change over the whole record no inshyhomogeneities will result For a more detailed disshycussion of this problem see next chapter

From MCD monthly mean air temperatures and dew point temperatures at 500 hPa and 700 hPa have been extracted together with the geoshypotential heights of the 850 hPa (for Bogota and Nairobi 700 hPa) and 200 hPa level

From air temperature T and dew point Ttl the mixing ratio m and the relative humidity r at presshysure p have been evaluated following Eq (1) and (2)

In = e (T) R (1)

pR

r = 100 e (T) e (T) (2)

218 A Hense et aL

Slatton ANTOFAGASTA WMONR 854-4-2

nnnual menn Ix) and trend (-I 700 hPa

=J middot ~ lOr j WG)bull ~ ~ x x 019ttO215

1965-1984shy

1970 1980

annual mean Ix) and trend (-J 500 hPn

I 1 x tJ

1965-1984shy

1970 1980

annual mean (xl and trend -

E ta~er 700500 hPa

E

x

x x gtt

d ~

Jgt d

Trend [kgemmla c 00370027

1965-1984U Il-

Fig 2 Time series orannual mean relative humidity in at 500 and 700 hPa (crosses) and precipitable water in kgfm2 between 500 and 700 hPa at Antoragasta with the trend orthis time series ror the period 1965-1984 slope and 95 confidence interval are indicated in numbers

For temperature no station revealed abrupt diosondes has been reported by Angell et al (1984) changes Thus the temperature data set appears around 196364 resulting from a change in the to be fairly reliable except for the Indian stations humidity sensor and related data processing Acshywhich show some pecularities with regard to cording to Angell et al (1984) a further improveshyneighbouring stations (see below) ment of the sensor around 1972 did not introduce

Regarding moisture the perspectives are not as additional inhomogeneities for monthly means positive A marked inhomogeneity of the US ra- Recently Liu (1986) reported for the equatorial

~ r gt

E 25 OJ c gt

r j1m WG) ~ 20r x )( 0204~01B6

3S

x

1970 1980

year

219 Recent Fluctuations of Tropospheric Temperature and Water Vapour Content in the Tropics

stations Yap Truk and Majuro a sudden increase in the precipitable water from 1971 to 1972 and claimed that this could be the result of introducing new radiation shieldings for the humidity sensor to avoid the observed daytime biases in the hushymidity measurements (Teweless 1970) An inshyspection of our time series for the stations in quesshytion led to identical conclusions as Angell et al (1984) and also Riehl and Betts (1972) namely no apparent inhomogeneity for the layers 500 and 700 hPa One might speculate that the inhomoshygeneity observed by Liu (1986) is a problem of the layers below 700 hPa which roughly contain 80 of the total atmospheric water column Some indications supporting this speculation can be found in Friedman (1972) In summary we will therefore concentrate this study on the time from 1965 onward Since then the following stations

Ifxhibit rather strong changes in their time series 1 Antofagasta from 1971 to 1972 with an inshy

crease of 05 gkg at 700 hPa and 025 gkg at 500 hPa (Fig 2) Here it should be mentioned that this increase in moisture content occurred during the EI Nino event 1972 and could therefore be of some reality

2 Singapore from 1970 to 1911 with a decrease of 05 gkg at 700 hPa and 025 gkg at 500 hPa

3 Bogota from 1966 to 1967 with an increase of 05 gkg at 700 hPa but no obvious change in 500 hPa Since this change occurred rather early in the record only the first two years are affected we will treat Bogota as effectively homogeneous

e 4 Abidjan from 1967 to 1968 with an increase of 10 gkg at both levels

All other stations seem to be rather reliable but may still contain minor discrepancies which can

Iy be evaluated if station logs would be availshyable

4 Temperature Trend

The results derived from the temperature data are quite convincing (Tables 1 and 2) In accordance with Parkers (1985) results nearly all series inshydicated a warming trend during these 20 years Near the equator there is only one exception Naishyrobi (Table 2) all other stations show an intershyannual warming of + 004 (plusmn 002) degCJa In this area the trends of the four seasons are undistinshyguishable from the annual mean and from anshyother Since in a 20 year series this could be an

effect of the exceptional year 19823 one should compare the 35 year series of Parker given sepshyarately for 200500 and 500850 hPa Figure 3 shows the deviation from the 1980 value as given by Parker together with a linear regression line This can be compared with Fig4l0 given by Wigshyley et al (1985) which shows also a similar warmshying for the southern polar zone the tropospheric data are highly correlated with surface data In the outer Tropics the trend is decreasing to near zero In some cases a warming of a similar degree as at the equator is limited to the summer of this hemisphere - this could be interpreted as a warmshying of the equatorial air mass with its seasonal latitudinal shifts

Only the results of Bombay and Calcutta apshyparently showed a downward trend as mentioned

Annual 850-500hPa thickness (gpm)

for the zone 20N to 20S (relative to 1980)

o 1970 1980

00t~ 00

middots 00 0

E 0 0

middot10 o 00 0 000

oIsf o

0

o

middot~o

Trend 0211gpm per Q


for the zone 20N to 20S (relotive to 1980)

10

If o o

o 19S0 197Q 1980 o 0

0

-5 o o o o 0

E shy0 -~ o o

-15 0

o o obull 20 o 0

-15 o

o

o-lO o

Trend 0166gpm per a

Fig 3 Time series of annual mean of relative thickness anomalies 200500 and 500850 hPa relative to their value in 1980 in gpdm redrawn after Parker (1985) The line indicates the trend for the period 1949-1983 (ca + 013 and + 006middotC(lOa)-)

220 A Hense et al

by Parker this is obviously due to instrumental changes or changes in the time of ascent During the 1950s and 1960s these stations indicated slightly higher temperatures than at adjacent stashytions a bias confirmed by the observed vertical wind shear (thermal wind) The bias also effects the analysis recently given by Barnett (1986) In the same region Bangkok (Fig 4 not included in Table 1) shows the normal trend see also Fig 5 An average trend for the equatorial belt is + 0037degCa excluding Nairobi it amounts to + 0047 DCa this means + I DC in about 25 years

Annual mean temperature 200 850 hPa (C)

at 8angkok

-80

-85

Q) 00-90shy

gt 0 -95 -lshy 0

Q)

shyE Q)

-100Ishy

-105 0 0

0 0 o

-llo~I-r--r--r--r-rT-r~-r--middot--r 1960 1970 1980

Trend 0035C per a

Fig 4 Time series of annultl mean layer temperature 200 850 hPa at Bangkok in C with the trend for the period 1955 to 1982

Annual mean temperature (C) at

Nuwara ELL ja 17

0

0 0Q)

l 0

0 0

- 0 00gt degR oO00 0 co 0 0 00t1 o 6

- 0 0 0 0

Q) o 0shyE OJ 15I-

Trend OOllC per a 14

1950 1960 1970 1980

Fig 5 Time series of annual mean air temperature at Nuwara Eliya Sri Lanka (1 900 m) in C with the trend for the period 1950 to 1981

For other purposes some homogeneous long surface series from non-urban tropical mountains stations [eg Nuwara Eliya at Sri Lanka since 1869 (cf Fig 5) Kodaikanal Observatory at southern India] and isolated islands had been evaluated showing a trend near or above + 001 degCa since the turn of the century Hastenrath (1984) has demonstrated that the glaciers at isolated mounshytain peaks of the equatorial belt (Ecuador East Africa New Guinea) were subject to a general retreat since the turn of the century if not (Ecshyuador) since 1850 Careful comparison of maps of Lewis Glacier (Mt Kenya) indicated a shrinkshying of 90 of its volume since 1899 here hyposhythetical changes of cloudiness or precipitation are very unlikely Such data may be considered as representative point measurements of free-air temshyperature at a level of about 560hPa (or 4800m)

5 Water Vapour Trends

Water vapour measurements with radiosondes are used mainly for a determination of virtual temshyperature - here only a limited accuracy is needed Quite different types of sensors are in use and the use of a network of different radiosonde types for evaluating eg evaporation values above large areas by closing a regional water budget leads often to incoherent results Nevertheless Peixoto and Oort (1983) have published convincing results on the water vapour balance at a global or hemishyspheric basis Similarly the seasonal fluctuations of tropospheric water vapour content above inshydividual stations in the Tropics agree quite well with the seasonal march of rainfall and cloudiness

Here we present results of a comparative study of the time fluctuations of the water vapour conshytent of the middle troposphere limited to the 700 and 500 hPa level equivalent - in the Tropics - to about 3 and 6 km altitude We omitted the layers 850 hPa and lower representing the planetary boundary layer and possibly contaminated by the data inhomogeneity discussed above above 500 hPa (ie below a temperature of - 10 0c) some humidity sensors are subject to increasing errors From the available dewpoint averages speshycific and relative humidities have been calculated to obtain more representative values the precipshyitable water content ( = P W in kgm2 or mm liquid

Recent Fluctuations of Tropospheric Temperature and Water Vapour Content in the Tropics 221

ng I Table 3 Precipitahle Water (mm =kgm) at 500700 hPa A lerages and Trel(l~ Indo-Pacific

ns Station Annual DJF MAM JJA SON Year69

average (ml1lja)rn

(0101)d ce Singapore 90 0047 0004 0061 + 0019 - 0023 as Yap 76 + 0081 + 0020 + 0164 + 0147 + 0103middot

n- Truk 82 + 0168 + 0156 + 0176 + 0170 + 0164middot Majuro 80 + 0092 + 0167middot +0155middot + 0166 + 01451st Atuona 46 + 0245middot + 0222middot + 0151middot + 0106middot + 0181

~al Hongkong 72 0044 + 0009 + 0001 - 0035 - 0019~c-Guam 66 + 0029 + 0004 + 0040 + 0039 + 0034middot ps Wake 49 + 0037middot + 0011 + 0011 - 0006 + 0013

k- Hila 36 - 0015 - 0029 + 0022 + 0009 0003 0shy

Cocos lsI 60 - 0040 + 0084 + 0033 + 0015 + 0018lre Port Hedland 46 + 0047 + 0011 + 0025 + 0014 + 0021

as Townsville 47 + 0053 + 0015 - 0010 + 0028 + 0022 TIshy Nandi 70 + 0020 + 0048 + 0029 + 0018 + 0029 l) Tahiti 70 - 0026 + 0006 + 0009 - 0019 - 0003

= Trend significantly different from zero at the 95 level

water column) of the layer 500700 hPa was comshyre puted according to TIshy

22 p(2J)d

PW= f p[qdz = llg f qdp (4)be or 21 p(22) ge ds by fitting a profile of the form q = qo (PPo) and to integrating (4) analytically rts Table 3 gives for 14 stations in the Indo-Pacific lishy area the annual averages of PW together with the ns seasonal and annual trends in mmla (see Fig 1) nshy With the exception of Singapore the four equashy~ll torial stations (3 with US sondes one with French So ~ondes) are quite coherent At Singapore seasonal ly values of the trend deviate from the annual avshyflshy erage indicating the lack of homogeneity deshy)0 scribed above Similar to temperature the annual to trend values appear to decrease towards both rs poles the data of Guam Port Hedland and Nandi ry fit during all seasons quite well into the pattern le At Hongkong Hilo and Tahiti the boundaries of ie the equatorial belt apparently have been crossed ) One may remember that during ENSO events an 19 intensification of both Hadley cells dominates - (Rasmussen and Carpenter 1982) with increasing j upward components near the equator and downshyi)shy ward components near the Tropics This seems to d be confirmed by more positive H~O trends during

the summer of the hemisphere more negative trends during the cool season

If the data from the four stations of the equashytorial Pacific (Yap Truk Majuro and Atuona) can be taken as representative the 20 years trend is remarkable (Fig 6a) it yields at the three US stations up to 27-41 of the average at Atuona even up to 71 (which might be unrepresentative) At the other stations the trend amounts to someshything like 10 of the average Taking all 7 stations in the equatorial belt together (see also Table 5) PW at the 500700 hPa layer increased by 128 mm20 a or about 20 (Fig 6 b) only two stations show a weak decrease However this layer contains only about 20 of the total PW The layer above 500 hPa contains only 5 its time variations should be proportional The bulk of PW (75) remains below 700 hPa its recent varishyation may be assumed to be smaller but a comshyplete investigation is needed Thus no estimate of the trend of total P W can be given

Regarding the reliability of the trend with reshyspect to possible changes in the radiosonde meashysurements we should state the following US sondes like Hilo Wake Brownsville or Great Falls (after Angell et aI 1984) show no trend or even a decrease in moisture over the last 20 years while again US radiosondes like Guam Yap Truk or Majuro exhibit a rather strong positive trend On

222 A Hense el al

onnuol mean Ixl anJ t(nd (-)

loyer 700S00 hPo F

e Equatorial9 0 Pacific ~~I a -----shyd ~-- )

w 7 -~~ D o

Trend [lg (mom) ioJ J

0- 6 O 1 2 1 0 044x u 1965-198401 ~

Il 1970 1980

year

Yap TrukMajuroAtuona a

Fig 6 a Time series of annual mean precipitable water between 500 and 700 hPa averaged for the stations Yap Trnk Majuro and Atuona Equatorial Pacific The line indicates the linear trend for the period 1965 to 1984 slope and 95 confidence interval are indicated E

~ 9 shy

~

) 8

0 o ~

0

u _

IltshyP-

IJnnlJol ITCOft ( 1 and trend -

700500 hPo

~

---shy

~~ -------shy

1970 1980

year

Bogota Abidjan Nairobi Pacific

Equatorial

Tropics

Tr~nd (~gilrirn(~]

005 10025

19G5-1984

b

Fig 6 b Same as Fig 6 a but averaged for the stations Nairobi Bogota Abidjan and the four stations of Fig 6a Equatorial Tropics

the other hand stations in the equatorial IndoshyPacific with different radiosonde types all give an increase Port Hedland Cocos Island (Australia) and Atuona (France) compare reasonably well in the tendencies with Yap Truk or Majuro The trend pattern in the Pacific seems to be coherent in space but not dependent on the radiosonde type

If the absolute humidity is constant a rising temperature will produce an increase of specific humidity and a decrease of relative humidity If the relative humidity is constant absolute and speshycific humidity are expected to rise with increasing temperatures Thus with the relative humidity the role of the temperature effect on humidity can be checked (Table 4) Again the four equatorial Pashycific stations show a drastic rise of relative hushy

midity which yields at both levels an increase of 10-20 since 1965 The relative increase at Atuona must be compared with the average value- which is itself not a priori incredible at the mountaineous islands around to oS which are situated at the fluctuating margins of the dry equashytorial tongue the rainfall data average to I 000 mm annually or less in contrast to 3000shy4000 mm a t Micronesia

Table 5 gives similar values -limited to the anshynual averages (for relative humidity) and the exshytreme seasons - for 10 stations in other parts of the Tropics In contrast to temperature no clear pattern can be recognized While in the Americas most trend values are positive with smallest valshyues however at Bogota the only equatorial

Recent Fluctuations of Tropospheric Temperature and Willa Vapour Content in the Tropics 22

Table 4 Relative Humidity () at 700 and 500hPa Averages and Trends Indo-Paciic

Station Annual mean Trend 700hPa (a) Trend 500hPa (a)

700hPa 500 hPa DJF JJA Year DJF JJA Year

Singapore 651 574 - 052 - 070 - 041 - 06S - 076 - 056 Yap 520 416 + 034 + 069 + 045 + 041 + 092 + 052 Truk 546 439 + 087 + 079 + OSl + 081 + 09 + 089 Majuro 543 421 + 045 + 06S + 071 + 042 + 089 + on Atuona 37 222 + 150 + 10S + 09S + 112 + 066 + OSO

Hongkong 568 37S 038 - 012 - 013 - 040 - 029 - 038 Guam 45S 352 - 00] + 016 + 011 + 022 + 005 + 010 Wake 366 2S2 + 019 - OOS + 002 + 016 + 005 + 002 Hilo 304 24S - 034 + 003 - OIS - 022 + 019 - 004

Cvvs lsI 458 327 - 042 + 004 + 001 - 022 + 026 + 006 nce ~ro

P Hedland 3S8 271 + 023 + 030 + 018 + 022 + 006 + 007 Townsville 3S4 27S + OlS - 014 + 004 + 016 - 010 + 001 Nandi 494 409 016 + 022 + 009 013 - 014 010 Tahiti 472 3S2 - 034 - 025 - 025 - 023 + 015 - 0Q3

ial

~f 1t


Table 5 Precipitable Water and Relative Humidity at 700500hPa Americas and Africa

Station Precipitable water Relative humidity

annual mean

mm DJF

Trend (mma)

JJA Year

annual mean (mm)

700 500

Trend (a)

700 500

Brownsville 46 + 0006 + 0039 + 0024 375 318 + 011 + 012 San Juan P 46 + 0041 + 0057 + 0049 377 275 + 027 + 031 Bogota (E) 97 + 0012 + 0008 + 0020 813 489 + 027 - 006 Rio de J 43 + 0086 + 0010 + 0042 396 235 + 029 + 007 Antofagasta 33 + 0056 + 0022 + 0037 223 232 + 019 + 020

Niamey 66 - 0043 - 0014 - 0045 430 411 - 030 - 034 Khartoum 54 + 0015 + 0068 + 0050 325 349 + 015 - 012 Abidjan (E) 90 + 0220 + 0060 + OOSO 657 4S7 + 098 - 019 Nairobi (E) 83 - 0054 0066 0051 766 370 - 012 - 077 Bulawayo 58 - 0049 - 0053 - 0055 487 311 - 065 - 049

~----------------------------------~----------------------~ bull I = At layer 500700 hPa mm kgm2it

= Trend significantly different from zero at the 95 level e

1shy

station - the results in Africa are rather contrashy It should be stressed that the distribution ofo dictory In the drought-affected Sahel belt at water vapour does not follow the same rules as

about 15deg N Niamey and Khartoum show an opshy that of other greenhouse gases (C02 CH4 N 20) 1shy posite trend the same is true for the equatorial due to its frequent phase changes its averaged

stations Abidjan and Nairobi as well as for the residence time in the atmosphere is only 9 days f two stations using French radiosondes (Niamey to be compared with several years of the other

and Abidjan) Unfortunately it is as yet impossible gases According to the results given by Peixoto s r

to interpret these discrepancies some of them may and Oort (1983) the vertically averaged daily be the consequences of instrumental inhomoshy transport of H20 above tropical oceans (or conshygeneities within the series tinents) is in the order of 2-3 mjs or 200-250 kmjd

124 A Hense et al

this means a distance of not more than 2000 km from source to sink Above Africa this value coshyincides well with the results of Flohn et al (1974) and the data given in Flohn et a1 (1965) This excludes any uniform distribution over the globe the observed irregular pattern agrees with this conshysideration

6 Additional Evidence

Theoretically the increased temperature could be the result of the radiative greenhouse warming of the tropical troposphere by the higher content of the water vapour within the atmosphere (Ramashynathan 1981) But finding observational evidence for this hypothesis eg by applying to the data the sensitivity parameters derived by Ramanathan (1981) appears very difficult in view of the noisshyiness of the data and the quasi-global character

of those parameters But if the recent increase of water vapour above

the tropical Indo-Pacific area is realistic it should be accompanied by a coherent change of other climatic parameters The simultaneous increase of tropospheric temperature was the initial point of our investigations it can also be interpreted as a consequence of increasing release of latent heat by precipitating convective cloids which in turn could result from an increased ocean evaporation either via higher sea surface temperature via higher surface wind speed or via increasing satshyuration deficit of air

Before discussing these parameters a study of vertically integrated mass-weighted atmospheric water vapour content (PW) above the ocean by means of satellite-based microwave measureshyments (flown on NIMBUS 7) must be mentioned (Prabhakara et aI 1985) For the 36 month period 1979-81 the seasonal mean distribution of PW shows in each season a single maximum around Indonesia mostly concentrated above the westshyernmost Pacific (1400-1600 E) with values of 53shy5S gcm2 (or cm PW) with a bias of probably less than 03 cm An empirical orthogonal function (EOF) analysis was done for the global ocean The first eigenvector nearly everywhere with a positive sign and therefore not published acshycounted for 19 of the variance Even if the EOF analysis based on such a short period is not roshybust the posititve sign of the first EOF (Prabhashykara 1986) can probably be interpreted as evishy

dence for a general increase and the pattern shows clearly a broad maximum above the equatorial Indo-Pacific but not over the Atlantic This threeshyyear trend agrees well with our limited data in the lower troposphere the African continent and the Andes are effective barriers for zonal water vapour transport from a source around Indonesia

Discussing any large-scale change in precipishytation from direct measurements is hampered by the large gaps between stations - ocean data are still controversial island data often unrepresenshytative and wind-biased (see also Barnett 1985) In the tropics satellite measurements of outgoing longwave radiation (OLR) from cloud tops give valuable results (Heddinghaus and Krueger 1981) In the belt 5middot N_So S the departures ofOLR from the base period (1974-771979-83) remained negative - ie colder cloud tops - during 1983-8S (after the 1982 drought) for the area tOO-I50middotE thus indicating higher convection and more rainshyfall (NOAA May 1986) However in the central Pacific (1600 E-160deg W) the OLR time series show irregular fluctuations and no clear trend

Regarding sea-surface temperatures most tropshyical areas show a clear positive trend since about 19S0 Figure 7 describes such a case for the SST in the North Australian region (after Wright 1986) 1000 W-160middotW and SON-SoS Recent data confirm a tendency of warming in the equatorial seas 100-160deg E (NOAA May 1986) While at the central Pacific (route Hawaii-Fiji) no clear trend exists the upwelling region along the Ecuador-

AprlL - March SST - Anomaly (Kl

North Australla after WrLght (1986)

o o

o 0 0

o o Il) o 0I- ol

-shyl shyll) PshyI _I Il)

o

-24 deg0 00 o

o o -3

o-4

Trend O059K per Q

Fig 7 Time series of the anomalies of annual mean of sea surface temperatures in the area north of Australia after Wright (1986) the line indicates the linear trend for the period 1950 to 1979

-- --

225

bull

Recent Fluctuations or Tropospheric Temperature and Water Vapour Content in the Tropics

Peru coast (4-12 S) shows a positive trend also between 1967 and the Nino year 1983 here as in the equatorial Pacific no really cold period - as between 1967 and 1975-has been observed since 1976 To estimate whether the observed changes in the tropical ocean and air temperature are sufshyficient to explain the increase in the atmospheric water column let us assume the following model The balance of the water vapour density pqL inshytegrated over a volume such as the atmosphere above the Pacific basin between 20middot Nand 20 S reads

a -shy-pw=pound-P (5)at

where PW is the total atmospheric water column pound the evaporation and P the precipitation at the ocean surface and horizontal transports out off

r into the region have been neglected Integrating poundq (S) over the time Il t for which we observe a

change in P W one gets

IlPW--=- E(t)dlI f fP(t)d rIl t Il t tJ 1 111

= pound(10) + ~tf (pound(t) - E(to)dt

tJ1

-PUo) IlP (6)

To parameterize E we use the bulk formulae

E = PLeD vo(qs(ToJ - rPBLqs(TpBL)) (7)

where qs is the saturation mixing ratio with respect to ocean (To) or the marine planetary boundary layer air temperature (TPHIJ and rPBL is the relative hPmidity within the boundary layer

-If we keep the surface wind Vo and the relative humidity constant (5 mls and 7S respectively) choose a representative PL and CD (12 kgm3 and 13 10- 3

) and assume an initial equilibium beshytween E and P1E(lo) = P(to)] we may estimate the changes of PW due to changes in evaporation

Table 6 shows for selected initial temperatures the resulting changes in E or if one assumes no change in P the theoretical increase in PW Since about 20 of the total water column is between SOO and 700 hPa that is PW = 02 PW Table 6 indicates that the increased evaporation from the ocean surface is capable to produce the observed changes in the atmospheric water column Wigley et al (198S their Fig412) reported that during

Table 6 Estimated Changes of the Oceanic Evaporation lor Different Initial Ocean and Air Temperatures alld Different Increases of These Variables per 10 Ye(lrs (Oct lOa)

I1Tnr I1TpBL I1T( I1Tp8 t I1Tor I1TPBL 05 05 05 00 025 025

11 Tor = 29C 26mmlOa 11 T psL =28middotC

92 mmIOa 7mmlOa

11 Toc= 26C 23mmlOa 11 TPBL =25C

78mmIOa 5mmlOa

11 Tnr =28C 22mmlOa 11 TpBL =28middotC

87mmlOa 5mmlOa

11 T= 17middotC 14mmlOa 11 TPBt =16C

47mmlOa 4mmflOa

the last 20 years the static stability between the lower and upper troposphere measured by the temperature difference between 850300 hPa and 300100 hPa showed a marked decrease arising basically from changes in the tropics of southern hemisphere Thus one could speculate that intenshysified deep convective activity might be the mechshyanism for distributing the excess water vapour at the surface into higher levels A more detailed investigation of the changes of vertical stability of the tropical atmosphere seems necessary

An increase of tropospheric temperatures censhytered in the tropics should lead to increasing westshyerlies in the sUbtropics This has been evidenced by Namias and Cayan (1984) (their Fig 6) for the 700 hPa winds in the subtropical Pacific (20shy3So N ISOmiddot E-I1Odeg W) During the period winter 19478-19823 the intensity of the westerlies rose linearily from 73 to 109 mis ie about SO the significance of this trend (with a correlation coefshyficient of plusmn 049) is well above the 99 level

7 Preliminary Comments

Regarding the temperature trend our data from individual stations verify the trend which can be seen most clearly in Parkers Fig 3 representing annual averages (December-November) since 1950 In the lower troposphere (5008S0 hPa) the 34 year trend is + 0014 Cia during 1974-83 it amounts to 0082 aCta (both significant at the 99 level) Surface data from isolated mountain stashytions give similar values since the end of the last century Hastenrath (1984) estimated the tempershyature increase since 1899 at Mt Kenya to 08OCI

bull

116 A Hense et al

80 a The reality of a warming of at least the lower half of the equatorial atmosphere seems to be warshyranted above the equatorial belt this warming has intensified during the last two decades to a value in the order of 004 Ca ie definitely more than the CO2-induced warming in the order of 0006 degCI a (DOE)

In some contrast to this warming the moisture data given here can only be first guesses limited to a narrow layer containing less than 20 of the total precipitable water of the atmospheric colshyumn The results are hampered by a lack of inshystrumental homogeneity and by a patchy distrishybution which does not allow to draw more general conclusions However if the trend observed above the equatorial Pacific is reliable it could have sigshynificantly contributed to the extraordinary intenshysity of the ENSO event 19823 enhancing conshy vective activity and release oflatent heat and thus intensifying large-scale circulation processes

As mentioned before water vapour is through its radiation properties not only the most effective greenhouse gas its phase changes are also reshysponsible for a highly effective warming through convective rainfall-producing processes (Ramashynathan 1981) in the Tropics Our PW and espeshycially relative humidity data suggest that above the equatorial Pacific this warming could be caused (at least partly) by increasing water vapour content Since 1974 no major cold ENSO-epshyisode occurred in the equatorial Pacific east of the date line during these warmer years both (upshyward) fluxes of sensible and latent heat (evaposhyration) should be expected to be higher than norshymal above this area A strong positive correlation between sea surface temperature and evaporation

in the upwelling region of the equatorial Atlantic has been shown by Weber and Flohn (1984)

These recent experiences suggest the occurrence of weak (but effective) changes of sea surface temshyperature as correlated with small changes in the intensity of wind-driven upwelling or downwelling at the ocean surface layers These should have significant effects on temperature and water vashypour content of the equatorial troposphere at time-scales in the order of decades (or more) with far-reaching consequences for atmospheric cirshyculation and climate They deserve also interest as possibly being related to the problem of abrupt climatic changes as discussed recently (Ghazi 1983 Flohn 1986) Increasing intensity and freshy

quency of downwelling processes in the tropical ocean mixing layer is apparently causing troposhyspheric warming and rising water vapour content This should also be taken into account in comshyprehensive interactive general circulation models

In a recent paper Schlesinger (1986) has inshyvestigated the role of different feedback mechashynisms on a CO2-induced warming One of the most important results is that the water vapour feedshyback is much more important for a general cirshyculation model than the surface albedo feedback (066 instead of 009) This result if it can be applied to the real climatic system emphasizes the possible role of the observed humidity increase

Acknowledgements

This work is sponsored by the Climate Program of the Rheishyni5ch-Westfiilische Akademie der Wissenschaften Diisselshydorf Furthermore this study would have been impossible without the patient help of our students Martina Petznick Antke Hinrichs and Hennann Machel who carefully exshytracted the MCDs and Hennann Suer who ran the programs Dr Peter Wright (MPI fUr Meteorologie Hamburg) kindly provided the data ror Fig 7 Ms I Hayes took care or the manuscript The data or this study are available on request on 525 discettes written on a standard Pc

References

Angell J K Korshover J 1983 Global temperature varishyation in the troposphere and stratosphere 1958-1982 Mon Wea Rev 111901-921

Angelll K Elliott W P Smith M E 1984 Tropospheric humidity variations at Brownsville Texas and Great Falls Montana 1958-80 1 Climate Appl Melear 23 1286-1295

Barnett T P 1985 Long-term changes in precipitation patshyterns In McCracken M c Luther F M (Eds) Deshylecling fhe Climatic Efforts ofIncreasing Carbon Dioxide US Dept of Energy DOEER-0235 149-162

Barnett T P 1986 Detcction or changes in the global troshypospheric temperature field induced by greenhouse gases 1 Geophys Res bull D6 91 6659-6667

Dickinson R in Clark W C (Ed) 1983 Carbon Dioide Review 982 Oxrord Clarendon Press 101-133

Flohn H 1986 Singular events and catastrophes now and in climatic history Naturwissenschqften 73 136-149

Flohn H Henning D Korrf H c 1965 Studies on the water-vapor transport Ovel Northern Arrica Bonner Meshyleorol AM 6 36 pp

Flohn H bull Henning D Korff H c 1974 Possibilities and limitations or a large scale water budget modification in the Sudan-Sahel belt of Africa Meleor Rdsch 27 97shy100

Friedman M 1972 A new radiosonde case the problem and the solution Bull Amer Melear Soc 53 884-887

bull bull


Ghazi A (Ed) 1983 Palaeoclimatic Research and Models Dordrecht D Reidel Publ Compo

Gray W Mbull Ruprecht E Phleps R 1975 Relative hushymidity in tropical weather systems Mon Wea Rev 103 685-690

Hastenrath St 1984 The Glaciers of Equatorial East Africa Dordrecht D Reidel Pub Comp 353 pp

Heddinghaus T R Krueger A F 1981 Annual and inshyterannual variations in outgoing longwave radiation over the tropics Month Wea Rev 114 1208-1218

Liu W T 1986 Statistical relation between monthly mean precipitable water and surface-level humidity over the global oceans Month Wea Rev bull 114 1591-1602

Namias J Cayan D R 1984 EI Nino Implications for Forecasting Oceanus 27 41--47

Newell R E Hsiung J 1984 Sea surface temperature atmospheric CO2 and the global energy budget some comparisons between the past and the present In Morshyner N A Karlen W (Eds) Climatic Changeona Yearly to Millennial Basis Dordrecht D Reidel Pub Comp 533-561

NOAANational Weather Service Climate Diagnostic Bulshyletin (monthly) NOAA Climate Analysis Center Washshyington DC 20233

Parker D E 1985 The influence of the southern oscillation and volcanic eruptions on temperature in the tropical troposphere J Climbull 5 273-282

Peixoto J P Oort A R 1983 The atmospheric branch of the hydrologic cycle and climate In Street-Perrott A Beran M Ratcliffe R (Eds) Variations in the Global Water Budget Dordrecht D Reidel Pub Comp 5-65

Prabhakara c Short D A Vollmer B E 1985 EI Niiio and atmospheric water vapor Observations from Nimbus 7SMMR J Climate Appl Meteor bull 24 1311-1324

Prabhakara C (Goddard Space Flight Center) personal communication (June 23 1986)

Ramanathan V 1981 The role of ocean-atmosphere intershyactions in the COrciimate problem J Atmos Sci bull 38 918-930

Rasmussen E M Carpenter T H 1982 Variations in the tropical sea surface temperature and surface wind fields associated with the Southern OscillationEI Niiio Mon Wea Rev 110 365-384

Riehl H Betts A K 1972 Humidity observations with the 1972 US radiosonde instrument Bull Amer Meteor Socbull 53 887-888

Ruprecht E 1975 Diurnal temperature correlations for rawinsonde humidity sensors Mon Wea Revbull ]03 352shy355

Schlesinger M E 1986 Equilibrium and transient climatic warming induced by increased atmospheric CO2 Climate Dynamics 135-51

Teweles S 1970 A spurious diurnal variation in radiosonde humidity records BullAmer Meteor Soc 51 836-840

Van Loon H Shea D J 1985 The southern oscillation Part IV Mon Wea Rev bull 113 2063-2074

Weber K-H Flohn H 1984 Oceanic upwelling and airshysea exchange of carbon dioxide and water vapour as a key for large-scale climatic change Bonner Meteor Abshyhand 31 73-98

Weber KmiddotH Hense A Glowienka-Hense R Flohn H 1986 Variationen des Wasserdampfgehaltes in der unshyteren Troposphiire zwischen 20middot N und 20middot S wiihrend der letzten 20 Jahre Ann Meteor NF 23 5-6

Wigley T M L Angell Z K Jones P D 1985 Analysis of the temperature record In McCracken M c Luther F M (Eds) Detecting the Climatic Effects of Increasing Carbon Dioxide DOE-ER-0235 Washington DC 55shy90

Wright P B 1986 Precursors of the Southern Oscillation J Clim 6 17-30

Authors address Dr A Hense A Krahe and Prof Dr R Frohn Meteorologisches Institut Universitiit Bonn Auf dem Hiigel20 D-5300 Bonn I Federal Republic of Germany

Prinled in Aus

110 liS ISO I)S 120 IllS to 15 IIIJ CS lG IS u

10 I I I I I ] C6~ ~l I I I r III

H

lsi I 0 1 1 1 I~I~ 1 II I I - JI III

Atbull 1

( I

-0 I BO 165 1$0 ilS (10 ~

Fig I Spatial distribution of the radiosonde network utilized in this study The symbols at each station indicate the observed linear trend in the annual mean precipitable water between 500 and 700 hPa A question mark signifies possible inhomogeneities

216 A Hense et al

2 Data All station data are taken rrom the joint WMOshyThe radiosonde network utilized in this study NOAA publication Monthly Climatic Dataor the (Fig I Tables 1 and 2) is essentially identical with World (MCD) supplemented ir available by data that orAngell and Korshover (1983) between 20middot S rrom the archive or the Meteorological Institute and 20middot N except in the Pacific Here several adshy or the University or Bonn For most stations the ditional stations have been introduced to enhance monthly mean 1200 GMT ascent is recorded in the coverage in this critical area the MCD but some report the 0000 GMT or the

-I ]1 -S -so ll $0 -lOS middot120 middotus -110 I~ JO I I t i I middotuo 1tO

bull lisl)NI ~ t f I I) ~ 11 EB I I

bull tv

I I 1 toex 1 1

J ~ ilV middotmiddot1 1 1

EB

1f I~~ f 0 -IS -)0 middots -so middot15 middot11 middot01 1111 -m -ISO middots middot110

_ II

rot ~(_ I

1middot~~tts$ Imiddot

~ ow -O2mmOo b~tween -02 and O2mmllOa

between O2and 1Ommll0a

bull above bull 10 mml0a

1 1 -

in the humidity record

217










1968-84 1965-84

+ 0OS3 + 0OS3


Bulawayo 200 S 29deg E 1 96S-84 + 00143


level


so = 6105 hPa To 2731 K (3)









10--22degN


200N 15SoW rIO

10-22degS


1 96S-82 1965-84i 1965-84i 1 96S-82 1967-84i

I 96S-84 1965-84 1 96S-84 I96S-84

1965-84i I 96S-84 1965-84i 1965-84i I 96S-84

+ 0067 + OOSS + 0043 + 0039 + 0046

+ 0009 1

+ 0043 + 0030 + 0042

+ 0009 + 000S2 - 0006 + 0064 + 00313


level





In = e (T) R (1)

pR

r = 100 e (T) e (T) (2)

218 A Hense et aL




1965-1984shy

1970 1980


I 1 x tJ

1965-1984shy

1970 1980


E ta~er 700500 hPa

E

x

x x gtt

d ~

Jgt d


1965-1984U Il-




~ r gt

E 25 OJ c gt

r j1m WG) ~ 20r x )( 0204~01B6

3S

x

1970 1980

year










4 Temperature Trend






o 1970 1980

00t~ 00

middots 00 0

E 0 0

middot10 o 00 0 000

oIsf o

0

o

middot~o

Trend 0211gpm per Q



10

If o o

o 19S0 197Q 1980 o 0

0

-5 o o o o 0

E shy0 -~ o o

-15 0

o o obull 20 o 0

-15 o

o

o-lO o

Trend 0166gpm per a


220 A Hense et al



at 8angkok

-80

-85

Q) 00-90shy

gt 0 -95 -lshy 0

Q)

shyE Q)

-100Ishy

-105 0 0

0 0 o


Trend 0035C per a



Nuwara ELL ja 17

0

0 0Q)

l 0

0 0

- 0 00gt degR oO00 0 co 0 0 00t1 o 6

- 0 0 0 0

Q) o 0shyE OJ 15I-


1950 1960 1970 1980









average (ml1lja)rn




k- Hila 36 - 0015 - 0029 + 0022 + 0009 0003 0shy





22 p(2J)d





222 A Hense el al


loyer 700S00 hPo F


w 7 -~~ D o


0- 6 O 1 2 1 0 044x u 1965-198401 ~

Il 1970 1980

year



~ 9 shy

~

) 8

0 o ~

0

u _

IltshyP-


700500 hPo

~

---shy

~~ -------shy

1970 1980

year


Equatorial

Tropics

Tr~nd (~gilrirn(~]

005 10025

19G5-1984

b












Cvvs lsI 458 327 - 042 + 004 + 001 - 022 + 026 + 006 nce ~ro


ial

~f 1t




annual mean

mm DJF

Trend (mma)

JJA Year

annual mean (mm)

700 500

Trend (a)

700 500





1shy






124 A Hense et al












o o

o 0 0

o o Il) o 0I- ol


o

-24 deg0 00 o

o o -3

o-4

Trend O059K per Q


-- --

225

bull









tJ1

-PUo) IlP (6)










92 mmIOa 7mmlOa


78mmIOa 5mmlOa


87mmlOa 5mmlOa


47mmlOa 4mmflOa





bull

116 A Hense et al








Acknowledgements


References










bull bull


























Prinled in Aus

217










1968-84 1965-84

+ 0OS3 + 0OS3


Bulawayo 200 S 29deg E 1 96S-84 + 00143


level


so = 6105 hPa To 2731 K (3)









10--22degN


200N 15SoW rIO

10-22degS


1 96S-82 1965-84i 1965-84i 1 96S-82 1967-84i

I 96S-84 1965-84 1 96S-84 I96S-84

1965-84i I 96S-84 1965-84i 1965-84i I 96S-84

+ 0067 + OOSS + 0043 + 0039 + 0046

+ 0009 1

+ 0043 + 0030 + 0042

+ 0009 + 000S2 - 0006 + 0064 + 00313


level





In = e (T) R (1)

pR

r = 100 e (T) e (T) (2)

218 A Hense et aL




1965-1984shy

1970 1980


I 1 x tJ

1965-1984shy

1970 1980


E ta~er 700500 hPa

E

x

x x gtt

d ~

Jgt d


1965-1984U Il-




~ r gt

E 25 OJ c gt

r j1m WG) ~ 20r x )( 0204~01B6

3S

x

1970 1980

year










4 Temperature Trend






o 1970 1980

00t~ 00

middots 00 0

E 0 0

middot10 o 00 0 000

oIsf o

0

o

middot~o

Trend 0211gpm per Q



10

If o o

o 19S0 197Q 1980 o 0

0

-5 o o o o 0

E shy0 -~ o o

-15 0

o o obull 20 o 0

-15 o

o

o-lO o

Trend 0166gpm per a


220 A Hense et al



at 8angkok

-80

-85

Q) 00-90shy

gt 0 -95 -lshy 0

Q)

shyE Q)

-100Ishy

-105 0 0

0 0 o


Trend 0035C per a



Nuwara ELL ja 17

0

0 0Q)

l 0

0 0

- 0 00gt degR oO00 0 co 0 0 00t1 o 6

- 0 0 0 0

Q) o 0shyE OJ 15I-


1950 1960 1970 1980









average (ml1lja)rn




k- Hila 36 - 0015 - 0029 + 0022 + 0009 0003 0shy





22 p(2J)d





222 A Hense el al


loyer 700S00 hPo F


w 7 -~~ D o


0- 6 O 1 2 1 0 044x u 1965-198401 ~

Il 1970 1980

year



~ 9 shy

~

) 8

0 o ~

0

u _

IltshyP-


700500 hPo

~

---shy

~~ -------shy

1970 1980

year


Equatorial

Tropics

Tr~nd (~gilrirn(~]

005 10025

19G5-1984

b












Cvvs lsI 458 327 - 042 + 004 + 001 - 022 + 026 + 006 nce ~ro


ial

~f 1t




annual mean

mm DJF

Trend (mma)

JJA Year

annual mean (mm)

700 500

Trend (a)

700 500





1shy






124 A Hense et al












o o

o 0 0

o o Il) o 0I- ol


o

-24 deg0 00 o

o o -3

o-4

Trend O059K per Q


-- --

225

bull









tJ1

-PUo) IlP (6)










92 mmIOa 7mmlOa


78mmIOa 5mmlOa


87mmlOa 5mmlOa


47mmlOa 4mmflOa





bull

116 A Hense et al








Acknowledgements


References










bull bull


























Prinled in Aus

218 A Hense et aL




1965-1984shy

1970 1980


I 1 x tJ

1965-1984shy

1970 1980


E ta~er 700500 hPa

E

x

x x gtt

d ~

Jgt d


1965-1984U Il-




~ r gt

E 25 OJ c gt

r j1m WG) ~ 20r x )( 0204~01B6

3S

x

1970 1980

year










4 Temperature Trend






o 1970 1980

00t~ 00

middots 00 0

E 0 0

middot10 o 00 0 000

oIsf o

0

o

middot~o

Trend 0211gpm per Q



10

If o o

o 19S0 197Q 1980 o 0

0

-5 o o o o 0

E shy0 -~ o o

-15 0

o o obull 20 o 0

-15 o

o

o-lO o

Trend 0166gpm per a


220 A Hense et al



at 8angkok

-80

-85

Q) 00-90shy

gt 0 -95 -lshy 0

Q)

shyE Q)

-100Ishy

-105 0 0

0 0 o


Trend 0035C per a



Nuwara ELL ja 17

0

0 0Q)

l 0

0 0

- 0 00gt degR oO00 0 co 0 0 00t1 o 6

- 0 0 0 0

Q) o 0shyE OJ 15I-


1950 1960 1970 1980









average (ml1lja)rn




k- Hila 36 - 0015 - 0029 + 0022 + 0009 0003 0shy





22 p(2J)d





222 A Hense el al


loyer 700S00 hPo F


w 7 -~~ D o


0- 6 O 1 2 1 0 044x u 1965-198401 ~

Il 1970 1980

year



~ 9 shy

~

) 8

0 o ~

0

u _

IltshyP-


700500 hPo

~

---shy

~~ -------shy

1970 1980

year


Equatorial

Tropics

Tr~nd (~gilrirn(~]

005 10025

19G5-1984

b












Cvvs lsI 458 327 - 042 + 004 + 001 - 022 + 026 + 006 nce ~ro


ial

~f 1t




annual mean

mm DJF

Trend (mma)

JJA Year

annual mean (mm)

700 500

Trend (a)

700 500





1shy






124 A Hense et al












o o

o 0 0

o o Il) o 0I- ol


o

-24 deg0 00 o

o o -3

o-4

Trend O059K per Q


-- --

225

bull









tJ1

-PUo) IlP (6)










92 mmIOa 7mmlOa


78mmIOa 5mmlOa


87mmlOa 5mmlOa


47mmlOa 4mmflOa





bull

116 A Hense et al








Acknowledgements


References










bull bull


























Prinled in Aus










4 Temperature Trend






o 1970 1980

00t~ 00

middots 00 0

E 0 0

middot10 o 00 0 000

oIsf o

0

o

middot~o

Trend 0211gpm per Q



10

If o o

o 19S0 197Q 1980 o 0

0

-5 o o o o 0

E shy0 -~ o o

-15 0

o o obull 20 o 0

-15 o

o

o-lO o

Trend 0166gpm per a


220 A Hense et al



at 8angkok

-80

-85

Q) 00-90shy

gt 0 -95 -lshy 0

Q)

shyE Q)

-100Ishy

-105 0 0

0 0 o


Trend 0035C per a



Nuwara ELL ja 17

0

0 0Q)

l 0

0 0

- 0 00gt degR oO00 0 co 0 0 00t1 o 6

- 0 0 0 0

Q) o 0shyE OJ 15I-


1950 1960 1970 1980









average (ml1lja)rn




k- Hila 36 - 0015 - 0029 + 0022 + 0009 0003 0shy





22 p(2J)d





222 A Hense el al


loyer 700S00 hPo F


w 7 -~~ D o


0- 6 O 1 2 1 0 044x u 1965-198401 ~

Il 1970 1980

year



~ 9 shy

~

) 8

0 o ~

0

u _

IltshyP-


700500 hPo

~

---shy

~~ -------shy

1970 1980

year


Equatorial

Tropics

Tr~nd (~gilrirn(~]

005 10025

19G5-1984

b












Cvvs lsI 458 327 - 042 + 004 + 001 - 022 + 026 + 006 nce ~ro


ial

~f 1t




annual mean

mm DJF

Trend (mma)

JJA Year

annual mean (mm)

700 500

Trend (a)

700 500





1shy






124 A Hense et al












o o

o 0 0

o o Il) o 0I- ol


o

-24 deg0 00 o

o o -3

o-4

Trend O059K per Q


-- --

225

bull









tJ1

-PUo) IlP (6)










92 mmIOa 7mmlOa


78mmIOa 5mmlOa


87mmlOa 5mmlOa


47mmlOa 4mmflOa





bull

116 A Hense et al








Acknowledgements


References










bull bull


























Prinled in Aus

220 A Hense et al



at 8angkok

-80

-85

Q) 00-90shy

gt 0 -95 -lshy 0

Q)

shyE Q)

-100Ishy

-105 0 0

0 0 o


Trend 0035C per a



Nuwara ELL ja 17

0

0 0Q)

l 0

0 0

- 0 00gt degR oO00 0 co 0 0 00t1 o 6

- 0 0 0 0

Q) o 0shyE OJ 15I-


1950 1960 1970 1980









average (ml1lja)rn




k- Hila 36 - 0015 - 0029 + 0022 + 0009 0003 0shy





22 p(2J)d





222 A Hense el al


loyer 700S00 hPo F


w 7 -~~ D o


0- 6 O 1 2 1 0 044x u 1965-198401 ~

Il 1970 1980

year



~ 9 shy

~

) 8

0 o ~

0

u _

IltshyP-


700500 hPo

~

---shy

~~ -------shy

1970 1980

year


Equatorial

Tropics

Tr~nd (~gilrirn(~]

005 10025

19G5-1984

b












Cvvs lsI 458 327 - 042 + 004 + 001 - 022 + 026 + 006 nce ~ro


ial

~f 1t




annual mean

mm DJF

Trend (mma)

JJA Year

annual mean (mm)

700 500

Trend (a)

700 500





1shy






124 A Hense et al












o o

o 0 0

o o Il) o 0I- ol


o

-24 deg0 00 o

o o -3

o-4

Trend O059K per Q


-- --

225

bull









tJ1

-PUo) IlP (6)










92 mmIOa 7mmlOa


78mmIOa 5mmlOa


87mmlOa 5mmlOa


47mmlOa 4mmflOa





bull

116 A Hense et al








Acknowledgements


References










bull bull


























Prinled in Aus




average (ml1lja)rn




k- Hila 36 - 0015 - 0029 + 0022 + 0009 0003 0shy





22 p(2J)d





222 A Hense el al


loyer 700S00 hPo F


w 7 -~~ D o


0- 6 O 1 2 1 0 044x u 1965-198401 ~

Il 1970 1980

year



~ 9 shy

~

) 8

0 o ~

0

u _

IltshyP-


700500 hPo

~

---shy

~~ -------shy

1970 1980

year


Equatorial

Tropics

Tr~nd (~gilrirn(~]

005 10025

19G5-1984

b












Cvvs lsI 458 327 - 042 + 004 + 001 - 022 + 026 + 006 nce ~ro


ial

~f 1t




annual mean

mm DJF

Trend (mma)

JJA Year

annual mean (mm)

700 500

Trend (a)

700 500





1shy






124 A Hense et al












o o

o 0 0

o o Il) o 0I- ol


o

-24 deg0 00 o

o o -3

o-4

Trend O059K per Q


-- --

225

bull









tJ1

-PUo) IlP (6)










92 mmIOa 7mmlOa


78mmIOa 5mmlOa


87mmlOa 5mmlOa


47mmlOa 4mmflOa





bull

116 A Hense et al








Acknowledgements


References










bull bull


























Prinled in Aus

222 A Hense el al


loyer 700S00 hPo F


w 7 -~~ D o


0- 6 O 1 2 1 0 044x u 1965-198401 ~

Il 1970 1980

year



~ 9 shy

~

) 8

0 o ~

0

u _

IltshyP-


700500 hPo

~

---shy

~~ -------shy

1970 1980

year


Equatorial

Tropics

Tr~nd (~gilrirn(~]

005 10025

19G5-1984

b












Cvvs lsI 458 327 - 042 + 004 + 001 - 022 + 026 + 006 nce ~ro


ial

~f 1t




annual mean

mm DJF

Trend (mma)

JJA Year

annual mean (mm)

700 500

Trend (a)

700 500





1shy






124 A Hense et al












o o

o 0 0

o o Il) o 0I- ol


o

-24 deg0 00 o

o o -3

o-4

Trend O059K per Q


-- --

225

bull









tJ1

-PUo) IlP (6)










92 mmIOa 7mmlOa


78mmIOa 5mmlOa


87mmlOa 5mmlOa


47mmlOa 4mmflOa





bull

116 A Hense et al








Acknowledgements


References










bull bull


























Prinled in Aus







Cvvs lsI 458 327 - 042 + 004 + 001 - 022 + 026 + 006 nce ~ro


ial

~f 1t




annual mean

mm DJF

Trend (mma)

JJA Year

annual mean (mm)

700 500

Trend (a)

700 500





1shy






124 A Hense et al












o o

o 0 0

o o Il) o 0I- ol


o

-24 deg0 00 o

o o -3

o-4

Trend O059K per Q


-- --

225

bull









tJ1

-PUo) IlP (6)










92 mmIOa 7mmlOa


78mmIOa 5mmlOa


87mmlOa 5mmlOa


47mmlOa 4mmflOa





bull

116 A Hense et al








Acknowledgements


References










bull bull


























Prinled in Aus

124 A Hense et al












o o

o 0 0

o o Il) o 0I- ol


o

-24 deg0 00 o

o o -3

o-4

Trend O059K per Q


-- --

225

bull









tJ1

-PUo) IlP (6)










92 mmIOa 7mmlOa


78mmIOa 5mmlOa


87mmlOa 5mmlOa


47mmlOa 4mmflOa





bull

116 A Hense et al








Acknowledgements


References










bull bull


























Prinled in Aus

-- --

225

bull









tJ1

-PUo) IlP (6)










92 mmIOa 7mmlOa


78mmIOa 5mmlOa


87mmlOa 5mmlOa


47mmlOa 4mmflOa





bull

116 A Hense et al








Acknowledgements


References










bull bull


























Prinled in Aus

bull

116 A Hense et al








Acknowledgements


References










bull bull


























Prinled in Aus

bull bull


























Prinled in Aus

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