DISCUSSION OF THE RESULTS

It

w i l l

be seen that the m e a n temperature varies during

A s regards the secular changes which are brought out

by

the values of x’s for the various depths, the following tendencies are observed. T h e variance contri- buted

by the

first degree is very significant and posiiive, for all the months and at all the depths showing thai.

during the period undes consideration there is a definite tendency for the soil temperature to increase. S o m e of the higher degree curves are also significant in certain cases, chiefly the third degree curve at the depths of

9, 20

and

60 in.

and the

fifth

degree curve at

the

depth of

20

and

60 in.

88

Secular trends in soil temperatures

85

8

84

c O ..

a7 86 84

83

FIG.

1. Soil temperatures, Bombay (depth, 60 in.).

Fig. 1

shows, for example, the actual and smooth polynomial values of the soil temperatures for the months of January, May,

July

and October. T h e increasing tendency of soil temperature is very clearly brought out

by

these curves.

As

a rcsult of this investigation, the Colaba

Obser-

vatory decided to reinstall these thermometers. Data are again being recorded since

1939.

These show that the higher temperatures recorded in

1925

are being maintained.

W e m a y examine the smooth polynomial curves for different depths and estimate from the m a x i m u m

(X)

and the minimum

(N)

values of the curve the range of the variation of the soil temperatures during the series of years under consideration. Table

3

gives the m e a n

values of

(X) - (N)

for the year as a whole. T h e m e a n values of

(X) - (N)

m a y be compared with the correc- tions of the instruments as determined

in 1928

which are also given

in

Table

3.

T A B L E

3. Mean values for 1928

Depth (in inches)

Mean vdue of (X)

-

^(N)

for the year QS a whole

Correction of thermometer

(OF.)

1 9 20 60 132

3.7 3.7 4.7 3.9 2.5

-0.8 -1.0 -2.0 -2.1 0.9

T h e values of

(X) - ^(N)

indicate that the soil temper- atures have a n increasing tendency

during

the period as a whole and that these tendencies are large compared to the corrections of the thermometers. E v e n

if

it is argued that thermometers had a “nil” correction w h e n they were originally installed and that the corrections found in

1928

were the result of s o m e slow changes

in

the instruments, it is clear that the increasing tendency of the temperatures actually recorded is more than the instrumental corrections. It is very significant in this connexion that the records obtained from the n e w thermometer installed so late as

1914

(to replace the instrument broken in

1912)

fit

in

with the trends shown earlier

by

the previous instrument at the same depth and

by

the instruments at the other depths. This appears to be against the suggestion that the changes

in

the instruments themselves m a y account for the actual trends observed.

A

visual examination of the actual instruments

did

not show any deterioration in their external surfaces.

T h e present investigation had been completed some time ago but the publication of the detailed results was delayed due to other preoccupations. T h e present symposium on climatic changes demands that their publication be no longer delayed.

In

conclusion, the present writers wish to thank the successive directors of the Colaba Observatory for giving the necessary facilities for the compilation of the data and for examining the instruments which were actually used for recording them.

89

C h a n g e s of climate L e s changements de climat

R E S U M E

Tendances séculaires des températures du sol à Colaba (Bombay)

(L. A.

R a m d a s et

N.

Rajagopalan)

Les auteurs cxaminent les tendances ascendantes significatives des températures

du

sol enregistrées

à

l’observatoire de Colaba,

à

B o m b a y (Inde), de

1860 à 1925 à

des profondeurs de

2,5

cm,

23

cm,

50

c m et

150

c m au-dessous de la surface

du

sol, et

de 1879

à

1925

à une profondeur de

335

cm. Ces tendances ont été étu-

diées en ajustant des polynômes orthogonaux aux séries chronologiques.

I1

apparaît qu’à toutes les profondeurs les tempéra- tures du sol présentent pendant l’ensemble de la période considérée des tendances ascendantes très marquées eu égard aux corrections des thermomètres.

Ces observations ont pris fin en

1925;

mais les ther- momètres ont été remis en place en

1939,

et les données enregistrées par la suite indiquent que les températures élevées enregistrées en

1925

se maintiennent.

D I S C U S S I O N

V. YEVDJEVICH.

W a s there any change in the ground water level due to irrigation or otherwise?

L. A. RAMDAS.

The observatory is situated on a rocky island with the sub-soil water table sdñciently deep. There is heavy rainfall during the south-west monsoon, but this too has shown a secular trend.

B I B L I O G R A P H Y / B I B L I O G R A P H I E

FISHER, R. A.

1954. Statisticd methods for research. workers.

KINCER, J. B.

1933.

Is

our climate changing?

A

study of London, Oliver

&

Boyd. long-term temperature trends, M o n t h l y Feather R e v i e w

(U.S.A.),

vol. 61, no. 9, p. 251-259.

CLIMATIC F L U C T U A T I O N S

IN T H E ARID Z O N E O F T H E U K R A I N E

bY

I. E. BUCHINSKY

Ulwainian Research Hydrometeorological Institute, Kiev

F r o m our point of view the aridity of a climate can be reliably defined

by

means of “coefficients of moistening”

which are given

by

the ratio of the rainfall to the evap- orative capacity. The latter is defined as the potentially possible evaporation in a given locality under prevailing atmospheric conditions. For our purposes w e use values of evaporation from a n open water surface. T o the northern part of the arid zone one m a y allocate the steppe districts of the Ukrainian Soviet Socialist Repub- lic in Lhe most droughty districts of which the “coeffi- cients of moistening” are

0.4-0.5

whilst in the rest of the territory of the steppe the coefficients are

0.5-0.75.

T h e boundary of the arid zone passes, approximately, from Krizhopol to Uman-Cherkassi-Poltava-Kharkov.

T h e semi-arid or forest-steppe zone with a “coefficient of moistening” of

0.75

to

1.0

reaches the line of

Chernovzi-Ternopol-Zhitomir-Chernigov.

T h e north- west part of the republic is in a zone of sufficient moisten-

ing

and the mountain districts are in a zone of excessive moistening.

T h e first information about the plains adjoining the Black Sea and the Sea of Azov to the north dates from deep antiquity. However, particulars about climate are available from the time w h e n Herodotus iirst visited the Scythian land, about

2,500

years ago.

F r o m an examination of antique source material about the climate of the northern lands located close to the Black Sea, the analysis of Homer’s poems carried out

by B. P.

Multanovski, and also

A. A.

Borisov’s investi- gation into climatic fluctuations in the Crimea, and considering the presence of large amounts of pine pollen in peat bogs, one m a y conclude that

in

the middle of the first millennium B.C. and in the beginning of our epoch the climate of the Ukraine was somewhat colder and more

humid

than it is now.

T h e Scythia accounl from R o m a n sources stops

in

the fifth to sixth century and from then till the tenth century veily little information about climate can be

found.

There is only a very little mention of a “hard frost”

in 791

and of a severe winter in

794-95

w h e n deep

snow brought death to a great number of people and horses in the north-west part of the Black Sea.

Only

from the time of the formation of the state of Kiev with its

high

original culture does information about striking meteorological phenomena appear

in

chronicles. Simultaneously with accounts of state events chroniclers diligenlly wrote d o w n unusual natural pheno- mena: droughts, floods, severe and w a r m winters.

There are also descriptions in the chronicles of northern lights and optical phenomena.

There is no doubt of the authenticity of the pheno- m e n a described in the chronicles. In

his

day,

M. A.

Bogo- lepov

(1908)

was the first to utilize the Russian annals for the study of climatic fluctuations. Supplementary to historical records about weather are the “tales of foreigners” w h o have visited Russia since the thirteenth century, and also the diaries of Russian travellers.

Having

systematized these data w e have published a s u m m a r y (Buchinsky,

1954)

showing the number of years with various meteorological phenomena, harmful to man’s activity, in each fifty years (from

850

to

1800).

T h e data

in

this summary indicate that striking meteo- rological phenomena were most frequent in the fifteenth century, i.e., this was a period when the climate w a s noticeably more disturbed as revealed

by

the increased number of droughts, floods, storms and thunderstorms, severe and snowy winters and, as the result, of hungry years. F r o m the fourteenth to the fifteenth century one m a y deduce a deterioration of climate a n d then, beginning with the sixteenth century, a n improvement.

T h e apparent discrepancy

in

the simultaneous increase

in

the number of droughts and floods

in

the fifteenth century reminds one of the sequence of events observed in recent years w h e n droughts have alternated

with

high floods.

As

w e approach modern times, meteorological sources of data become more plentiful. Computations of a

“drought index” have been m a d e for each

100

years in the

following

way: column (u) of Table

1

contains the number of years having abundant rains, floods, storms

91

Changes of climate Les changements de climat

and thunderstorms and column

(b)

the number of years with droughts based o n direct evidence and indirect indications (mainly raids of locusts). T h e numbers

in

column

(b)

are then expressed as a percentage of the total of the numbers in columns (u

+ b),

thus giving the degree of drought

in

each century.

TABLE 1.

Drought index century based o n odd historical sources are not quite reliable but, nevertheless, it is clear that in the eleventh century the number of drought years exceeded the number of rainy years. T h e drought index of

67

per cent is the highest for all the nine centuries examined.

In

this century, a pronounced sinking of the Caspian Sea level took place.

Moreover,

in

one of the earlier works on the history of Kiev (Zagrevsky,

1868)

w e are told that in the eleventh century “Kiev district and the capital itself were suffering from great calamities.

All

the plants and cornfields dried

up

from continuous excessive heat, the wood in marshes caught fire, the work of rural inhabi- tants ceased.”. Hence, there is reason to assume a most

droughty

period at that time.

In

the twelfth century the drought index decreased and it reached a minimum of

8

per cent in the thirteenth century.

In

the fourteenth century the drought index increases sharply-up to

36

per cent (but it is still lower than

in

the eleventh century)

;

the number of

dry

seasons also increases, but seasons abounding

in

water remain at the level of the previous century (Chvez,

1957).

It should be mentioned that after Kiev was ravaged

by

Tatars, a chronicle was compiled in the north where it is known that droughts were considerably rare. Thus, for the thirteenth century the drought index must be considered CriLically, especially as there w a s nothing

in

the literature to confirm the unusual lowering of the drought index. T h e fifteenth and sixteenth centuries are characterized with a lowering o€ the drought index which fits in

with

data indicating a greater wetness of the territory at that Lime.

In

the seventeenth century the degree o€ drought somewhat increased again.

It should be noted that the average drought index for the tenth to fourteenth century is somewhat higher than

it is for the fifteenth to eighteenth century. This provides a basis for supposing that, beginning from the fifteenth century, the observed territory experienced increased wetness. Moreover, in describing droughts in the first half of the second millennium, the chronicles refer more often to burning woods, dried-up rivers, lakes and s w a m p s than in the second half. This also suggests that

in

the first half of the current millennium droughts were more intensive. Thus one m a y imagine that, having begun in the first millennium of our age, a centuiy-old drought cycle continued

up

to the middle of the current millennium

but

was interrupted

with

moist intervals in the eighth, tenth and, perhaps, the thirteenth century.

In

the middle of the second millen- nium the degree of drought decreased.

In

the Middle Ages droughts in the area of the Russian plain embraced vast spaces right

up

to Pskov, Novgorod and Moscow,

in

spite of the fact the area was almost completely afforested at that time.

For m a n y places in the Ukraine there are long meteo- rological observations but the wars which were going on in this territory from

1914

till

1923

ancl from

1939

to

1945

broke the continuity of the records. This has hampered the development of research on climatic fluctuations and m u c h spade-work

in filling

the gaps must first of all be carried out for several “basic”

meLeorologica1 stations.

Curves of running 10-year average temperatures at Odessa, Nikolayev and Lugansk are given Fig.

1.

Each point of the curves corresponds to a 10-year average temperature for the period indicated below o n the horizontal scale. T h e horizontal straight lines on the graphs indicate values of average temperature for the period for which the running averages were computed.

T h e numbers on the right of the horizontal lines indicate average values based on m a n y years.

If

observations were missing,

the

running averages were calculated from

“restored” values. T h e decades which have a “restored”

values even for a year, are shown

by

the figures

with

a dotted line.

Curves o£ running means provide interesting infor- mation about

the

character of temperature and preci- pitation fluctuations.

F r o m

Fig. 1

it b e seen that the course of air temperature in the arid zone of the Ukraine has a contin- uous character for the last

150

years, except during the middle of the last century when it w a s broken, apparently

by

the heterogeneity of the series of obser- vations. It m a y be noted also that the course of air temperature in the Ukraine has a cyclic character

but

with recurrence periods o€ different duration.

T h e temperature curves for the neighbouring stations of Odessa and Nikolayev show a parallelism from thc second half of the nineteenth century.

It should be noted that the temperature íìuctuations consist of five cycles

;

only at Nilrolayev is a sixth one observed. The curve for Lugansk differs somewhat bu1 even here, il

will

be noliced, there are five cycles,

92

Clintuticfluctuations in the arid zone ofthe Ukraine

1 1 1 l ~ 1 l t 1 1 ~ 1 ~ ~ 1

o

O P 0

m . - N : 0 9

" " " - - Z " " Z

- - .

-Fig.

1. Running 10-year means of annual temperature for Lugansk, Nikolaev and Odessa.

O 0 0

N T *

-

-" Y I

, z =

- -

-FIG.

2. Secular variation of positive anomalies of the precipitation in the zones of the

U.S.S.R.

(as percentage from the area of each zone) : Changeable moisture zone, insufficient moisture zone and droughty zone.

5.0 r-

1.0

L

2.5

FIG. 3. Secdar variation of the degree of drought at Odessa during spring, summer, autumn and warm period.

It

is

characteristic of the nineteenth century that the duration of the cycles is somewhat larger than in the twentieth century. Thus, the duration of the first three cycles was

20-32

years and the duration of the following fourth and fifth cycles was

only 16-17

years, both occurring simultaneously at

all

the stations of the Ukraine. T h e amplitude of fluctuations in average 10-year temperatures is of the order of

1.30.

It should be borne in

mind

that some other period of duration might b e derived

by

using a different averaging period.

F r o m

Fig. 1

it

will

be seen that an increase of temper- ature began in the middle of the last century and reached a m a x i m u m

in 1848-57;

there was then a decrease to the next minimum, which was ai a higher level than the previous one at several stations (e.g. Nikolayev).

Later, warming took place

in

the south of the republic : in the east there was a smoother rise of temperature followed

by

a decrease in the years

1890-99.

T h e last years of the nineteenth century were notable for a higher temperature compared

with

the norm.

In 1897-1906, a m a x i m u m was recorded for the whole period of observations at several stations (Lugansk, Odessa). After this, there

was a

temperature decrease

which continued till the end of the 1920s when temper- ature reached a normal level. T h e n a warming began again which continued ti111930-39, foliowed

by

a temper- ature fall till

1940-49

at Lugansk and Odessa and somewhat below normal at Nikolayev.

In

all the following decades the temperature exceeded the n o r m

by 0.30-0.70.

T h e pardelism observed

in

the temperature graphs is absent in the curves of annual total precipitation.

S o m e intersecular cycles are observed at each separate station, lasting more than a hundred years, but with W e r e n t duration.

For the purpose of eliminating inaccuracies in the data of individual stations and in order to reveal preci- pitation fluctuations a general review of data for the whole territory of the republic has been carried out.

Average values of annual total precipitation for m a n y years (norms), computed for each station, were sub- tracted from average values for running 10-year periods.

T h e resulting differences were expressed as percentages of the norm. Calculations were m a d e for

30

stations evenly distributed throughout the temtory for the period

1881-1959.

T h e fluctuations

in

each running 10-year period were plotted on a

map ; 10

per cent isolines were drawn for both positive and negative anomalies. Altogether

93

Changes of climate

/

Les changements de climat ^.)

70

maps were plotted; for the early decades of obser- vations

(1881-99

and so on) the maps were based on the data for

11-14

stations but from

1885-99

till

1890-99

they were based on

15-23

stations.

Only

from

1896

to

1905

were data for all the stations plotted.

Plotted

in

sueh a way, the m a p s reveal fluctuations in the differences from normal precipitation over the territory of the

U.S.S.R.

and each zone separately, from decennium to decennium.

By

means of the plani- metry of areas

with

identical fluctuations (within the limits of isolines having positive and negative values

0-10

per cent,

11-20

per cent,

21-30

per cent and

30

per cent) information about the zonal distribution of preci- pitation anomalies was obtained for each successive decennium.

In Fig. 2

data are given showing the extent of areas with a positive precipitation anomaly, the relation of each area of each zone being expressed as a percentage. It should be noted that a territory with a coefficient of moistening

0.4-0.5

is chosen as a drought zone, a coefficient

0.5-0.75

applying to a zone of insua- cient moistening and

0.75-1.0

to a zone of changeable moistening. T h e end of the last century saw considerable drought as the positive precipitation anomalies embraced a m u c h smaller area than the negative ones.

In

the beginning of the current century, the territory became wetter and

by

the second decade the precipita- tion was everywhere above normal. Thereafter the pre- cipitation began to decrease until a minimum w a s reached

in 1921-30,

when

90

per cent of the area w a s enveloped in negative anomalies in the drought zone.

In 1922-31

the area with positive precipitation anomalies increased sharply

;

the increase continued until

1932-41,

w h e n precipitation was above normal in

98

per cent of the territory of the

U.S.S.R.

T h e increased wetness in a large zone

in

the centre and in the south of the territory amounted to

16-28

per cent above normal.

T h e following five running decades were marked

by

an exceptionally abundant fall of precipitation

in

the Crimea amounting to

37

per cent above normal.

A s from

1933-42

the area with positive anomalies began to decrease whilst the area with negative ano- malies gradually spread to the south-east and enveloped almost the whole territory of the republic

by 1942-51.

In

the following years the area with positive anomalies began to increase and towards the end of the period of observations these anomalies enveloped almost the whole drought zone and a considerable part of other zones.

Apparently, a drought cycle had come to an end.

Thus, in the last

80

years t w o wet cycles with an

thermic coefficient,

PTC,

is userl.

PTC

represents thc relation of pyeeipitation totals to average monthly temperature totals for a definite period or season (spring, summer, autumn).

A

comparison of

PTC with

crop fields showed that

PTC = 2.0

characterizes a territory inflicted with drought.

PTC

values computed for seasons for

89

years

(1871-1959)

were plotted on maps. Analysis of these maps made it possible to determine the distribution of areas affected

by

each drought separately and pro- vided an opportunity to compute the extent of the area of the territory involved

by

each drought.

PTC = 2.0

characterizes a territory inflicted with drought.

PTC

values computed for seasons for

89

years

(1871-1959)

were plotted on maps. Analysis of these maps made it possible to determine the distribution of areas affected

by

each drought separately and pro- vided an opportunity to compute the extent of the area of the territory involved

by

each drought.

Dans le document CHANGEMENTS DE CLIMAT OF CLIMATE (Page 94-102)