QUARTERLY JOURNAL OP THE

ROYAL METEOROLOGICAL SOCIETY

VOL XXXVII.] J A N U A R Y ' 1911 [No. 157

RESULTS OF THE HOURLY BALLOON ASCENTS MADE FROM THE METEOROLOGICAL DEPARTMENT OF THE MAN- CHESTER UNIVERSITY, MARCH 18-1 9, 19 10.

BY MARGARET WHITE, M.Sc., F.R.Mm,Soc.

[Read November 16, 1910.1

A KNOWLEDGE of the variations in the temperature of the upper atmosphere which occur from month to month and from place to place, has formed the object of a systematic series of experiments organised by an International Committee, but with regard to the diurnal variation few results are available. At the suggestion of Professor A. Schuster, F.R.S., two series of experiments have been undertaken with a view to obtaining information on this point. An account of the first series, June 2-3, 1909, by Mr. W. A. Harwood, M.Sc., was published in the Quarterly Jozlrnal of the Royal Metewologieal Society, April 1910 ; the second series of ascents, made on March 18 and 19,1910, forms the subject of the present paper.

Twenty-eight small rubber baIIoons carrying Dines' Meteorographs were liberated hourly from the Physical Laboratories of the Manchester University, and of these, up to the present date, twenty have been recovered.

The balloons left Manchester going at first in a Southerly and later in a South-easterly direction, and were found in the Worcester, Hereford, Monmouth district (Fig. l), one reaching North Devon. Table I. shows the direction in which each balloon started, the maximum height reached, and the distance and direction of the place of fall (measured from Manchester). It will be seen that while- the maximum height reached varied from 9 to 20 km., the direction of the places of fall was constant within less than 20". Further, this slight change was progressive and in the same direction as the variation in the direction of start. It thus appears that the direction of the upper wind was constant during the

B

2 WHITERESULTS OF HOURLY BALLOON ASCENTS

period over which the ascents extended and did not vary with height. The direction followed waa practically that of the isobars a t the ground, as reference to Figs. 8, 3, 4, reproductions from the FeekZy Weather &port of the pressure distribution a t the time, will show.

The time a t which the balloons were found was carefully recorded,

and in one case a t least the balloon was seen falling. The duration of the asceut seems frequently not to exceed two hours, which assuming a uniform increase of wind velocity with height, would indicate a maximum velocity of more than 100 miles per hour, a result not incompatihle with the measurements of the velocity of cirriform clouds. The average vertical velocity, taking ascent and descent, is of the order of 5 niilea per hour, or 900 feet per minute.

Ya&h of Tmperature with Eeight.-The general character of the

WHITE-RESULTS OF HOURLY BALLOON MCENT9

TABLE I . - P u c ~ s OF FALL OF BALLOONS, MAECH 18 AND 19, 1910.

kmS. 8.7

11.5 11.4 I 98 I47 14.1 18.2 136 136 12.1 I 6.0 19.0 9.4

17" 18.0 20-0

18.9

Date.

Distance. -- k m s 161 I77 177 230 228 228 281 206 I37 196 I82 148 14

I93 I20

161

March 18 8 ,

, I

, I

M&h 19 I ,

1 1

,, I 1

I ,

I ,

1 1

,! 1,

I ,

$ 9

I ,

11

,

SIIh

Time.

7.10 p.m. 8.58 1 ,

10.0 ,, 11.0 ) )

12.0 ,, 1.5 a.m. 2.2 I ,

3.2 3 ,

4-35 1)

5-15 1 ,

6.18 ,, 7-13 I *

7.47 ? l

9.10 f ,

10.2 , I

10.58 1)

11.57 3 1

2.59 p.m. 9.0 11

10.10 1 ,

Direction.

I to I80 I80 I& I80 170 170 170 I 8 0 180 I80 I80

r58 then I& r56 then I&

158 '35 I35 I57 I I2 ...

Place of Fall. Maximum Height.

3

variation with height of the temperature of the earth's atmosphere, tw obtained from observations on mountains, and from the results of

Fro. 2.-F'reasnre Distribution, March 18, 6 p.m.

4 WHITE-RESULTS OF HOURLY BALLOON ASCENTS

F’IO. 1.--presSure Distribution, March 19, 7 am.

FIG. rl.-Pressare Distribntion, March 19, 6 p.m.

WHITE-RESULTS OF HOURLY BALLOON ASCENT8

registering balloon and kite ascents, is clearly shown by the results of this series. - '-A large gradient for the first kilometre is followed by a small gradient from 1 to 3 km., which gradually increase up to 7 or 8 km. A large gradient continues np to about 10 km., when it suddenly decreases rapidly and changes sign between 10 and 12 km. a t the lower limit of

5

(See Fig. 5 and Table 11.)

Fro. Q.-Temperatum with Height, March 18-19, 1910.

the stratosphere or advective region. This small negative gradient in general persisted up to about 15 km., above which a very small gradient either negative or positive was recorded. Such an inversion of temperature was shown in every ascent at the lower limit of the strato- sphere, and the truth of its existence is confirmed by the records of the hourly balloon series, June 2 to 3, 1909, when again it waa observed in every ascent, and by the fact that it exists in every record obtained from Manchester during the past year, granted, of course, that the balloon reached a auficiently high altitude to encounter the stratosphere.

6 WHITF,-RESULTS OF HOURLY BALLOON ASCENTS

Table III. gives in degrees centi,gade per 100 metres, the average temperature gradient for each kilometre riae for the series.

TABLE III.-AVEEAOE TIIXPEB~TURE G R A D ~ N T S FROM BALLOONS, MA~-~oHEBTEB, m C E 18 AND 19, 1910.

Height I '5%- 11 Height. p a 100 Metres.

Temperatun Gradient

per ICO Metres.

kms 0-1 1-2

2-3 3-4 4 5 5-6 6-7 7-8 8-9 9-10

kms. 10-11 11-12 12-13 13-14 14- I 5 15-16 16-17 17-18 18-19 1g20

0 c. 0.2 I

-0.11 - 0.12 -0.12 - 0.08 - 0.03 - 0.02 +O.OI - 0.02 - 0.05

A n average temperature height curve was obtained by joining up the mean temperatures at each successive kilometre (Fig. 6). Owing to the slight variation in the height of the stratosphere in the different ascents the sudden bend back so clearly shown in individual sscents is somewhat cloaked. The average height of the stratosphere was 10.7 km.

Table IV. gives the height (H) at which the sudden temperature inversion occurred in the different ascents, and the temperature (T) at that height. It appears roughly that as the base layer of the stratosphere rises its temperature becomes lower, a result in agreement with previous observations.

TABLE IV.

Date

March 18 ,, 1,

March 19 11

7 9

, ,, ,, 9 ,

,, , 9

, I

, I

,, 9 ,

Time of Axent.

7. I 0 p.m. 10.2 ,, 11.0 ,, 12.0 a.m. 1.5 1 9

2.2 ,t

3-2 1 3

k35 ,, 53 :: 7.13 , I

9-10 8 )

10.2 ,, 11-57 ,t

9.0 3 3

raro

3.0 p.m.

~

Height.

-- km. 8.7 9 3

10.4 10.8 11.6

11.7 10.7 10.5 11.5 11.5 10-8 I 1-4 10.8 12.3

10-0

11.0

11.2

~

Temperature.

c.

- P35 - 53.5 - 54 - 57 - 55.5 - 59 - 57 - 59 - 59 - 56 - 495 - 54 - 57 -60 - 59.5 - 625 - 61

Each of two of the balloons carried in addition to an instrument in the ordinary thin aluminium cylinder, a second instrument enclosed in a double case formed of two coaxial aluminium cylinders. The object of

WHITE-RESULTS OF HOURLY BALLOON ASCENTS 7

this experiment was to test whether the single case efficiently shielded the instrument from solar radiation. Only one of these pairs was recovered.

The two corresponding temperature-height curves are shown in Fig. 7. Down to about - 25" C. the two traces agree fairly well, but at lower

TEMP€RATUR€ C€NTlQRADE

FIO. &-Average Temperature with Height, March 18-19, 1910.

temperatures considerable discrepancies arise, the double case instrument not falling so low as the single case by 5" C. The first instrument was suspended, as is usual, some 4 metres below the balloon, and the double cases 4 metres below this, so the result cannot be ascribed to radiation from the balloon. There appears, therefore, to be some evidence that the use of several coaxial cases is not to be recommended ; possibly the additional thermal inertia more than compensates any increased protection.

8 W HITEBFBULTS OF HOWLY BALLOON ASCENTS

In the reduction of the results some difficulty arose with regard to the midday records, which showed double traces differing by as much aa 10" C. On due consideration it appears that this is caused by the direct radiation on a part of the thermometer by the sun when a t its highest,

TEMPERATURE ABSOLUTE

-70 -60

20

2

8 F 10 $

15 $

h h

P

5

0 1

TEMPERA TURE CENTIGRADE

FIG. 7.-Temperature with Height, single and double cases, March 19, 3 p.m., 1910.

the protecting caaes used being short enough to allow this. In the rapid descent this radiation error is very smalI, and in such cases the trace indicating the lower temperature haa been taken.

The diagam, Fig. 8, shows the isothermal lines for March 18 to 19, the date of the ascents, plotted at intervala of 6' C., the temperatures marked being in absolute u n i k To avoid complication the results obtained from each balloon have been referred to the time at which the ascent was commenced, although the readings at the higher levels actually

WHITE-RESULTS OF HOURLY BALLOON ASCENTS

correspond to an hour or two later, and to a different geographical position.

9

FIQ. 8.-Isothermals (degrees Absolute), March 18-19, 1910.

For purposes of reference, a curve showing the variation of the baro- metric pressure at the ground level is inserted. The general trend of the barometric curve is similar to that of the isotherms a t the higher levels,

FIG. g.-Isothermsls (degrees Absolute), June 2-3, 1909.

but as an opposite effect was noticed in the June 1909 ascents, the results are scarcely sufficient to regard this as more than a coincidence.

10 WRITE-RESULTS OF HOURLY BALLOON ASCENTS

Whereas at the ground level the temperature was remarkably constant throughout the course of the experiments, showing a maximum variation of less than 2" from the mean, the isothermals at the higher levels show a well-marked rise throughout the first 15 hours ; e.g. a temperature of - 40" C. was a t first encountered at a height of 6 km., but continued to

recede, until a t the end of 12 hours it was not met with until 8 km. height.

Generally speaking, the curves obtained show a remarkable similarity to those of June last year, which are given in Fig. 9 for comparison.

The effect of solar radiation on the temperature of the upper atmo- sphere is in both cases almost inappreciable, but is just noticeable in this series at the probable lower cloud level. Again, a comparison with the June 1509 results shows a remarkably close agreement of both the height and temperature of the stratosphere. Bot4 series indicate a gradual drift of temperature, but the most noteworthy result is the absence of any considerable effecta which can be attributed either to seasonal or diurnal change.

My thanks are due to Professor J. E Petavel, F.R.S., for advice and encouragement during the progress of this work

Influence of Height and Evaporation on Eain-Giauges. Mr. H. 0. Barnard in the &port of the Colo7nbo Obsnvatory for 1909, states

that during the latter part of 1909 a series of esperiments were carried out on the influence of the height of the gauges above the ground on the accuracy of the records of rainfall in Ceylon. "hie inquiry was suggested by the remark- able deficiencies in the amount registered by the Fort gauge, which was trans- ferred in 1904 to the top of the Survey Office (on account of the repeated thefts of gauges placed nearer the ground), as compared with those registered by the three other gauges in Colombo, situated at the Observatory, the Agricultural School, and at Elie House. Gauges were placed at the Observatory at heights above the ground varying from 2 inches to 15 feet, and the amounts recorded carefully compared. Unfortunately the experiments were begun too late to take full advantage of the North-east monsoon rainfalls, and, although it is quite clear that high gauges r ee t e r considerably less than those clme to the surface of the ground (as is well known), the number of observations is still insufficient to deduce a formula connecting the amounts recorded with the altitude of the gauge. It is hoped that by the end of the preeent year it will be possible to obtain such a formula, which w i l l enable the records of gauges all over the Island to be more accurately compared than can be done at present.

During the course of this investigation it WBB found that evaporation due to the considerable temperature attained in the sun by unprotected gauges is a factor of great importance to the accuracy of the results. The amount of evaporation varies, of course, with the nature of the metal of which the gauge is couatructed, aa well as the condition of its surface. Experiments are now in progress to determine the extent by which the records are effected by these causes of error.