ELLIS-PREVALENCd O F DIFFERENT WINDS AT GREENWICH, 1847-89. 221

ON THE RELATIVE PREVALENCE OF DIFFERENT Wik105. AT THE ROYAL OBSERVATORY, GREENWICH,

1841 -1 889.

EY WILLI-kII ELLIS, F.R.A.S., of the Royal Observatory.

[Received April 29th.-Read June lSth, 1890.1

DIP.. Prince, of Crowborongh Observatory, Sussex, having in his Meteorologicnl Report for the year 1889 drawn attention to the greater prevalence of Noith- east winds which he has found to exist at Crowborongh in recent years, I Enve thought that it would be interesting to put together the resnlts derived fxom the records of the self-registering Osler anemometer of the Royal Observatory, Greenwich. The numbers contained in the annexed table are eitlier copied or derived from those given in the annual volnmes of G~~eeiiir ich Obsnuntions. The results from 1641 to 1360 are given in an Appendix to the volume for 1860, and for the remaining years in the several annual volumes. Until 1869 the resnlts are given for days, and since 1870 fcr honrs. The day unit is, however, here retained for better comparison with Mi.. Prince's values, or with those of other observers, that is to say the values for hours since 1870 have been divided by 24.

In consiclering this Table it would appear that in some of the earlier years the number of calm (lays is in excess ,of the true amonnt, mising probably from some rule having been adopted for t.he classification of days as callu which admitted too many, otherwise the same general balance of winds seems to be maintained thronghont, the several merwIs for 24 years and 25 years giving no indication of any great ch,ange in this respect, neither is there any appearance of change in late years such as Mr. Prince finds at Cromborongh.

He says, '( The great preponderance of North-east wind over all other wind cnsrents, and niore particularly over that from the Sonth-west, which has obtained clnrizlg the last five years, has indncecl me to look through my journal since 1855 in order to ascertain whether I had a record of any similar condition of the principal mind currents of the Sontli-east of England. FOY the thirty-one years, ending with 1889, I f k d ouIy tmo instances in which the North-east has been in escess, viz. in the y e a s 1864 and 18'70."

The corresponding nnmber of days of North-east and South-west minds for Crodorough and Greecwich in the years 186.1 and 1870 are as follotvs :--

Year. Cromborongh. Greenmich.

But to consider now the statements of Mr. Prince.

NE. SW. NE. 6W. 1864 ... 104 89 43 10s 1870 ... 107 88 65 96

223 ELLIS-PREVALENCE OF DMFERENT WINDS AT GREENWICH, 1547-69.

NW.

17 25 29 26 38

-.--

23 10 20 12

'9

25 8

27 30 26

26 21

29 31 31

2 j

2s 16

21-

22

22 26 18 27 1-8

I7 17 20 21 I4

16 25 28 16 15

22 I

NUMEIER OF DAYS OF PBEVALENOE O F DIFFERENT WMDS I N EACH YEAR 1841 to 1889, AS DERIVED P R O P TEE RECORDS O F TEE SELF-REGISTERING OBLER hEYOYETER OF THE ROYAL OBSERVATORY, (~REENWIOH.

Calm

37 27 63 57 34

86 69 23

31

43 11

41 33 30

24 24 12 11

7

25

19 34 59

34 9

23 10

9

9 16 17. 5

11

I 2

1

o 3 7

11 I3

;;

- Year.

1841 1842

--

I843 1844 1845

1846 I847 1848 1849 1850

1851 1852 I853 I854 1555

I557

1859

1856

1858

1860

1861 1862 1863 1864 1865

1866 1867 1868 1869 1870

1871 1872 1873 1874 I875

1876 I877 1878 I879 1880

1881 1882 1S83 1884 185;

- N.

40 46 42 48 30

27 41 53 59 49

52 45 43 31 56

---

44

26 31 30

26 27

44 40

28 43 39 38 39

37 35 30 37 42

45

21

21

36 48

38 39

39 26 41 40 44

- NE.

I9 40 44 57 49

25 23 38 54 48

58 65

_I

39

45 74

54 58 61 54 47

43 46 33 43 30

31 40 43 51 65

50 23 46 36 54

40 30 36 50 65

49 35 37 42 55

E. - 22

22

11

21

31

18

16 I9

24

36 16 '7 23

'7 28 38 16 26

29

20

21

20 20 34 18

27 29

24 29

38 '7 29 29 38

40 25 37 41 34

34 25 26 35 35

20

SE . 9

'5 8

'4 I3

I8 4

36 23

--

21

20 21

20 27

'7

30 27 27 29 19

I7 32 24 27 28

'4 21

'9 26 24

31 24 I9 23 26

35 18 20 21 16

25 28 30 25 30

- S.

49 3' I8

43

39 55 58 39 30

28 52 28 30 25

3r 33 26 25

-

22

22

22

22 I7

28 24

28 37 37 27 26

- SW. - 112 I12 I02

89 104

9%

90

I 16

108 86

1'7 84

80 119 106 I28 I20

I11

I02

I00

119 I18 138 I08 97

1 19 119 1'3

96 I12

W.

60 38 37 35 43

32 36 29 35 27

37 27 32 42 30

50 34 40 40 64

59 71 60 32 47

62 41 54 50 49

47 61 69 80 51

55 69 63 39 42

38

--

41 4 0 49 30

Again, on the average of 25 years, 1859 to 1883, Mr. Prince finds for The corresponding Crowborough, North-east 63 days, South-west 99 days.

Greenwich ralues are 43 and 111.

ELLIS-PREVALENCE OF DIFFERENT WINDS AT GREENWICH, 1847-89. 223

NUUBEB OF D4YS 03' PREV4LENCe OF DIFFERENT WINDS IN EACH YEAU 1841 TO 1889, A9 DERIVED FROI THB RECORDS OF THE SELF-REWSTERIBQ OSLEB ~ E Y O I E T E R OF THE ROYAL OBSERVATORY, GREENwIcH.-Continued.

1886 42 49 40 97 1887 58 62 30 94 1 :; 1888 49 49 33 24 39 105 1889 51 44 28 a4 40 96

I-____ - -- -- -- -- Means

1864.

Means

1889.

Means 1841- 1 40 45 27 22 35 I06 188s.

1841- 1 39 46 23 21 32 I07

-----------

40 44 31 23 37 106 ------ -__--

Mr. Prince gives the average frequency of different winds 1885 to 1889. From the accompanying Table I have prepared corresponding numbers for Greenwich. We thus have :-

Mean prevalence of different winds, 1885 to 1889. AT CROWBOROUGH.

N. NE. E. SE. S. SW. W. NW. Calm. 41 102 21 28 38 72 50 17 ...

AT GEEXNWIGH, N. NE, E. BE. S. SW. W. NW. Calm. 49 52 35 23 37 100 40 19 10

Mr. Prince further gives averages of 47 years, which he has since informed

N. NE. E. SE. S. SW. W. N%. Calm. 33 63 29 27 28 91 59 35 ...

The Greenwich values for the corresponding 47 years from the annexed

N. NE. E. SE. S. SW. W. NW. Calm. 39 46 27 23 34 106 46 22 28

For the individual years, 1885 to 1889, the comparison as regards North-

me are for the years 1843 to 1889, as follows :-

Table, we :-

cast and South-west winds is as follows :- Year. Crowborough. Greenwich.

NE. SW. NE. SW. 1885 ... 98 74 55 107 1886 ... 102 83 49 97 1887 ... 128 67 62 94 1888 ... 95 71 49 105 1ss9 ... 88 65 44 96

Means ... 102 73 52 100 - - - - -

224 ELLIS-PREVALENCE OF DIFFERENT WINDS AT GREENWICH, 1847-89.

Thus the results for the two places are entirely at variance in late yems in a way that has not previously been experienced in such persistent fashion. It would be now interesting to malie comparison, if possible, with similar statistics derived from observations made at some southern station nearer to Crowborongh.

Crowborough. Forest Lodge.

NE. Years.

SW. 1 NE. 1 SV. 15;;: -__ -- ---- ---I- 77 77 I 51

23 98 74 88 80 1885 1886 102 83 1887 128 67 120 71 33

DISCUSSION. The PRESIDENT (Mr. Latham) said that he always preferred to ascertain the

direction of the wind from the motion of low clouds or smoke. H e did not trust to vmes, as they so frequently got fixed; and probably some of the differences shown in the paper might be due to errors in the vanes.

Mr. SYXONS, read the following letter from Mr. Prince, of Crowborongh Beacon:-

" Dear Mr. Symons,-As I find that I shall not be able to attend the Meeting of the Royal Meteorological Society on the 16th instant, I send you records as to the prevalence of North-east and South-west winds at Forest Lodge, Maresfield, and Crowborough respectively , the former from data kindly supplied to me by Capt. Noble, F.R.A.S.

" The vane at Forest Lodge is about 230 feet and mine 850 feet above sea- level. The observations were made at both stations at 9 a.m. Forest Lodge 1s situated nearly five miles in a south-west direction from Crowborough.

Greenwich.

NE. SW.

55 107 49 97 62 94

-- ---

102 72 103 81 52 100 1: The application of this correction shows that the net reduced results at both

places are practically the srwne.-Yours faithfully, C. LEESON PRINCE." BIr. SYBIONS said that he did not think that Mr. Prince's vane was open to the

chwge of being fixed or stuck. He then described the position of the vane and the method by which its indications were read, and showed how he had thought that it was possible the vane may have become affected by a lofty addition to Mr. Prince's house. It &id not, however, appear that such was the case, a6 the ob- servations made by Capt. Noble at Maresfield, about five miles distant from Crowborough, confirmed Mr. Prince's results. A vane fixed to a pole or mast often gave very unreliable observations. H e had had a vane so fined in his own garden, 'wd had found that in dry weather the pole cracked and gradually

DISCUSSION-PREVALENCE OF DIFFERENT WINDS AT GREENWICH, 1847-89. 225

Burst Castle.

NE. SW. ---- 72 63 78 67 92 5 1 72 75 73 56

77 - --

52

twisted round until the cardinal points had moved as mnch as 40' from their trne position. When damp weather set in the pole twisted back to its proper position.

Mr. C. ~ D I H G said that he had composed the wind observations obtained by the Meteorological Ofice for 8 a.m. each day at London, Dungeness and Hurst Castle for the five yems 1885 to 1889, and had found the number of days of North-east and South-west winds to be &s follows :-

Years.

---- 1885 1886 1887 1888 1889

Mean for 5 years .... -

Consideriug the mean result for the five years 1885-3, and taking the North- east winds P.S unity, the respective results are-

NE. sw. Crowborongh . . . . . . . . . . . . 1 0.7 Greenwich . . . . . . . . . . . . . . . 1 1.2 London . . . . . . . . . . . . . . . 1 1-3 Dungeness . . . . . . . . . . . . 1 1.2 Hurst Castle . . . . . . . . . . . . 1 0 7

H e could not say whether the last few years had been exceptional with respect to the prevalence of North-east winds, but it was noteworthy that recent years have been marked by an absence of great storms so far as the British Islands are concerned, and more especially over the South of England.

Mr. ELLIS said, regarding the question of periodical variations of the wind, that he did not himself attach much importance to such periodicities as were pointed out by Mr. McDowaJl (see next paper), considering them to be more of accidental character, rather t h m 8s indicating recurring phenomena. On the quesiion of the sticking of vmes he might, perhaps, mention an experiment which he once made with the Greenwich Osler vane, as showing the delicacy of its action. I t may be premised that a collar on the vane shaft bears upon anti- friction rollers, running in a cup of oil, rende-0 the vane very sensitive to changes of direction in light winds. On the occasion in question the Robinson cups mere twning at the rate of about four revolutions per minute, indicating a very low velocity. The Osler v m e was pointing South-b west. It was tnmed by h m d to East, but, when reletwed, slowly came beck to &nth-by-west. I t was then turned to West, and similmly came back nemly to South-by-west. Other trials have been made with similar results.

NEW SERIES.-VOL. Y V f .