Daily rainfall at the royal observatory, Greenwich, 1841-1903

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  • QUARTERLY JOURNAL OF THE

    ROYAL METEOROLOGICAL SOCIETY - VOL. XXXVI.] OCTOBER 1910 [No. 156

    DAILY RAINFALL AT THE ROYAL OBSERVATORY, GREENWICH, 1841-1 903.

    By WILLIAM CARPENTER NASH.

    [Read May 25, 1910.1

    THE primary object of this analysis was the determination of the average daily run of the rainfall, with subsequent development of the accumulated materials into monthly and annual periods. The total number of calendar days in the years under discussion, amounts to 23,009, of which 9930 are classed as rain days, distributed throughout the years of observation as shown in Table I. In this enumeration it is to be understood that a rain day is considered to be one on which the rainfall amounted to -005 in. (at least), but in the calculations all smaller recorded amounts have been taken into account. In the cases of deposition from dew, frost, or fog, the small amounts derived from those sources have usually been merged into the next succeeding rainfall, but in every case they have always been taken into consideration.

    The daily rainfalls having been extracted from the printed records were arranged in sequence on convenient forms, and the means for each nominal day taken throughout the period. In the few cases in some of the earlier years in which the references have been made to different gauges, care has been exercised in referring the whole of the records to one standard. And for facilitating the process of calculation with these numerous entries, the values were split up into three groups, each twenty-one years in length, extending from 1841 to 1861, 1862 to 1882, and 1883 to 1903, thus giving greater certainty in dealing with so large a mass of figures, the separate means being afterwards combined to obtain values for the whole period. These mean values are given in Table 11.

    It will be seen that considerable variation exists from day to day in the values in this table, especially in the summer and autumn months.

    Y

  • TABLE I.-&~ONTHLY NUVBEB OF RAIN DAYS AS EECORDED AT THE ROYAL OBSERVATORY, GREENWICH, IX THE 63 YEARS, 1841-1903.

    _,- - 22 4

    19 I9 9 24 I4 24 IS 8

    15 27 17

    12

    22 I 0 9 9

    I 8 I 0

    I 0 I7 I7 7 19

    I3

    16

    I 0 21

    I1

    12 22 14 17 18

    '3 13

    18 13 23 I4

    23 14

    6 I7 9

    I 2

    I2

    I2

    11

    20 22

    '5 I 8 15 I9

    17

    14

    14 24

    rg.1

    I 1

    I0

    I 1

    - -

    14 I7 6

    I0 I2 8

    13 I3 '5

    7 13 15 9 6

    17 13

    17 I7 15

    I4 16

    I2

    I 0

    I2

    I

    19

    7 8 16 I3

    16 '5

    6 19

    16

    13 6

    14 I7 16

    17 8

    I0

    I1

    I 2

    I2

    I S

    I 0

    I 0 I0

    I2 IS

    23 13

    '7

    6

    I4

    I7 16

    1.5

    15 17

    22

    21

    I2

    22

    I 0

    3 3 16

    13 9

    I7

    16 IS 19

    18

    I 0

    X I

    22

    I0

    :d 1s I3

    14.2

    I2 - -

    1841 1842 1843 1844 1845

    1847 1848 1849 I850 1851 1852 '853 I854

    I 846

    ::;i ::$ 1859 I860 I861 1862 1863 I 864 I 865 1866

    1869 1870 1871 1872 I873 I874 I875 1876 1877 1878 I879 I 880 1881 I882 I 883 I 884 1885 I 886 1887 I888 1889 1890

    3

    1 0

    I 0 I2

    8

    16 I7 16

    17 9

    15 16

    15

    18

    5

    I0

    20

    20

    20

    11 21

    7 I7 16

    16 I 7 I8

    I4 '5 I8

    15

    17 13 23

    I 1

    21

    20

    I2

    I 1 12

    9 9

    I9 15 15 22

    14 I1 I2

    I 0

    19 I?

    9

    15 16 8 9

    14 17

    I 1

    I 0 I 1

    I2 I 0

    I d I 1 I 0 3 6

    '3

    6 9

    19 18 I 3

    I 2

    I 1

    I2

    '5 16 6

    16

    15

    8 6

    3 I4 6

    6

    8

    IS

    10

    I0 22

    20

    I2

    10

    10

    21 21 I0

    10

    20

    '5

    15

    I2 , I 8 13

    15 15 17

    14

    20

    I0

    20 I 0 I2

    I 0 22 I1 I2

    so 17

    8 7

    13

    15

    I3 I 8 '3 5

    13 9

    24 15

    16 16 IS 15

    I4 16 19

    X I

    I 0 I 1

    12

    I 0

    I 0

    12

    21 I2 I7 '5 20 I8 9

    19 IS 18 16 17

    9

    I3 9

    19 8

    rz 16

    I40

    20

    10

    - -

    16 16 7

    I3

    19 14 I2 29 8

    7 '5

    I 1

    11

    I 0 12 I 0 I 0 I 1

    I 1 8

    25

    9

    13 S

    I1

    14 14

    7

    18 3

    15

    22

    21 I 0

    20

    10 I2 I 2

    I2 16

    I 8 5

    17 9

    I4 8

    16 I 0 10

    I3 8

    6

    5 7

    15 I2 7

    I 1

    5 I 0 22 15 4

    '3 I 1 9

    I0 19 15 '9 5

    '5 14 18

    9 17 6 5

    I2

    21

    I 1

    I 1 22 I2 9 5

    15 12.3

    22

    -

    -

    8 14 5

    IS I3

    I9 15

    14

    16 7 4

    I2

    21

    2

    3 I 1

    I3 13 6

    13 9 4 7

    13 2 0 I 0 I 0 6

    18 13

    8 9

    I2 12

    20

    :i 16 8

    13

    I S 9

    I 0

    I 2 I 1 I4 17 I4 8

    3 '3

    16

    I 0

    I2 I 0

    I 0 20 I 1

    '3 7

    11

    !2.0 - -

    8 I4

    I3 8

    16

    5

    I 0

    22

    I 0

    I1 21

    I 2 17

    9 7 9 5 7

    23 15 17 14

    5 1 5 7 5 9 4

    I 8 '5

    I 0

    I 1 I 1 I 1 I 0 7

    14 20 20

    9 19

    ' d

    '2 7 9 3

    16

    I4

    I4 8

    14 I 2 I1

    X I

    a

    6 17 9

    ' 5 I0

    1 5 1 5 '3 19

    6 17

    15 16 4

    17 15

    I3 9

    7

    I2

    I2

    I 0

    12

    I 0

    20 12

    3 3

    9

    6

    I1

    12

    2 I 0

    I7 16 9

    16 8

    15 9

    I9 24

    I9 16 16 5

    13

    26 16 I8 17

    18

    16 7 7 9 8 5 8

    '3

    10

    I2

    I 0

    I2

    22

    I2

    II ' 16 17 11

    I 0 16 '5 I 1 7

    I 8 17

    14 4

    I 1

    11 I 1

    11 14

    I 1 I 0

    6

    14 I 0

    I2 I 1

    13 17 I9

    6 17 15

    8

    20

    I 0

    10 10

    I2 9

    14 '5

    16

    17 '5 '5

    6

    22

    I 1

    20 I 1

    12

    I 0 19 17

    '3 '3 14 14

    9

    19 18 '3

    18 18 9

    '5

    I 1

    I2

    21

    8 15

    16

    I 1 I 0

    I1 22 I 1 9

    14

    15 I4 17

    I2

    I2 21 I 0

    I2 16

    7 6 I2 14 14 13 5

    23 16

    5 15 6 6 8

    15

    I s g I . 1802 I I

    15

    '9 9

    I7 8

    18

    21

    22

    '2.4 ' '3.2 11.6 , 12.6

    N.B.-These numbem are given as printed in the abstract tables in the Greenwich There are a few discrepancies in the earlier volumes which cannot Xeteorological Volurnes.

    be satisfactorily explained.

  • NASH-DAILY RAINFALL AT GREENWICH OBSERVATORY 311

    They were therefore subjected to a numerical smoothing process by tak- ing the means of each five consecutive values, and repeating the process with the resulting means. The smoothed values thus obtained are given in Table III., but aa there were rather large irregularities still remaining, the numbers were plotted on a diagram, and a mean drawn by hand to

    TABLE II.-MEAN DAILY VALUE OF TEE OBSEEVATION~ OF RAINFALL MADE AT TEE ROYAL OBSERVATORY, GREENWICH, IN THE 63 YEARS, 1841-1903.

    -

    Aug.

    - h y s of the Month.

    -

    Dee. Mu. June. Fcb. Jan. I

    I Apr. ' May. Nov.

    I 2

    3 4 5 6 7 8 9 I 0 11 I 2 13 14 15 16 I7 18 19 20 21 22 23 24 25 26 27 28 29 30 31

    Jeans -

    .06 I _.

    ,052 -062 .076 .072 -074 449

    1 Suitable allowance M d e for Febraary 29th in taking the monthly m a n .

    represent the general run of the curve cleared from its minor irregularities (Fig. 1).

    The ordinates, aa read from this mean curve, are considered to represent fairly well the average daily rainfall. They are given in Table IV.

    The monthly means at the foot of thb table differ slightly from those in Table II., tbe variations arising naturally from the overlapping of the monthly values in the curve, which is of c o m e unavoidable.

    It hae notbeen considered necessary in this paper to followMr. Gleisher's

  • ^.

    DU

    fMO

    Ll

    JAM

    UA

    RV

    N

    IIU

    AR

    V

    MA

    RC

    H

    AP

    RIL

    M

    AY

    J

    UM

    L

    JULY

    A

    UG

    US

    T

    LIPT

    ENBI

    R o

    crn

    wn

    M

    OV

    LUB

    ER

    D

    cctu

    cmu

    JAN

    UA

    RY

    5 IS

    25

    5 15

    25

    5

    15

    251

    5 I5

    25

    5 15

    25

    5

    I5 I5

    S

    I5 25

    5

    15 I5

    S

    I5

    25

    5 I5

    I5

    5 I5

    75

    5 IS

    I5

    5 15

    25

    S

    IS C

    S . ,..

    I

    '.

    . .

    :n

    .

    FIo.

    l.--

    Lie

    an

    Dai

    ly f

    liiuf

    all

    at th

    e Royal

    Obn

    erva

    toiy

    , Qre

    enw

    ich,

    184

    1-19

    05.

    The

    Dot

    ted

    Lin

    e re

    pres

    ents

    the

    adop

    ted

    Ave

    rage

    Val

    ues.

  • NASH-DAILY RAINFALL AT GREENWICH OBSERVATORY 313

    example, by printing the whole of the daily records ; but should fuller information be required with regard to particular cases, reference should be made to the annual.volumes of Gremwich Meteorological Obsnvatians. The monthly totals for the whole period were given in my former paper I Nonthly Rainfall a t the Royal Observatory, Greenwich, 18 15-1 903. 2

    TABLE IIL-DAILY SMOOTHED VALUES OF TEE GBEENWICH RAINFALLS AS DEDUCED FROM THE 83 YEARS OBSEBVATIONS, 1841-1903.

    /Days of the i . Month.

    I 4 3

    6

    9 I 0 I 1 I2 3 14

    i :s

    I 2 27 28 29 30 31

    Means --

    The aggregate rainfall, 1624.206 ins., recorded in these 63 years represents a mean daily amount throughout the whole period of *066 in. The mean monthly values vary from *091 in. in October to .048 in. in March. The total number of rain days in the period as given in Table I. is 9920, the mean fall per rain day is therefore -154 in. (Fig. 2).

    J. Olaisher, On the Fall of Rain on every Day of the Year, 1815-1889, Proc. Jiet. SOC. vol. 6, 1870.

    * W r t . Jmcm. Roy. Met. Soc. vol. 30, 1904, p. 291.

  • 314 NASH-DAILY RAINFALL AT GREENWICH OBSEBVATORY

    TABLE IV.-APPROXIMATE AWRAQZ DAILY RAINFALL AT TEE ROYAL OBSERVATORY, GREENWICH, A S DEDUCED FBOY 63 YEARS' OBSXRVATIONS MADE IN THE YEARS 1841-1903. -

    %E Month.

    I Ocr Nov.

    --

    I I I !

    June. July. ~ --

    in. ~ in. -068 s o 6 8

    I / Jan. i Feb.

    I S p t . Mu.

    in. I in. .082 I

    2

    3 4 5 6 7 8 9

    I 0 X I I2 '3 14 15 16 I7 I8 19 m 21 22

    23 zq 25 26 27 28 29 30 31

    HCalU

    - -078 -072 -076 -067 , -076

  • NASH-DAILY RAINFALL AT GREENWICH OBSERVATORY 315

    The relative percentages of rainy and rainless days in each month are as follows :-

    1s41-13ti1.

    Months.

    January February March . April . May . June . July .

    1862-158?. Isa~-l90.?.

    Monthly Percentage. Rain Days. Rainless Days.

    % % 47.6 52.4 44.0 56.0 42.4 57.6 40.0 60.0 39.8 60.2 38.7 61.3 40.5 59.5

    Date.

    1852, Jan. 13 1858, Feb. 14 1851, Mar. 15 1851, Apr. 20 1849, May 28 1852, June 9 1853, July 14 1843, Aug. 23 1859, Sep. 26 1857, Oct. 22 1861, Nov. 13 1860, Dec. 30

    Xonthly Percentage. b i n Daya. Rainless Days. Mouths.

    % % A u p t . 41.7 58.3 September . 41.1 58.9 October . 4P.8 51.2 November . 46.8 53.2 December . 45.8 54.2

    56.9 - --

    Year. . - 43.1 - - -

    .haunt.

    ins. 1.607 .77I 990 2.510 x,;x8 1.456 3.6661 1.788 1.354 1.224 .855 '950

    Excessive Rninfnlls.-In Table V. the heaviest daily falls recorded in each month of the year, in each of the three 21-year periods are giveu.

    Date.

    1866, Jan. X I 1869, Feb. 12 1870, Mar. 4 1878, Apr. X I 1878, May 7 1863, June 19 1867, July 26 1865, Aug. 23 1S80, Sep. X I 1880, OCt. I 0 1864, Nov. zq 1876, Dec. 23

    Amount.

    ins. 4359 4 1 5 4 8 5 ,804

    1.280 1.703 2.491 1.441

    1.193 1.370

    1.007 1.196

    hfUNTHS. - Amount.

    January . February . March . April. . M a y . . June . . July . . August . September October . November. December.

    ins.

    .880 1.520 -8Yo 1.135 1.305 2.455 2.280 1.295 2.510 1.287 .925

    1.120

    Date.

    1886, Jan. 6 1890, Feb. 15 1896, Mar. 18 1885, Apr. 16 1886, May 24 1888, June 26 1888, July 30 1888, Aug. I 1883, Sep. X I 1894, Oct. 30 1887, Nov. 3 1898, Dec. 7

    During the 63 years there were 94 occasions on which the rainfall exceeded 1 in. in the d3y, as given in the following Table TI. Sixty of these falls ranged between 1.00 in. and 1-25 in. ; 1 9 between 1.25 in. and 1.50 ins. ; 8 between 1.50 in. and 2 ins. ; 6 between 2 ins. and 3 ins. ; and 1 fall exceeded 3 ins. The 7 falls exceeding 2 ins. in amount were :-

    2.280 ins. on 1843, August 23 2.456 _ _ 1853. Julv 14 - _.. 2.465 1903; July 23 2.491 ,, 1888, July 30

    I 1 3.666? ,, 1867, July 26l 2610 ins. on 1857, October 22 2.510 ,, 1878, April 11

    The recurrence of heavy falls on, or about, certain days is remarkable. In this connection it may be pointed out that excessive falls occurred four

    With reference to the rainfall recorded on July 26, 1867, to which some degree of suspicion is attached, it may be mentioned that check observations of thu fall were d e by the gauges at the heightr of 10 feet and 22 feet above theground, giving 3.19 ins. and 9.01 ins. respectively. Reducing these values to corresponding ground values (naing the reliible ratios for July, deduced from the observations made in the years 1871-1880), the followhg values are obtained ; 3-27 ins. and 3.32 ins. ; @ping a mean value, 3.30 ins. It would seem therefore that the value given above should be diminished by about one-tenth of its recorded ~ N O U U ~ . but this is purely hypothetical.

  • 316 BASH-DAILY RAINFALL AT GREENWICH OBSERVATORY

    times on August 23 ; three times on June 10, July 11, August 17, and October 30; and twice on June 5 and 13, July 23 and 26, September 10 and 11, and October 22.

    TABLE VI.-DAILY RAINFALLS EXCKEDINQ OXE INCH IN AMOUNT.

    ins. ' 1 1.12 1889. June 10 1.25 1' 1896 ,, 10 1.61 !i 1903 ,,

    ins. 1.37 I .04 1.32

    ::$ 2.45

    I .06 367 1.28 1.03 1.28 2.49 1.17 1.19

    I .08 2.46

    2.28 1.81

    1.w 1.26 1-79

    I.jZ 1.10

    1.10 1.01

    I .02

    - 7 ' % IOU1 ,, l j

    1.17 ~ 1.23 I 1861 1887 " ,, 22 3

    -- ins. I 44 1.15

    1.20 1-10 1.29 1.14 1.35 1-37 I .og I .og 1.03

    I .os 1.42 r .02 1.13 2.51 I .06

    I .05

    1.14

    1.19 1.05

    i&

    1.10

    1.11

    1-12

    1.22

    1.01

    1.m 1.01

    I .06

    I .2g

    1.20

    Frequency of the Rainfall.-The distribution of the amount of rsinfall throughout the year has been mainly dwelt upon in the preceding summaries, but no roference has been made hitherto to the subject of its frequency. It is true that in Table I. an abstract of the monthly number of rain days recorded in the whole period is given, but this conveys no information with regard to the distribution of the rainfall- frequency in the course of the months. A rearrangement of the rain days as referred to each nominal day is shown in Table VII:

    The day with the maximum number of rain days to its credit is December 5, with 41 days, which is equivalent to 65 per cent of the total number of days of observation ; the days with least number of rain days are April 18, 19, June 27 and September 13, on each of which the recorded number of days of rainfall is 17, equivalent to 27 per cent of the possible number.

    The numbers in Table VII. being subjected to a numerical smoothing

  • NASH-DAILY RAINFALL AT GREENWICH OBSERVATORY 317

    proceae similar to that applied to the rainfalls (as already described), and the daily resulting values divided by the number of the years of observa-

    TABLE VIL-DISTRIBUTION THBOUDHOUT: THE YEAB OF THZ TOTAL NUXBER OF RAIN DAYS A8 REFERRED TO EACH NOMINAL DAY, RECOXDED IN TEE 63 YEARS, ~1841-1903.

    Days of the Month

    Day. I 2

    3 4 5 6 7 8 9 I0 I 1 I2 13 I 4 15 16 I7 I8 I 9 20 21 22

    23 24 25 26 '7 28 -9 30 37

    iggrcgate iumber of

    Days.

    Or the 14 proportionally

    - J a n -

    Days 31 31 34 30 34 28 31 25 33 26 30 31 33

    24 27 36 32 30 30 23 32 27 32 32 29 31 29 28 31 37

    '29

    22

    -

    -

    - Feb.

    Days 34 39 28 27 28

    34 31 28

    28 26 27 33 29 27 23 23 31 29 25 28 30 23 24 27 28 29

    -

    22

    21

    - MU.

    Days 37 27 28

    24 24 26 33 3' 28 23 25 27 25 23

    26 I9 29 25 32 28 26 23

    26 27

    -

    22

    22

    ::

    - April

    Days 23

    2.5 23 26 26 29 28 30 28 25 29 30 26 26 24 I7 I7 23

    26 28 24 24 28

    30 25

    -

    2

    22

    22

    21

    - May - Days

    21 21

    29 23 23

    25 3' 32

    30 28

    22

    21

    21 22 21 28 27 30 27 26 23 30 25

    26

    25 31 28 I 9

    20

    22

    21 -

    - Juh

    Day 26 25 25

    24 27 26 26 31 26

    23

    I8

    30 23 26 30 25 23 28 30 33 26 32 27 28 25

    -

    21

    22

    21

    22

    22 20 - 91

    - Oct

    Day! 29 32 25 30 28 38 36 34 33 34 35 26 27 33 32 36 25 28 35 28 32 33 30 29 29 34 27 31 3' 51 23

    '54

    -

    -

    - atercalar days in the 63 yean, 184;-15.03, g were rainy : and these havl this tabre throughout the month of Fehruvy in order to maintain the t

    - Nov.

    Days - 30 31 35

    27 27 25 25 31 29 24

    35 32

    26 26 29 29 26 34 38 38 28 3' 29 33

    2

    f S

    3

    - 84 - :en d ncc.

    - Dee. - Days 33 24 30 33 41 35 34 32 28 27 27 29 30 31 31 29 29 37 24 25 26 28 I8 2 0 21

    25 30 33 31 28 26 - 95

    ributed -

    tion, a m...

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