British Rainfall 1956 [Frontispiece M.*L P L>-Ct.Wi 3*33-2075 M.O
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RELATION OF RAINFALL IN 1956 TO THE AVERAGE OF 1881-1915 12 II RAINFALL SCALE OF TINTS 1956 PER CENT OF AVERAGE 120 100 80 130 HO 90 The area coloured Red had rainfall below the average, that coloured Blue had rainfall above the average British Rainfall 1956 [Frontispiece M.*l P L>-ct.Wi 3*33-2075 M.O. 644 AIR MINISTRY METEOROLOGICAL OFFICE BRITISH RAINFALL 1956 THE NINETY-SIXTH ANNUAL VOLUME OF THE BRITISH RAINFALL ORGANIZATION Report on the Distribution of Rain x^ in space and time over Great Britain and Northern Ireland during the year 1956 as recorded by about 5,000 observers WITH MAPS LONDON HER MAJESTY'S STATIONERY OFFICE 1958 © Crown copyright 1958 Published by HER MAJESTY'S STATIONERY OFFICE To be purchased from York House, Kingsway, London w.c.2 423 Oxford Street, London w.l 13A Castle Street, Edinburgh 2 109 St. Mary Street, Cardiff 39 King Street, Manchester 2 Tower Lane, Bristol 1 2 Edmund Street, Birmingham 3 80 Chichester Street, Belfast or from any bookseller Price £1 Is. 6d. net CONTENTS PAGE PAGE PART I PART H 1 THE WORK OF THE BRITISH RAINFALL EXPLANATORY NOTE . .95 AND HYDROLOGY BRANCH OF THE COUNTY INDEX TO GENERAL METEOROLOGICAL OFFICE TABLE . 97 British Rainfall — The Observers GENERAL TABLE: THE RAINFALL OF —Co-operation with other Bodies THE YEAR 98 — Snow Survey of Great Britain —Averages of Rainfall 1916-1950 — Surface Water Survey — River LIST OF ILLUSTRATIONS Boards — Inspections — Inquiries — Obituary .... 1 Relation of the Rainfall of 1956 to the Average (coloured plate) frontispiece 2 DISTRIBUTION OF RAIN IN TIME DAYS WITH RAIN ... 6 Distribution of Wet-Days in 1956 (map) 7 3 DROUGHTS AND DRY SPELLS . .12 Percentage of the Average in each Month in 1956 (12 maps) . 51-62 4 RAIN SPELLS AND WET SPELLS . 18 Percentage of the Average in the 5 DURATION OF RAINFALL . 22 Seasons 6 HEAVY FALLS IN SHORT PERIODS . 29 Winter Half-Year, 1955-1956 (map). 76 7 HEAVY FALLS ON RAINFALL DAYS . 38 Summer Half-Year, 1956 (map) . 77 8 MONTHLY RAINFALL . .48 Twelve Months, October 1955- 9 SEASONAL RAINFALL . .76 September 1956 (map)... 79 10 TOTAL FALL OF RAIN IN 1956 . 82 Total Rainfall in 1956 (map) . 83 11 EVAPORATION AND PERCOLATION . 86 Divisions used in British Rainfall (map) 94 in List of Principal Tables TABLE PART I PAGE TABLE PAGE 2A Wet-days over England and Wales, 7 A Maximum Daily Fall and Maxi 1942-1956 .... 8 mum Percentage, 1935-1956 . 38 2s Number of Rain-days and of Wet- ?B Largest Daily Rainfalls in 1956 . 39 days, 1956. (Monthly and Annual Values at 82 Stations) . 9 7c Falls of 7 inches or more in a Rainfall Day, 1865-1956. 39 SA Number of Droughts at 82 Sta tions, 1940-1956 . .13 SA General Rainfall for 1956 Monthly and Annual Values . 48 SB Number of Dry Spells at 82 Sta tions, 1940-1956 ... 14 SB General Monthly and Annual Averages of Rainfall, 1881-1915 49 3c Periods of Droughts and Dry Spells at 82 Stations, 1956 . .15 8c Monthly Rainfall at 334 Stations, 1956 ..... 63 4A Number of Rain Spells at 82 Sta tions, 1940-1956 . .19 So Monthly Rainfall in 1956 as Per 4B Number of Wet Spells at 82 Sta centage of Average (123 Stations, tions, 1940-1956 ... 19 together with General Values) . 72 4c Rain Spells and Wet Spells at 82 9A Seasonal Rainfall, 1955-1956, in Stations, 1956 . .20 Relation to Average . 78 5A Duration of Rainfall, 1956. 9s Serial Values of Seasonal Rainfall (Monthly and Annual Values at as Percentage of Average . 81 .... 24 145 Stations) 10A General Rainfall 1956 Compared SB Mean Rate of Rainfall, 1956. with Average .... 82 (Monthly and Annual Values 10s Rainfall of 1956 at 93 Stations as at 15 Stations) ... 28 Percentage of Average . 85 6A Lower Limits of Intense Rainfalls 29 HA Evaporation in 1956 at 14 Stations 89 6s Number of Noteworthy Rains of HB Rainfall, Percolation and Inferred Two Hours' Duration or less, Evaporation, 1956 . 90 1956 ..... 30 lie Drainage Gauge Records, 1956 . 91 6c Heavy Falls in Short Periods in 35 1956 ..... PART II 60 Number of Days on which Speci County Index to General Table . 97 fied Amounts of Rain fell in Specified Times, 1956 . 37 General Table ..... 98 IV BRITISH RAINFALL 1956 PART I 1 The Work of the British Rainfall and Hydrology Branch of the Meteorological Office "BRITISH RAINFALL." As mentioned in Returns are contributed either by private the previous volume the contents and lay-out persons who measure the rainfall primarily as were recently reviewed, but it has been decided a matter of personal interest, or by local not to make any major changes at present. agencies, especially the engineers of water- Developments which are now taking place, supply undertakings and, in England and however, may lead to some changes within a Wales, of river boards, who find that a know few years. The grid references of rainfall ledge of rainfall is essential to them in their stations are now being collected, and when work. The goodwill of the observers and they have all been obtained it is intended to authorities who voluntarily forward copies of publish them in the General Table (Part II of their observations for preservation is gratefully this volume). It should then be possible to acknowledged. Without their co-operation introduce a simplification of station names. the compilation of British Rainfall would not An important development which is now in its be possible. very early stages is the introduction of punched Most of the rainfall returns are sent by the cards and machine methods of analysis for observers direct to the Meteorological Office, rainfall data. New methods of summarizing but in some regions there are local organiza and presenting data, which are far too tions who considerably assist by collecting laborious to be practicable without the use of rainfall returns for forwarding to the Office machine methods, will be possible when the and by stimulating interest in weather record punched card programme is sufficiently ing. Such organizations include four old- developed. Finally, it is hoped that the established county rainfall associations, one of increasing interest in hydrology in Britain and which, for Somerset, is now merged with the elsewhere will, in the near future, be reflected corresponding river board organization. in the form and contents of British Rainfall, Several other river board engineers are now though the detailed arrangements have yet to acting in a similar way, collecting data from be worked out; suggestions from interested voluntary observers in their areas, as well as authorities outside the Meteorological Office from stations for which they are fully respon will be welcomed. sible. This is a development which is greatly to be welcomed. Although, as pointed out THE OBSERVERS. The information on the by Dr. H. R. Mill in British Rainfall 1910, rainfall in 1956 presented in this volume is "there is a good deal of county patriotism based on the collection of more than 5,000 which helps people to work for the credit of returns of rainfall received from all parts of the their county, and a river basin fails to make country. Not all of these are included in the the same appeal", nevertheless the river General Table, the Table being shortened by board areas form a more realistic division of the omission of returns from check gauges the country for the scientific application of the and of some records which are not complete. invaluable work done by rainfall observers. 1 BRITISH RAINFALL 1956 The time has come to move away from of the Ministry of Housing and Local Govern the hydrologically arbitrary division into ment and on the Joint Committee on Rainfall counties. and Run-off set up by the Department of Data for the new stations are included from Scientific and Industrial Research, Road private observers in all parts of Great Britain Research Board, and the Ministry of Housing and Northern Ireland, and among organiza and Local Government. tions which have established new stations are Co-operation has continued with the the Lee Conservancy Catchment Board, the Department of Scientific and Industrial Cheshire River Board, the Clydeside and Research, Road Research Laboratory, on District Water Trust and the River Tweed surface water drainage problems. Purification Board. The Nature Conservancy The aims of the Joint Committee on Rain contributed new returns from stations in fall and Run-off were outlined in British Wales and Scotland while the North of Scot Rainfall 1954. Local authorities for county land Hydro-Electric Board sent in additional and municipal boroughs were invited, by returns, mainly from Argyllshire. The most means of a circular issued through the important gains in the network of rainfall Ministry of Housing and Local Government, stations were a number in previously un to co-operate in a scheme, sponsored by the represented areas in north Scotland. Committee, to obtain more abundant and The total number of records printed in more accurate data on intense falls of rain in Part II of this volume is 4,982. There are all parts of the country. The subsequent 175 additional records while 242 records correspondence with engineers and surveyors printed in British Rainfall 1955 have dropped regarding the establishment of a network of out of the Table. open-scale rain recorders was handled by the The net loss in England was 24, in Wales 9, Meteorological Office and about 150 of the in Scotland 29, and in Northern Ireland 5, a local authorities agreed to take part, the total loss of 67. large majority with encouraging enthusiasm.