As a Percentage of the Average for the \Ears 1881-1915 M.O
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As a percentage of the average for the \ears 1881-1915 M.O. 663 AIR MINISTRY METEOROLOGICAL OFFICE BRITISH RAINFALL 1957 THE NINETY-SEVENTH ANNUAL VOLUME A .,, , .-.».<•& fcno't/O Report on the Distribution of Rain in space and time over Great Britain and Northern Ireland during the year 1957 as recorded by about 5,000 observers WITH MAPS LONDON HER MAJESTY'S STATIONERY OFFICE 1960 © Crown copyright 1960 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 1 or from any bookseller Price £1 \2s. 6d. net CONTENTS PAGE PAGE PART I GENERAL TABLE: THE RAINFALL OF THE YEAR . .115 1 THE WORK OF THE BRITISH RAINFALL AND HYDROLOGY BRANCH OF THE PART III METEOROLOGICAL OFFICE British Rainfall — The Observers SNOW SURVEY OF GREAT BRITAIN, SEASON —Co-operation with other Bodies 1956-57 . .233 — Snow Survey of Great Britain THE VARIANCE OF EVAPORATION, RAIN —Averages of Rainfall 1916-1950 FALL, SOIL MOISTURE DEFICIT AND — Surface Water Survey — Dr. J. RUN-OFF By G. Stanhill . .240 Glasspoole—Inspections—Inquiries — Obituary .... 1 LIST OF ILLUSTRATIONS 2 DISTRIBUTION OF RAIN IN TIME Relation of the Rainfall of 1957 to the DAYS WITH RAIN ... 6 Average (coloured plate) frontispiece 3 DROUGHTS AND DRY SPELLS . .12 Distribution of Wet-Days in 1957 (map) 7 4 RAIN SPELLS AND WET SPELLS . 20 Rainfall January 31 (map) . 50 5 DURATION OF RAINFALL . 26 Rainfall August 10 (map) . 53 6 HEAVY FALLS IN SHORT PERIODS . 35 Rainfall August 12 (map) . 54 7 HEAVY FALLS ON RAINFALL DAYS . 46 Rainfall December 19 (map) . 59 Average in each RAINFALL . ; .60 Percentage of the 8 MONTHLY Month in 1957 (12 maps) . 67-78 . 92 9 SEASONAL RAINFALL Percentage of the Average in the 10 TOTAL FALL OF RAIN IN 1957 . 99 Seasons 11 EVAPORATION AND PERCOLATION . 103 Winter Half-Year, 1956-1957 (map) . 94 Summer Half-Year, 1957 (map) . 95 PART H Twelve Months, October 1956- INDEX TO DIVISION AND COUNTY MAP . Ill September 1957 (map)... 96 EXPLANATORY NOTE . .112 Total Rainfall in 1957 (map) . 100 COUNTY INDEX TO GENERAL TABLE .114 Divisions used in British Rainfall (map) 110 in List of Principal Tables TABLE PART I PAGE TABLE PAGE 2A Wet-days over England and Wales, 7A Maximum Daily Fall and Maxi 1943-1957 .... 8 mum Percentage, 1935-1957 . 46 2e Number of Rain-days and of Wet- 7s Largest Daily Rainfalls in 1957 . 47 days, 1957. (Monthly and Annual Values at 82 Stations) . 9 7c Falls of 7 inches or more in a SAB Number of Droughts at 82 Sta Rainfall Day, 1865-1957 . 47 tions, 1940-1957 . .13 SA General Rainfall for 1957 3c Periods of Droughts and Dry Spells Monthly and Annual Values . 60 at 82 Stations, 1957 . 14 SB General Monthly and Annual 4AB Number of Rain Spells at 82 Sta tions, 1940-1957 ... 21 Averages of Rainfall, 1881-1915 61 4c Rain Spells and Wet Spells at 82 8c Monthly Rainfall at 334 Stations, Stations, 1957 . .22 1957 ..... 79 5A Duration of Rainfall, 1957. 80 Monthly Rainfall in 1957 as Per (Monthly and Annual Values at centage of Average (123 Stations, 145 Stations) .... 28 together with General Values) . 88 SB Mean Rate of Rainfall, 1957. (Monthly and Annual Values 9A Seasonal Rainfall, 1956-1957, in at 15 Stations) ... 32 Relation to Average . 97 5c Mean Monthly and Annual Dura 9B Serial Values of Seasonal Rainfall tion of Rainfall in hours, 1941- as Percentage of Average . 98 1950 ..... 33 10A General Rainfall 1957 Compared 5o Mean Monthly and Annual Rates with Average .... 99 of Rainfall in in. an hour . 34 10B Rainfall of 1957 at 93 Stations as 6A Lower Limits of Intense Rainfalls 35 Percentage of Average . .102 6s Heavy Falls in Short Periods in 1957 ..... 40 HA Evaporation in 1957 . .105 6c Heavy Falls in Short Periods in HB Rainfall, Percolation and Inferred 1957 Supplementary List . 41 Evaporation, 1957 . .106 60 Number of Days on which Speci lie Drainage Gauge Records, 1957 . 107 fied Amounts of Rain fell in Specified Times, 1957 . 42 6E "Very Rare" Falls, 1936-50 . 43 PART II 6F Mean number of days per annum Index to Division and County Map . Ill on which specified amounts of County Index to General Table . 114 rain fell in specified times, 1937- 1956 ..... 45 General Table . .115 IV L 1957 1 The Work of the British Rainfall and Hydrology Branch of the Meteorological Office "BRITISH RAINFALL." Some important detailed nature which is now going on, in changes are introduced in this volume of order to provide readily available accurate British Rainfall. They represent the early information for future rainfall work, accounts stages of a general scheme of development in largely for the delays which are occurring in the processing and presentation of rainfall the preparation of current volumes of British data now being planned, which was briefly Rainfall. Apologies are offered for these foreshadowed in British Rainfall 1956. delays in the confident expectation that they In the General Table forming Part II of this will be justified within a few years by the more volume, particulars of the instruments installed prompt publication of an improved version of at stations have been omitted in order to British Rainfall. Unfortunately it was not make room for the grid references of stations. possible to secure acceptable grid references The details omitted are now standard for the from all rainfall observers and authorities in majority of stations; diameter of gauge 5 in. time for inclusion in the present volume. It and height of rim above ground 1 ft. A was considered proper, however, to go forward moderate number of 8 in. diameter gauges are with the plan with about 80 per cent of the still in use, there are still a few gauges of other references available, and with the intention of diameters, and there is still a regrettably large improving the list in each subsequent year. minority of stations where the run is not at the In this respect improvement must of course standard height of 1 ft. But continued pro also refer to accuracy in the references pub gress towards complete standardization can be lished. It is too much to hope that the expected, and as a result of a greatly intensified accuracy aimed for, in the 100-metre form of programme of inspections in recent years the reference adopted, has been uniformly decreasing number of non-standard stations achieved in this first step. Corrections will at can no longer be regarded as important, not at all times be welcomed. any rate to the extent that much valuable space The grid references of rainfall stations will can be used year after year simply to draw be particularly useful in special work of many attention to these stations. A proposal for kinds (in connection for instance with flood the future is that any station which is non- investigations and water-supply problems) for standard in any way will be simply marked which large-scale maps are used. The form with an asterisk in the General Table, and any of reference adopted aims at an accuracy fully detailed information about the station which appropriate for 1 in. to the mile (1:63,360) may be required will be available from the Ordnance Survey maps (or any smaller scale). Meteorological Office. This degree of accuracy will also serve with The collection and checking of the grid 1:25,000, or tolerably well even with 6 in. to references of rainfall stations, which are now the mile (1:10,560) O.S. maps, which are being published for the first time, was a very occasionally used. Such special work rarely large task. This and other work of similar appears in published form, however, at any 1 BRITISH RAINFALL 1957 rate with full-scale reproduction of the basic a number of decades. Where large amounts maps. The same also applies to much of the of data are handled annually by the old con routine rainfall work of the Meteorological ventional methods, it is necessary for statistical Office on the ^ in. and i in. to the mile scales purposes to adopt certain fixed conventions, of gridded maps. But the increasing emphasis which may often be quite arbitrary. It has on accurate large-scale map work has been been only with great reluctance that some of reflected in a complete review of all mapping these arbitrary statistical definitions have been techniques in rainfall work; for the general retained for so long, since misunderstanding monthly and annual routine of plotting rain can easily arise through confusion between fall maps (in inches) over the United Kingdom, the statistical definition of a term and either a a gridded map on the scale of 1:625,000 popular usage or some other quite justifiable (approximately 1/10 in. to the mile) has now application of the same term. Confusion of been adopted as standard. This is a great this kind has arisen, for instance, in connection improvement on the old standard map, for with the terms "drought" and "wet-day". such routine work, on a scale of 1/16 in. to the When sufficient data are available hi a form mile. The introduction of the new base map suitable for analysis by machine methods, has been accompanied by a revision of the the need for fixed statistical definitions will form of map used for reproduction in British disappear.