Types and spells of weather around the year in the British Isles : Annual trends, seasonal structure of the year, singularities

Abstract

SUMMARYFrom a classification of 50 years' daily weather maps (1898 -1947) the outstandingly long spells of weather, lasting over 25 days, have been picked out. Frequency curves show the occurrences of these long spells on each day of the year and also the occurrences of each of the seven defined weather-types individually. This leads to a suggested division of the year into five periods, to be considered as natural seasons, and appears to support the definition of more numerous shorter seasonal phases or episodes (singularities). Good correspondence is found with the long-year daily or weekly mean figures of pressure, temperature, rainfall, sunshine, etc. The significance of these phenomena, their dependability as regards date and their secular persistence are discussed. The curves presented in this paper show the varying frequencies of occurrence on each day of the year of these different types of weather pattern; and of long spells defined in terms of them.T o the material which came to hand in this way the writer has added a further classification, in which the cyclonic type (C) has been introduced. The frequency curves for this type therefore represent an alternative classification of certain days' weather maps.We shall find that consideration of the frequency curves brings out a number of evident seasonal trends, which we may use to define certain " natural seasons."A still finer subdivision of the year into rather over twenty shorter seasonal phases or episodes, agreeing with known singularities (recurrent features) in the annual cycle of weather in Europe, also seems to be suggested.Finally we shall seek to bring these facts into their right perspective with previous work and existing knowledge. Statistical work of this kind does not lead to positive forecasts of the weather on a particular day in a given year, any more than one would say that a particular day will be sunny and warm merely because it falls in summer ; but it may nevertheless be a reasonable and sound guide to the wisest choice of dates for activities that have to be planned long in advance. Our chief obiect however will be to gain knowledge of the more detailed structure of our climate and to look for pointers to a fuller understanding of the underlying causes and processes at work over the hemisphere at large. 393

The relationship between monthly and seasonal South‐west England rainfall anomalies and concurrent North Atlantic sea surface temperatures

“…Consequently, winds from the northerly and easterly quadrants are more frequent during spring months (Lamb, 1950(Lamb, , 1972. For instance, on 22.71% of spring days (MAM) during the period 1950-97 the wind direction over the British Isles was in the northerly quadrant (Jenkinson and Collison, 1977).…”

On two different objective procedures for classifying synoptic weather types over east Australia

“…The techniques used for classification can be purely manual (subjective; e.g. Lamb, 1950), computer-assisted (often described as 'objective', although subjective decisions are still unavoidable; e.g. Key and Crane, 1986), or a mixture of both (hybrid; e.g.…”

Relative impacts of land use and climate change on summer precipitation in the Netherlands

“…We make use of the nine-type JenkinsonCollison types (JCT) classification scheme. This method was developed by Jenkinson and Collison (1977) and is intended to provide an objective scheme that acceptably reproduces the subjective Lamb weather types (Jones et al, 1993;Lamb, 1950). The classification has eight weather types (WTs) representative of the prevailing wind direction (W, NW, N, NE, E, SE, S, and SW, where W = 1, etc.)…”