A procedure for blending manual and correlation-based synoptic classifications

Abstract

Manual and correlation‐based (also known as Lund or Kirchhofer) classifications are important to synoptic climatology, but both have significant drawbacks. Manual classifications are inherently subjective and labour intensive, whereas correlation‐based classifications give the investigator little control over the map‐patterns generated by the computer. This paper develops a simple procedure that combines these two classification methods, thereby minimizing these weaknesses. The hybrid procedure utilizes a relatively short‐term manual classification to generate composite pressure surfaces, which are then used as seeds in a long‐term correlation‐based computer classification. Overall, the results show that the hybrid classification reproduces the manual classification while optimizing speed, objectivity and investigator control, thus suggesting that the hybrid procedure is superior to the manual or correlation classifications as they are currently used. More specifically, the results demonstrate little difference between the hybrid procedure and the original manual classification at monthly and longer time‐scales, with less internal variation in the hybrid types than in the subjective categories. However, the two classifications showed substantial differences at the daily level, not because of poor performance by the hybrid procedure, but because of errors introduced by the subjectivity of the manual classification. © 1997 Royal Meteorological Society. Int.J.Climatol., Vol.17, 1381‐1396 (No. of Figures: 9 No. of Tables: 1 No. of References: 30)

Classifications of Atmospheric Circulation Patterns

“…A correlation‐based assignment of cases subsequent to a manual designation of initial seed patterns was also used in Ref. 60. Neural networks have not been used for the objectivization of subjective catalogs, although their architecture most widely used in the atmospheric sciences, multilayer perceptron, can be applied to pattern classification and is superior to traditional classification approaches 62 .…”

Spatial patterns and regimes of daily precipitation in Iran in relation to large‐scale atmospheric circulation

“…Space‐time variability of precipitation in a region plays an essential role in water resource management, motivating many research efforts to identify large‐scale atmospheric circulation types leading to precipitation events and their effects on the frequency and amount of precipitation (Lamb, 1977; Bogardi et al , 1994; Frakes and Yarnal, 1997). Many authors have studied the possible linkages between large‐scale atmospheric circulation and precipitation (e.g.…”

Relationship between daily atmospheric circulation types and winter dry/wet spells in western Iran

“…In fact, during the Northern Hemisphere winter, mid‐latitude meteorological conditions are mainly modulated by the intense activity of the synoptic eddies along the storm tracks, which also govern many precipitation mechanisms. Since precipitation variability in a region plays an essential role in water resource management, many efforts have been undertaken in order to identify the large‐scale atmospheric circulation patterns leading to precipitation (Bogardi et al , 1994; Frakes and Yarnal, 1997; Lamb, 1977).…”