Evaluation of Relationships between Precipitation, Temperature in Fukuoka and Climate Patterns

A number of studies have discussed connections between El Nino phenomenon and unusual weather. Although El Nino phenomenon has obvious impacts on weather of the low-latitude area surrounding the Pacific, the connections between El nino and unusual weather in mid-latitude area are not fully understood. The distance between mid-latitude and the area where the El Nino happens would be crucial reason why their relationships are rather obscure. Moreover, the weather in mid-latitude is not only affected by El Nino but also by several other kinds of climate factors such as intensity of Aleutian low pressure system. These complexities also obscure the influence of El Nino on the weather in mid-latitude and impose the need of considering several kinds of climate phenomena simultaneously in order to understand the unusual weather in mid-latitude. This study has two objectives. The first objective is to classify climate patterns in the past using non-linear classification method, which is Self-Organizing Maps. The Self-Organizing Maps (SOM) algorithm is utilized as a classification method, because the SOM is capable of classifying high dimensional data on low dimensional arrays, enabling us to recognize hidden patterns in high dimensional data. The second objective of this study is to investigate the possible relationships between the classified climate patterns and rainfall and temperature in the city of Fukuoka, Japan. In order to classify climate patterns, we use several kinds of climate indicators, namely the Southern Oscillation Index (SOI), Pacific Decadal Oscillation Index (PDOI), North Pacific Index (NPI), and Dipole Mode Index (DMI) for the period 1901 to 2002. The application of SOM for these indices detects climate patterns which occurred during the first two decades of the twentieth century and also detects the patterns which have been observed since the 1960s. Investigation of the relationships between the identified climate pattern and rainfall and temperature in Fukuoka reveals that when La Nina phenomenon happens, PDO is in strong negative phase, the development of Aleutian low is weak and dipole mode in the Indian Ocean is in strong negative mode, AMJ (April, May and June) and JAS (July, August and September) temperature of Fukuoka in the next year tend to become extremely low.