An examination of observed climatic trends/changes over Banks Peninsula and the surrounding plains area, and their synoptic climatology.

• Main Author: Jayet, D. F.
• Language: en
• Published: University of Canterbury. Department of Geography 2010
• Online Access: http://hdl.handle.net/10092/3866

Rainfall and temperature data were collected over the study area (approximately 50 sites ), using all existing climatic records, to analyse observed climatic trends/changes since instrumental records began. These trends, using multiple regression analysis, were then compared to changes in synoptic flow patterns based on daily surface charts for the 1929 to 1985 period. Results indicate that changes in synoptic flow pattern have a very significant impact on rainfall and temperature trends. Observed rainfall trends tend to show cyclic trends or spells of wet and dry periods. Comparison with the literature suggests that some of the observed 10 year rainfall trends were related to the sunspot cycle, such as the winter rainfall trend. However changes in synoptic flow patterns appear to be the most important factor influencing rainfall trends. Temperature trends show a much stronger relationship with synoptic flow patterns than rainfall,particularly for maximum temperature trends. Wet periods over the study area are categorised by increased cyclonic activity in combination with increased southerlies and or, easterly circulations while dry periods are related to anticyclonic conditions and increased westerly circulation. Southerly, and to a lesser exent easterly circulations, have the most significant influence on temperature trends with a negative impact. The synoptic climatology of daily rainfall patterns over the study area indicated that the dominant rain-bearing winds come from the southerly quarter, especially southwesterly airflows. Higher rainfall probability and significant daily rainfall totals occur under cyclonic conditions in association with southerly to northeasterly airflows while anticyclonic west to northerly airflows produce the lower values.