| || || Keremama, Milton Galokale|
| || || Solomon Islands : historical and projected temperature and rainfall trends and variability|
Author:Keremama, Milton Galokale
Institution: University of the South Pacific.
Subject: Climatic changes -- Solomon Islands, Atmospheric temperature -- Solomon Islands, Rain and rainfall -- Solomon Islands
Call No.: pac QC 903 .2 .S6 K472 2013
Copyright:Under 10% of this thesis may be copied without the authors written permission
Abstract: This study summarizes the trends in temperature and rainfall between 1951 and 2011 of all 7 weather stations on 6 islands throughout the Solomon Islands. The study also examines the climate projections compiled by the Pacific Climate Change Science Program (PCCSP; BoM & CSIRO 2011b) to provide a comprehensive picture of historical and future climate for the Solomon Islands. Past regional-scale studies either ignore the climate data of the Solomon Islands, or use only one or two local stations to describe the full climate of the 100s of islands that comprise the Solomon Islands. This study is the first to include all 7 weather stations operated by the Solomon Islands Meteorological Service (SIMS) network. I examined all available daily digitised minimum and maximum surface air temperature and rainfall data between 1951 and 2011. Time series analyses of monthly, seasonally and annually averaged temperature and rainfall, and their respective extreme indices were done for each station. Graphs and tables were generated using Excel 2007. Statistical analyses of variables were conducted using R software. Five statistical tools were used: Regression analysis was used for trend analysis; Wilcoxon rank sum test was used to test the seasonal difference; one-way ANOVA and Tukey HSD tests were used to test the pairwise comparisions between stations; Ward’s method was used to cluster stations; Pearson’s correlation coefficient (r) was used to test the association of ENSO indices (Niño3.4 and SOI) with temperature and rainfall at the seasonal time scale. PCCSP-selected model generated changes for the future periods, 2030, 2055 and 2090 were used to calculate the likely magnitude of the average annual temperature, rainfalls and heavy rainfalls for the Solomon Islands. The average, maximum and minimum temperature for all 7 stations increased significantly over the time period of measurement. Overall, mean surface air temperature increased by 0.13 to 0.40°C/decade. There was a corresponding increase in the frequency of warm days and nights and a decrease in the frequency of cool days and nights for most of the stations. Averaged over the Solomon Islands, annual frequency of warm days has increased by 2.2 days/decade and warm nights by 0.8 nights/decade whereas the frequency of cool days has decreased by 0.4 days/decade and cool nights by 1.4 nights/decade. Rainfall trends were less spatially coherent than those of temperature. The annual total rainfall trend varied between -1.7 and +1.7%/decade. Likewise, the frequencies of extreme rainfalls showed no clear trends at most stations. The Taro, Munda and Lata stations, all found on outlying islands, experienced more rainfall than the stations of the central region. Significant seasonal variability in both temperature and rainfall were correlated with the ENSO indices. Temperature was most strongly impacted by ENSO during the dry season (May-October) whereas rainfall was strongly impacted by ENSO during the wet season (November-April). The South Pacific Convergence Zone (SPCZ) and the West Pacific Monsoon (WPM) impacted the wet season rainfall in the central and eastern stations more strongly than the western stations. Munda and Taro have a more pronounced July rainfall peak than all other stations, because of the strong influence of the Intertropical Convergence Zone (ITCZ). Taro’s wet and dry seasons were opposite to the wet and dry seasons of all other stations because of its proximity to the ITCZ. Overall, average annual temperature trends increased, whereas rainfall trends either increased or decreased marginally in the Solomon Islands from 1951 through 2011. Projected temperature and heavy rainfall return periods increase throughout the 21st century.