ANALYSIS OF PROJECTED DATA AND RAINFALL DISTRIBUTION OF 2010-2018
NAHRIM had previously carried out studies on the climate change projection for Peninsular Malaysia in 2014 (NAHRIM 2014)1, and for Sabah & Sarawak in 2010 (NAHRIM 2010). taking into consideration technical information set out in The Fourth Assessment Report (AR4) of the United Nations Intergovernmental Panel on Climate Change (IPCC) under greenhouse gas scenarios A1B, A2 and B1 for the projected period of 2010-2100. The scope of study includes the temporal yearly rainfall pattern projection with the previously mentioned climate models for both Peninsular Malaysia and Sabah & Sarawak. These were done encompassing the various future scenarios for the periods of 2014-2018 and 2018. The results obtained were analysed and discussed on the state basis and also on the station basis. The differences between the projected and observed yearly rainfall were compared to assess the accuracy of the projections. The performances of the climate models were then assessed through estimating the average percentages of the over-projection or under-projection for the 2014-2018 yearly rainfalls. Spatial distributions of the 2018 yearly rainfall projections and observations, and their respective differences, were also mapped and discussed. Figures 1.3a & 1.3b show the state boundaries for Peninsular Malaysia and division boundaries for Sabah & Sarawak, respectively. The study continued with detection of the yearly rainfall trend direction. The trends for both the observed and projected 2018 rainfall for all the stations were estimated using the Mann- Kendall test, followed with the comparison of results between the observations and the projections to assess the accuracy of the models. The Mann-Kendall test (Mann 1945, Kendall 1975) is to statistically determine whether the normally distributed or linear yearly rainfall series has a monotonic upward or downward trend. A monotonic upward trend would mean that the variable consistently increases with time. Conversely, the monotonic downward trend would indicate that the variable consistently decreases over time. The changes in the trend slope for both the observed and the projected 2018 yearly rainfall were then quantified for each station using the Sen’s slope method (Sen 19683). The Sen’s slope method is commonly used to determine the magnitude or significance of the trend slope detected in the Mann-Kendall test. Lastly, the spatial distributions of these changes were presented with comparison to evaluate the accuracy of model projections.
Authors
Abstract
NAHRIM had previously carried out studies on the climate change projection for Peninsular Malaysia in 2014 (NAHRIM 2014)1, and for Sabah & Sarawak in 2010 (NAHRIM 2010). taking into consideration technical information set out in The Fourth Assessment Report (AR4) of the United Nations Intergovernmental Panel on Climate Change (IPCC) under greenhouse gas scenarios A1B, A2 and B1 for the projected period of 2010-2100. The scope of study includes the temporal yearly rainfall pattern projection with the previously mentioned climate models for both Peninsular Malaysia and Sabah & Sarawak. These were done encompassing the various future scenarios for the periods of 2014-2018 and 2018. The results obtained were analysed and discussed on the state basis and also on the station basis. The differences between the projected and observed yearly rainfall were compared to assess the accuracy of the projections. The performances of the climate models were then assessed through estimating the average percentages of the over-projection or under-projection for the 2014-2018 yearly rainfalls. Spatial distributions of the 2018 yearly rainfall projections and observations, and their respective differences, were also mapped and discussed. Figures 1.3a & 1.3b show the state boundaries for Peninsular Malaysia and division boundaries for Sabah & Sarawak, respectively. The study continued with detection of the yearly rainfall trend direction. The trends for both the observed and projected 2018 rainfall for all the stations were estimated using the Mann- Kendall test, followed with the comparison of results between the observations and the projections to assess the accuracy of the models. The Mann-Kendall test (Mann 1945, Kendall 1975) is to statistically determine whether the normally distributed or linear yearly rainfall series has a monotonic upward or downward trend. A monotonic upward trend would mean that the variable consistently increases with time. Conversely, the monotonic downward trend would indicate that the variable consistently decreases over time. The changes in the trend slope for both the observed and the projected 2018 yearly rainfall were then quantified for each station using the Sen’s slope method (Sen 19683). The Sen’s slope method is commonly used to determine the magnitude or significance of the trend slope detected in the Mann-Kendall test. Lastly, the spatial distributions of these changes were presented with comparison to evaluate the accuracy of model projections.
Citation
NAHRIM. 2021. ANALYSIS OF PROJECTED DATA AND RAINFALL DISTRIBUTION OF 2010-2018. Digital NAHRIM Publication Repository.