Pemanfaatan luaran RegCM3 untuk kajian dampak perubahan iklim terhadap perubahan waktu dan pola tanam padi di Jawa Barat
Abstract
Climate change could be indicated by the shifting in the patterns of climate variables, such as air temperature and rainfall in the long term. The changes of those two variables could affect water balance, which will impact agricultural management systems, especially related to planting time and cropping patterns. This research aims to study future climate change projections and their impact on the changing of planting time and cropping patterns in West Java. The analysis is based on the Thornhtwaite Mather water balance model calculated by using climate data from the output of regional climate model, namely RegCM3. The RegCM3 output shows a rainfall decrease in West Java ranging from 4.53% to 8.16%. The changes of rainfall pattern in the future are projected to increase during wet seasons and will decrease during transitional and dry seasons, with shorter rainfall peak of wet seasons and longer peak of dry seasons. The temperature in West Java is also projected to change in the future showed by a very significant increase compared to the reference period. Based on the observational data, the temperature trends in the region has showed an increase, ranging from 0.0174 °C/year to 0.0216 °C/year during 1985-1999 periods. Water balance are analyzed on three different areas in West Java based on the rainfall patterns defined by cluster analysis (cluster C1, C2, and C3). C1 rainfall pattern is a region with low rainfall, C2 with medium rainfall, and C3 with high rainfall. Based on the calculation of water balance in the future under SRES A1B scenario, it is shown that the planting time will be potentially delayed from 40 to 51 days especially in C1 and C2 regions, while there is no change of planting time in C3 region. In addition, the cropping pattern will also change in the future due to the change in water balance. Initial determination of growing season will experience a setback, which ranges from one to two of ten days period in C1 and C2 region with cropping patterns changing from paddy-paddy-fallow to paddy-fallow-fallow in C2 region.