Abstract:The main objective of this study is to assess the spatio-temporal dynamics of land cover/land use changes in the lower Mekong Delta over the last 40 years with the coastal Tran Van Thoi District of Ca Mau Province, Vietnam as a case study. Land cover/land use change dynamics are derived from moderate to high spatial resolution (Landsat and SPOT) satellite imagery in six time intervals ranging from 1973 to 2011. Multi-temporal satellite images were collected, georeferenced, classified using per-pixel method, validated, and compared in post classification for the land use/land cover change detection in decades. Seven major land cover/land use classes were obtained, including cultivated lands, aquaculture ponds, mangrove forest, melaleuca forest, built up areas, bare lands, and natural water bodies. The accuracies of the land cover/land use maps for

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In this study, change in rainfall, temperature and river discharge are analysed over the last three decades in Central Vietnam. Trends and rainfall indices are evaluated using non‐parametric tests at different temporal levels. To overcome the sparse locally available network, the high resolution APHRODITE gridded dataset is used in addition to the existing rain gauges. Finally, existing linkages between discharge changes and trends in rainfall and temperature are explored. Results are indicative of an intensification of rainfall (+15%/decade), with more extreme and longer events. A significant increase in winter rainfall and a decrease in consecutive dry days provides strong evidence for a lengthening wet season in Central Vietnam. In addition, trends based on APHRODITE suggest a strong orographic signal in winter and annual trends. These results underline the local variability in the impacts of climatic change at the global scale. Consequently, it is important that change detection investigations are conducted at the local scale. A very weak signal is detected in the trend of minimum temperature (+0.2°C/decade). River discharge trends show an increase in mean discharge (31 to 35%/decade) over the last decades. Between 54 and 74% of this increase is explained by the increase in precipitation. The maximum discharge also responds significantly to precipitation changes leading to a lengthened wet season and an increase in extreme rainfall events. Such trends can be linked with a likely increase in floods in Central Vietnam, which is important for future adaptation planning and management and flood preparedness in the region. Copyright © 2012 John Wiley & Sons, Ltd.

This article presents an assessment of the skill of regional climate model PRECIS in simulating seasonal climate over Vietnam. The simulations were conducted at a horizontal resolution of 25 km × 25 km. The model simulations were forced by the ERA-Interim reanalysis and five members of the Hadley Centre's perturbed physics ensemble (PPE). CRU, APHRODITE, ERA40 datasets and observations recorded at 61 meteorological stations over Vietnam were used to validate the model. The analysis compared seasonal averages of observed and simulated precipitation, temperature, 850 hPa wind speed and direction, as well as the 99th percentile of daily precipitation and the 95th and 5th percentile of daily minimum and maximum temperatures. Annual cycles of temperature and precipitation, and the interannual variability of precipitation were also assessed. The reanalysis-driven simulation accurately reproduced most of the important characteristics of the observed spatial patterns and annual cycles of circulation rainfall and temperature as well as capturing key characteristics of interannual variability in rainfall and of extremes in precipitation and temperature. Some apparent systematic cool biases were found most likely to be an artefact of inadequacies in the CRU-gridded temperature observations. The regional model was found to introduce some systematic wet-biases in rainfall. The five GCM driven simulations demonstrated errors with similar characteristics to the ERA-Interim-driven simulations, although with diversity in the magnitude of those errors resulting from the differences in the characteristics of the different members of the HadCM3-based PPE. By assessing the skill of these models at producing realistic baseline simulations, we gain valuable contextual information to guide the application and interpretation of the future projections over Vietnam generated using these models.

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