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Abstract:In order to gain an insight into the effects of air temperature on river water quality, data were statistically analysed using meteorological and river water quality data. Two types of data set were used for river water temperature. One type involved five sampling points within different rivers where water temperature data were obtained daily, and the other involved 82 sampling points located within 27 rivers where water temperature and other water quality data were obtained monthly. Influential factors for different time scales were investigated. From the analyses, the gradient of water temperature to air temperature considered on a daily scale was 0Ð1-0Ð5°C°C 1 and was influenced by the hydrological scale of the river basin. The gradient observed using an annual scale was 0Ð5-1Ð5°C°C 1 and was supposed to be influenced by solar radiation. Under the condition that solar radiation is constant, the gradient on an annual scale was predicted to be less than unity (0Ð5-0Ð85°C°C 1 ). As for the other indices, from the analysis on an annual scale, an increase in air temperature resulted in an increase in biological oxygen demand and suspended solids, and a decrease in dissolved oxygen in almost all rivers. Based on the results, it was suggested that global warming has a deteriorating effect on river water quality.

This paper examines the response of the climate of Small Island States (SIS) to transient increases in anthropogenic radiative forcing due to increases in atmospheric concentrations of greenhouse gases and/or sulfate aerosols using the data generated in a set of numerical experiments performed with a range of coupled atmosphere-ocean global climate models. Five of the 7 models considered in our validation exercise are found to have fair skill as regards their ability to simulate the broad features of present-day observed surface climatological features over the SIS in the Indian Ocean, the Mediterranean Sea, the Atlantic Ocean and the Pacific Ocean. The transient experiments with these models, which include the time-varying future anthropogenic radiative forcings, have been used here to develop regional projections of future climate change. An area-averaged annual mean warming of ca 2°C or higher for the 2050s and ca 3°C or higher for the 2080s are projected for the SIS as a consequence of increases in atmospheric concentration of greenhouse gases. In general, seasonal variations of the projected surface warming over the SIS are minimal. No significant change in diurnal temperature range is likely with an increase in surface temperatures. An increase in mean temperature would be accompanied by an increase in the frequency of extremely high temperatures. The aerosol forcing will only marginally reduce the surface warming. The models simulate only a marginal change (<10%) in annual mean rainfall over most of the SIS. During the northern hemisphere summer, however, rainfall is projected to decline (except over Pacific Ocean islands). An increase in daily rainfall intensity leading to more heavy rainfall events is also projected. The projected changes in temperature and rainfall could disrupt the terrestrial and marine ecosystems in most SIS. An integrated study of vulnerability assessment for SIS based on a better understanding of the precise magnitude of increase in surface air temperature and associated sea level rise is warranted for developing appropriate adaptation strategies.KEY WORDS: Global climate models · Regional climate change · Small Island States · Anthropogenic radiative forcings · Impact Assessment · Sea level rise Resale or republication not permitted without written consent of the publisher

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Abstract:In order to forecast the eects of global warming on the water environment, the relationship between meteorological conditions and lake water quality was investigated statistically using 17 years of monitoring data obtained from a shallow eutrophic lake, Lake Kasumigaura. The usefulness of the DPY (dierence from the previous year) method was con®rmed for removing the watershed change (e.g. land cover, population, etc.). From the analysis of the relationships between air temperature and water temperature on a monthly basis, the delay of time was seen to be negligible, but the gain was reduced due to the high frequency of change. As the amount of precipitation aected their relationship on a yearly basis, the slopes of 1 . 0±1 . 2 8C water temperature/ 8C air temperature were determined with the DPY method by excluding the combinations of the years having large dierence in annual precipitation. The deterioration of lake water quality, such as increases in COD (chemical oxygen demand) and decreases in transparency, was quantitatively assessed as corresponding to an increase in air temperature. In addition, we found that higher precipitation led to high nitrogen concentrations on a monthly basis, as well as on a yearly basis, probably induced by both the runo of soilwater having high concentrations and the lowering of residence times of lake water.

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