Palaeoclimate reconstruction is of paramount importance because the more we know about the patterns of past variability the better we understand the present climate. Precipitation is a key climate variable shaping the culture and economy of China. However, few studies are concerned with past changes in precipitation. The existing few are either reconstructed by one reconstruction approach or based on a single proxy, limiting reconstructions to a small region and a short period of time. The study presents the first high-resolution multi-proxy palaeoprecipitation reconstruction of China as a whole. Proxies used in the study are of annual-to-decadal resolution, mainly including historical written evidence, tree-ring chronologies and stable isotopic records. In accordance with the principle of “uniformity in the nature”, about 80 proxy series extend the precipitation records as far back in time as 2,000 years ago when there was a significant increase in natural proxy and documentary records of climate all over China. The top three popular reconstruction approaches are borrowed from multi-proxy temperature reconstructions to reconstruct the palaeoprecipitation. A pioneering attempt is taken to evaluate and compare these approaches in reconstructing precipitation over a long term in a large scale. The three common practices are respectively simple average, composite-plus-scale method, and covariance-based climate field reconstruction. All three reconstruction methods are modified catering to the unique characteristics of precipitation, especially in terms of its large spatial variance. Local reconstructions are carried out first before a national index in reconstructed. Though based on the same documentary and natural proxies, three reconstruction approaches adopt different rationales to decipher the precipitation variability, represented by different statistical models. Each model is assessed by conventional statistics and cross-compared. These models are found complementary to each other while the common shared among three models are considered the closest to the true precipitation condition. Though geographically biased to Eastern China, historical documents still capture the most inter-annual to multi-centennial variations in palaeoprecipitation, indicating the possible control of Asian Monsoon climate on China’s overall precipitation. Tree-ring widths preform worst due in part to the attribute of strong locality. Each reconstruction approach turns out to have its own strength and weakness. Three major falls at multi-centennial timescale are detected in most reconstructed precipitation series, which are at AD600-800, AD1000-1300 and AD1500-1700. Spectral analyses demonstrate a rhythmic pattern of around 400-500 years for all reconstructions. When the proxies are not extrapolated, an additional cycle of 700-800 years is significant in precipitation variability over the past 2,000 years. A cross-comparison with European reconstructions show a high agreement in precipitation variability for the past two millennia, leading to the suspect of dry Medieval Warm Period and wet Little Ice Age over the whole Eurasia. / published_or_final_version / Geography / Master / Master of Philosophy

Monthly and annual changes in precipitation in South China during 1990-2011 are examined in this study. As located in the sub-tropical climate zone, the annual rainfall in South China is concentrated in the summer. During the same period of time, an average of 9 tropical cyclones approaching South China each year which also contribute ample of rainfall to South China during the tropical cyclone season (June-September). Since the climatic system is interconnected, so this study attempts to examine the combined effect on inter annual rainfall variations in South China due to El Nino Southern Oscillation (ENSO), tropical cyclones affecting South China and the Asian Monsoon. It is generally agreed that during the El Nino onset years, South China would be more wetter, but with less than average tropical cyclones affecting South China. As such, effects on precipitation in South China caused by these two factors offsetting each other and data indicate there is no consistent trend of either more or less rainfall recorded for the El Nino onset years during 1990-2011. On the other hand, the first half of the year right after the El Nino years are in general more wetter than normal. This can be due to the lagging effect of El Nino events normally happened in the winter time, plus the fact that the strength of winter monsoon during the El Nino years is weak, resulting in more rainfall in the following year. Furthermore, annual changes in precipitation in South China directly affect the surface runoff of the Pearl River and a strong positive correlation between the two variables exists for the period 2000-2011. The +/- 25% annual variations and the seasonal variations of rainfall in South China post a challenge to the water resource management in the Pearl River Delta Region. Therefore dams and reservoirs built along the Pearl River are necessary to store surplus rainwater in order to supply sufficient fresh water to the Pearl River Delta Region during the dry seasons or years. On the other hand, further studies and monitoring programs are recommended to continue assessing and evaluating impacts of dam constructions to the environment and the ecosystem of the Pearl River Delta Region. / published_or_final_version / Applied Geosciences / Master / Master of Science