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Summary: Oxygen and hydrogen stable isotopes (δ 18O and δD) in precipitation collected in every event from 2007 to 2009 in Guangzhou, South China, are presented in this paper. The total correlation between δ 18O and δD is obtained as δD =(8.46±0.13) δ 18O+(15.0±0.9). More negative δ 18O and δD generally occur during summer and autumn, while less negative or even positive δ 18O and δD occur during winter and spring. Significant negative correlations between precipitation δ 18O and temperature, and between precipitation δ 18O and precipitation amount are observed. Regression line changes from year to year are likely due to changes in moisture sources for the precipitation. The moisture contributed by adjacent seas or local evaporation account for the main precipitation during winter and early spring, while summer monsoon brings huge amounts of moisture from remote seas associated with higher temperature and larger precipitation amounts. Seasonal variations of the precipitation D-excess provide more details for changes in moisture sources. Higher D-excess values during winter and early spring are estimated to correspond to a lesser proportion of remote moisture, while lower D-excess values during summer and autumn correspond to larger remote moisture transported by summer monsoons. This generally agrees with the results of model analysis on single isobaric backward trajectories for air parcels during specific time periods. Results of this study imply that precipitation δ 18O and δD, as well as some related paleoclimate proxies such as δ 18O in speleothem and tree ring, and δD in plant-derived organic compounds and tree ring, currently cannot indicate changes in temperature or precipitation amount separately, but should be comprehensive proxies for monsoon climate. [ABSTRACT FROM AUTHOR]

Summary: Alpine meadows in the upper catchments of the Yangtze River, China provide critical amounts of water to maintain regional water resources, but little is known about the hydrological processes in these alpine ecosystems. In this paper, we analyzed the sources of precipitation in an alpine meadow using the deuterium excess in rain, fog, soil water, shallow groundwater and stream water. Rain and fog in the alpine meadow had high deuterium excess, 35‰ and 38‰ compared to 10‰ of precipitation brought by monsoon at lower elevation. These high values suggested that a large part of rain at the alpine meadow derived from secondarily evaporated water and that fog derived from the evaporated water produced shortly after rain events. However, averaged evaporation rate calculated by an isotopic mass balance model of soil water was only 0.26mm/d, about 3.6% of the rainfall and 7.57‰ of the average deuterium excess value of rain. The contribution from evaporated water to precipitation in the alpine meadow therefore had to be mainly from sub-alpine vegetations in the region. This eco-hydrological relation between sub-alpine and alpine ecosystems can partly explain the high water yield of the alpine meadow and should be considered for regional resource management. [Copyright &y& Elsevier]