报告时间：12月27日（周四）上午11:00-12:00
报告地点：天津大学地科院（第16教学楼）221报告厅
主讲嘉宾：何少能 博士
报告摘要：
In tropical regions, anti-correlation between precipitation isotopes and rainfall amount or the “amount effect” has long been considered the major control of precipitation isotopes. However, it failed to explain the paleoclimate archives in tropical regions. Recent observation of daily precipitation and events reveals rather weak or no amount effect, and physical processes associated with atmospheric convection are believed more important. Isotope enabled climate models can reproduce the global distribution of mean annual isotope contents of modern precipitation reasonably well but tend to overestimate the amount effect in the tropics. These divergent findings show how limited our understanding is of stable isotopes of present-day precipitation and complexities of atmospheric and climate processes in the tropics. Earth Observatory of Singapore has an on-going research project - long-term monitoring stable isotopes of daily precipitation over Southeast Asia. The main objective is to understand the drivers of spatial and temporal variations in stable isotopic compositions of precipitation in the region. Such knowledge will help us to interpret past climate archives and understand regional to global climate dynamics, which can be used to predict future scenarios, particularly water resource sustainability.
Advance in analytical techniques makes it possible to accurately measure δ17O and thus to get more accurate 17Oexcess (17Oexcess=ln(17O+1)-0.528ln(18O+1)), a new tracer of hydrological cycle. 17Oexcess is independent of temperature at source region and therefore is considered a good tracer of humidity in moisture source region. In the polar region, kinetic fractionation due to high super-saturation under low temperature conditions is considered the primary control of 17Oexcess. Therefore, 17Oexcess has potential in hydrological studies to provide independent information on fractionation during evaporation, in transport and in the formation and deposition of precipitation. In our study, we also investigate 17Oexcess of precipitation in Singapore to obtain information about tropical precipitation and convection.
嘉宾简介：
Dr. Shaoneng He graduated from the University of Western Ontario in Canada with a Ph.D in stable isotope geochemistry and petroleum geology. Then, Dr. He worked as a senior scientist with Zymax Forensics, Sports Medicine Research and Testing Laboratory, and UC Davis Stable Isotope Facility with a focus on compound specific isotope analysis and its application. In 2012, he joined the Earth Observatory of Singapore (EOS) as a senior research fellow. In Singapore, Dr. He continues to pursue his research in stable isotope geochemistry. Currently, he is working on the controls of temporal and spatial variations in stable isotope composition of precipitation in Southeast Asia. He is also studying stable isotopes of nitrate in precipitation in Singapore to understand the source of nitrate in the region.
