应环境变化与地表过程重点实验室田立德研究员邀请, 清华大学Jonathon S. Wright博士前来我所交流并作学术报告。
报告题目：Diagnosing the Role of Transpiration in the Transition from Dry to Wet Season Over the Amazon
讲座教授：Dr. Jonathon S. Wright
Center for Earth System Science, Tsinghua University
地 点： 所办公楼915会议室
时 间： 2013年11月8日(星期五) 15:00-17:00
Reanalysis data indicates that land surface evapotranspiration plays a key role in determining the timing of wet season onset over the Amazon. Here, we use satellite observations of water vapor and its stable isotopes, carbon dioxide, leaf area index, clouds, and precipitation together with reanalysis data to explore the importance of transpiration in initiating the transition from dry season to wet season over the Amazon. The growth of vegetation in this region is primarily limited by the availability of sunlight rather than the availability of soil moisture, so that the increase of solar radiation during the late dry season is accompanied by dramatic increases in leaf area index within forested ecosystems. This period of plant growth is accompanied by uptake of carbon dioxide and enrichment of heavy isotopes in water vapor, particularly near the land surface. Reanalysis data indicate that this pre-wet season enrichment of HDO is accompanied by sharp increases in the surface latent heat flux, which triggers progressively increasing moist convective activity. The transport of transpiration-enriched near-surface air by this convection can be identified in a dramatic increase in free-tropospheric HDO in late August and September. The increase in convective activity during this period creates convergence, enhancing moisture transport into the region and initiating the wet season, when large amounts of precipitation deplete heavy isotopes at both levels in the troposphere.