美国宇航局戈德飞行中心二氧化碳激光雷达的进展和最新飞机试验结果
时间：
2019年10月22日，10:00—11:00
地点：
物理大楼北楼539室 
 (Physics Building, Room N539)

报告人：毛建平
单位：NASA Goddard Space Flight Center
研究方向：大气遥感
卫星遥感地球大气中的二氧化碳是对卫星大气遥感极限的挑战，要求精度0.25%! 美国宇航局化了十几年时间研究和发展出了一套用激光雷达遥感大气二氧化碳的方法和技术，并做了多次飞机试验。这个报告将介绍这套主动遥感技术的思路和特点，并展示近期飞机试验的分析结果。这套高精度的大气遥感系统可做全球二氧化碳浓度的全天候观测，不管有云没云，海洋陆地，高纬低纬，冬天夏天，白天黑夜，这必将大力推进碳循环的研究。
Statistical physics approach to Earth complex systems
时间：
2019年10月23日，15:00—16:00
地点：
物理大楼北楼547室 
 (Physics Building, Room N547)
报告人：Dr. Jingfang Fan
单位：Postdoctoral research associate in Potsdam Institute for Climate Impact Research (Germany)
研究方向：Statistical physics and complex systems
Global climate change, extreme weather events, earthquakes and the accompanying natural disasters pose significant risks to humanity. Due to the nonlinear and complex structure of the Earth system, the understanding and especially the forecasting of such events represent formidable challenges for the scientific community.  During the past years, we have developed and implemented sophisticated statistical physics and complex network based techniques to advance our knowledge about the Earth system, e.g., climate extreme events, earthquakes and Earth Geometric Relief features, leading to substantially improved predictive performance. In this talk, I wish to provide a review of how combined statistical physics approaches (critical phenomena, network theory, percolation, scaling theory, etc.) can be applied to Earth’s complex systems (climate, earthquakes and beyond). Combining different statistical physics-based methods can provide new insights and perspectives on the dynamics of the Earth systems and even enable more reliable forecasts.
A stratospheric pathway linking a colder Siberia to Barents-Kara Sea sea ice loss
时间：
2019年10月23日，16:00—17:00
地点：
物理大楼北楼547室 
 (Physics Building, Room N547)
报告人：Dr. Pengfei Zhang
单 位：Postdoc at University of California, Los Angeles
研究方向：气候动力、气候变化
Previous studies have extensively investigated the impact of Arctic sea ice anomalies on the midlatitude circulation and associated surface climate in winter. However, there is an ongoing scientific debate regarding whether and how sea ice retreat results in the observed cold anomaly over the adjacent continents. We present a robust “cold Siberia” pattern in the winter following sea ice loss over the Barents-Kara seas in late autumn in an advanced atmospheric general circulation model, with a well-resolved stratosphere. Additional targeted experiments re- veal that the stratospheric response to sea ice forcing is crucial in the development of cold conditions over Siberia, indicating the dominant role of the stratospheric pathway compared with the direct response within the troposphere. In particular, the downward influence of the stratospheric circulation anomaly significantly intensifies the ridge near the Ural Mountains and the trough over East Asia. The persistently intensified ridge and trough favor more frequent cold air outbreaks and colder winters over Siberia. This finding has important implications for improving seasonal climate prediction of midlatitude cold events. The results also suggest that the model performance in representing the stratosphere-troposphere coupling could be an important source of the discrepancy between recent studies. I will talk about some recent progresses if time permits. 
北京大学大气与海洋科学系
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