16 July，Dr. Adrian Simmons, Chair of the Steering Committee for the Global Climate Observing System. from European Centre for Medium-Range Weather Forecasts visited Institute of Earth Environment,CAS. Professor An Zhisheng, member of CAS, introduced to Dr. Simmons the history and development of IEECAS, the research fields and major achievements. They also chatted on the latest progresses of medium-range weather forecast.

Dr. Adrian Simmons presented a talk to staff and students of IEECAS on 16 July, titled "Reanalysis of trends and variability in temperature, humidity and precipitation over the past four decades". 

In his talk, Dr. Simmons briefly reviewed the development of atmospheric reanalysis -comprehensive records of atmospheric conditions synthesized from past meteorological observations using the systems employed today for numerical weather prediction, and presented low-frequency variability and trends in temperature and some aspects of the hydrological cycle. Dr. Simmons illustrated the remaining challenges posed by a changing in situ and space-based global observing system and by the presence of biases in observations, models and the way the data assimilation process brings them together.

Dr. Adrian Simmons is currently Coordinator of global environmental monitoring activities, he has extensive research and management experience in numerical modeling, data assimilation, reanalysis, predictability, dynamical meteorology and the use of high-performance computing.

（Photo by LIU Zhao）

（Photo by LIU Zhao）