西北干旱区陆—气相互作用试验(NWC-ALIEX)及其研究进展

简要阐述了国家重点基础研究发展规划项目“我国重大气候和天气灾害形成机理和预测理论的研究”支持的“我国西北干旱区陆—气相互作用野外试验(NWC ALIEX)”的科学意义、试验方案和科学目标,总结了该试验在最近几年取得的部分研究进展和研究成果,概括叙述了该项目在地表辐射平衡和热量平衡、总体输送系数、陆面过程参数、湍流通量参数化和地表水分循环以及陆面过程模式的改进和陆面过程的模拟等许多方面的重要发现和一些新的认识。最后,提出并讨论了在干旱区陆面过程方面需要进一步研究和思考的一些重要科学问题。

陆—气相互作用研究展望

综述了陆—气相互作用在观测、机制和模型方面的最新进展,指出现有陆—气相互作用观测研究没有同时考虑陆面生理生态与大气边界层变化对陆—气通量的影响,制约了陆面过程参数化或参数的卫星遥感反演以及陆面过程模式的业务应用。从全面认识陆—气相互作用与陆面过程模式发展出发,指出未来需进一步强化陆面生理生态与大气边界层变化对陆—气相互作用的影响研究以及陆面过程模式的业务应用研究,并提出了拟关注的重点任务:①陆—气相互作用的跨界面立体观测;②多源数据在跨界面陆—气相互作用中的应用;③陆面过程模式发展与业务应用。

论我国夏季风影响过渡区及其陆—气相互作用问题

我国季风影响过渡区既是典型的生态过渡区和生态环境脆弱带,也是我国干旱和水土流失最为严重的区域,其陆—气相互作用在天气气候演变过程中扮演着重要角色,所以该特殊区域陆—气相互作用研究是一个重要的科学问题。为此,国家自然科学基金重点资助"我国典型夏季风影响过渡区陆—气相互作用及其对夏季风响应研究"课题专门针对此问题开展研究。在归纳我国夏季风活动的特点、夏季风影响过渡区的形成及其气候环境特征的基础上,总结了目前夏季风影响过渡区及其陆—气相互作用研究进展,综合分析了该地区陆—气相互作用的特殊性。并且提出了该领域研究存在的主要科学问题及未来的研究方向。这对今后深入研究我国夏季风影响过渡区陆—气相互作用问题具有科学指导意义。

欧亚北部冬季增雪“影响”我国夏季气候异常的机理研究:欧洲冬季增雪的重要作用

在作者前期研究(穆松宁和周广庆,2012)的基础之上,本文主要利用了EOF分析和相关分析,对欧亚北部冬季新增雪盖面积(Total Fresh Snow Extent,记为TFSE)与我国夏季气候异常之间"隔季相关"的机理进行了更进一步的探讨,主要目的在于寻找TFSE气候效应的冬季增雪面积关键区。结果表明,虽然欧洲中纬冬季增雪面积(文中均以TFSE-1表示)与我国夏季气候异常的关系不很显著,但其变化维系了上述"隔季相关"的物理途径,其变化对TFSE的气候效应而言起关键作用,但是,亚洲中纬冬季增雪面积(文中均以TFSE-2表示)的贡献尚不清楚;另外,对TFSE的气候效应而言,起作用的实际上是欧亚中纬冬季增雪面积(文中均以TFSE-1-2表示),其不但与我国夏季气候异常具有更显著的"隔季相关",而且这种"隔季相关"还具有和TFSE非常相似的、但更为清晰的物理途径,因此,在气候预测的意义上,TFSE-1-2可替代TFSE。

Quantifying the impacts of fire aerosols on global terrestrial ecosystem productivity with the fully-coupled Earth system model CESM

Fire is a global phenomenon and a major source of aerosols from the terrestrial biosphere to the atmosphere.Most previous studies quantified the effect of fire aerosols on climate and atmospheric circulation,or on the regional and site-scale terrestrial ecosystem productivity.So far,only one work has quantified their global impacts on terrestrial ecosystem productivity based on offline simulations,which,however,did not consider the impacts of aerosol–cloud interactions and aerosol–climate feedbacks.This study quantitatively assesses the influence of fire aerosols on the global annual gross primary productivity(GPP)of terrestrial ecosystems using simulations with the fully coupled global Earth system model CESM1.2.Results show that fire aerosols generally decrease GPP in vegetated areas,with a global total of−1.6 Pg C yr^−1,mainly because fire aerosols cool and dry the land surface and weaken the direct photosynthetically active radiation(PAR).The exception to this is the Amazon region,which is mainly due to a fire-aerosol-induced wetter land surface and increased diffuse PAR.This study emphasizes the importance of the influence of fire aerosols on climate in quantifying global-scale fire aerosols’impacts on terrestrial ecosystem productivity.

Subseasonal variabilities of surface soil moisture in reanalysis datasets and CESM simulations

Using surface soil moisture(SM) from ERA-Interim reanalysis and Climate Forecast System Reanalysis(CFSR) data together with simulated results from CESM, the authors evaluated the subseasonal variability of SM and explored its basic features. Evident subseasonal variability of SM was detected in all seasons and with different datasets. However, the subseasonal variability of SM showed significant regional differences and varied with seasons. It was found that SM has large subseasonal variances in eastern China, North America, South Africa, and Australia in the summer hemisphere. The variances of the low-frequency SM variations given by ERA-Interim and CFSR are different. Overall, CFSR shows stronger variability than ERA-Interim. Through spectral analysis, it was noticed that low-frequency variations of surface SM mainly happen with periods of 10–30 days and 30–50 days. Subseasonal variations with a period of 10–30 days are dominant in eastern China and South Africa. However, subseasonal variations with periods of both 10–30 days and 30–50 days were detected in North America and Australia. Generally, CESM captures the main features of SM subseasonal variation. However, the model overestimates the subseasonal variability in all seasons in most regions, especially in the high latitudes of the Northern Hemisphere.

深厚大气边界层演变与湍流运动、沙尘滞空的研究

大气边界层是地球表面与大气之间水热、动量、能量和痕量气体等物质交换和输送的重要通道,在天气和气候的演变过程中有着重要作用。深厚大气边界层现象和特征、形成机理以及天气气候效应是大气边界层研究领域的热点问题,也是科学难题。着眼于对天气和气候高敏感、高影响的极端气候区和特殊地理区域,回顾梳理了深厚大气边界层的观测事实,归纳总结了不同地区深厚大气边界层的成因和影响因素,描述深厚大气边界层演变过程中独特的湍流运动图像,解析探讨了深厚大气边界层演变与沙尘滞空之间的关联。最后,提出了深厚大气边界层的未来研究关注重点和实现突破的4个关键科学问题,以期为更加系统地开展深厚大气边界层研究提供参考依据。

Influence of land evapotranspiration on climate variations

A coupled numerical model of the global atmosphere with a qualified biosphere (GOALS/LASG) has been used to assess the nature of the physical mechanisms for land-atmosphere interactions, and the impacts of the Asian/North American land-surface evapotranspiration on the regional and global climate. This sensitivity study suggests that the simulated climate would be relatively sensitive to land surface evapotranspiration, especially over the Asian regions. The removal of evapotranspiration in Asia would create a warmer and drier climate to a certain degree. Furthermore, the surface evapotranspiration anomalies would make a substantial contribution to the formation and variation of subtropical anticyclones through the changes in monsoon precipitation and the β -effect, but also make a large contribution to the variations of the atmospheric circulation in the Northern Hemisphere and even the globe. Therefore, besides the traditional perception that we have generally emphasized on the influence of subtropical anticyclones activities on the boreal summer precipitation over the regions of eastern China, the surface evapotranspiration anomalies, however, also have substantial impacts on the subtropical anticyclones through the changes in monsoon precipitation. For this reason, the variation in the internal heating sources of the atmosphere caused by the land surface evapotranspiration and the vapor phase change during the boreal summer is an important external factor forcing the weather and climate.

Climate change and infectious diseases of wildlife： Altered interactions between pathogens, vectors and hosts

Infectious diseases result from the interactions of host, pathogens, and, in the case of vector-borne diseases, also vec- tors. The interactions involve physiological and ecological mechanisms and they have evolved under a given set of environmental conditions. Environmental change, therefore, will alter host-pathogen-vector interactions and, consequently, the distribution, in- tensity, and dynamics of infectious diseases. Here, we review how climate change may impact infectious diseases of aquatic and terrestrial wildlife. Climate change can have direct impacts on distribution, life cycle, and physiological status of hosts, pathogens and vectors. While a change in either host, pathogen or vector does not necessarily translate into an alteration of the disease, it is the impact of climate change on the interactions between the disease components which is particularly critical for altered disease risks. Finally, climate factors can modulate disease through modifying the ecological networks host-pathogen-vector systems are belonging to, and climate change can combine with other environmental stressors to induce cumulative effects on infectious dis- eases. Overall, the influence of climate change on infectious diseases involves different mechanisms, it can be modulated by phenotypic acclimation and/or genotypic adaptation, it depends on the ecological context of the host-pathogen-vector interactions, and it can be modulated by impacts of other stressors. As a consequence of this complexity, non-linear responses of disease sys- tems under climate change are to be expected. To improve predictions on climate change impacts on infectious disease, we sug- gest that more emphasis should be given to the integration of biomedical and ecological research for studying both the physio- logical and ecological mechanisms which mediate climate change impacts on disease, and to the development of harmonized methods and approaches to obtain more comparable results, as this would support the discrimination of case-specific versus gen- eral mechanisms .