This paper attempts to reveal a long-distance-relayed water vapor transport(LRWVT) east of Tibetan Plateau and its impacts. The results show that from August to October, east of Tibetan Plateau, there exists a unique LRWVT,and the water vapor from the South China Sea and the western Pacific can affect the Sichuan Basin, Northwest China and other Chinese regions far from the tropical sea through this way. From August to October, the precipitation of the region east of the Plateau is closely linked both in the intra-annual and inter-annual variations, and the LRWVT from the South China Sea and the western Pacific is an important connection mechanism. The large-scale circulation background of the LRWVT impacting the precipitation of the region east of the Plateau is as follows: At high levels,the South Asian High is generally stronger than normal and significantly enhances with its northward advance and eastward extension over the region east of the Plateau. At mid-level, a broad low pressure trough is over Lake Balkhash and its surroundings, and the Western Pacific Subtropical High(WPSH) is northward and westward located, and the western part of Sichuan Basin and the eastern part of Northwest China are located in the west and northwest edge of WPSH.
藏东南地区是青藏高原山地复杂下垫面的典型代表,其边界层大气过程异常复杂,给数值模拟和预报带来较大困难。大气边界层参数化方案的选取关系到能否正确模拟和预报局地大气过程。本研究采用中尺度模式WRF(Weather Research and Forecasting Model)对藏东南林芝地区对流和稳定边界层大气过程进行模拟,与2013年夏季"藏东南地区复杂下垫面地气交换观测实验"资料对比,研究ACM2,Boulac,M YJ,QNSE和YSU5种边界层参数化方案在青藏高原复杂下垫面的适用性。结果表明:对于水汽混合比垂直结构的模拟,Boulac和MYJ方案分别在模拟对流边界层和稳定边界层时能力最优。ACM 2方案最适宜藏东南复杂下垫面条件下的位温和风速垂直分布的模拟。各边界层参数化方案模拟对流边界层高度均较实际观测偏低,其中,QNSE方案模拟的边界层高度最接近观测。同一种边界层参数化方案对于夜间稳定边界层和正午对流边界层的模拟能力也不相同。该地区边界层风场受地形影响显著,风速较小,模拟的近地层风场较观测偏弱,MYJ和QNSE方案对近地层风场的模拟效果较好。
Cloud-to-rain autoconversion process is an important player in aerosol loading, cloud morphology, and precipitation variations because it can modulate cloud microphysical characteristics depending on the participation of aerosols, and affects the spatio-temporal distribution and total amount of precipitation. By applying the Kessler, the Khairoutdinov-Kogan(KK), and the Dispersion autoconversion parameterization schemes in a set of sensitivity experiments, the indirect effects of aerosols on clouds and precipitation are investigated for a deep convective cloud system in Beijing under various aerosol concentration backgrounds from 50 to 10000 cm-3. Numerical experiments show that aerosol-induced precipitation change is strongly dependent on autoconversion parameterization schemes. For the Kessler scheme, the average cumulative precipitation is enhanced slightly with increasing aerosols, whereas surface precipitation is reduced significantly with increasing aerosols for the KK scheme. Moreover, precipitation varies non-monotonically for the Dispersion scheme, increasing with aerosols at lower concentrations and decreasing at higher concentrations.These different trends of aerosol-induced precipitation change are mainly ascribed to differences in rain water content under these three autoconversion parameterization schemes. Therefore, this study suggests that accurate parameterization of cloud microphysical processes, particularly the cloud-to-rain autoconversion process, is needed for improving the scientific understanding of aerosol-cloud-precipitation interactions.
As one of the most important geological events in Cenozoic era,the uplift of the Tibetan Plateau(TP)has had profound influences on the Asian and global climate and environment evolution.During the past four decades,many scholars from China and abroad have studied climatic and environmental effects of the TP uplift by using a variety of geological records and paleoclimate numerical simulations.The existing research results enrich our understanding of the mechanisms of Asian monsoon changes and interior aridification,but so far there are still a lot of issues that need to be thought deeply and investigated further.This paper attempts to review the research on the influence of the TP uplift on the Asian monsoon-arid environment,summarize three types of numerical simulations including bulk-plateau uplift,phased uplift and sub-regional uplift,and especially to analyze regional differences in responses of climate and environment to different forms of tectonic uplifts.From previous modeling results,the land-sea distribution and the Himalayan uplift may have a large effect in the establishment and development of the South Asian monsoon.However,the formation and evolution of the monsoon in northern East Asia,the intensified dryness north of the TP and enhanced Asian dust cycle may be more closely related to the uplift of the main body,especially the northern part of the TP.In this review,we also discuss relative roles of the TP uplift and other impact factors,origins of the South Asian monsoon and East Asian monsoon,feedback effects and nonlinear responses of climatic and environmental changes to the plateau uplift.Finally,we make comparisons between numerical simulations and geological records,discuss their uncertainties,and highlight some problems worthy of further studying.
