报告摘要

The Earth's space environment (mesosphere, thermosphere and ionosphere) is known to be strongly driven by solar and magnetospheric forcing. The influence of the lower atmosphere, on the other hand, has long been speculated but the specific pathways or their relative significance are not well understood. This has been changing rapidly thanks to both new observations, in particular those during the last extended solar minimum, and the development of numerical models that treat the whole atmosphere as an integrated system, such as the NCAR Whole Atmosphere Community Climate Model (WACCM). In this talk, I will focus on the roles of atmospheric waves in the coupling process, and on how they affect the circulation, transport, and electrodynamics in the space environment. I will explore how the day-to-day variability (i.e. weather) of the space environment is related to atmospheric waves, and the predictability of the system. As shown in our recent study, the poor representation of gravity wave forcing in whole atmosphere models is a major cause of bias in modeling the space environment, and thus leads to the loss of skills in its forecast. As an effort to better understand and quantify gravity waves in the upper atmosphere, we have recently explored the feasibility of directly simulating down to mesoscales using WACCM. I will present some preliminary results from this simulation..

 

学者简介: 

Han-Li Liu's research includes the theoretical, numerical, and interpretive studies of the dynamics, structure, and solar/terrestrial responses of the Earth's middle and upper atmosphere, with special emphasis on modeling physical and chemical processes on both global and local scales, and the nonlinear couplings of the global and local scale processes and different regions of the atmosphere. He also works on the development and improvement of general circulation models (GCMs) and parameterization schemes for the GCMs, including the NCAR Thermosphere-Ionosphere-Mesosphere-Electrodynamics GCM (TIME-GCM) and the Whole Atmosphere Community Climate Model (WACCM); thermospheric extension of WACCM; development of diagnostic tools for analyzing the large scale data sets of the model results and interpretive studies of observations using model diagnostics; geophysical turbulence and self-organized critical phenomena in geophysics.