Welcome to the Lu Group!
The research focuses of Dr. Lu's group are to explore two of the fundamental processes in the Sun-Earth system, i.e., the wave dynamics and coupling from the lower to the upper atmosphere and the magnetosphere-ionosphere-thermosphere (MIT) coupling from the topside down. The majority of the Earth's energy originates from the Sun through the solar radiation and one way that the Earth responds and provides the feedback is via atmospheric wave activities. Some waves such as the migrating tides and stationary planetary waves are directly generated by the differential solar radiation, while other waves, such as gravity waves, nonmigrating tides and planetary waves associated with instability are indirectly generated by the weather and wind systems forced by the solar radiation. The atmospheric waves not only control the mean state of the atmosphere in the mesosphere and lower thermosphere region, but also contribute to the variability of the upper atmosphere, i.e., the space "weather". In climate models, the atmospheric waves are also the key element that affects the prediction of the climate change. The generation, propagation, and coupling of the waves that carry and transport energy and momentum are found to be universal in some of the other planets. It is imperative to study the characteristics and impacts of the atmospheric waves, in order to better understand the atmosphere of the Earth and other planets, and help predict their futures!
The polar region is always important to explore because it is the most sensitive area to climate change, the polar vortex is so dynamic that produces a broad spectrum of wave activities, and it is the most open region that interacts with the space. The planetary waves generated by the instability of the polar vortex are the strongest waves in the winter stratosphere, while the inertia-gravity waves with the wave source still being a mystery become dominant in the mesospehre and lower thermosphere. Above this region where we start to see auroras, the variations of tempererature with harmonics of a solar day increase super-exponentially and become dominant. We call them "aurora-related tides" because they are generated by the hall-ion-drag-induced adiabatic heating and their distribution closely follows the auroral oval. Now, a picture comes into a place that the polar atmospheric waves are playing a relay game from 30 to 150 km. Planetary waves and gravity waves are the perfect examples of the vertical wave coupling from below, while the "tides" are the manifestitation of the magnetospheric control from above. Behind this game, these two fundamental coupling processes are the real physical drivers. Although recent studies have significantly advanced our understanding of the wave coupling and the MIT coupling, the associated fundamental processes are still not yet well quantified and predicted by atmospheric models. It is critical to improve the model capabitilites of simulating the wave activities and the responses to the geomagnetic storms by combining the observations and more advanced mechanistic and global models.
The research interests of our group are of course not limited to the polar region. There are active investigations in the group that focus on the low and middle latitudes as well. To further explore, please check Publications, Projects, and The introduction to the research in Lu group.