Meteorological Effects In Mid-and Low-Latitude Ionosphere

The ionosphere is influenced by solar, geomagnetic and meteorological activities simultaneously. Exploring the meteorological effects in the ionosphere has been an important task in ionospheric research. In this dissertation, we carry out a systemic study on the meteorological effects in mid- and low-latitude ionosphere with various methods, such as superposed epoch method, partial correlation method, and so on.The main researches and results of this dissertation are as follows.(1) The meteorological effects on the ionosphere of extreme heavy rainfall and cold wave over Wuhan are studied. When extreme heavy rainfall happens, the blanketing frequency fbEs and maximum frequency foEs of sporadic E-layer decrease clearly, and so do the virtual height h′F and equivalent peak height hpF of F-layer; when cold wave passes, sporadic-E tends to occur more frequently and with higher values of fbEs and foEs at nighttime. The dynamical processes associated with atmospheric waves might be responsible for these meteorological effects.(2) The correlation between NmF2 (the peak electron density of F2-layer) and h (the height of isobaric level) in the lower atmosphere over Wuhan is investigated. There is no significant correlation between NmF2 and h in the troposphere and even the lower stratosphere, but a weak positive correlation is found between NmF2 and h in the middle stratosphere.(3) The correlation relationship between TEC (the total electron content of the ionosphere) over China and IZ (Asian zonal circulation index) is analyzed. It is found that TEC over China has no significant correlation with IZ, but the day-to-day variability of TEC over China has a significant positive correlation with IZ. The positive correlation might be closely associated with the topography of Qinghai-Tibet Plateau.(4) The correlation between Es occurrence frequency over China and Va (arctic vortex area index) is explored. At mid-latitude, a positive correlation is found between Es occurrence frequency and Va, and the magnitude of the correlation coefficient increases with the increasing latitude; but at low-latitude, Es occurrence frequency has no significant correlation with Va.(5) A method for estimating the meteorological contribution to the ionospheric variability is improved. With the improved method, the meteorological contribution to the variability of NmF2 over Wuhan is obtained, which are 20.4% and 38.9% in daytime and at nighttime, respectively. In addition, the meteorological contribution to the variability of TEC over China is also estimated, which are 14.5% and 19.5% in daytime and at nighttime, respectively. These results imply that meteorological activity plays an important role in the ionospheric variability.The research results in this dissertation can not only further our understanding of the ionosphere-lower atmosphere coupling but also benefit us in describing and forecasting ionospheric weather precisely.