Spatial Structions of TEC Climatology and Variability in North America

High spatial and temporal resolution TEC data obtained with a network of dense GPS receivers in a wide area allows for revealing ionospheric variations with unprecendented details, leading to new discoveries. In this presentation, we examine variations of TEC and its varaibility over North America based on monthly mean and standard deviation information of TEC, derived from a ground-based data base spanning the years 2000-2012 with 1x1 (latitude x longitude) and 5-min resolutions. The main new findings include: (1) a longitudinal variation of TEC associated with changing magnetic declination with longitude and thermospheric zonal wind climatology with solar geophysical conditions; (2) the transitional latitudinal zone of ~ 40 magnetic latitudes, where the dominant characteristic seasonal variaiton of winter anomaly in electron density yields to that of non-anomaly (with the summer TEC > winter TEC during the day); (3) zones of high TEC variability in the west of the continent US without apparent known origins, in addition to the major one in the north associated with magnetic activity. Temporal variations of these structures will be also discussed.