Through the coupling between the near-earth space environment and the polar ionosphere via geomagnetic field lines, the variations occurred in the magnetosphere are transferred to the polar region. According to recent studies, however, the polar ionosphere reacts not only passively to such variations, but also plays active roles in modifying the near-earth space environment. So the study of the polar ionosphere in terms of geomagnetic disturbance becomes one of the major elements in space weather research. Although it is an indirect method, ground magnetic disturbance data can be used in estimating the ionospheric current distribution. By employing a realistic ionospheric conductivity model, it is further possible to obtain the distributions of electric potential, field-aligned current, Joule heating rate and energy injection rate associated with precipitating auroral particles and their energy spectra in a global scale with a high time resolution. Considering that the ground magnetic disturbances are recorded simultaneously over the entire polar region wherever magnetic station is located, we are able to separate temporal disturbances from spatial ones. On the other hand, satellite measurements are indispensible in the space weather research, since they provide us with in situ measurements. Unfortunately it is not easy to separate temporal variations from spatial ones specifically measured by a single satellite. To demonstrate the usefulness of ground magnetic disturbance data in space weather research, various ionospheric quantities are calculated through the KRM method, one of the magneto gram inversion methods. In particular, we attempt to show how these quantities depend on the ionospheric conductivity model employed.

The climatological characteristics at the Choejung-san site were statistically analyzed using monthly normals for the various meteorological elements at Taegu meteorological station for 30 years from January 1960 to December 1990. Various synoptic weather conditions were classified by the estimated geostrophic wind speeds and direction determined using the 850 hPa geopotential height field for 10 years from December 1980 to November 1989. Also the analysis of number of clear days were monthly and seasonally performed using the satellite infrared image data which were obtained from GMS 5 for 5 years from December 1990 to November 1995. The results reveal that the meteorological environments of astronomical observation at Choejung-san site were very good conditions during three hours after midnight except for summer season.

The magnetogram inversion technique (MIT) is a computational method for calculating the global pattern of ionospheric current using ground magnetic disturbance data as input. By assuming the ionospheric electric conductivity distribution, the technique makes it further possible to estimate the distribution patterns of such electrodynamic quantities as electric field, electric potential, field-aligned current and Joule heating rate. Although the MIT is an indirect method, it provides instantaneous electrodynamical pictures of the entire polar ionosphere with a high time resolution while more direct measurements by radar, rocket and satellite are vital to understand the ionospheric phenomena but they provide informations only over a limited area. Since the output of the MIT are very sensitive to the choice of the ionospheric conductivity distribution, a companion paper will be devoted to the topic. Various electrodynamic quantities over the polar ionosphere, which are now available through the magnetogram inversion technique, will be also discussed in another companion paper.

Diurnal variations of air quality due to the characteristic features of local weather phenomena over Kunsan, Taegu, and Pohang are analyzed using various synoptic wind fields and the characteristics of local weather during the period of 1990 to 1992. The air pollutants analyzed are sulfur dioxide(SO_2), nitrogen dioxide(NO_2), and oxidants (O_3). The synoptic wind fields estimated at over the 850 hPa geopotential height are divided in terms of four wind directions and two wind speed categories for each season. The synoptic weather conditions are also classified into two categories depending on the total cloud amounts. The present study shows that the SO_2 concentration over Kunsan, and Taegu was maximum at the two or three hours after sunrise and second primary was three or four hours after sunset. On the other hand, its concentration over Kunsan was maximum at 1900 LST or 2000 LST. The O_3 concentration over the three cities shows its maximum in the afternoon when the solar radiation is strong. The NO_2 concentration over Kunsan shows in reverse proportion to the 0_3 concentration over the Kunsan.