Acknowledgments Introduction Part Ⅰ The Measurements and Data Analysis Conducted in this Work Chapter 1 The Experimental Work Chapter 2 UV Measurements with NILU-UV Irradiance Meters Chapter 3 Data Analysis and Instrumentation Part Ⅱ Background Physics of Solar Ultraviolet Radiation and Ozone Chapter 4 Solar Ultraviolet Radiation Chapter 5 Photochemical Description of Solar UV Attenuation in the Earth's Atmosphere Chapter 6 Science of Ozone Depletion Part Ⅲ Radiative Transfer Equation for Model Calculations Chapter 7 Model Calculation Method for Surface UV Irradiance Part Ⅳ Papers Paper 1 UV Measurements in the 3000-5000 m Altitude Region in Tibet Paper 2 The Vitamin D Status among Tibetans Paper 3 Ground-based Measurements and Modeling of Solar UV-B Radiation in Lhasa,Tibet Paper 4 Solar UV Irradiance Measurements at Four Sites in Tibet Paper 5 Spatial Distribution and Temporal Variation of Solar UV Radiation over the Tibetan Plateau Paper 6 Solar UV Radiation Measurements across the Tibetan Plateau Paper 7 Comparison of Ground-based Measurements of Solar UV Radiation at Four Sites on the Tibetan Plateau Paper 8 Impact of Particulate and Dissolved Material on Light Absorption Properties in a High-altitude Lake in Tibet,China Paper 9 Human Vitamin D Deficiency in Tibet Paper 10 The Observational Study of Erythemal UV Radiation on the Land Surface of Tibet