Solar radiation data is important for a wide range of applications, e.g. in engineering, agriculture, health sector, and in many fields of the natural sciences. A few examples showing the diversity of applications may include: architecture and building design e.g. air conditioning and cooling systems; solar heating system design and use; solar power generation; weather and climate prediction models; evaporation and irrigation; calculation of water requirements for crops; monitoring plant growth and disease control; skin cancer research. Solar radiation data must be provided in a variety of forms to suit these applications. The radiation reaching the upper atmosphere of the Earth is a quantity rather constant in time. But the radiation reaching some point on Earth surface is random in nature. The main cause is the fact that various gases within the atmosphere absorb solar radiation at different wavelengths, and clouds and dust also affect it. There are two ways to obtaining solar radiation data at ground level: by measurement and by modelling. The book will facilitate the calculation of solar radiation required by engineers, designers and scientists and, as a result, will increase the access to needed solar radiation data.