Main objective of the I.R. of Iran Meteorological Organization, along with obtaining national and international goals, is protecting life and property of people against the hazards related to water, weather and climate. While in a broad vision, in many operational fields, from management to tourism, there is a major for science of meteorology, but in order to get access and provide a scientific, common and sensible view, which covers most of them, meteorological majors can be classified as follows: 1. Aeronautical Meteorology 2. Agricultural Meteorology 3. Marine Meteorology 4. Physical Meteorology 5. Dynamic and Synoptic Meteorology 6. Hydrological Meteorology 7. Atmospheric research 8. Climatology 9. Atmospheric chemistry and air Pollution Atmospheric hazards should be considered as an important and effective subject in above all above mentioned majors, furthermore, regarding the main objective of the meteorology (protecting life and property of people), this issue is especially highlighted in majors like agricultural meteorology, climatology and marine meteorology. Along with these majors, there are very valuable and vital factors and parameters that it is impossible to lead and drive science of meteorology toward the objectives of the country without taking advantage of the information resulted from them. These factors are as follows: 1. Observation 2. Data management and homogenize 3. Data modeling and synchronizing 4. Numerical prediction and producing reliable products 5. Providing information to public and expert users