Atmospheric sciences Atmospheric sciences Atmospheric sciences are the study of the Earth's atmosphere, its processes, the effects other systems have on the atmosphere, and the effects of the atmosphere on these other systems. Meteorology includes atmospheric chemistry and atmospheric physics with a major focus on weather forecasting. Climatology is the study of atmospheric changes (both long and short-term) that define average climates and their change over time, due to both natural and anthropogenic climate variability. Aeronomy is the study of the upper layers of the atmosphere, where dissociation and ionization are important. Atmospheric science has been extended to the field of planetary
Short-term exposure limit Short-term exposure limit A short-term exposure limit (STEL) is the acceptable average exposure over a short period of time, usually 15 minutes as long as the time-weighted average is not exceeded. STEL is a term used in occupational health, industrial hygiene and toxicology. The STEL may be a legal limit in the United States for exposure of an employee to a chemical substance. The Occupational Safety and Health Administration (U.S. OSHA) has set OSHA-STELs for 1,3-Butadiene, benzene and ethylene oxide. For chemicals, STEL assessments are usually done for 15 minutes and expressed in parts per million (ppm), or sometimes in