Ozone gas in the stratosphere (upper atmosphere) absorbs ultraviolet light, thus protecting living things from the sun's harmful ultraviolet radiation. Man-made chemicals and weather conditions over Antarctica combine to deplete stratospheric ozone concentrations during the winter months there. (Data from Total Ozone Mapping Spectrometer [TOMS] project). Sensor: TOMS/TOMS. Data Start Date: 1/1/03. Data End Date: 7/31/05.