These maps show TES measurements taken on September 20, 2004 of ozone concentrations in the lower and upper troposphere. Each map covers the Earth from 82° N to 82° S. The dividing line between lower and upper troposphere in any local area is where the atmospheric pressure is 500 hectopascals (hPa, the unit that replaced millibars in scientific use). This point is at an altitude of roughly 6 km (under 4 miles), but varies from place to place -- it is higher over the equator than over the poles, for example. The color scale is in Dobson units (DU), a measurement of the number of ozone molecules per square centimeter of air in a column of atmosphere. The numbers superimposed on the maps indicate latitude and longitude.

Lower Tropospheric Ozone	Upper Tropospheric Ozone