The exosphere is the uppermost region of earths atmosphere as it gradually fades into the space.The Earth’s exosphere begins about 500 km (300 miles) above the terrestrial surface and extends out through the magnetosphere and beyond to the interplanetary medium. Temperatures in the Earth’s exosphere remain constant with altitude, averaging about 1500 K. The Earth’s exosphere contains the hydrogen geocorona and the Van Allen radiation belts.
The thermosphere is the layer of the earths atmosphere directly above the mesosphere and directly below the exosphere.The boundary between the thermosphere and the exosphere above it is called the thermopause. At the bottom of the thermosphere is the mesopause, the boundary between the thermosphere and the mesosphere below.
The mesosphere is located about 50 to 85 kilometers (30 to 50 miles) above the earths surface.
The troposphere contains 99% of the water vapor in the atmosphere. Water vapor concentrations vary with latitudinal position(north to south). They are greatest above the tropics, where they might be as high as 3% and decrease toward the polar regions