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The total volume of water in rivers is estimated at 2,120 km 3 (510 cu mi), or 0.49% of the surface fresh water on Earth. [2] Rivers and basins are often compared not according to their static volume, but to their flow of water, or surface run off. The distribution of river runoff across the Earth's surface is very uneven.
The Earth's average surface absolute temperature for the 1961–1990 period has been derived by spatial interpolation of average observed near-surface air temperatures from over the land, oceans and sea ice regions, with a best estimate of 14 °C (57.2 °F). [44] The estimate is uncertain, but probably lies within 0.5 °C of the true value. [44]
Water covers about 71% of the Earth's surface, with seas and oceans making up most of the water volume (about 96.5%). [23] Small portions of water occur as groundwater (1.7%), in the glaciers and the ice caps of Antarctica and Greenland (1.7%), and in the air as vapor , clouds (consisting of ice and liquid water suspended in air), and ...
At any given time, about 2 × 10 13 tonnes of this is in the form of water vapor in the Earth's atmosphere (for practical purposes, 1 cubic metre of water weighs 1 tonne). Approximately 71% of Earth's surface, an area of some 361 million square kilometres (139.5 million square miles), is covered by ocean.
Warm surface water is generally saltier than the cooler deep or polar waters. [1] In polar regions, the upper layers of ocean water are cold and fresh. [2] Deep ocean water is cold, salty water found deep below the surface of Earth's oceans. This water has a uniform temperature of around 0-3 °C. [3]
A wet-bulb temperature at 500 hPa in a tropical atmosphere of −13.2 °C (8.2 °F) is required to initiate convection if the water temperature is 26.5 °C (79.7 °F), and this temperature requirement increases or decreases proportionally by 1 °C in the sea surface temperature for each 1 °C change at 500 hpa.
Waves mix the water near the surface layer and distribute heat to deeper water such that the temperature may be relatively uniform in the upper 100 metres (330 ft), depending on wave strength and the existence of surface turbulence caused by currents.
The atmosphere envelops the earth and extends hundreds of kilometres from the surface. It consists mostly of inert nitrogen (78%), oxygen (21%) and argon (0.9%). [4] Some trace gases in the atmosphere, such as water vapour and carbon dioxide, are the gases most important for the workings of the climate system, as they are greenhouse gases which allow visible light from the Sun to penetrate to ...