The water cycle: water vapor in the air (Copernicus ERA5)

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Interpretation

Total column water vapor: all the water vapor above each square meter of Earth's surface, from the ground to the top of the atmosphere, averaged over the whole globe (weighted by area). 1 kg/m² equals a 1 mm layer of liquid water, which is why it is also called precipitable water. "Normal" is the 1991–2020 average for the same calendar month. ERA5 is a reanalysis: a weather model that takes in millions of observations (weather balloons, satellites, ships, stations) to rebuild the state of the atmosphere for every hour since 1940. Before satellites (1979) it has far fewer humidity observations to work with, so the early decades are less certain. Monthly values appear about 5 days after the month ends; the newest months can still be revised slightly. Data: Copernicus Climate Change Service, ERA5 monthly averaged data on single levels (doi:10.24381/cds.f17050d7).