2016-07-28. How Irrigation in Asia Affects Rainfall in Africa.

posted Jul 30, 2016, 9:48 AM by Alan Gould
By Sarah Stanley, EoS Earth and Space News, AGU. For GSS Energy Flow chapter 9, Life and Climate chapter 12, and Population Growth chapter 5. Excerpt: Agricultural irrigation is so widespread that it accounts for about 4% of the total evapotranspiration of water from Earth’s surface. Scientists have known for some time that water vapor from irrigation affects regional and global climates. Now, for the first time, researchers have shown that irrigation in one region can directly affect the climate of another region thousands of kilometers away. De Vrese et al. used the Max Planck Institute for Meteorology’s Earth System Model to simulate the fate and impact of water used for irrigation in South Asia from 1979 to 1999. In the simulations, early spring winds carried water vapor from irrigation in South Asia across the Arabian Sea and into East Africa, increasing humidity there. By late spring, when irrigation in the Middle East, Turkmenistan, and Afghanistan is in full swing, wind transported water vapor into Africa, increasing humidity as far west as Nigeria. ...The simulations show that water vapor transport from South Asian irrigation increases springtime rainfall in Africa by up to 1 millimeter per day. Increased rainfall and cloud cover may cool the surface by up to 0.5 kelvin. In the arid parts of East Africa, as much as 40% of the total yearly rainfall may be attributed to irrigation in Asia....  https://eos.org/research-spotlights/how-irrigation-in-asia-affects-rainfall-in-africa