The globally averaged annual rainfall is about 1 meter. That is, if one collects all rain water that falls in a year and spreads it over the entire surface of Earth, the depth of the water will be about one meter (1 m). (a) Calculate the volume of rain water that falls in a year in cubic meters (m3). The surface area of sphere is 4a2, where a is radius and = 3.1416. The radius of Earth is 6378 km. If necessary, use short-hand notations (e.g. 3400000 = 3.4 x 10^6). (b) Earth's surface is 70 percent oceans and 30 percent land. Suppose 30 percent of the total annual rainfall computed in (a) falls on the land surface. And further assume that, of the rain that falls on the land, 75 percent infiltrates the ground and stays there, whereas 25 percent becomes the surface runoff and flows into river streams, and eventually exits to the oceans. Estimate how much river water is discharged into the oceans globally and annually (in m3)? (c) The Amazon River has the average discharge of 2.2 x 105 m3/s. How many Amazon Rivers would it take to achieve the global discharge calculated in (b)? The globally averaged annual rainfall is about 1 meter. That is, if one collects all rain water that falls in a year and spreads it over the entire surface of Earth, the depth of the water will be about one meter (1 m). (a) Calculate the volume of rain water that falls in a year in cubic meters (m3). The surface area of sphere is 4a2, where a is radius and = 3.1416. The radius of Earth is 6378 km. If necessary, use short-hand notations (e.g. 3400000 = 3.4 x 10^6). (b) Earth's surface is 70 percent oceans and 30 percent land. Suppose 30 percent of the total annual rainfall computed in (a) falls on the land surface. And further assume that, of the rain that falls on the land, 75 percent infiltrates the ground and stays there, whereas 25 percent becomes the surface runoff and flows into river streams, and eventually exits to the oceans. Estimate how much river water is discharged into the oceans globally and annually (in m3)? (c) The Amazon River has the average discharge of 2.2 x 105 m3/s. How many Amazon Rivers would it take to achieve the global discharge calculated in (b)