Arakawa was the youngest of three sons. Living through World War II in Japan, he recalled his two older brothers served in the Japanese military without incident, while he was drafted to work as a fireman part-time while finishing high school.[2] He entered the University of Tokyo in 1947, and spent three years majoring in physics. After graduating in 1950, he applied for one of the few jobs available for physics graduates, with the Japan Meteorological Agency. The agency stationed him on a weather ship to gain experience, and after working in that area for a year and a half, he sought another role in the agency, and was able to gain a position in the forecast research division.[2]
In the 1950s, Arakawa developed mathematics that "permitted the use of a coarser grid" to reduce the computational time needed to estimate climate changes from air sampling data. During this time, Arakawa consulted on the early Goddard Institute for Space Studies (GISS) weather model, later taken up and further advanced by meteorologist Dr. James Hansen.[8]