Arakawa, Tokyo Arakawa, Tokyo Arakawa has sister-city relationships with Donaustadt in Vienna, Austria, and with Corvallis, Oregon, U.S. Domestically, it has similar relationships with nine cities, towns and villages. As of May 1, 2015, the ward has an estimated population of 208,763, and a population density of about 20,550 persons per km². The total area is 10.16 km². Arakawa is in the northeastern part of Tokyo. The shape is long and narrow, stretching from west to east. The Sumida River forms the northern boundary. The ward is surrounded by five other special wards. To the north lies Adachi; to the west, Kita;
Arakawa grids grid cell, e.g., at the grid center or at the grid corners. The Arakawa A-grid is the only unstaggered grid type. The "staggered" Arakawa B-grid separates the evaluation of the two sets of quantities. e.g., one might evaluate velocities at the grid center and masses at grid corners. The "staggered" Arakawa C-grid further separates evaluation of vector quantities compared to the Arakawa B-grid. e.g., instead of evaluating both east-west (u) and north-south (v) velocity components at the grid center, one might evaluate the u components at the centers of the left and right grid faces, and the v components at