The typical areas where kosa is generated are the following three areas, listed from the in order from the most western, the Takla Makan Desert (located in the western part of China), the Gobi Desert (located in the northern part of China and the southern part of Mongolia) and the Loess Plateau (located in the central part of China).
代表的な発生地としては、西からタクラマカン砂漠（中国西部）、ゴビ砂漠（中国北部・モンゴル南部）、黄土高原（中国中央部）の3か所が挙げられる。