Remote sensing investigation of the main sand-supplying areas of dust storm hitting northern China

Based on the national sand dust storm data dated from 1951 to 1980, the distributions of sand dust storm-influenced areas that total 440×10⁴ km² are analyzed. The number of dust storm days in a year is used as an indicator, by which five heavy dust storm regions are marked off. The main trajectories of the sand dust storm are traced to derive the position of main storm hit region using the meteorological data dated from 1971-1996. Then the nationally remote sensing investigation of wind erosion is carried out. Total area of wind erosion is 228×10⁴ km², accounting 23.8% of the whole country area. Comparison of the data of sand dust storm with that of wind erosion shows that all wind erosion places fall in the sand dust storm-influenced areas. With the strengthening of the soil erosion, the number of dust storm days in a year also increases. The windily eroded areas can be perceived as the source areas that are supplying sand for the dust storm. The land use of the sand supplying area is discussed. And their contribution to the sand dust storm is probed. The main areas that supply sand for the sand dust storms are mostly bare land and heavily desertified land, accounting 59.5% of total sand supplying areas. Occupying 30.4% of the total sand-supplying region, nearly 75×10⁴ km² grassland is providing sand for the sand dust storm, equaling to 38% of all grassland of China, most of which are over-grazed. Moreover almost 5.2% eroded area of the sand source region is cropland