Abstract:

Dust is an active component in the earth's surface system， highly sensitive to global climate changes， and capable of influencing global radiation， energy balance， and material cycling through a series of feedbacks. In recent years， an increasing number of remote sensing products have been used to monitor sand and dust storms， such as Dust Aerosol Optical Depth （DOD）. However， quantitative characterization of the relationship between DOD and other remote sensing-derived sand and dust storms indexes with the intensity of sand and dust storms remains limited. This study utilizes sand and dust storms observation data from meteorological stations in northern China and data from the Annual Report on Dust Weather in China to statistically analyze the frequency of dust occurrence （FoO） in northern China and Mongolia from 2001 to 2007， verifying DOD as an indicator for frequency of dust occurrence. Based on these analyses， this study distinguishes sand and dust storms of different intensities in various regions based on DOD and FoO， thereby exploring the spatiotemporal variations and driving factors of sand and dust storms in the study area from 2001 to 2022. The results show that： （1） DOD increases with the intensity of sand and dust storms， from suspended dust to blowing sand and dust， sand and dust storms， and severe sand and dust storms， but DOD threshold values for distinguishing various types of sand and dust storms vary by region. It shows more distinct DOD thresholds in western study area for different dust intensities， with a lower threshold for suspended dust and blowing sand and dust （0.2） compared to central and eastern study area（0.4）. （2） High FoO areas were primarily located in Xinjiang， gobi and deserts in northern Inner Mongolia and southern Mongolia， and deserts in Qaidam Basin， where FoO is generally higher in spring and summer than in autumn and winter. （3） Over the past two decades， FoO has generally declined across northern China， especially in deserts and dune fields of north-central China and the Loess Plateau. In contrast， Mongolia shows a pattern of decreasing FoO in the southeast and increasing FoO in the southwest. （4） Changes in FoO in most areas strongly correlate with vegetation index， NDVI， and spring wind speed， reflecting that reduced near-surface wind speeds and increased vegetation， driven by climate change and extensive ecological restoration efforts， have suppressed dust activity in northern China.

Key words: sand and dust storms, dust optical depth （DOD）, frequency of dust occurrence （FoO）, remote sensing, ecological restoration, climate change