Regional Characteristics of Recent Dust Occurrence and Its Controlling Factors in East Asia

Abstract

Aeolian dust, resulting from wind erosion, is controlled by two major factors: aeolian erosivity (i.e., wind speed) and aeolian erodibility (i.e., land surface conditions). Erodibility factors include a number of land surface parameters that interact in complicated manners. Thus far, the extent to which each of the factors contributes to dust outbreaks, which vary regionally and seasonally, remains unclear. As such, we present a novel map of the controlling factors for dust outbreaks in dryland of East Asia by quantifying the relative contributions of the erosivity and various erodibility parameters to inter-annual dust variations on a station basis during the period of 1999 to 2013. Erosivity controls dust outbreaks in the Taklimakan Desert, west of the Hexi Corridor, and on the north side of the Altai Mountain. On the other hand, dust outbreaks are dependent on erodibility in steppe regions: lower precipitation or less abundant vegetation during the previous summer was found to be related to dusty springs in the Mongolian steppe, whereas the less abundant spring vegetation and reduced snow cover enhanced dust outbreaks in the Inner Mongolian steppe. Anthropogenically restored vegetation in desertified areas was found to be likely to suppress dust outbreaks in the Loess Plateau.(Citation: Wu, J., Y. Kurosaki, M. Shinoda, and K. Kai, 2016: Regional characteristics of recent dust occurrence and its con-

Evaluation of Climatic and Anthropogenic Impacts on Dust Erodibility: A Case Study in Xilingol Grassland, China

“…The ecosystem of grasslands is affected by climate change and climate variability as well as anthropogenic impacts. Wu et al [7] suggested that erodibility has a stronger effect than erosivity on dust occurrence at most stations of the steppe regions in East Asia. They conducted a simple regression analysis on DOR and each of the variables (temperature, precipitation, and NDVI) and clarified the most important influencing erodibility factor at a station scale.…”

“…For long-term spatiotemporal characteristics, a gradual reduction in wind speed was the main cause for the decreasing trend in dust occurrence in most regions of northern China during 1960-2007 [6]. However, the responsibility of erosivity for the interannual variation in dust occurrence mainly appears in desert regions, whereas erodibility plays a more important role in other regions [7]. 2 of 13 Erodibility is the susceptibility of land surface to wind erosion and is influenced by various factors such as vegetation cover, soil moisture, and snow cover.…”

“…Igarashi et al [11] suggested that there would be a shift of source areas for Asian dust from the arid zone to the desert-steppe zone. Variations in erodibility, rather than erosivity, caused this change [7,11]. Due to a lack of continuous observation data of erodibility factors, there are still uncertainties in erodibility and its relationship with dust occurrence.…”

“…This dead-leaf hypothesis has also been proposed by Kurosaki et al [14] by using normalized dust occurrence frequency, which is the ratio of dust occurrence frequency to strong wind frequency. This erodibility index was the same as in Kimura et al [15] and Wu et al [7] except that a different value was used for the threshold wind speed. Although erodibility is the major factor effecting dust occurrence in the Mongolian and Xilingol grasslands, Wu et al [7] demonstrated that the controlling erodibility factor for interannual variations in dust occurrence during the period of 1999-2013 differed from region to region.…”

“…This erodibility index was the same as in Kimura et al [15] and Wu et al [7] except that a different value was used for the threshold wind speed. Although erodibility is the major factor effecting dust occurrence in the Mongolian and Xilingol grasslands, Wu et al [7] demonstrated that the controlling erodibility factor for interannual variations in dust occurrence during the period of 1999-2013 differed from region to region. One possible reason is the different grazing patterns, i.e., settled grazing activities in Xilingol Grassland versus traditional nomadic grazing in Mongolian grasslands.…”