关键词: 东亚干旱半干旱区, 反馈, 进展, 气候系统, 沙漠化过程

Abstract: Interactions between climate change and land surface processes, especially in arid and semiarid areas, have received increasing attention in recent years from climate scientists and geographers globally. In this paper, progresses in existing research on the interaction between desertification and the climate system in arid, semiarid, and semi-humid East Asia are outlined and discussed. Although there are large regional differences, the climate system affects regional desertification process by altering temperature, precipitation, wind field, and other meteorological factors. The current findings indicate that precipitation has a relative explicit impact on desertification: increases in precipitation are beneficial for vegetation growth and the reversal of desertification, and decreases in precipitation may result in increased desertification. Comparatively, the influences of temperature and wind field on desertification are more complicated and differ among various subregions: in the eastern monsoonal area, rises in temperature and the upper dominant southwest wind may be accompanied by increases in precipitation, contributing to reversals of desertification; in the western non-monsoonal area, rises in temperature promote increases in both surface evaporation and river runoff as a result of enhanced glacier thawing and snow melting, thus it is uncertain how this temperature change affects desertification; in the higher latitudes and altitudes, droughts and frost disasters often act together and give rise to severe damages to regional ecosystem, triggering increased desertification. On the other hand, desertification to some extent affects the local climate system by altering the characteristics of vegetation, land surface and soil. Increased desertification leads to vegetation degradation and subsequently changes in surface albedo, latent heat flux, as well as surface roughness height, which may in turn alter temperature, probabilities of precipitation events, and the wind regimes of local areas. Desertification also leads to the release of higher amount of fine particulates into the atmosphere, which may negatively affect the occurrence of precipitation. Overall, the interactions between desertification and the climate system include many feedbacks, among which the positive albedo-temperature-vegetation feedback and the positive sand-dust-precipitation-vegetation feedback are the principal mechanisms. Despite considerable progresses made in existing research, however, there remain many important issues that are yet to be addressed or difficult to address, such as the spatial and temporal aspects of processes involved in desertification, which are critical for understanding the interactions between climate change and desertification, and thus further studies are needed in the future.

Key words: arid and semiarid East Asia, climate system, desertification, feedbacks, progress