东亚干旱半干旱区沙漠化与气候变化相互影响研究进展

气候系统主要通过气温、降水及风场等因素影响沙漠化过程，但不同区域其影响机制存在较大差异。目前的研究结果表明，总体上，降水对沙漠化的影响较为明确，降水量增加有利于沙漠化逆转。气温和风场变化对沙漠化的影响存在明显区域差异：在季风带沙漠化区，气温升高及高空盛行西南风有利于沙漠化逆转；在非季风带沙漠化区，一方面气温升高导致蒸发量增加，沙漠化发展；另一方面，其增加了冰川、冰雪融水的补给，沙漠化逆转；在高寒带沙漠化区，旱灾和寒冻灾害是沙漠化的主因。此外，沙漠化过程通过植被、地表及土壤特征等的改变影响气候系统。例如沙漠化过程的发生伴随地表植被覆盖的变化，并通过改变地表反照率、潜热通量、粗糙度等来影响气温、降水等气候因子；还通过沙尘释放量的变化来影响降水的发生。虽然沙漠化与气候系统间存在多种反馈机制，但反照率—气温—降水—植被的正反馈及沙尘—降水—植被的正反馈是其主要反馈机制。

Research progresses on the interaction between desertification and climate change in arid and semiarid East Asia

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.