Response of Surface Temperature and Precipitation over Ecotone in Northern China to the Global Warming during 1964-2013

Based on observed temperature and precipitation data in the period of 1964-2013 from China Meteorological Administration (CMA), the climate response of ecotone in Northern China were analyzed in this paper. The result shows that: ecotone of northern China can be divided into 4 regions using the rotated empirical orthogonal decomposition (REOF)：northwest region, north region, the southern section of the northeast region, and the northern section of the northeast region. During recent 50 years, ecotone of northern China experienced a significant warming(0.41℃/10a) compared to the warming over china(0.39℃/10a) and the warming around the world(0.15℃/10a), which is mainly contributed by minimum temperature increasing and cold season warming. The surface temperature showed declined during 1964-1969 but shifted to accelerating warming in 1970s-1990s(0.55℃/10a), and started to cooling since 2000s(-0.68℃/10a), which indicates the temperature of ecotone in Northern China has experienced a warming hiatus resembled to the global warming hiatus since 2000s, while it has decreased much more. Besides, the annual precipitation dropped about 13mm during 1964-2013 overall, of which the north region has declined the most (21mm). Seasonal differences also exist in individual regions. The decline of precipitation in southern section of northeast region was mainly occurred in summer, while the decrease of precipitation in northwest region was mainly resulted from the decrease of spring precipitation. As for the increase of precipitation in northern section of northeast region, spring precipitation contributed the most.