区域气候模式RegCM3对华北地区未来气候变化的数值模拟

采用高水平分辨率区域气候模式进行区域未来气候变化预估,对理解全球增暖对区域气候的潜在影响和科学评估区域气候变化有很好的参考价值.这里对国家气候中心使用25 km高水平分辨率区域气候模式RegCM3单向嵌套全球模式MIROC3.2_hires在观测温室气体(1951—2000)和IPCC A1B温室气体排放情景下(2001—2100)进行的共计150年长时间模拟结果,进行华北地区未来气温、降水和极端气候事件变化的分析.模式检验结果表明:模式对当代(1981—2000)气温以及和气温有关的极端气候事件(霜冻日数、生长季长度)的空间分布和数值模拟较好;对降水及和降水有关的极端气候事件(强降水日期、降水强度、五日最大降水量)能够模拟出它们各自的主要空间分布特征,但在模拟数值上存在偏大、偏强的误差.和全球模式驱动场相比,区域模式模拟的气温、降水和极端气候事件有明显的改进.2010—2100年华北地区随时间区域平均气温升高幅度逐渐增大,随之霜冻日数逐渐减少,生长季长度逐渐增多;同时随温室效应的不断加剧,未来降水呈增加的趋势,强降水日期和五日最大降水量逐渐增多、降水强度逐渐增大.从空间分布看,21世纪末期(2081—2100)气温、降水以及有关的极端气候事件变化比21世纪中期(2041—2060)更加明显.

Numerical simulation of climate changes over North China by the RegCM3 model

Using the high resolution regional climate model to estimate the regional future climate can help us to understand and assess the regional climate changes under the global warming. Based on the simulation conducted by National Climate Center with a high resolution regional climate model (RegCM3) at 25 km grid spacing nested within a global model of MIROC3.2_hires, changes in precipitation, temperature and some related extreme climate events (frost days, growing season length, number of heavy precipitation days, simple daily intensity index and max 5-day precipitation amount) over North China under global warming are analyzed in this work. The simulation is carried out for the period of 1951—2100 following the observed greenhouse gases (1951—2000) and the IPCC SRES A1B emission scenario (2001—2100). The results suggest that the model is capable of simulating well the present (1981—2000) mean temperature, frost days and growing season length in both spatial distributions and values; but with some discrepancies in values of present mean precipitation, number of heavy precipitation days, simple daily intensity index and max 5-day precipitation amount. The RegCM3 model overestimates the values of present mean precipitation and related extreme indices. Compared to the driving global model, significant improvements have been shown by RegCM3 about the simulation of temperature, precipitation and extreme climate events. Increasing area averaged temperature and growing season length, together with decreasing frost days are simulated during the period of 2010—2100, at the same time an increasing trend of area averaged precipitation, number of heavy precipitation days, simple daily intensity index and max 5-day precipitation amount is indicated with the increasing greenhouse effect. In general, more obvious changes of temperature, precipitation and extreme climate events would occur in the late 21^st century (2081—2100) compared to the middle 21^st century (2041—2060) over North China.