中文摘要：

干旱河谷是我国民族多样性、文化多样性、环境异质性及生物多样性最为丰富的地区，以其较好的光热等条件成为整个川西地区人口和城镇分布集中的核心地带，但是由于日益增加的人口压力和随之而来的人地矛盾，加之干旱河谷脆弱的生态系统，引发了严重的水土流失、泥石流、山体滑坡等自然灾害。以岷江上游干旱河谷为例，探讨了干旱河谷气候成因的自然因素和人为因素，指出人类活动是叠加于自然因素作用之上的，不是起主导作用，大气环流、局地环流、地理位置和地形地势造就了当今干旱河谷气候形成，是干旱河谷气候形成的主要因素；其气候特征具有：（1）气温年较差小，日较差大，春季气温回升快，秋季下降迅速，≥10℃的积温大，持续时间较长，地温稳定，在冬、夏季均能对地温起调节作用，但在部分地段有极值出现，对作物和林木生长造成不利影响；（2）降水较充沛，干湿季明显，但由于蒸发量大，表现为全年水分亏损，从作物和林木生长而言，雨季的水分亏损更为严重；（3）日照充足，太阳辐射强烈等典型特征。

英文摘要：

Dry valley, with heterogeneity in China, is landscape. Most population preferable living conditions and seasonal drought have most abundant diversity one of the particularities and and m tow ore nships of this level cropland. been caused under the in nationality, culture, W area ith unique natural, c distribute in the dry biology limatic, valleys However, serious soil erosion, landsl increasing pressure of local popu and environment and geographical due to relatively ide, frequent flood lation expansion, irrational development and frail ecosystem of dry valley. Taking the upper dry valley of Minjiang River as an example, this paper discusses the natural and human-induced reasons of climatic formation of dry valley. It indicates that atmospheric circulation, local circumflence, geographical location, terrain and topography were main reasons of dry valley formation and that human activities only were secondary reasons. The results show that air temperature in the upper valley of Minjiang River increases quickly in spring and decreases rapidly in autumn with a small annual but a large diurnal variation. Soil temperature with adjusting ground temperature in winter and in summer is very steady in the area but in some regions extreme value can harm crops and seedlings. In the same time,the accumulated temperature of ≥10℃ was large in amount and continued long days. Precipitation is abundant, whereas the dry season is significantly lower than the humid season. Due to large evaporation, soil water is deficient and threatens the growth of crops and seedlings in whole years, especially in growth season. This area is also provided with abundant sunshine and intense solar radiation.