Research on air pumping effects over central Japanese Alps in summer

山区上空的抽气效应是由太阳对山坡的加热引起的。空气泵送效应可能会将大量污染空气注入日本上空的自由对流层。为了描述日本中部阿尔卑斯地区的空气泵送效应，我们在2001年和2002年利用气象参数对norikura山的大气气溶胶粒子、臭氧和氡浓度进行了原位测量。我们用天空辐射计和天花板计观测了气溶胶的柱量和垂直分布。在夏季和初秋的密集观察期，还采样了用于化学分析的大小分离的气溶胶颗粒。在夏季晴朗的天气条件下，来自山谷地区的污染空气被抬升到norikura山上约4km的高度（山顶以上1km）。白天（受污染的山谷风）与夜间（干净的自由对流层）的气溶胶体积浓度之比约为10。在夏季，日本中部阿尔卑斯山脉上空的空气泵送效应将气溶胶浓度提高了10倍左右带到日本上空的自由对流层。在以西北太平洋为中心的高压系统下，典型夏季条件下，从西北太平洋向norikura山产生的向后气流轨迹和向北太平洋返回的向前气流轨迹有偏向俄罗斯东部和千岛群岛。山区的抽气效应为包括东亚在内的西太平洋地区的自由对流层提供了强有力的污染源机制。

Air pumping effects over mountain areas are caused by solar heating of the mountain slope. The air pumping effect may inject significant amount of polluted air into the free-troposphere over Japan. To characterize the air pumping effect over the central Japanese Alps, we conducted in-situ measurements on atmospheric aerosol particles, ozone, and radon concentrations with meteorological parameters at Mt.Norikura during the study period of 2001 and 2002. We observed column amount and vertical distribution of aerosols by using a sky-radiometer and a ceilometer. Size-segregated aerosol particles for chemical analysis were also sampled during intensive observation periods during summer and early fall.Under the clear sky conditions in summer, polluted air from mountain valley area is lifted up about 4km of altitude (1km above the mountain top) over Mt.Norikura. The ratio of aerosol volume concentration for daytime (polluted valley wind) to nighttime (clean free-tropospheric) conditions was about 10. The air pumping effects over central Japanese Alps carry about 10 time higher concentration of aerosols to the free-troposphere over Japan in summer. Under the high pressure system centered over the northwest Pacific in typical summer condition, backward air trajectories were originated from the northwest Pacific to Mt.Norikura and forward trajectories returned to the north Pacific with some deviations to east Russia and the Kurile Islands. The air pumping effects over mountain area provide a strong pollution source mechanism to the free-troposphere over the western Pacific region including east Asia.