A composite analysis of diurnal cycle of GPS precipitable water vapor in central Japan during Calm Summer Days
A composite analysis of diurnal cycle of GPS precipitable water vapor in central Japan during Calm Summer Days
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DOI：
10.1007/s00704-006-0293-x
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发表时间：
2008-03
影响因子：
3.4
通讯作者：
G. Li;F. Kimura;T. Sato;D. Huang
中科院分区：
文献类型：
--
作者：
G. Li;F. Kimura;T. Sato;D. Huang
利用GPS可降水量（PWV）和地面气象资料，对日本中部三种不同地点的水汽日变化进行了研究。对2000年8月日本中部25个晴天进行了研究，以阐明水汽在对流降雨日周期夜间最大值中的作用。6个站点所选天数内PWV与部分气象因子的日变化呈复合关系。PWV有明显的日变化，振幅为3.4 ~ 8.8mm，从早晨到中午变化不大。PWV的日振幅在盆地最大，平原最小，但在平原平均值保持较高值。日本中部日变化的一个典型特征是最大值出现在晚上。最大值出现在1800 - 2000 LST之间，山区和盆地的最小值几乎出现在中午，平原的最小值出现在清晨。结果表明，山区比湿日最大值出现的时间早于平原地区，各地区比湿日变化均存在明显的日变化，且山区比湿日变化幅度大于盆地和平原地区。值得注意的是，六个站点之间的比湿度存在显着差异。结果表明，PWV的日变化似乎强烈的影响，所产生的局部热力环流的地形周围的这些站。水汽输送导致了不同地点PWV日循环的相位差异以及降水的相位差异。地面气温的日变化与太阳辐射相似，早晨最低，午后最高。地面风速最大值与降水峰值有很好的对应关系。结果表明，太阳辐射的振幅随高度的增加而增加，而PWV的变化则相反。傍晚降水的日变化规律与PWV相似，表明日本中部地区的降水峰值出现在傍晚或傍晚。同时，PWV达到夜间最大值。观测降水的日变化与PWV的日变化有很好的对应关系。
The diurnal variations of water vapor in central Japan were investigated with GPS-derived precipitable water (PWV) and surface meteorological data as classified to three kinds of locations. Twenty-five clear days in central Japan in August 2000 were investigated to clarify the role of water vapor in the nocturnal maximum in the diurnal cycle of convective rainfall. The diurnal variations of PWV and some meteorological factors were composite during the selected days at 6 stations. The PWV shows a clear diurnal cycle with the amplitude of 3.4 mm to 8.8 mm and changes little during the period from the morning to noon. The daily amplitude of PWV is the largest in basin and smallest in plain although mean of PWV keeps high value in plain. A typical feature of the diurnal variation in central Japan is a maximum appearing in the evening. The time of maximum is from 1800 LST to 2000 LST, and minima appears at noon nearly in mountainous area and basin, while in early morning in plain. The diurnal maximum of PWV appears earlier in mountainous region than in plain.A diurnal cycle of specific humidity can be observed in all locations, and the amplitude in mountainous region is especially large compared with that in basin and plain. It is important to notice that there are remarkable differences in specific humidity among the six stations. The results suggest that the diurnal variation of PWV seems to be strongly affected by the local thermal circulations generated by the topography around these stations. The moisture transport causes the differences in phase of the diurnal cycle of PWV between different locations as well as the phase difference in precipitation. A very clear diurnal variation in surface air temperature is similar to that of solar radiation, with a minimum in the morning and a maximum in early afternoon. Maximum of surface wind speed are corresponded to peak of precipitation very well. It can be concluded that the amplitude of solar radiation increases with altitude as opposed to the situation of PWV generally.The precipitation observed frequently in the evening also shows a similar diurnal variation to that of the PWV, indicating the peak of precipitation appearing in late afternoon or in the evening over central Japan. Meanwhile the PWV reaches its nocturnal maximum. There is a good relationship between the diurnal cycle of observed precipitation and that of the PWV.