Dominant components of spatio-temporal variations were derived from principal component analysis of spatially high-density data on air temperature and pressure over the Kanto region in summer, obtained from our own observation network. Their connectivity is discussed from the viewpoints of meteorological conditions and diurnal variations. The spatial patterns of the three major components for the pressure and temperature fields resemble each other in order of their contribution, and the temporal variations in these scores also show statistically significant correlations.
The characteristics of spatial variations, as indicated by the distributions of factor loadings and related composite maps, are as follows: the first principal components represent the variation between the inland area of the Kanto plain and the Pacific coast region with land-sea breeze circulation; the second components relate to variations in urban heat island phenomena in the core of the Tokyo metropolitan area; and the third components are connected to the northeast wind system. In general, the spatial relationships between air temperature and pressure fields for these components are characterized by the relatively low-pressure region corresponding to the high-temperature region.
The major characteristics of the diurnal variation in air temperature and pressure fields on sunny days can be summarized as follows: 1) in the daytime, a relatively high-temperature, low-pressure area is located in the inland area, and then a southerly sea breeze gradually prevails over the whole Kanto plain as it develops; and 2) during the nighttime after sunset, the urban heat island phenomenon in the core of the Tokyo metropolitan area and northern suburbs appears clearly, corresponding to the low-pressure area.
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