Assessment of Impacts of Ocean and Urban Landscape on Precipitations by Two-Dimensional Idealized Numerical Experiments.

  • Mayumi Mizunari, 2012: Assessment of Impacts of Ocean and Urban Landscape on Precipitations by Two-Dimensional Idealized Numerical Experiments. .

Abstract

In this study, a statistical analysis of short-time heavy precipitations observed in Tokyo in summer was conducted using rain gauge data from a high spatial resolution network, integrated radar data and GPS precipitable water vapor (GPS-PWV) data. First, 140 days with short-time heavy rainfalls in Tokyo were selected and the features were investigated according to the rain gauge data for the past 15 years (1995-2009). Second, the features of the short-time heavy rainfalls in Tokyo were investigated using the integrated radar. Third, Compared with GPS-PWV at 0900, the distribution of increased GPS-PWV was also analyzed every three hours on tropical days, general heavy rainfall days and short-time heavy rainfall days respectively. The results are as follows. (i) The total amount of short-time heavy rainfalls is large in the west of Tokyo and the west of the Tokyo 23 wards. (ii) The short-time heavy rainfalls are observed with a high frequency in the above areas. (iii) These features are also generally seen on general heavy rainfall days. Features (ii) and (iii) are also indicated by integrated radar data, which show a high frequency of strong radar echo from 2000 to 2400 especially in the west of the Tokyo 23 wards. The results also reveal that the amount of precipitation and the frequency of short-time heavy rainfall days are approximately proportional to elevation. However, in the west of the Tokyo 23 wards, they are prominent at an elevation of about 50m. Besides, the increased amount of GPS-PWV near Okutama is larger on short-time heavy rainfall days than on the other days. The largest increased areas extend to the west of the Tokyo 23 wards.


Keyword : short-time heavy rainfall , Tokyo, rain gauge, synthetic radar, GPS-PWV