DIURNAL VARIATION OF RAINFALL PROFILES BASED ON 120YEARS HOURLY DATA AT TOKYO

Abstract

Various problems concerning the global environment such as climate change, urbanization, and the heat island phenomenon are paid to attention, especially in terms of rainfall characteristics. This paper focused on characteristics of diurnal patterns of rainfall at Tokyo (Ohtemachi) based on 120-years hourly data from 1890 to 2008. Diurnal patterns were analyzed by using the "P/D" diagnostics which indicates the shape of a single rainfall event by the peak rainfall amount and its duration (whole duration). The P/D diagnostics showed the intensification of short-time rainfall amount in recent. In addition, we proposed a new "P/D" diagnostics which indicates the shape of a single rainfall event with the peak rainfall amount and its duration (from the starting time to the peak time). The results we obtained are following. 1) There is an increasing tendency in the short-time afternoon rainfall. 2) The duration to reaching peak amount for each single rainfall event is clearly decreased particularly at 15LST and 19LST in the recent two decades.