As we know tropical intraseasonal oscillation (ISO) was described as 2 modes such as Boreal summer intraseasonal oscillation (BSISO) during boreal summer and Madden-Julian Oscillation (MJO) dominates during boreal winter. In summer time, Thailand where located at the coastal region at the Equator which is effected by BSISO. Some week there is strong diurnal cycle but some week is opposite. The purpose of this work is to study the evolution of BSISO and to study the change of diurnal precipitation in different phases of BSISO. Tropical Rainfall Measuring Mission (TRMM) version 3B42 data on 0.25° X 0.25° grid for JJA 1998-2010 and EOF analysis are used to answer how BSISO modulates the global diurnal precipitation cycle.
This study displays the spatial pattern to show daily mean precipitation, diurnal range and also EOF analysis in different phases of BSISO for summer from 1998-2010. All figures from this study can explain that the effect of BSISO on the diurnal cycle is depended on location. For example in BSISO1 phase 2 (wet phase) over Maritime Continent both ocean and land area have enhance diurnal cycle but over South Asia is different. Over South Asia only the diurnal cycle over land enhances but over ocean at Bay of Bengal the diurnal cycle is depress. On the other hand, in BSISO 1 phase 6 (dry phase) over ocean area such as Bay of Bengal and Philippines Sea have enhance diurnal cycle but over Maritime Continent the diurnal cycle is depress.
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