In this paper, the seasonal changes in the diurnal variations of wind and the cloud activity at Serpong (106.7°E, 6.4°S), near Jakarta, are climatologically described. In the dry season (May-October), diurnal variation of wind accompanied with sea-land breeze circulation was prominent. In the rainy season (November-April), the diurnal variation was consistent with sea-land breeze circulation, but was not as clear as that in the dry season. The peak time of the northerly in the rainy season, similarly to that of the sea breezes at Serpong in the low level (below 1.0 km height), was earlier than that in the dry season. The maximum time in the climatological diurnal variation of the surface temperature at Serpong in the rainy season was earlier than that in the dry season. The vertical structure which was consistent with sea breeze circulation was clearer when the prevailing (daily-mean) wind was weaker in the rainy season. These results are consistent with the features of the local circulation; in other words, the local circulation depends on the diurnal variation of surface temperature and is prominent when the prevailing wind is weak. The typical diurnal variation of the wind in the rainy season was unclear when the prevailing northwesterly to westerly was strong around Serpong. Interannual variation of the diurnal variation could be detected in the transitional period from the dry to the rainy season. Cloud activity had prominent diurnal variation over West Jawa in the rainy season and was active in the early evening over land, particularly, in the mountainous area in the south of Serpong. When cloud activity was active over the mountainous area, the northerly below 1.0 km in height was prominent at Serpong, which is consistent with the feature that the development of a local cloud system is accompanied with local circulation.
2006 by Meteorological Society of Japan