Climatic patterns in a tropical rainforest in Brunei

Meteorological parameters were monitored on an hourly basis over ten months during 1991-2, from altitudes of 45 and 913 metres in an undisturbed tropi cal rainforest in Brunei, near the north-west coast of Borneo. In general, the observed characteristics of the climate accorded with the regional mete orological systems and with published results from other studies in norther n Borneo, although a greater degree of temporal variability was apparent. T he seasonal variability was probably enhanced by the EI Nino Southern Oscil lation event of early 1992. Rainfall events were typically highly variable in nature, although storm intensity profiles were broadly similar. High mag nitude and high intensity events are common among the large total number of events. More rain, of generally higher intensity, fell on the mountain. Th e total daily solar energy receipt was similar at both altitudes owing to g reater cloud cover on the mountain. Temperatures varied significantly with season at both altitudes and the mean lapse rate was 4.5 degrees C/km. Rela tive humidity at 913 metres tended to be significantly higher during the da y and significantly lower at night than at 45 metres. Wind directions were dominantly controlled by local mountain and valley wind systems. Wind speed s were significantly higher during the dry seasons and at the higher altitu de. Previous studies have shown that small but significant variations in me teorological parameters can have distinct ecological responses, and rainfal l characteristics are important controls on geomorphological processes.