Climate of the Summit Region of Mount Kinabalu (Borneo) in 1992, an El Nino Year

An extensive El Niflo, which normally causes droughts on the western side of the tropical Pacific basin, occurred from the spring of 1991 to May 1992. Measurements were taken of climatic variables associated with this irregular but reoccurring event in a high-altitude environment at 3,780 m near the upper timberline on Mount Kinabalu, Borneo, for one year in 1992. These included temperature above and below ground, vapor pressure, global radiation, photosynthetically active radiation, and rainfall. Mean monthly air temperatures at 1.5 m ranged from 6.6 (October) to 9.7?C (March) with an annual mean of 8.1?C. Relatively dry periods with monthly rainfall less than 100 mm ocurred from January to April and in August. Total rainfall for the year was 2,418 mm. Monthly rainfall minus potential evapotranspiration indicated net negative water budgets in the dry periods for all albedo values (0.1-0.5) which were used in the calculation. Associated with these droughts were freezing ground-air temperatures and an extremely high soil temperature. It is inferred that the marked aridity resulted from the ocurrence of air subsidence which adiabatically becomes dry and isolates the summit from uplifting moist air. However, the mechanisms causing putative subsidence remain unknown and I cannot conclude if the 1992 drought on Mount Kinabalu is attributable to the El Nifio only. Nevertheless, this study suggests the possibility of extensive water stress to plants in the summit region. Small-sized leaves and sclerophylly, which characterize the site, appear to be morphological adaptations primarily to such water stress.