海南岛干旱的气象特征及监测指标

为科学制定应对干旱措施，减轻干旱对海南生态和生产的影响，从降水分布、干旱成因、干湿状况、水分平衡及监测指标等角度描述海南岛干旱的气象特征。结果表明，海南岛降水时空分布不均匀：冬春少、夏秋多，空间上东多西少；从干湿指数看，11月到翌年4月气候干燥，5月开始逐渐变湿，8、9、10月最为湿润。地表实际蒸散发量中间山区高，四周平原台地低。从月降水满足实际蒸散发需水量的能力来看，海南岛的冬春季节降水充沛月比例较低，普遍在20%以下;南部和西部尤为严重，监测海南岛干旱发生发展，旱季适宜用6个月或12个月时间尺度的SPEI指数，而雨季适宜用3个月时间尺度的SPEI指数。

Meteorological characteristics and monitoring index of drought in Hainan Island

Drought is one of the main meteorological disasters affecting ecology and production in Hainan. The meteorological drought in Hainan Island was analyzed from the perspectives of precipitation distribution, drought causes, dry and wet conditions, water balance and drought monitoring index, in order to provide a reference for relevant decision-making and research. Hainan Island is located on the north edge of the South China Sea. Affected by the tropical monsoon climate and topography, the temporal and spatial distribution of precipitation is uneven. Hainan Island has low precipitation in winter and spring, high in summer and autumn, and spatially higher in the east part than in the west part. From the dry-wet indices, it can be seen that Hainan Island is dry from November to April, and gradually becomes wet since May, and wettest in August, September and October. The actual evapotranspiration of the surface is high in the central mountain area and low in the surrounding plains and terraces. The months with the ratio of abundant precipitation to evapotranspiration are very few in winter and spring (December to April), generally below 20 %. It is particularly seriously dry in the south and west of Hainan Island. The Standardize Precipitation Evapotranspiration index (SPEI) is calculated for different timescales to determine the drought in Hainan. It is found that SPEI for a 6 or 12-months timescale in the dry season and for a 3-months timescale in the wet season can be used to determine the drought in Hainan Island to monitor the occurrence and development of drought in the Island.