利用4年（1999～2002）的雾观测资料,对西双版纳热带季节雨林内雾特征进行了观测研究。结果表明，雾首先形成于最上林冠层，林下雾是由上层雾变浓、下沉而来。夜间，雾形成前，气温高于叶表温；雾形成后，气温则低于叶表温。热带雨林内各季节雾日数和雾日频率均高于无林地。热带雨林内平均全年雾日数可达258 d，其中雾季和干热季共占154 d（59.6%），而雾季的雾日频率高达90%。雾日数的季节变化与各季节雨量呈明显的负相关。雾季，雾在23∶00左右生成，比干热季、雨季分别提前0.7、2.3 h，而消散时间则分别推迟0.8、2.2 h。雾生成和消散时间呈现出较明显的负相关。雾季雾的持续时间达12.2 h·d-1，比干热季、雨季分别长1.5、4.6 h·d-1。全年雾总持续时间占全年时间的39.7%，而雾季的相应值为50.8%。雾的形成不仅凝结了水汽进入森林（全年89.4 mm），同时也对森林起到了一定的保温作用，这对热带雨林的生存和发展具有至关重要的作用。
Fog frequency and duration were measured between November 1998 and February 2003 in a seasonal rain forest in Xishuangbanna, Southwest China. The amount of fog and dew precipitation was measured daily using twelve bottle-funnel collectors set in a random pattern on the forest floor. Related microclimatic variables including air temperature, relative humidity, wind speed, solar radiation and rainfall were recorded by a meteorological observation system mounted on a 72 m tall meteorological tower in the study site. At night the fog occurred first at the top layer of the canopy, and then a thick fog penetrated the understory. Before fog occurred, the air temperature was greater at 0.5 m above the canopy than on the canopy surface but was lower after fog occurred. The number of fog days was much higher inside the rain forest (258 days/year) than in open areas (188 days/year). Fog frequency in the rain forest was 90% during the foggy season (November-February), slightly lower (78.7%) in the dry-hot season (March-April), and lowest (55.4%) in the rainy season (May-October). The number of fog days in each season was negatively correlated with the amount of rainfall. The onset of fog occurred on average at 2 300 and lifted at 1 100 hours during the foggy season. During the dry-hot season and rainy season, the fog occurred 0.7 and 2.3 hours later and lifted 0.8 and 2.2 hours earlier, respectively. Meanwhile, there was a negative correlation between the time of fog occurrence and lift. Average fog duration per day during the foggy season was 12.2 hours, and was 1.2 and 1.6 times longer than average fog duration of the dry-hot and rainy season, respectively. During the study period, the absolute amount of mean annual fog and dew precipitation was (89.4±13.5) mm (mean±SD), which was 4.9%±1.7% of the annual precipitation. Of the total annual amount of fog and dew precipitation, 85.9%±6.6% was collected during the foggy season and dry-hot season. The results suggest that fog, which both condenses water vapor into available precipitation in the forest and buffers temperature changes, plays an important role in the hydrology of the forest, especially during the foggy and dry-hot seasons. Therefore, horizontal precipitation (fog interception) needs to be included in calculations of the water balance in this forest. These results also demonstrate the importance of understanding the impacts of climate factors, and have important implications for ecologists and hydrologists interested in fog-inundated ecosystems.