Air obscurity caused by smoke reduce horizontal visibility and profoundly affects aviation regularity, efficiency and safety. Various sector have been severely impacted, including air transportation. Land and forest fires smoke has been regularly revealed over Sumatera and Borneo Islands for past two decades. Drainage undoubtedly deepened the GWL, and ET severely decreased in cases with extremely deep GWL. However, the decreasing effect was cancelled by increased evaporation from the waterlogged ground surface during the subsequent La Niña event. Fire potentially decreased ET due to decreased transpiration by burning of vegetation.

This may be due to the hydrophobic dried peat soil, which prevents rainwater infiltration, disconnection of capillary force, or disabled root water uptake as GWL excessively deepened. After drainage by canal excavation, fluctuation of GWL did not significantly influence ET, although ET decreased. This is because atmospheric dryness facilitated evaporation from exposed water on the ground surface, which canceled out the negative effect of transpiration due to stomatal closure. However, the effect was negligible during the water-logged periods. Generally, VPD negatively affected ET due to stomatal regulation functions under dry atmospheric conditions. Alternately, the results of path analysis showed that some environmental factors controlled ET differently depending on environmental conditions. ET had no correlation with the Enhanced Vegetation Index (EVI), which represents above ground biomass for the entire observation period. Half-hourly ET had a strong positive correlation with Rn (R=0.89, p <0.01), and partial positive relationship with VPD when VPD<20 hPa and with GWL when GWL<-0.5 m. In the case of ET > precipitation (P), ET decreased when the GWL was deeper than -0.5 m. Troughs of ET, groundwater level (GWL) and Rn and crests of vapor pressure deficit (VPD) coincided in their time-series variations. Monthly ET and net radiation (Rn) fluctuated in synchrony and thus they decreased considerably under fire-induced dense haze during the El Niño drought. The site burned in 20, and was drained in 2014. The continuous observation of energy fluxes was conducted for approximately 13 years between 20 by using the eddy covariance technique. To elucidate these influences, we examined long-term variation of ET in a degraded peat swamp forest in Central Kalimantan, Indonesia that was affected by drainage and repeated fire. Furthermore, repeated fire occurrences and their corresponding influence on the ET by recurrent burning and smoldering is unexplored. Although there is concern on the influence of fire and drainage on water circulation, their influence on evapotranspiration (ET) is insufficiently understood.

However, fire and drainage have been expanding in PSFs in recent decades. Tropical peat swamp forests (PSFs) play a significant role in the exchange of water between land and the atmosphere.

Vfr visibility requirements