Changing evapotranspiration in a natural Cambodian tropical seasonal forest under the effect of a strong El Niño
Abstract
Forests play an important role in the biosphere-atmosphere interactions of the Earth. However, heat and mass exchanges are less well understood in tropical seasonal forests than boreal or temperate forests. With the rapid disappearance of these tropical forests in Southeast Asia, there is an urgent need to better understand them. Thus, for the past decade we have measured sensible- and latent-heat fluxes over natural forests in the Kingdom of Cambodia, where natural forests remain relatively intact compared to neighboring countries, despite no access to commercial electricity. We applied the bandpass eddy covariance method, in which a paired sonic anemo-thermometer and a capacitance hygrometer was used to save power consumption. Because of the slow time response of the hygrometer, the high-frequency signal was calibrated by applying an empirical function with a variable parameter which was determined by the signal drop-down rate (due to the status of instrument and/or environment). The estimated flux values generally agreed with those with open-path IRGA which was installed temporarily. Although observation was often intermittent due to instrumental troubles, data for four dry- and wet-seasons were continuously obtained over a dry-evergreen forest. In 2015-2016, our data included a severe drought and higher temperatures in the dry season induced by an exceptionally strong El-Niño. Usually, seasonal variation of latent heat flux (λE) was synchronized with that of net radiation (Rn), and daily λE was always larger than sensible heat flux (H). However, we found the reverse situation (λE < H) in the 2015-2016 dry season. In this presentation, we present the relationships of heat fluxes with hydro-meteorological factors in those periods in detail, and also show how the 2015-2016 El-Niño affected the variations of λE, H and other factors simultaneously observed in a dry deciduous forest.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.H52E..03S
- Keywords:
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- 1818 Evapotranspiration;
- HYDROLOGYDE: 1895 Instruments and techniques: monitoring;
- HYDROLOGY