The Impact of a Heterogeneous Surface on Spatiotemporal Uncertainties of Sensible Heat, Latent Heat, and CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; Flux Measured over the Secondary Forest

Nanami Sakai,Masafumi Kon,Daisuke Komori,Wonsik Kim

doi:10.4236/jwarp.2020.123011

Abstract

The turbulent fluxes, such as sensible and latent heat fluxes and CO2 flux, are globally observed over various terrestrial areas in order to understand the interaction between biosphere and atmosphere. Although the turbulent flux observations are generally performed on a horizontally homogeneous surface, the spatial distribution of the soil moisture is not homogeneous even on cultivated land with homogeneous vegetation, indicating that the development of each plant would be different and that the plant physiology, such as photosynthesis and growth, would be heterogeneous. In this study, to clarify the impact of a heterogeneous surface on spatiotemporal uncertainty of turbulent fluxes, a simultaneous flux observation experiment was conducted at different heights (20 m and 30 m) above the ground surface in a secondary seasonal tropical forest located in the Tak Province, Thailand. We defined e as the spatial uncertainty of the turbulent flow flux, as proposed by Kim et al. (2011b) [1], and observed that e of CO2 flux was high, whereas e of sensible and latent heat fluxes were low. This is likely to be caused by spatial uncertainty such as a heterogeneous surface. The CO2 environment was heterogeneous; however, sensible and latent heat environments were homogeneous because the source area received insolation uniformly. Therefore, the analytical results for the CO2 flux presented a different pattern from those exhibited by the analytical results of the latent and sensible heat fluxes.

Highlights

Studies on turbulent diffusion have considerably progressed after Kolmogorov (1941) [2] derived a theoretical interpretation for the turbulent energy spectrum and after Obukhov (1946) [3] discovered that there was a scaling parameter for turbulent diffusion
To clarify the impact of a heterogeneous surface on spatiotemporal uncertainty of turbulent fluxes, a simultaneous flux observation experiment was conducted at different heights (20 m and 30 m) above the ground surface in a secondary seasonal tropical forest located in the Tak Province, Thailand
We defined ε as the spatial uncertainty of the turbulent flow flux, as proposed by Kim et al (2011b) [1], and observed that ε of CO2 flux was high, whereas ε of sensible and latent heat fluxes were low. This is likely to be caused by spatial uncertainty such as a heterogeneous surface

Summary

Introduction

Studies on turbulent diffusion have considerably progressed after Kolmogorov (1941) [2] derived a theoretical interpretation for the turbulent energy spectrum and after Obukhov (1946) [3] discovered that there was a scaling parameter for turbulent diffusion. The turbulence data are currently being collected at more than 500 flux observation sites from various vegetation zones, such as cultivated land and forests, across the world. Using these data, studies are being conducted to quantify the spatiotemporal variations in the global carbon stock and to estimate the global potential evapotranspiration based on biometeorology (Saegusa et al 2008 [6]; Fisher and Baldocchi 2008 [7]). The collected heat, water, and CO2 fluxes are extremely important for studies on the response of the terrestrial ecosystem to the regional differences in global climate change and for the development of models that are necessary to predict these responses

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