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Bowen Ratio Measurements of Energy Budget Components Over Various Ecosystems in Mymensingh, Bangladesh

R. Khatun
Department of Environmental Science, Bangladesh Agricultural UniversityMymensingh-2202, BANGLADESH

M. A. Farukh
Department of Environmental Science, Bangladesh Agricultural UniversityMymensingh-2202, BANGLADESH

A. MIYATA
National Institute for Agro-Environmental Sciences, Tsukuba, JAPAN

M. A. Baten
Department of Environmental Science, Bangladesh Agricultural UniversityMymensingh-2202, BANGLADESH

Abstract/ Executive Summary:

Surface energy budget components were measured over four different surfaces in the campus of Bangladesh Agricultural University, Mymensingh, Bangladesh (24.75ºN, 90.5ºE) at the beginning of dry season (August to December 2004) using Bowen Ratio Energy Balance (BREB) technique. Under sufficient soil moisture conditions, surface energy budget during the study period was characterized by dominant latent heat flux (79% to 92% of net radiation) and negligibly small sensible heat flux with small modification by vegetation.

Keywords: Bowen Ratio, Energy Budget Components, Ecosystems, Bangladesh

Location: Bangladesh Agricultural University, Mymensingh, Bangladesh

Start Date: 00-08-2004

End Date: 00-12-2004

Program Area: Crop-Soil-Water Management

Commodity: Water management

Objectives:

1. To provide preliminary information on partitioning of net radiation (Rn) into latent heat flux (lE), sensible heat flux (H) and ground heat flux (G) over various ecosystems in Bangladesh.

Methodology:

An experiment was conducted to compute energy balance components over rice field, harvested rice field, grass land and bare land at the Environmental Science Field Laboratory, Bangladesh Agricultural University, Mymensingh during August to December 2004. Soil of experimental field is non-calcareous dark grey floodplain soil with sandy loam texture. The pH value of the soil ranges from 5.9 to 6.5 (According to Soil Science Department, BAU, Mymensingh). The experimental site is under subtropical climate characterized by moderately high temperature and heavy rainfall during the kharif (monsoon) season (April to September) and scanty rainfall with moderately low temperature during Rabi (dry) season (October to March). The energy budget components were calculated using the following equation, Rn = H +lE + G where Rn and G were measured directly using a naturally ventilated net radiometer (Q*6, REBS) and soil heat flux plates (MF-81, EKO), respectively. H and lE were determined using BREB Method. Bowen ratio (β) was calculated from vertical gradients of air temperature and water vapor pressure, which were measured with temperature-humidity sensors (HMP-45A, Vaisala) equipped with homemade ventilators.

Source of Information: J. Environ. Sci. & Natural Resources, 7(1): 21–25, 2014; ISSN 1999-7361

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The present study conducted at the beginning of dry season under sufficient soil moisture conditions, lE was dominant in the surface energy budget, and it accounted for about 80% or more of Rn at all of the four ecosystem types. Further studies in other periods of the year, including rainy season, are desirable for understanding seasonality of surface energy budget in typical ecosystem types in Bangladesh.

Knowledge Management: Journal