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Estimation of Heat Storage Flux in Soybean Field

M. G. Mostafa
Additional Agriculture Officer , DAE, Sreebordi, Sherpur

M. A. Baten
Department of Environmental Science, Bangladesh Agricultural University, Mymensingh

Abstract/ Executive Summary:

The findings showed that heat storage terms ranged significantly in the daytime and weakly in the nighttime and the absolute values of sensible and latent heat storage fluxes were obviously greater than other heat storage terms. In addition, the absolute values of total heat storage fluxes reached the peak in clear day (67.65 Wm-2), then were long at the cloudy day (44.16 Wm-2), and reached the minimum at the rainy day (41.75 Wm-2). The ratios of heat storage fluxes to net radiation generally decreased with time in the daytime. In the daytime, the ratios of the total heat storage to net radiation were greater and difference in these ratios were distinct among day before 12:00 (with a peak value of 26.22%, 21.89% and 28.73% at clear, cloudy and rainy day, respectively) and then they became lower and differences were small after 12:00 hours.

Keywords: Heat storage flux, Net radiation, Soybean field

Location: Field Laboratory of the Department of Environmental Science, Bangladesh Agricultural University,Mymensingh

Start Date: 00-01-2007

End Date: 00-04-2007

Program Area: Risk Management in Agriculture

Commodity: Soybean

Objectives:

1. To calculate the heat storage in different weather (clear, cloudy and rainy day) conditions in soybean field.

Methodology:

An experiment was conducted at the Field Laboratory of the Department of Environmental Science, Bangladesh Agricultural University, Mymensingh during the period from January to April 2007 to estimate daytime variation of heat storage fluxes in a soybean field at clear, cloudy and rainy days observed over soybean field. In order to discuss the values and daily variation characteristics of heat storage fluxes in soybean field, the sensible and latent heat storage flux within air column, canopy heat storage flux, and ground heat storage above the soil heat flux, as well as the ratios of these heat fluxes to the net radiation at the clear, cloudy and rainy day were compared and analyzed. The size of the experimental plot was 10m x 10m. North - South (N-S) row orientation was maintained to grow soybean. Plant to plant distance was 10 cm and row-to-row distance was 50 cm. Micrometeorological elements were measured using instruments. Rs, Solar radiation (W m-2) was measured using Pyranometers. Light (μ molm-2s-1) was measured using PAR sensor. Ta, Air temperature (°C) and RH (Relative humidity) over and below the canopy was measured using Vaisala sensors. Ts, Soil temperature (°C) were measured using Thermocouples. Tc, Canopy temperature (°C) was measured using Infrared radiation thermometer, G, Soil heat flux was measured by Soil heat flow plate. Ten seconds interval data was recorded by CR 23X Data logger, which again was automatically averaged as 30 minutes average and stored in storage module (SM4M, Campbell Scientifics, USA). The experimental raw data at 15 min intervals were retrieved from the storage module periodically for further averaging and mathematical interpolation. All collected data were in mV. Then average data were corrected and converted into Wm-2 (incase of solar radiation, net radiation and soil heat flux), μmol m-2s-1 (incase of light intensity), °C (in case of air and soil temperature) and percentage (in case of relative humidity).

Source of Information: J. Environ. Sci. & Natural Resources , 2 (1): 205-210, 2009; ISSN 1999-7361

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The sensible and latent heat storage flux within air column, canopy heat storage flux, and ground heat storage above the soil heat flux plate, as well as the ratios of these heat storage fluxes to the net radiation at the clear, cloudy and rainy days were compared and analyzed based on the observation data, meteorological factors and biomass. The findings showed that the values of sensible heat flux changed from positive to negative earlier in the morning and from negative to positive later in the dusk. Sensible heat flux also reached a peak at 9:30 am at clear and cloudy day, while at rainy day; it reached a peak at 8:00 am. Values of latent heat flux varying significantly in the daytime and weakly in the night time and reached negative after 12:30 pm. The values of soil heat storage was positive after 7:30 hours to 15:00 hours except rainy day where it was positive till 12:30. The ratios of heat storage fluxes to net radiation decreased with time in the daytime.

Knowledge Management: Journal