The measurement of surface energy balance over a land surface in an open area in Bangalore is reported. Measurements of all variables needed to calculate the surface energy balance on time scales longer than a week are made. Components of radiative ﬂuxes are measured while sensible and latent heat ﬂuxes are based on the bulk method using measurements made at two levels on a micrometeorological tower of 10 m height. The bulk ﬂux formulation is veriﬁed by comparing its ﬂuxes with direct ﬂuxes using sonic anemometer data sampled at 10 Hz.Soil temperature is measured at 4 depths. Data have been continuously collected for over 6 months covering pre-monsoon and monsoon periods during the year 2006. The study ﬁrst addresses the issue of getting the ﬂuxes accurately.It is shown that water vapour measurements are the most crucial. A bias of 0.25% in relative humidity,which is well above the normal accuracy assumed by the manufacturers but achievable in the ﬁeld using a combination of laboratory calibration and ﬁeld intercomparisons, results in about 20 W m−2 change in the latent heat ﬂux on the seasonal time scale. When seen on the seasonal time scale,the net longwave radiation is the largest energy loss term at the experimental site. The seasonal variation in the energy sink term is small compared to that in the energy source term.
Volume 128 | Issue 8
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