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Abstract:
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Atmospheric surface boundary layer parameters vary anomalously in response to the occurrence of
annular solar eclipse on 15th January 2010 over Cochin. It was the longest annular solar eclipse
occurred over South India with high intensity. As it occurred during the noon hours, it is considered to
be much more significant because of its effects in all the regions of atmosphere including ionosphere.
Since the insolation is the main driving factor responsible for the anomalous changes occurred in the
surface layer due to annular solar eclipse, occurred on 15th January 2010, that played very important
role in understanding dynamics of the atmosphere during the eclipse period because of its coincidence
with the noon time. The Sonic anemometer is able to give data of zonal, meridional and vertical wind as
well as the air temperature at a temporal resolution of 1 s. Different surface boundary layer parameters
and turbulent fluxes were computed by the application of eddy correlation technique using the high
resolution station data. The surface boundary layer parameters that are computed using the sonic
anemometer data during the period are momentum flux, sensible heat flux, turbulent kinetic energy,
frictional velocity (u*), variance of temperature, variances of u, v and w wind. In order to compare the
results, a control run has been done using the data of previous day as well as next day. It is noted that
over the specified time period of annular solar eclipse, all the above stated surface boundary layer
parameters vary anomalously when compared with the control run. From the observations we could
note that momentum flux was 0.1 Nm 2 instead of the mean value 0.2 Nm-2 when there was eclipse.
Sensible heat flux anomalously decreases to 50 Nm 2 instead of the mean value 200 Nm 2 at the time
of solar eclipse. The turbulent kinetic energy decreases to 0.2 m2s 2 from the mean value 1 m2s 2. The
frictional velocity value decreases to 0.05 ms 1 instead of the mean value 0.2 ms 1. The present study
aimed at understanding the dynamics of surface layer in response to the annular solar eclipse over a
tropical coastal station, occurred during the noon hours. Key words: annular solar eclipse, surface
boundary layer, sonic anemometer |