Evaluation of Atmospheric Transmittance for Composite Climate

In this paper, an attempt has been made to estimate the cloudiness/haziness factors and atmospheric transmittances for the composite climate of New Delhi (latitude:28.58o N; longitude: 77.02o E; elevation: 216 m above msl). To predict the hourly variation of beam and diffuse radiation on a horizontal surface for any day, atmospheric transmittances for beam and diffuse radiation have been introduced to take into account the uncertain behaviour of atmospheric conditions. For the present study, the hourly data of global and diffuse solar radiation on a horizontal surface for a period of 11 years (1991–2001) have been used and analyzed using polynomial regression analysis. The data have been obtained from the Indian Meteorological Department, Pune, India. It has been observed that there is about 11% maximum and 01% minimum root mean square error between predicted and observed values of hourly varying beam radiation for clear (blue sky) weather condition