Evaluation of cloudiness/haziness factor for composite climate

In this communication, an attempt has been made to evaluate the cloudiness/haziness factor for the composite climate of New Delhi (latitude: 28.58° N; longitude: 77.02° E; elevation: 216 m above msl). To estimate 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 10 years (1989–1998) have been used and analyzed using linear regression analysis. The data have been obtained from the Indian Meteorological Department, Pune, India. It has been observed that there is about 15% maximum deviation between predicted and observed values of hourly varying beam and diffuse radiation for clear (blue sky) weather condition.