(i) Surface Observations
There are at present 45 radiation observatories recording various radiation parameters. At all these stations, measurement of global solar radiation is being carried out while at a few selected stations other parameters like diffuse, direct, net, net-terrestrial and reflected radiation and atmospheric turbidity are also measured. Data loggers have been introduced at four stations viz. New Delhi, Patna, Jaipur and Thiruvanathapuram. The primary objective of the observational programme is to have an understanding of basic physical processes involved in the conversion of the Sun's radiant energy into atmospheric motions as also into chemical and biochemical energy. The observations made at national network of radiation stations are useful in the assessment of solar energy potential in different parts of the country.
(ii) Upper Air Observatories
Besides the measurements on the surface, fortnightly airborne soundings are made with radiometersondes to measure directly the vertical distribution of the infrared radiation flux and radiation cooling from surface upto a height of 20 Km or more in the free atmosphere, at New Delhi, Srinagar, Thiruvananthapuram, Pune, Nagpur, Jodhpur, Calcutta and Bhubaneshwar. Radiometersonde ascents are being conducted regularly at Maitri, the Indian Antaractic station also.