Answer:
Atmospheric temperature
The temperature of the atmosphere plays a major role in the heat loss during radiation, if the atmospheric temperature is lower than the radiating temperature then some of the heat is rejected to the atmosphere.
2.Ground surface reflectivity.
This indicates that how much of the rays are reflected from the ground,Metal surfaces, concrete and beach sand can all reflect UV ,while some surfaces do not.The more is the reflection the more will be the intensity of radiation.
3.Presence of pollutants in the atmosphere
Presence of impurities in the atmosphere can become an obstacle in the way of radiation,as rays after striking particles of impurity may get reflected or refracted depending upon the type of impurity present.