He gained a Doctorate in Atmospheric Physics on the subject of remote sensing of cloud properties, where his supervisor was Stuart Bradley.
[4] He worked for a short time in UV research at the New Zealand Meteorological Service before taking up a post-doctoral position in the Physics Department in Oxford, where his research was focused on measurement of stratospheric aerosols using the ISAMS satellite instrument designed at Oxford.
[5] In 1998, he returned to New Zealand to accept a Lectureship at the University of Canterbury, where he conducted new instrumental work to measure aerosol properties.
Grainger is the Principal Investigator of the Optimal Retrieval of Aerosol and Cloud (ORAC) project,[6] which is a community code to optimally estimate aerosol and cloud properties from satellite imagery, and was principally responsible for starting this project.
The Earth Observation Data Group which he heads is primarily interested in atmospheric trace gases and clouds (especially with regard to processes which control climate), and conducts satellite studies of atmospheric aerosols.