The phrase "balloon measurements" refers to estimating or guessing measurements without using precise tools. It means making rough or approximate calculations rather than exact ones. Full definition
We have satellite data plus weather balloon measurements of temperature and wind strength. (skepticalscience.com)
Weather balloon measurements and other data showed that last September, the ozone hole was 4 million square kilometers smaller than its peak size. (sciencemag.org)
Since then, satellite reading of temperatures and the occlusion of numerous infrared bands, ground based, aircraft and balloon measurements of same, and an ever - increasing data base of the optical properties of CO2 (and other gases, like water vapour), have helped refine radiation calculations towards determining the atmospheric heat budget. (illconsidered.blogspot.ru)