Atmospheric water vapor is the most important of the greenhouse gases in the climate system. It is greatly variable on multiple temporal/spatial scales and has been predicted to increase under a global warming scenario. Satellite observations had been very useful to determine water vapor distributions, but these are not sufficient to understand the complicated system that upper tropospheric moisture represents. In order to achive a somewhat better understanding, it is necessary to implement empirical observations hence, the implementation of in-situ appraisals. This work investigates the variation of upper-tropospheric water vapor in relation to high-level clouds using data from in situ relative humidity measurement by commercial aircraft (MOZAIC) and satellite observations (ISCCP). The in-situ data is correlated with the cold clouds identified by satellites that retrieve cloud top temperature, cloud top pressure, and cloud optical depth. Preliminary results will be shown and discussed.