A time series of the hemispheric distribution of integrated water vapor measured with the ASMUWARA radiometer are analyzed by means of Empirical Orthogonal Functions (EOFs). The data were acquired in February 2007 at the Zimmerwald observatory in Switzerland. It is shown that the analysis of temporally demeaned time series yields information about passing fronts. With EOF analysis of the spatially demeaned time series, information about the spatial distribution of IWV is obtained. Our results also indicate that water vapor behaves like a conservative and passive tracer within the examined sampling volume and with the given temporal sampling resolution of 12 minutes.