In 1993 and 1994 TNO-FEL participated in the execution of experiments over the North Sea in order to derive the infrared atmospheric scintillation and beam deformation process. In 1993 the NATO MAPTIP trial allowed us to observe an infrared point source from a platform at sea with a 10 micron FLIR, at various ranges (0.5 - 5 NM) and in various directions. In 1994 an infrared source was used at fixed distances on a platform at sea, with heights at the platform ranging between 1.5 and 7 m above the sea level. Some additional sources, at different height levels, were installed later in the experiment. The receiver system was placed at 18 km on a pier near the Dutch coast. Recordings took place with the receiver at two heights, 40 and 15 m above the average sea level. A single recording consisted of 10 seconds of measurements at 25 Hz with a 64 by 64 Cincinnati IRC-64A camera in the 3 - 5 micrometer band. Also data in the 10 micrometer band is available. We have also executed experiments with a source on a boat sailing out from close by to the optical horizon. Examples of these recordings are presented. The data were analyzed for scintillation effects, atmospheric APSF effects, and refraction effects. These data are compared to the atmospheric conditions that were recorded simultaneously, in order to model the infrared scintillation effects with meteorological conditions. In the paper we describe the analysis and results on the atmospheric effects with meteorological condition and with range. Results of these comparisons are also shown. We discuss the effects that these results have on the performance of IRSTs, and how improvements can be made to the IRST based on these results.