Atmospheric turbulence may have a strong impact on the imaging quality of long range warning sensors and other electro-optical systems. Major effects are beam broadening, intensity fluctuations (or scintillation) and angle-of- arrival fluctuations. The structure constant of refractive index fluctuations, Cn2, is the parameter most commonly used to describe the strength of atmospheric turbulence. FGAN-FOM measured Cn2 values in two different climates, moderate climate in mid-Europe, Germany and arid climate in Israel. The measurements in arid climate were carried out in cooperation with the EORD (Electro-Optics Research & Development Foundation Ltd.), TECHNION, Haifa, Israel. The measurements were performed with identical laser scintillometers along a horizontal optical path of about 100 m, above grassland in mid-Europe, and above stony ground without vegetation in Israel. The data were collected continuously for a time period of at least one year at a time resolution of 5 minutes. For both climates examples of the diurnal cycle of Cn2 are given. Since Cn2 usually changes as a function of time-of-day and of season its influence on electro-optical systems can only be expressed in a statistical way. Therefore the cumulative frequencies of occurrence of Cn2 were calculated for a time period of one month for both climates. These results were used to calculate the corresponding turbulence modulation transfer function (MTF) and point spread function (PSF) for a typical IR sensor with a Cadmium Mercury Telluride detector (CMT) and a UV sensor.