In this paper, local meteorological data for a period of 35 years (from 1979 to 2013) from Kuujuaq station have been used to calculate the surface refractivity, N (a link for the data is available in the acknowledgements), and to estimate the vertical refractivity gradient, dN1, in the lowest atmospheric layer above the ground. Monthly and yearly variations of the mean of N and dN1 are provided. The values obtained are compared with the corresponding values from the ITU maps. The long‐term trend of the surface refractivity is also investigated. The data demonstrate that the indices N and dN1 are subject to an evolution that may have significance in the context of climate change. Monthly means of N show an increasing departure from ITU‐R values since 1990. Yearly mean values of the dN1 show a progressive decrease over the period of study. Seasonal means of dN1 show a decrease over time, especially for summer. Such a trend may increase the occurrence of superrefraction. However, currently available ITU‐R recommendations for microwave link design assume a stationary climate, so there is a need for a new modeling approach.

Microwave telecommunications links are severely influenced by the frequency and climatic parameters as refractivity gradient (dN1), geoclimatic factor (K), rain, temperature, pressure, and humidity. This influence increases with the frequency of the wave. In microwave band, recent research has shown that the geoclimatic factor (K), rain and temperature are the most important parameters affecting the performance of terrestrial links. K is an important parameter as directly proportional to the worst month outage probability P w . K depends on the refractivity gradient dN1. The dN1 depends itself on the pressure, the temperature and the humidity. In this paper, we demonstrated from the data of the terrestrial links located in Quebec, Canada, that there is a seasonal variation of the geoclimatic factor, K mes . This variation of K mes is mainly due to the variation of the humidity. The variation of the geoclimatic factor is not limited to the seasonal variation. But it is true from one year to another. IUT recommendations do not embed climate change, but assume a stationary climate. We recommend to improve data analysis and predictive models by taking into account the temporal changes.

No abstract

No abstract

Thirty-nine years of archived meteorological data measured at two stations located in the northern and southern parts of Quebec, Canada are used to estimate the surface refractivity and its dry and wet components. The results of the comparison of the obtained estimates showed that for all months the values of the dry component are higher in the northern part, whereas the values of the wet component are higher in the southern part. Due to this, for several months of the year, the values of the surface refractivity are higher in the northern part and for the remaining months in the southern part. Moreover, in both parts, August is the month where the highest values of the surface refractivity were recorded. In this particular month, the slope of the surface refractivity trend in the northern part is several times higher than that in the southern part. The obtained results show that the performance of the used direct smoothing forecasting technique depends on the deviation between the values of N in the current year and the previous year.