Long-Term Evolution of The Surface Refractivity for Arctic Regions

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.