An Arctic inversion climatology based on the European Centre Reanalysis ERA-40

A low-level temperature inversion is a frequent phenomenon in the Arctic boundary layer as known from various observational sources and is investigated in a number of studies. These investigations, however, focus on certain regions and are based on limited observational periods. In this paper, a coherent (in space and time) climatology of the boundary-layer inversion in the Arctic (>60°N) is presented for the first time using the six-hourly ERA-40 reanalysis data for the period 1957-2002. The frequency of inversion occurrence and the height, depth and strength of the inversion are analysed. The investigation concentrates on the spatial distribution of the inversion characteristics in various regions of the Arctic, on the mean annual cycle and the inter-annual variability and the long-term trends.