Diurnal cycles in Arctic surface radiative fluxes in a blended satellite-climate reanalysis data set

General circulation models studies have demonstrated that the Arctic is one of the most sensitive regions on Earth to global climate change. Recent studies show that the Arctic is indeed the region of the greatest warming, with central and northern Siberia experiencing the most pronounced anomalies. Changes in the Arctic climate are associated with the changes in the hydrological cycle, cloud and aerosol variations, evolving ecosystems, and dynamical perturbations, which eventually feed back to the global climate. Unfortunately, the Arctic is also a data sparse region with very few in-situ observations, most of them being in the coastal areas. Field experiments and buoy measurements provide only short time period data for some specific locations.

An alternative approach to gaining a better understanding of Arctic weather and climate is to use numerical climate model analyses combined with satellite data, because satellites can provide more realistic estimates of some geophysical variables and do so with high resolution spatial and temporal coverage. While some satellite data have been assimilated in reanalysis efforts from the National Centers for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) and the European Center for Medium Range Weather Forecasts (ECMWF) reanalyses, new satellite products can be used to adjust or “correct” the reanalysis products, especially for the polar regions.

In this study, the 6-hourly ECMWF Reanalysis product ERA-40 is blended with cloud amount and radiative fluxes from the extended AVHRR Polar Pathfinder (APP-x) data set, then interpolated to hourly values to capture the diurnal cycle. Comparison of the blended data set with observations from two Arctic meteorological stations, Council and Kougarok, Alaska, clearly shows that the blended radiative fluxes are more accurate than those from ERA-40 alone, and that useful information on the diurnal cycle can be obtained. The goal of this paper is to examine the spatial variability and temporal trends in surface radiative fluxes, cloud amount, and surface temperature across the Arctic over the period 1982-2004.