A 20-year data set of downwelling longwave flux at the Arctic surface from TOVS satellite data

A reliable estimate of the surface downwelling longwave radiation flux (DLF) is a glaring void in available forcing data sets for models of Arctic sea ice and ocean circulation. A new data set of DLFs is derived from a combination of satellite sounder retrievals and brightness temperatures from the TIROS Operational Vertical Sounder (TOVS), which has flown on NOAA polar-orbiting satellites continuously since late 1979. The fundamental concepts behind our methodology were published in Francis, 1997. Further validation and improvement of the method has been done using surface radiation measurements and surface-based cloud remote sensing retrievals from the ARM (Atmosphereic Radiation Measurement) site in Barrow, AK, and from the SHEBA field experiment. We have also transitioned to using a neural-network version of a forward radiative transfer model to achieve a substantioal increase in computing speed. We produce daily fields between late 1979 and 1999 on a grid with a spatial resolution of 100 km x 100 km north of 60? deg. N. Comparisons with SHEBA and ARM radiation measurements reveal biases of approximately 4 W/m2 and correlations near 0.85.