Direct thermal radiative forcing of tropospheric aerosol in the Arctic measured by ground based infrared spectrometry

We present, to our knowledge for the first time in the high Arctic, atmospheric thermal emission spectra recorded by ground-based FTIR spectrometry revealing an excess emission contribution, which can only be attributed to the presence of tropospheric aerosols. Consideration of direct thermal forcing in climatological sensitive and remote regions as the Arctic seems to be important for more realistic modelling. According to our measurements, the aerosols can alter the flux density of downward longwave radiation by up to + 2.99 to + 4.66 W m(-2), and the flux density of outgoing longwave radiation by - 0.23 to + 1.17 W m(-2).