This study first analyses the vertical structure of the lowest troposphere from soundings made during the SHEBA experiment. Temperature profiles from ERA-40 are then compared with the observations, both directly and in a climatological sense. One problem with such an evaluation is that the SHEBA soundings were also assimilated in the reanalysis; thus an agreement may be caused by this rather than by the quality of the reanalysis model. We employ several methods to analyze this effect: i) Comparing ERA-40 first-.guess profiles to the observations; ii) Comparing ERA-40 analysis to first-guess (the so-called analysis increment); iii) Comparing the annual climatology in ERA-40 for years without and with assimulations of soundings in the SHEBA region.
The results of this study are: 1) The lower Arctic troposphere is stably stratified in both winter and summer, although less so in the summer; 2) A significant annual cycle exist in inversion properties. Winter is characterized by strong inversions alternating between surface inversions and elevated inversions, while summer is characterized by weaker elevated inversions; 3) ERA-40 has a significant low-level warm bias and a smaller mid-troposphere cool bias and the assimilation of the SHEBA soundings has a significant impact on details in the reanalysis; 5) ERA-40 provides a surprisingly good description of the climatology of inversion characteristics.