Assessment of ERA-Interim Reanalysis Data Quality for the Caspian Sea Area

G. S. Dyakonov, R. A. Ibrayev, and P. O. Shishkova

The analysis of the ERA-Interim atmospheric circulation reanalysis data for the Caspian Sea area is carried out.The possibility of their use for specifying external forcing in a numerical model of thermo- and hydrodynamic processes in the Caspian Seais considered. The quality of these data is estimated based on a comparison with the climate atlases of the sea.The most significant differences between the average long-term fields of ERA-Interim and climate dataare revealed, the possible errors in the numerical simulation of the thermohaline circulation, water and heat budgets of the Caspian Sea are analyzed. It is concluded that, in general, the ERA-Interim fields are in relatively good agreement with the climate and can be used to simulate the dynamics of the Caspian Sea. Wind speed during the autumn-winter period is underestimatedover the Absheron Sill by 1–1.5 m/s and is overestimated in the Northern Caspian Sea by 1–2 m/s, whereas deviations from climate datain the warm season are minimal. The direction of the resulting wind qualitatively coincides with the climate throughout the year. The discrepancies in the fields of air temperature and dew point during most of the year do not exceed 1C and reach 2–3C only in winter in the Northern Caspian. Quite large deviations from climatic data (up to 35%) are registered in radiation fields. However, most likely, they are associated with errors in climate atlases. According to reanalysis data, total precipitation is consistent with the existing quantitative estimates. The spatial and temporal distribution of precipitation qualitatively corresponds to the climate.