Assessment of reanalysis datasets against radiosonde observation over the Eastern Mediterranean region

Abstract Four meteorological components (geopotential height Z, air temperature T, dew point temperature Td, and relative humidity RH) collected from ERA-5 and ERA-Interim were compared with the observations of nine radiosonde stations with different climatic changes, at different isobaric levels (850, 700, 500, and 200 hPa) during the period 2000–2017, in order to assess the accuracy of the aforementioned reanalysis datasets. The results showed that both reanalysis datasets have a strong correlation with the observed variables, except with dew point temperature and relative humidity in the upper troposphere. The mean values of geopotential height and temperature from both grid dataset are generally consistent with the radiosonde values, whereas considerable bias in the mean Td and RH exists and increases upwards. The study clearly proved that the reanalysis datasets can be used to compensate for the lack of radiosonde observation. Furthermore, air temperature (during 1959–2021) showed an increasing trend from the surface to the lower troposphere, while the temperature decreased in the upper troposphere and lower stratosphere. Finally in this study, the impact of the North Atlantic Oscillation Index (NAOI) on the air temperature was also examined, and a negative relationship was found between NAOI and temperature at the levels: surface, 850, 700, and 500 hPa, while a positive relationship was found, only in winter, at 200 hPa. At the level of 100 hPa, the correlation is positive for both seasons.