Long-term variability of air temperature in the Aral sea region

The interannual and interdecadal variability of the air temperature in the Aral sea region at surface and at different isobaric levels is investigated using NCAR/NCEP reanalysis data, CARDS aerological data, data collected at the former USSR and the present Kazakhstan and Uzbekistan meteorological stations. Five groups of stations are identified in the study region using an objective classification algorithm. The reanalysis data for the Aral sea region are first validated against the observational data. The analysis reveals that during the pre-desiccation period, negative air temperature trends were dominant for all seasons except winter. In contrast, the desiccation period was mainly characterized by trends towards warming. The largest trend values corresponded to related winter, and the second largest with summer. The character of the long-term air temperature variability at different isobaric levels over the Aral sea region was essentially same as that of the larger spatial scale background variability. However, the southwestern part of the Aral sea region up to 700 mb exhibits statistically significant local anomalies possibly associated with the Aral sea desiccation. The wavelet analysis is used to investigate the frequency structure of the air temperature variability in the Aral sea region.