Assessment of sea surface wind field pattern over the Caspian Sea using EOF analysis

In this study, sea surface wind speed was investigated over the Caspian Sea. To do this, the accuracy of sea surface wind speed was evaluated using the Advanced Scatterometer (ASCAT) data, ERA-Interim and ERAS reanalysis data based on the offshore platform measurements from 01 June 2014 until 09 July 2014. The analysis of data showed the ERA-Interim reanalysis data underestimated for winds greater than 6 mks, while the ERAS reanalysis data underestimated lower than 2 mks. Also, the ASCAT wind speed data was found to have suitable agreements with in-situ measurements in the offshore of the south Caspian Sea. Then, the Empirical Orthogonal Functions (EOFs) analysis method was used to extract sea surface wind speed patterns over the study area using the ERA5 reanalysis data. Three main modes of EOFs respectively revealed 52, 17, and 10% of the total variance of sea surface wind speed over the Caspian Sea. The first mode of the EOFs indicated the most prevailing winds anomaly over the center and north of the region. The second EOFs pattern revealed storms and existence of a dipole system between southern and northern parts. Finally, the third EOFs pattern showed a small cyclone accounting for 10% of total variance over the northwest part of the Caspian Sea caused by the blocked cyclones from the Caucasus Mountains in the west and northwest of the study area. (C) 2020 Elsevier B.V. All rights reserved.