Long-term observational and numerical study of low level wind field in the Strait of Hormuz

Wind field is known as an important variable that has significant effects on the behavior of other key meteorological variables. In the present study, wind observational data at 10m AGL from three meteorological stations (Bandar Abbas, Qeshm Airport and Dubai), monthly average and 6-hour ECMWF ERA-Interim data, three key indicators of oceanic climatological oscillation (El Niño–Southern Oscillations, North Atlantic Oscillations and Indian Ocean Dipole) have been used to study the low level wind field of the Strait of Hormuz from 1996 to 2019. For this purpose, the correlations of the MEI.v2, NAO and DMI indexes with the surface wind speed of the Strait of Hormuz has been investigated respectively. The results showed that in the Strait of Hormuz, the direction of prevailing wind has occurred westerly during winter and spring, Southerly to Southeasterly during summer and Southwesterly during autumn. The maximum of 10m daily observational mean wind speed was observed about 5.3 m/s and it was occurred at airport Qeshm station, which shows the western parts of Qeshm island is experiencing higher wind potential than other coasts. A lower level of wind speed was observed on the Strait of Hormuz compared to the middle of the Persian Gulf, which indicates lower synoptical forcing and also the importance of meso-local forcing over this region. The decrease in wind field speed with its counterclockwise deviation at the western entrance of the Strait of Hormuz, which can be due to the presence of islands surface roughness and drag, differences of synoptic forcing between two sea sides of this Strait, especially during summer and autumn (slight convergence in low level) contrary to the funnel-shaped coastline at the western entrance of wind. Also, by examining the correlation between the time variation of MEI.v2, NAO and DMI telecommunication indices and zonal s (zonal / meridional) in Bandar Abbas (OIKB), Qeshm Airport (OIKQ) and Dubai (OMDB) stations, it was observed that the meridional wind components (v) with each index has a different behavior correlation in the northern regions (OIKB and OIKQ) and in the southern part (OMDB) of the Strait of Hormuz. On the contrary, zonal wind components (u) with the different telecommunication indices of oceanic oscillations in all three stations had almost the same behavior correlation. In all seasons and throughout the Strait of Hormuz, the mean value of wind speed in the neutral phase of ENSO, compared to the average of twenty-four years and the positive (El Niño) and negative (La Niña) phases has experienced higher values. The results of the correlation between zonal/meridional wind components and MEI.v2, NAO and DMI indices with a time delay up to 12 months in each station were studied. All three indices show a low level correlation of around 0.30 with the zonal/meridional wind components at all three stations. Simultaneous negative (positive) correlation is observed in all three stations between the u-wind component, with the selected triple indexes. Also, in all three selected stations, diurnal variation of wind speed and direction (daily wind regime) confirm the occurrence of sea breeze and land breeze in the coastal areas of the study area and among stations, the highest incidence of sea breeze and land breeze was observed in Bandar Abbas station.