Persian Gulf Water mass tracking by surface temperature and salinity properties

The Persian Gulf is a shallow, semi-closed environment with an average depth of 35 meters and a maximum depth of 90 meters, connected to the Gulf of Oman through the Strait of Hormuz. The Persian Gulf is one of the main sources of saline water masses in the world. In the past, passive detectors have been used to track water mass. The use of satellite data in the study of water patterns and masses is a new science. The reasons of satellite data usage are its low costs and its availability. The purpose of this research is to investigate the location of Persian Gulf Water mass (PGW) in both warm and cold seasons which by using satellite data analysis, the distribution and dynamics of the Persian Gulf Water mass have been investigated and its possible areas in the Oman Sea have been identified.

The sea surface temperature of the studied area (47.00-59.45˚E, 22.60-32.00˚N) prepared from the Group for High Resoulation Sea Surface Temperature (SST) of NOAA named OSTIA (by the resolution of 0.05˚), and Sea Surface Salinity (SSS) prepared from NOAA NESDIS STAR (by the resolution of 0.25˚), respectively. First, daily statistical data for six years (2014-2019) were extracted annually, in both warm and cold seasons. Then, temporal mean, maximum, minimum, range and standard deviation were obtained for the whole basin and the means of the basin were illustrated separately for each season. The spatial mean of annual SST of basin in the studied years (2014-2019) was calculated for all cells, but the spatial mean of annual SSS was not calculated due to the lack of data in many cells. Then, the SST and SSS satellite data, according to the 73-years measured historical data, were spatially filtered in MATLAB to obtain the filtered range of SST and SSS and determine the expansion of the PGW mass in Oman Sea.

From the filter of OSTIA satellite data in the warm season of the studied years (2014-2019), it was observed that the PGW mass has shifted, so that PGW mass has gone further and moved to east about 0.12 degrees equal to 14 km in 2016 in compared with 2015 and about 0.08 degrees, equivalent to 9 km in 2017 in compared with 2016. The PGW can be transported in the Oman Sea, 300 to 350 km from the Strait of Hormuz. The width of PGW in the Oman Sea is about one degree (56-57˚E) in the warm season and 2.5 degrees (57-59.5˚E) in the cold season, by annual changes. (The widest expansion happened in 2015.).

This study represents that the difference of the highest daily SST of the warm and cold seasons (35.87˚C and 34.06˚C, respectively) were about 1.8˚C and the lowest daily SST difference of  the warm and cold seasons (18.27˚C and 13.11˚C, respectively) were about 5.16˚C. The average salinity in the warm season is about 34.08 psu to 36.49 psu with a range of changes of 2.4 psu. Whereas the average salinity is in the range of 34.51 psu to 36.50 psu with a range of changes of 2.01 psu in the cold season. Moreover, the surface water of the cold season (by filtered temperature of 28.5-30˚C) is located in the west of Oman Sea (58.5˚E to 59.5˚E). In the warm season, this water progress farther to the middle of Oman Sea (longitudes more than 59.5˚E), which indicates that the PGW mass penetrates more from its subsurface to the Oman Sea in the warm season.