همرفت پخش دوگانه و وارونگي دما در آب هاي خليج فارس و درياي عمان

Double diffusive convection and temperature inversion in the Persian Gulf and Oman sea

Double diffusive convection (DDC) is a common phenomenon which is often associated with temperature inversion (increase of T with depth) (Tl) for the greater part of the worldʹs oceans. The fact that Tl with widely varying properties (thickness, intensity, and stability) occur quite often in the ocean and that they are, as a rule, hydrostatical ly stable, has attracted special attention. Here we investigate the structure of temperature inversions in the Persian Gulf and Oman sea. Tl regions in the Persian Gulf is observed in the winter time at depth of about 40 m, but are observed in the Persian Gulf outflow in Oman sea at a depth of about 250 m in summer and winter. In the Persian Gulf, the diffusive regime of DDC is often observed and the density ratio is in the range of 0.2-0.7. In Oman sea the finger as well as the diffusive regimes are observed with density ratio of about 0.4 Tl in the Persian Gulf is also found to be more intensive than that of the Omanʹs. Tl often appear in the boundary of outgoing water of the Gulf and incoming water of open sea, a region prone to instability (large scale) and eddy for motion. Using a relation ofA5= a^T + b for Tl regions, we found that a and b are respectively 0.92, 0.34 and 0.37, 0.04 for the Persian Gulf and Oman sea, indicating that the flow in these regions is isopycnal in Oman sea but highly non isopycnal in the Persian Gulf. Therefore, mixing mechanisms are expected to be different in the two situations. Here the DDC fluxes have been estimated to be about 22 W/m2 for 0.5