Surface heat fluxes over the northern Arabian Gulf and the northern Red Sea: Evaluation of ECMWF-ERA5 and NASA-MERRA2 reanalyses

© The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Al Senafi, F., Anis, A., & Menezes, V. Surface heat fluxes over the northern Arabian Gulf and the northern Red Sea: Evaluation of ECMWF-ERA5 and NASA-MERRA2 reanalyses. Atmosphere, 10(9), (2019): 504, doi:10.3390/atmos10090504.The air–sea heat fluxes in marginal seas and under extreme weather conditions constitute an essential source for energy transport and mixing dynamics. To reproduce these effects in numerical models, we need a better understanding of these fluxes. In response to this demand, we undertook a study to examine the surface heat fluxes in the Arabian Gulf (2013 to 2014) and Red Sea (2008 to 2010)—the two salty Indian Ocean marginal seas. We use high-quality buoy observations from offshore meteorological stations and data from two reanalysis products, the Modern-Era Retrospective analysis for Research and Applications version 2 (MERRA2) from the National Aeronautics and Space Administration (NASA) and ERA5, the fifth generation of the European Centre for Medium-Range Weather Forecasts (ECMWF) atmospheric reanalyses of global climate. Comparison of the reanalyses with the in situ-derived fluxes shows that both products underestimate the net heat fluxes in the Gulf and the Red Sea, with biases up to −45 W/m 2 in MERRA2. The reanalyses reproduce relatively well the seasonal variability in the two regions and the effects of wind events on air–sea fluxes. The results suggest that when forcing numerical models, ERA5 might provide a preferable dataset of surface heat fluxes for the Arabian Gulf while for the Red Sea the MERRA2 seems preferable.This study was funded by the Research Sector at Kuwait University (project #ZS03/16) and by NSF (grant #OCE-1435665) supporting V.M

Galveston Bay dynamics under different wind conditions

Summary: The Regional Ocean Model System (ROMS) was used to simulate flow and hydrographic (temperature, salinity) patterns in a shallow, relatively flat-bottomed estuary with two subestuaries, one with an elongated shape and the other with a roughly circular shape. Simulations were used to elucidate the wind stress effect on a tidally formed cyclonic gyre in Galveston Bay, Texas (USA). The form factor suggests that Galveston Bay is a mixed, mainly diurnal system with tides that propagate out of phase by less than 1 h from side to side of the estuary. Temperature and salinity patterns suggest that the influence of the estuary extends oceanward, up to a distance commensurate with the 14 m depth isobath (∼10 km offshore), during a diurnal tidal cycle. A tidally generated cyclonic gyre was observed to form in the circular subestuary, suggesting that this region may be more productive than others. This tidally formed gyre appeared to weaken and even disappear under certain wind stress conditions. Simulations suggest that the entire bay was able to flush only under northeasterly wind conditions, while for all other wind directions (northwesterly, southeasterly and southwesterly), the water appeared to pile up in the circular subestuary. Furthermore, most of the ocean-bay exchange was found to occur through the north entrance to the bay where the effects of the gyre were observed. Thus, it is expected that much of the exchange of water-borne substances, pollutants and plankton between the bay and the ocean occurs through this entrance. Keywords: Suspended particle dispersion, Shallow estuarine dynamics, Galveston Bay dynamics, Ocean shallow water gyre