Surface Heat Fluxes over the Northern Arabian Gulf and the Northern Red Sea: Evaluation of ECMWF-ERA5 and NASA-MERRA2 Reanalyses

Abstract

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.

Influences of Physical and Biogeochemical Variability of the Central Red Sea During Winter

“…Wind stress was calculated from wind speed using the method of Large and Pond (1981). We use daily mean values for the deployment period from December 2, 2014 to March 2, 2013 retrieved from NASA's Modern Era Retrospective Analysis for Research and Applications (Al Senafi et al., 2019; Rienecker et al., 2011) with a resolution 2/3° by 1/2°. The spatial average of the air temperature, wind stress, relative humidity and Qnet has been estimated over the study area (between 21.9° and 24.1°N and from 38.1°to 38.8°E).…”

“…. We use daily mean values for the deployment period from December 2, 2014 to March 2, 2013 retrieved from NASA's Modern Era Retrospective Analysis for Research and Applications(Rienecker et al 2011;Al Senafi et al 2019) with a resolution 2/3˚ by 1/2˚. The spatial average of the air temperature, wind stress, relative humidity and Qnet has been estimated over the study area (between 21.9˚ and 24.1˚ N and from 38.1˚ to 38.8˚ E.2.3 Satellite dataTo place the glider observations into the larger context of the CRS two relatively clear daily MODIS Level-3 images with 4 km horizontal resolution were obtained from NASA's Ocean Color Web (http://oceancolor.gsfc.nasa.gov/) for 2 and 7…”

Characteristics of the Reanalysis and Satellite-Based Surface Net Radiation Data in the Arctic

“…ERA5 is based on the new numerical weather product (IFS Cycle 41r2, 2016 version) [18]. Compared to ERA-Interim, ERA5 offers improved spatial resolution, from 79 km to 31 km, and a higher output frequency, from every 6 hours (h) to hourly sampling from 1979 [31]. Therefore, ERA5 is a higher-resolution model, as a replacement for ERA-Interim [32,33].…”

Satellite Observations of Wind Wake and Associated Oceanic Thermal Responses: A Case Study of Hainan Island Wind Wake

“…To fully investigate the character of the wind wake, gridded wind vectors from the cross-calibrated multi-platform (CCMP, v2.0) [32] from RSS are also used as a reference in the present study, with a 25 km spatial resolution and 6-h temporal resolution. The sea surface latent heat flux (LHF), sensible heat flux (SHF), longwave thermal radiation, and surface net solar radiation are used as components of the air-sea heat flux, and are available from ERA5 reanalysis [33] of Copernicus Climate Change Service (C3S) (2017) on a grid size of 0.25 • with a temporal resolution of 6 h. Senafi et al [34] evaluated the performance of surface heat flux components of ERA5 by comparing with in-situ measurements and MERRA2/NASA reanalysis at the Arabian Gulf and the Red Sea, showing a bias of 4.5 W/m 2 and 1.59 W/m 2 respectively. Wind vectors from ERA5 03:00 UTC of December 10th, 2011 are also examined qualitatively to make sure the wind wake feature is captured, but no further analysis or calculation is conducted with ERA5 wind fields.…”