An Investigation of the Coastal Circulations and Aerosol Transport in the Arabian Gulf Region

Abstract

An observational and modeling study was performed over the Arabian Gulf region to investigate the coastal circulations and aerosol transport in the area. Climatological data and observations from the United Arab Emirates — Unified Aerosol Experiment (UAE²) were used to develop a better understanding of the complex meteorological processes in the Arabian Gulf region. The geography of this region is unique because it can cause land-sea-air-land interactions that will modify the overlying air masses.

Climatological data suggests that sea breezes occur on more than 77% of days in all months of the year and land breezes occur on more than 70% of the days. The occurrence of the sea and land breeze circulations are higher (90-99%) during the summer months when large-scale weather patterns are quiescent. The timing and horizontal extents of the sea breeze circulation, both onshore and offshore were determined by a network of surface meteorological stations throughout the UAE. Sea breezes typically form along the southern Arabian Gulf coast between 1300 and 1600 LT. Further inland and offshore, the sea breeze circulation forms between 1600 and 1900 LT. The vertical extent of the sea breeze circulation was determined using radiosonde observations.

Measurements of aerosol concentration taken during the UAE² experiment are used to investigate aerosols, namely dust, transported in the Arabian Gulf region. Vertical profiles of dust concentration along with vertical profiles of potential temperature and wind are used to determine the source region, transport distance, and height of the dust layer. The aircraft aerosol vertical profiles suggest highest dust concentrations occur near the surface.

Numerical simulations of two periods during the summer of 2004 were performed to test the ability of a mesoscale model to resolve the sea breeze circulation. The Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS®) was used in the numerical simulations. A statistical evaluation of COAMPS® was also done for a two-month period from August to early October 2004 to determine the model root mean square error and bias error in predicting surface variables, vertical profiles, and the planetary boundary layer height. COAMPS® model error is smaller during the daytime than the nighttime for the surface variables and forecast integration time does not appear to have an effect on the model forecast errors. Error in the predicted boundary layer height increases with model integration time.

COAMPS® is a registered trademark of the Naval Research Laboratory.