Abstract
Abstract. The first aircraft-based observations of an Icelandic dust storm are presented. The measurements were carried out over the ocean near Iceland's south coast in February 2007. This dust event occurred in conjunction with an easterly barrier jet of more than 30 m s−1. The aircraft measurements show high particle mass mixing ratios in an area of low wind speeds in the wake of Iceland near the coast, decreasing abruptly towards the jet. Simulations from the Weather Research and Forecasting Model coupled with Chemistry (WRF/Chem) indicate that the measured high mass mixing ratios and observed low visibility inside the wake are due to dust transported from Icelandic sand fields towards the ocean. This is confirmed by meteorological station data. Glacial outwash terrains located near the Mýrdalsjökull glacier are among simulated dust sources. Sea salt aerosols produced by the impact of strong winds on the ocean surface started to dominate as the aircraft flew away from Iceland into the jet. The present results support recent studies which suggest that Icelandic deserts should be considered as important dust sources in global and regional climate models.
Highlights
Iceland has over 20 000 km2 of sandy deserts (Arnalds et al, 2001)
Other particle types have not been accounted for when correcting Passive Cavity Aerosol Spectrometer Probe (PCASP) data for the scattering properties of the sampled particles. This results in an uncertainty in PCASP measurements presented here for areas dominated by sea salt, which is the case inside the jet
The Weather Research and Forecasting (WRF) model is a mesoscale numerical weather prediction and atmospheric simulation system which was developed at the National Center for Atmospheric Research (NCAR) (Skamarock et al, 2008)
Summary
Iceland has over 20 000 km of sandy deserts (Arnalds et al, 2001). The sand originates to a large extent from volcanic fly ash and glacial outwash. Together with the effect of Iceland’s orography on the airflow, this favors the development of high wind speeds in the vicinity of the sandy areas The latter can, under dry, snowfree conditions lead to sand storms. Iceland experiences considerable amounts of precipitation throughout the year (Crochet et al, 2007; Rögnvaldsson et al, 2007) It is a substantial global dust source with deposition rates comparable to or higher than those found for other areas that are usually considered to contribute to major global dust emissions (Arnalds, 2010; Prospero et al, 2012). The measurements ing model coupled with Chemistry (WRF/Chem) is used in were carried out during flight B269 of the GFDex (Green- the present study to better characterise the type of particles land Flow Distortion experiment; Renfrew et al, 2008) on sampled by the aircraft.
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