Preprint Article Version 1 This version is not peer-reviewed

From Tropospheric Folding to Khamsin and Foehn Winds: How Atmospheric Dynamics Advanced a Record-Breaking Dust Episode in Crete

Version 1 : Received: 21 May 2018 / Approved: 23 May 2018 / Online: 23 May 2018 (09:05:47 CEST)

A peer-reviewed article of this Preprint also exists.

Solomos, S.; Kalivitis, N.; Mihalopoulos, N.; Amiridis, V.; Kouvarakis, G.; Gkikas, A.; Binietoglou, I.; Tsekeri, A.; Kazadzis, S.; Kottas, M.; Pradhan, Y.; Proestakis, E.; Nastos, P.T.; Marenco, F. From Tropospheric Folding to Khamsin and Foehn Winds: How Atmospheric Dynamics Advanced a Record-Breaking Dust Episode in Crete. Atmosphere 2018, 9, 240. Solomos, S.; Kalivitis, N.; Mihalopoulos, N.; Amiridis, V.; Kouvarakis, G.; Gkikas, A.; Binietoglou, I.; Tsekeri, A.; Kazadzis, S.; Kottas, M.; Pradhan, Y.; Proestakis, E.; Nastos, P.T.; Marenco, F. From Tropospheric Folding to Khamsin and Foehn Winds: How Atmospheric Dynamics Advanced a Record-Breaking Dust Episode in Crete. Atmosphere 2018, 9, 240.

Journal reference: Atmosphere 2018, 9, 240
DOI: 10.3390/atmos9070240

Abstract

A record-breaking dust episode took place in Crete on 22 March 2018. The event was characterized by surface concentrations exceeding 1 mg m-3 for a period of 4-7 hours, reaching record values higher than 6 mg m-3 at the background station of Finokalia. We present here a detailed analysis of the atmospheric dynamical processes during this period, to identify the main reasons that resulted in such extreme dust advection over Crete. At synoptic scale, the weakening of the polar vortex and the meridional transport of polar air masses at upper tropospheric layers resulted in a strong jet streak over N. Africa and Central Mediterranean and corresponding tropospheric folding that brought cold stratospheric air in mid and upper troposphere. Cyclogenesis occurred at the Gulf of Sirte in Libya, resulting on strong winds over the NE parts of Libya, enhancing particle emissions. The dust plume traveled at low heights (0.5-3 km) along the warm conveyor belt preceding the depression cold front. This type of dusty southerly wind is commonly known as “Khamsin”. As the flow approached Crete, Foehn winds at the lee side of the island favored the downward mixing of dust towards the surface, resulting in local maxima of PM10 in Heraklion and Finokalia. The analysis is based on the synergy of high resolution WRF-Chem simulations reaching up to 1×1 km grid space over Crete, ground-based and satellite remote sensing of the dust plumes (PollyXT lidar, MSG-SEVIRI, MODIS) and detailed surface aerosol in-situ measurements at urban (Heraklion, Chania) and background (Finokalia) stations in Crete.

Subject Areas

dust; polar vortex; Finokalia; Foehn; Khamsin

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