Meteorological Patterns Associated with Intense Saharan Dust Outbreaks over Greece in Winter

P T Nastos

doi:10.1155/2012/828301

Abstract

The Mediterranean Basin and southern Europe are often affected by Saharan dust outbreaks, which influence the aerosol load and properties, air quality standards, visibility and human health. The present work examines, mainly of the meteorological point of view, three intense dust outbreaks occurred over Greece with duration of one or two days, on 4 and 6 February and 5-6 March 2009. The synoptic analysis on the dusty days showed the presence of low-pressure systems in the west coasts of Europe and the north Tyrrhenian Sea, respectively, associated with a trough reaching the north African coast. The result of these conditions was the strong surface and mid troposphere winds that carried significant amounts of dust over Greece. During the dusty days extensive cloud cover associated with the dust plume occurred over Greece. The air-mass trajectories showed a clear Saharan origin in all atmospheric levels, while the satellite (MODIS Terra/Aqua) observations as well as the model (DREAM) predictions verified the intense dust outbreaks over eastern Mediterranean and Greece. The ground based particulate matter concentrations in Athens were excessively increased on the dusty days (PM10: 150–560 μg/m3), while significant dry and wet deposition occurred as forecasted by DREAM model.

Highlights

According to the Earth Observatory website, intense dust outbreaks are considered natural hazards, which affect the global and regional radiative balance, cloud microphysical properties, atmospheric heating and stability, tropical cyclone activity, ecosystems, marine environments and phytoplankton, photolysis rates, ozone chemistry, and human health [1, 2]
Desert dust can be transported over long distances from the source regions [6], with the larger particles to be deposited near the source, while the smaller ones to be suspended in the air for a few days or weeks, travelling over large distances
The present study focuses on the analysis of three dust events occurred over Greece in the cold period of the year (February 4, 6, 2009 and March 5-6, 2009), mainly from the meteorological aspect based on National Center for Environmental Prediction (NCEP)-National Center for Atmospheric Research (NCAR) reanalysis

Summary

Introduction

According to the Earth Observatory website (http://earthobservatory.nasa.gov/), intense dust outbreaks are considered natural hazards, which affect the global and regional radiative balance, cloud microphysical properties, atmospheric heating and stability, tropical cyclone activity, ecosystems, marine environments and phytoplankton, photolysis rates, ozone chemistry, and human health [1, 2]. Many studies [8, 12,13,14] have shown that the Saharan dust events over Mediterranean are mainly driven by the intense cyclones called Sharav, south of Atlas Mountains (Morocco) These cyclones are generated by the thermal contrast between cold Atlantic air and warm continental air that cross North Africa during spring and summer. The close relation of the dust exposure and transport with the prevailing local and regional meteorology is well established To this respect, Dunion and Velden [19] have shown that an elevated Saharan dust layer may play a crucial role in suppressing tropical cyclone activity in the Atlantic and the tropical cyclones in the Bay of Bengal cause mineral dust exposure from the continental India over the Bay of Bengal and Arabian Sea [20, 21]. Focusing in the Mediterranean several studies [1, 15, 22] have analyzed the prevailing meteorology during the dust events, while Meloni et al [18] and Carmona and Alpert [23] classified the weather types responsible for the dust outbreaks in Lampedusa and Israel, respectively

Results

Discussion

Conclusion