Multiplatform observations of dust vertical distribution during transport over northwest Iran in the summertime
Abstract
Dynamical processes leading to dust emission over Iran and surrounding countries in the summer as well as the subsequent transport of dust toward northwest Iran are analyzed on the basis of two case studies using a suite of ground-based and spaceborne remote sensing platforms together with modeling tools. Ground-based lidar measurements acquired in Zanjan provide new insight into the vertical distribution of dust linked to transport over northwest Iran and highlight the importance of low-level transport of dust from both Iraq and Iran for air quality issues in Tehran. During the 3-5 August 2007 case, dust emission regions are located in Syria/Iraq and close to Qom, Iran, in a large intermittent salt lake in the western part of the Dasht-e Kavir desert. The visibility in Tehran associated with this event decreases significantly (reaching 7 km) on 5 August 2007 only. During the 11-13 September 2008 case, the dust transported to northwest Iran originates from Syria/Iraq only. The visibility in Tehran during this case is low throughout the period, sometimes less than 5 km due to the transport of dust at low levels. In both cases, emissions in Syria and Iraq occur in response to strong Shamal winds. However, transport of dust toward Iran takes place at different levels: above 700 hPa in August and below 700 hPa in September. This is found to be related to the presence of strong northeasterly winds over the Zagros Mountains as well as in its lee (south of the range) in the August case only. In August also, dust emissions in the Qom region results from strong winds blowing over the Dasht-e Kavir desert.
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