"My colleague Sam [Assouline] noticed a lot of speculation in the media around the time of the dust storm questioning the role conflict may have played in creating what turned out to be one of the most severe storms in recent history," Tony Parolari, formerly at Duke University and now at Marquette University, US, told environmentalresearchweb. "We were curious whether we could find evidence for the role of conflict, or whether there was a more conventional explanation for the storm."
The storm started along the northeastern border between Syria and Iraq around 31 August 2015, satellite images show. It moved southeast towards and across the Persian Gulf over the next two days before spreading westward over Syria, Lebanon and the eastern Mediterranean Sea. Scores of people were hospitalized, while the extreme aerosol optical depth in the atmosphere was in the 99th percentile.
Parolari and colleagues used a number of approaches to investigate. They looked at MODIS (Moderate Resolution Imaging Spectroradiometer) data on aerosol optical depth, assessed vegetation cover, simulated regional meteorology using the Advanced Research Weather Research and Forecasting model (WRF-ARW), and estimated critical shear stress from surface temperature and relative humidity data. The researchers could not quantify the impact of increased military traffic on dust emission because there wasn’t enough data.
The results tell us two things, according to Parolari. Firstly, that more dust could be eroded from the surface during the storm because the soil surface was much drier and hotter than normal. And secondly that the dust was spread over the entire region by winds blowing to the west.
"During dust storms in the Middle East, winds typically blow to the south and east, which made this particular storm unique," he said. "Therefore, our results suggest that this storm was associated with rare climatic conditions. These conditions lead to significant disruptions in Israel and Lebanon, areas that typically see less dust than the central region of the Middle East."
Dust storms in the Middle East are often associated with the Shamal winds that flow in from the northwest from time to time, generally in the summer. In this instance the Shamal took place as normal before low-level winds reversed direction, transporting previously suspended particles westward.
Although the area experienced drought in 2013 and 2014, the following year saw greater than average vegetation density and wheat yields; vegetation cover in 2015 was nearly double the 2007–2010 average. This finding indicates that land cover changes associated with the ongoing conflict were unlikely to be at the origin of increased erodibility of the soil surface and suggests meteorological conditions as the more probable driver for enhanced dust uplift and transport, writes the team in Environmental Research Letters (ERL).
"Previous work has shown a drying trend in the Middle East and the increased likelihood of extreme drought, with implications for water supply and agricultural productivity," said Parolari. "Our results connect these elements of climate change to wind-driven soil erosion and transport."
Dust storms negatively affect public health and the economy, and also play a role in biogeochemical cycling, Parolari added. "If the dust storm is related to the long-term effects of climate change, as opposed to a short-term conflict, it may be difficult or impossible to mitigate the negative impacts."
Now the team is interested in estimating how likely dust-storm-creating conditions will be in the future.
Related links
- Climate, not conflict, explains extreme Middle East dust storm Anthony J Parolari et al 2016 Environ. Res. Lett. 11 114013
- ERL
- Tony Parolari, Marquette University