Journal of Geophysical Research - Atmospheres
Supporting Information for
Climatology of summer Shamal wind in the Middle East
Yan Yu1, Michael Notaro1, Olga V. Kalashnikova2, Michael J. Garay2
1.
Nelson Institute Center for Climatic Research, University of Wisconsin-Madison
2. Jet Propulsion Laboratory, California Institute of Technology
Contents of this file
Figures S1 to S8
Introduction
The supporting information contains eight figures that support the main text. All the datasets
used in the supporting information are described in the “Data and method” section in the main
text.
Figure S1. Data coverage at 184 stations measured by the percentage available daily wind
observations during May-August of 1970-2013.
Figure S2. 85th percentile of wind speed (m s-1) among all observations at each station during all
months of 1970-2013. The highest wind speed largely occurs in the Shamal region. At a given
station, the minimum wind speed for defining a Shamal day was assigned as the 85th percentile
wind speed if the 85th percentile of wind speed exceeds 7 m s-1, and 7 m s-1 otherwise.
Figure S3. Frequency of days satisfying the Shamal wind (a) speed and (b) direction criteria
during May-August of 1970-2013. Most stations experience persistently north-northwesterly
wind. However, strong winds only occur frequently at stations in the Shamal region.
Figure S4. Hour of day (UTC) with climatologically minimum visibility during May-August of
1970-2013, measured at stations. The visibility minimizes around noon UTC at the peak time of
Shamal frequency across Iraq and Kuwait.
Figure S5. Time series of standardized anomalies in May-August sea-level pressure (SLP, blue)
over and land-surface temperature (LST, red) across the Zagros Mountain (25N-40N, 60E-80E),
and average wind speed (green) across the Shamal stations during 2000-2013. The data source
for SLP, LST, and Shamal wind speed is MERRA reanalysis, MODIS, and station observations,
respectively. The temporal correlation between (SLP, Shamal wind speed), (SLP, LST), and
(Shamal wind speed, LST), are -0.39, -0.45, and 0.46, respectively (n = 14, all p’s < 0.1).
Figure S6. Histogram of (a,c) speed (m s-1) and (b,d) height (m) of dust plumes from the MISR
CMV product during May-August of 2000-2013, when (a,b) both dust and Shamal occur and
(c,d) dust is present but Shamal is not. Dust plumes are closer to surface and faster-moving on
Shamal days than on non-Shamal days.
Figure S7. Climatology of Aerosol Extinction coefficient (km -1) vertical profile at grid cells in
Iraq (33.5˚N, 43.5˚E), Kuwait (28.5˚N, 48.5˚), Saudi Arabia/Qatar (24.5˚N, 50.5˚E) and United
Arab Emirates (23.5˚N, 52.5˚E) during winter (Dec-Feb, blue), spring (Mar-May, green), summer
(Jun-Aug, red), autumn (Sep-Nov, yellow), and annual average (gray). The summertime Aerosol
Extinction coefficient maximizes near surface in Iraq and Kuwait, and spreads out into higher
altitudes in Saudi Arabia/Qatar and United Arab Emirates, confirming that the dust sources
during Shamal are likely located in Iraq and Kuwait. The data is from CALIPSO and the figures
are obtained from the Lidar climatology of Vertical Aerosol Structure for space-based lidar
simulation studies (LIVAS) web portal (http://lidar.space.noa.gr:8080/livas/climatology.html)
Figure S8. Dust source regions identified with (a,b) MISR plume motion vector, (c,d) MISR
AOD, and (e,f) MISR dust AOD on (a,c,e) Shamal days and (b,d,f) non-Shamal days during
May-August of 2000-2013. The intensity of the dust source regions are measured by the
frequency of fast-moving dust plumes (> 10 m s-1) within 2 km above ground in a and b, and
the frequency of exceeding the 90th percentile of all observations across the study region in
AOD (c,d) and DAOD (e,f), respectively.