This document analyzes dust weather categorization in Mongolia using satellite data from 2000-2013. Ground-based meteorological data from 113 stations is compared to satellite-retrieved aerosol optical depth to categorize dust haze, blowing dust, and dust storms. Dust phenomenon types are categorized based on the correlation between aerosol optical depth and horizontal visibility. The study finds a good exponential relationship between aerosol optical depth and visibility in April, allowing dust weather to be categorized from satellite data with spatial frequencies consistent with ground reports.

1. Dust weather categorization with satellite
in Mongolia
Amgalan Ganbat
2017-03-15

2.  The comparison of the satellite retrieved aerosol
optical depth (AOD) with ground-based
observation
 Dust phenomenon types are categorized based
on the correlation between AOD and horizontal
visibility
 This study attempts to categorize dust weather
(dust haze, blowing dust, dust storm) with
satellite if correlation can be established
between the retrieved AOD and surface visibility.

3. Data and Method
• Data used from 113 meteorological stations in Mongolia, from 2000 to 2013.
• All stations are categorized into the four zones: forest steppe(FS), steppe (S), Gobi
Desert (GD), and mountains (M).
FS: the coldest in Mongolia, -7 0C,
precipitation falls 250-350 mm per year,
with a dry sub-humidity 71%;
S: the steppe provides many of the nation's
most important grazing lands for domestic
livestock;
GD: one of the great deserts in the world;
vegetation is sparse; precipitation fall less
than 200 mm; temperatures climb as high
as 40°С in summer;
M: the higher elevations of these ranges
(1580 m); The climate in the high mountain
zone is cold and drier,
Vegetation cover of the FS, S and GD is 53,
25, and 15% respectively.
Fig 1. Location of meteorological stations and
natural zones in Mongolia

4. : the result of strong turbulent wind systems entraining
particles of dust into the air, so that the visibility is reduced less than
10 km.
: dust is raised above the ground at eye level (<2m)
locally through strong winds. The horizontal visibility may more than
10 km.
: the sum of days with dust storm and/or drifting dust
 These are defined as those occurrence in one month or one
year.

5. Fig 2. Annual distribution of a) dust storm days and b) dusty days.
Spatiotemporal distribution of dust events

6. Fig 3. Comparison of monthly dusty days,
strong wind days and precipitation in the
specified years in different natural zones
Seasonal variations
Dusty days are the greater in years
of 2006, 2008 and 2009, and will
hereafter be referred to as the
,
similarly, the least dusty years as
dust-less years (2003 and 2011)
and
other 9 years as dust-mean years
(2000–2002, 2004, 2005, 2007,
2010, 2012 and 2013).

7.  Dust clouds from satellite are identified on basis of the radiation and
scattering characteristics of dust particles.
 Satellite-retrieved aerosol properties, such as aerosol optical depth (AOD)
and particle size (Ångström exponent; AE) are estimated from the
MODIS/Aqua using Deep Blue approach data.
 Daily Level 2 (MYD 04) data for period of 2003-2008 are used in this
study and its spatial resolution is 10km.

8. MODIS/Aqua daily data used
which passes over Mongolia 3 –
7am (UTC)+8.

9. Ground observation sites observe in accordance with the
following Manual

11. Obs.time
ww

13. AOD_March_2003 AOD_April_2003 AOD_May_2003
AE_March_2003 AE_April_2003 AE_May_2003
Aerosol optical depth (AOD) retrieved from MODIS/Aqua Deep-Blue algorithm over bright
surfaces. Combined daily data for each month and AE during the period from March to
May 2003.

14. AOD_March_2004 AOD_April_2004 AOD_May_2004
AE_March_2004 AE_April_2004 AE_May_2004

15. AOD_March_2005 AOD_April_2005 AOD_May_2005
AE_May_2005
AE_March_2005 AE_April_2005 AE_May_2005

16. AOD_March_2006
AE_March_2006
AOD_April_2006
AE_April_2006
AOD_May_2006
AE_May_2006

17. AOD_March_2007
AE_March_2007
AOD_April_2007
AE_April_2007
AOD_May_2007
AE_May_2007

18. AOD_March_2008
AE_March_2008
AOD_April_2008
AE_April_2008
AOD_May_2008
AE_May_2008

19. Fig 4. Dust event during 12-14 April 2004. (a) The spatial distribution of the AOD (for
values of AE<0.80) retrieved from MODIS and (b) ground observation of dust
phenomenon types

20. Fig 5. Correlation between AOD and visibility in April 2003 and 2004

21. Table 4. Criteria used for dust phenomenon classification

22. Blowing dust Dust storm
Fig 6. (a) spatial dust event frequencies from MODIS/Aqua data and (b) the
corresponding dust reports of the ground observation in April 2004.

23. Fig 7. (a) spatial frequency from MODIS/Aqua data and (b) the corresponding
dust reports of the ground observation in May 2004.
Blowing dust Dust storm

24. Fig 8. The number of days (shown as a percentage) where the AOD can
be retrieved from MODIS/Aqua in April and May 2004.

25. Conclusions
 High AOD values found over the southern and the east part of the western
Mongolia during March to May.
 According to AE, anthropogenic pollutants are heavily concentrated in the
northern and eastern Mongolia where the main agriculture and livestock
industries are being developed.
 A good exponential relationship found between the AOD values and
visibility and its correlation coefficient is about 0.70 over the country in
April.
 Spatial frequency of dust phenomenon classification (dust storm and
blowing dust) from the satellite observations well consistent with surface
meteorological station reports, but their discrepancies require further study.

26. Thank you
for your attention