5. Average: 31 days
Standard Deviation: 14 days
The number of 90 degree days is
extremely variable!
2 standard
deviations from
the mean
suggests a
strong outlier in
2010
MAY JUNE JULY AUG SEP
2 6 7 4 7
No. Days
each month
6. MAY JUNE JULY AUG SEP
11 16 23 20 12
Above average 85 degree days
(65). What has changed to not
have as many exceedances?
No. Days
each month
17. Monthly CAMD Emissions from:
IN, OH, WV, VA, PA, MD, DC
Emissions of Indiana, Ohio, West Virginia, Virginia, Pennsylvania, Maryland and
the District of Columbia were summed together on a monthly basis
20. Source region for NOx transport in to
Maryland has seen a drastic drop in TOTAL
ozone season (April – October) coal NOx
emissions. Approximately a 20% to 40%
reduction has occurred in the past 2 years,
compared to a 160,000 ton level.
Coal EGUs
Blue dots are EGUs
included in the NOx
summations below
Region bounded by
rectangle is roughly
the transport region
of Maryland
2009: 45135 fewer NOx tons emitted than in 2011
2010: 7011 fewer NOx tons emitted than in 2011
2012: 14830 fewer NOx tons emitted than in 2011
2013: 40462 fewer NOx tons emitted than in 2011
2014: 67983 fewer NOx tons emitted than in 2011
21. 2015 Summary
• Relatively cool ozone season in the Midwest
– Cool and wet June and July in Midwest (upstream)
– Lowest emissions ever seen “upstream” of Maryland
• Warm in Maryland (much warmer than 2013 & 2014)
with slightly below average extreme heat
– 15th warmest year for maximum temperature (statewide)
– “Normal” July temperatures and precipitation (NCDC)
• No Exceedances
• Smoke was a big contributor this year – potentially 3
exceedance days with smoke influence
23. NARR 1000m Trajectory Density for all Baltimore NAA Exceedance Days (1980-2014)
April – October
1589 Trajectories
24. This map is showing, by rank (1 is greatest, 37 least), which state’s summer cooling degree day (CDDs)
numbers most correlate with the number of Maryland’s ozone exceedance days. Indiana, Illinois and
Kentucky’s summer CDDs are the top three.
Correlation does not mean causation: Indiana’s CDDs correlate most with Maryland ozone exceedance days but this does not
mean Indiana is causing Maryland’s exceedances. It does mean that of all the states considered, Indiana’s temperature record
most closely follows Maryland ozone exceedance annual variability. It is also quite profound the lack of correlation between
Maryland CDDs and Maryland exceedance days.
25. “Strongly” Anti-correlated
Not Correlated
“Strongly” Correlated
The correlation between cooling degree days for
individual states with the number of Maryland ozone
exceedance days (1980-2013)
The highest correlation between cooling degree days and Maryland ozone exceedance days is found from
Iowa southeastward to Tennessee (red areas). This suggests that when these states experience a hot summer
Maryland is more likely to have a greater than average number of ozone exceedance days. Also, the
electrical demand of these states appears to be more closely connected to Maryland exceedance day annual
variability than other states. This correlation is likely due to the position of the continental ridge which is
stronger in some years than others. This CAN NOT be directly interpreted that any state showing a higher
correlation is actually causing the poor air quality (e.g., contains the actual emissions sources).
26. The GUT of Maryland’s Ozone
• In years with a weak Bermuda High
– Continental (U.S.) Highs/Ridges are more prevalent
– Increased temperatures across the Midwest
– Continental ridging near PBL top creates a long fetch across ORV
emissions (which are increased due to regionally higher
temperatures)
– Amplified lee-troughing with W to WSW surface winds due to
increase “mountain-top” orthogonal component
• This causes local I-95 transport within Maryland (Edgewood??)
• In years with a strong Bermuda High
– Continental Highs/Ridges are less prevalent
• 850mb flow is more cyclonic preventing ridging (and subsidence)
• Cooler temperatures across the MidWest (less emissions)
– Weaker lee-troughing (less orthogonal mountain flow)
– Less fetch from ORV (if any) entering Maryland (more across PA)
– Increased southerly winds and maritime influence (cleaner)
• Accounts for the wide variability in both O3 days and 90F days.
27. 2010: Bad Year (43) 2011: Bad Year (29)
2013: Good Year (9) 2014: Good Year (5)
Composite Sea Level
Pressure (mb)
28. 2015: May (Hot, bad AQ in Northeast) 2015: Sept (Hot, bad AQ along East Coast)
Cool in MW. No exceedances in Maryland except with smoke)
Composite Sea Level
Pressure (mb)
2015: June and July
31. 2011: 29
2014: 5
Exceedance Days
2011
2014
Comparison of the atmosphere
Approximately 750 m above earth’s
surface. The largest differences between
a bad year such as 2011 and a clean year
in 2014 is:
•The strength of the Bermuda High in the
Western Atlantic (A)
• The amplitude of the Midwest
Continental Ridge, and (B)
•The shift in wind direction (angle of the
lines) across Maryland, which switches
from West-Northwest in 2011 to West-
Southwest (C)
(A)
(B)
(C)
32. 2011: 29
2014: 5
Exceedance Days
Comparison of southerly wind strength
at the surface between 2011 and 2014
shows cleaner years have stronger
southerly winds. In fact, 2011, a dirty
year, has slightly northerly winds
(negative color – bright purple). The
largest differences between a bad year
such as 2011 and a clean year in 2014 is:
•The strength of the southerly winds in
Maryland (A)
2011
2014
(A)
