Some Aspects of the 2005 Ozone Season William F. Ryan Department of Meteorology The Pennsylvania State University 2005 MARAMA Monitoring Committee Meeting Ocean City, Maryland November 15-17, 2005
Three Topics of Interest Was 2005 a typical summer O 3 season? Is it enough to just be hot? Are O 3 concentrations falling in response to regional NO x controls? Is the ground moving under our feet? Improvements in O 3 forecast capability. Now a reliable forecast tool?
Philadelphia Mean Daily Peak O 3 80 Mean Daily 8-h Ozone (ppbv) 75 70 65 60 2005 mean is 5 ppbv (~ 8%) lower than the 1994-2002 average 55 50 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 Year
Philadelphia O 3 Concentrations by Color Code Orange 16% Red 5% Orange 10% Red 4% Green 48% Green 53% Yellow 33% Yellow 31% 1994-2004 2005 In 2005, less Code Orange and more Code Green
18 16 14 12 10 8 6 4 2 0 Frequency of Code Red Days Philadelphia Code Red Ozone (1994-2005) 2005 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 Year 1994 Number of Days
Frequency of Days 85 ppbv Philadelphia Red and Orange (1994-2005) 60 50 Number of Code Orange or Red days in 2005 is 45% less than 1994-2002 40 Number of Days 30 20 10 0 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 Year
But It Was a Hot Summer..
Hot Even by Recent Standards
Hot and Dry.Usually Means Bad Air
Is Hot Weather Enough for High O 3? Average maximum temperature for Code Red cases in Baltimore (1990-2000) is 93 F For PHL average maximum temperature is also 93 F (1994-2004) Count 30 20 10 0 80 82 84 86 88 90 92 94 96 98 100 102 BWI Hourly Maximum Temperature (F) 104 0.2 0.1 0.0 Proportion per Bar
Hot Days Very Frequent in 2005 45 40 35 Number of Days >= 90 F 30 25 20 15 10 5 0 1997 1998 1999 2000 2001 2002 2003 2004 2005
Hot Weather is Necessary but not Sufficient for Code Red though usually for Code Orange Only 30% of all cases where maximum temperature reaches or exceeds 90 F reach the Code Red threshold. Count 250 200 150 100 All Cases Code Red Cases 0.14 0.12 0.10 0.08 0.06 Value For PHL ~ 29% of hot days are Code Red but 74% are at least Code Orange. (1994-2004) 50 0.04 0.02 0 0.00 40 50 60 70 80 90 100 110 BWI Maximum Temperature (F)
Why Doesn t Hot Weather Always Mean High O 3? Cloud cover, rain and wind associated with convection (thunderstorms). Strong winds alone can be enough to keep O 3 below the Code Red range. Source of the air mass can matter, onshore winds with maritime air mass characteristics are low in O 3 and precursors.
No Significant Difference in Transport Pattern Aloft in 2005 HYSPLIT (NOAA/ARL) back trajectory model results. 24-hour back trajectories terminating at 1000 m above ground level at 1200 UTC (0800 am local).
But, More Likely to Have Stagnation and Reverse Corridor Flow at Low Levels
Very Hot in 2005 but Weaker O 3 Response 60 3.00 Number of Days 50 40 30 20 10 2.50 2.00 1.50 1.00 0.50 0.00-0.50-1.00 Departure from Normal Temperature (F) 0 1997 1998 1999 2000 2001 2002 2003 2004 2005 Year -1.50 O3 > 85 Ave T While departure from normal temperature was > 2º F (similar to 1999, 2001-2002), number of days > 85 ppbv was 40% less frequent
Since 2003, the Number of Days 90 ºF Exceed the Number of Days 85 ppbv 60 50 Number of Days 40 30 20 High O3 T > 90 10 0 1997 1998 1999 2000 2001 2002 2003 2004 2005 Year
Are We Seeing the Impact of the 22 State NO x Rule?
Regional NO x Controls and Local O 3 The working scientific hypothesis for O 3 control was: O 3 concentrations are limited by NO x for most of the eastern US excluding urban and nearurban areas. Point source NO x controls will decrease regional-scale (baseline) O 3. A lower baseline concentration would make it less likely for urban area O 3 spikes to exceed the NAAQS standard.
Phase in of Regional NO x Controls
Expected NO x Reductions are Significant Figure courtesy of DOE: http://www.eia.doe.gov/oiaf/aeo/
What Predictions from Hypothesis? If baseline O 3 is falling: Should see fewer total Code Red and Code Orange days While urban areas will still have local emissions sufficient for Code Red, should see fewer extreme O 3 cases Urban plume of high O3 should be smaller so that fewer monitors exceed Code Red or Code Orange for any given bad air day. Rural monitors should show lower O 3.
Number of Code Orange or Red Days (PHL) Philadelphia Red and Orange (1994-2005) 60 50 Recall: Number of Code Orange or Red days in 2005 is 45% less than 1994-2002 40 Number of Days 30 20 10 0 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 Year
In MARAMA Region, Number of Monitors Exceeding 85 ppbv Much Reduced 1600 1400 1200 Number of Monitors 1000 800 600 400 200 0 2001 2002 2003 2004 2005 But 2003 and 2004 were not O 3 conducive although 2005 was.
And the Number of Monitors Exceeding 85 ppbv per Code Orange (or Red) Day are Lower as Well 8 7 6 Monitors/Day 5 4 3 2 1 0 2001 2002 2003 2004 2005 Year
Total number of extreme O 3 Days (8-hour O 3 110 ppbv) for all MARAMA states 120 100 Number of Days > 110 ppbv 80 60 40 20 0 2001 2002 2003 2004 2005
Mean O 3 and Frequency of High O 3 Days at Shenandoah NP 30 70 Days > 70 ppbv 25 20 15 10 5 65 60 55 50 45 40 35 Mean Ozone (ppbv) >= 70 median 0 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 30
Caveats No statistical significance with small data sample containing strong serial correlation. Although 2005 was hot and dry, classical high O 3 patterns not as frequent as 2002. 2003 and 2004 were low O 3 summer weather-wise.
NOAA O 3 Forecast Models: Current Configuration 1X 5X 3X
NOAA Forecast Model Assumes Large NO x Reductions
Overall Performance of Model Encouraging Figure Courtesy of Rohit Mathur (ARL/NOAA)
Analysis of Forecast Skill in PHL Performance in Difficult Cases Was Good Onset of high O 3 episode Termination of high O 3 episode Non-standard high O 3 cases Code Red Cases Large Error Cases Caught by Other Methods Systematic Errors Did Occur Urban core over-prediction High concentrations at sea/land boundary
Forecast Accuracy for O 3 Episode Days in PHL (Developmental Model 5X) PHL Domain 8-h Maximum Ozone (ppbv) During High Ozone Episodes (n = 8) Bias MAE Median rms NOAA -2.4 7 3.5 9.7 PHL-FC -4.4 7.8 6 9.9 Stat -3.2 7.2 5.5 8.9
July 26: Code Red Forecast Verifies But over-prediction in the urban corridor from Wilmington through Philadelphia.
July 22: Code Red Forecast Verifies Forecast 1-h Downtown PHL: 61-90 ppbv observed The opposite problem was found in 2003 (see below).
August 12: Missed Code Red Slight Westward Displacement of High O 3 Plume
August 4: Missed Code Red Convection in NJ Forecast Convection observed as forecast, no one told northern Delaware though..
Non-Standard Case: Low level winds drain from north to south
Systematic Errors: Abnormally high O 3 at bay/land interfaces
Large Error Case: False Alarm of Code Orange NAM-12 did not forecast cloud cover, statistical models handled case well.
Large Error Case: Offshore circulation causes stagnation near I-95
Conclusions for NOAA Model Performance in high O 3 episodes very promising: Onset and termination of high O 3 episodes well forecast Code Red cases identified Over-prediction in near-urban environment, adjusted for by post-processing? Large error cases occurred but caught by other forecasting approaches (e.g., statistical models) so didn t impact operational forecasting Problems remain with water surfaces: Atlantic coast and Chesapeake and Delaware Bays
Overall Conclusions 2005 was a hot summer and generally conducive to high O 3 although frequency of westerly transport a bit less. Peak O 3 concentrations lower, given the weather, than we would have expected. Suggestion, not proof, of NO x Rule impact. NOAA O 3 Forecast model shows promise but all bets off next year (WRF).