diurnal variability of aerosols observed by ground-based networks
DESCRIPTION
Diurnal Variability of Aerosols Observed by Ground-based Networks. Qian Tan (USRA), Mian Chin (GSFC), Jack Summers (EPA), Tom Eck (GSFC), Hongbin Yu (UMD), Caterina Tassone (NOAA ), Yan Zhang (MSU), EPA/AQS, NASA/AERONET, NOAA/NCDC . Outline. Diurnal variability of surface PM2.5 - PowerPoint PPT PresentationTRANSCRIPT
Diurnal Variability of Aerosols Observed by Ground-based
NetworksQian Tan (USRA), Mian Chin (GSFC), Jack Summers (EPA), Tom Eck (GSFC), Hongbin Yu (UMD), Caterina Tassone (NOAA), Yan Zhang
(MSU), EPA/AQS, NASA/AERONET, NOAA/NCDC
Outline Diurnal variability of surface PM2.5
How significant Variations on other time scales.
Linkage between diurnal cycle of surface PM2.5 and column AOT Correlation on their diurnal cycles Possible meteorological impacts
Measuring Aerosol Variations in Different Ways
Day 1 Day 2 Day 3 Day 4 Day 5 ……… Day n
Day-to-day variation (EPA
24-hr filter)
Sun-synchronized orbitBetter spatial coverage
Geo-stationary orbit
EPA hourly obs.
Aerosols Diurnal Variation Continuous ground based
observations. EPA AQS hourly PM2.5 observations.
Diurnal variation vs daily average Comparison to seasonal variations.
Averaged PM 2.5 Diurnal VariationsPM
2.5
(ug/
m^3
)
Max-Min
Std. Dev
2004 2005 2006 2007
Significant diurnal variation is observed: ~ 15-22 ug/m3, EPA PM2.5 standard: 35 ug/m3 for 24hr, 15 ug/m3 annual average.
Compared with Daily AveragePe
rcen
tage
(%
) (Max-Min) / Mean
Std. Dev/ Mean
Variations of surface PM2.5 within a day is comparable to its daily mean:
Maximum-minimum is 120-170% of its meanStandard deviation is ~30-50%.
2004 2005 2006 2007
Seasonal & Year-Year DifferenceMax-Min Std
Dev
On average, the standard deviation of PM2.5 within a day
is comparable to the seasonal variation.
Co-located PM2.5 and AOT Using column AOT, i.e. what satellites
observe, to estimate the surface concentration of PM2.5 (criteria pollutant) Chu et al., (2003), Wang & Christopher (2003), Engel-
Cox (2004), Al-Saadi et al., (2005),…, Hoff & Christopher (2009)
Co-located AERONET and AQS observations New York City (CCNY) Baltimore (MD Science Center) Houston (University of Houston) Fresno (California)
Within 8km. Hourly data available Close by hourly meteorological & PBL observations
Day-to-Day PM2.5 vs AOT
On daily based, AOT shows good correspondence with surface PM2.5 concentration. Their correlation has large spatial differences (both r2 and slope).
Diurnal Cycle of PM2.5 & AOT -- Houston
PM2.5 shows clearer diurnal pattern, it changes with season.AOT diurnal pattern is less pronounced, larger seasonal variationDaily PM2.5 minimum is at noon time during fall and winter.
Correlation between AOT and PM2.5 on finer temporal frequency
€
AOD =PM2.5∗H∗f (RH)∗3Qext / dry4ρ reff
= PM2.5∗H∗S
Koelemeijer et al., 2006; Hoff & Christopher (2009)
Causes of variationsPM2.5 emissions, chemistry, deposition, dynamics, … AOT all of above
aerosol optical property
compositionsize and shape
aerosol vertical profilePBLlocal, regional, and long range transport
other factors clouds, (surface albedo)solar zenith angle
Diurnal Variation of PBL
PBL peaks in the early afternoonPBL is higher in summer (in Houston, less seasonal difference)
PBL vs. PM2.5Houston Baltimore New York
City
Winter
In winter, if PBL is high, then PM2.5 will be low -- in Houston, the minimum PM2.5 occurred around noon time.
AOT vs. PM 2.5 * PBL
R2 = 0.39
(2010)
R2=0.26
When PBL is high (>1000m), AOT is more correlated with PM2.5 R2 = 0.
51
PBL > 1000m
AOT vs PM2.5 * PBL *f(RH)R2 = 0.17
R2 = 0.40
R2 = 0.064
* F (RH)
R2 = 0.42
All PBL condition
PBL >1000m
+ surface RH
1. Low PBL will degrade correlation between AOT and PM2.52. When PBL is high, it is more likely to estimate PM2.5 using
AOT.
Conclusion Significant daily variation is observed
in surface PM2.5 concentration. Daily average of PM2.5 and AOT is
correlated well at urban sites. Diurnal cycle of PM2.5 and AOT is
different. better correlated when PBL is high
Extra slides
Diurnal Cycle of PM2.5 and AOT -- NYC
PM2.5 diurnal variation follow emission (traffic) pattern, & PBLAOT diurnal pattern is less pronounced, large seasonal variationNo clear pattern in summer months.
Correlation between AOT and PM2.5 Many studies to explore the linkage
between the two Using column AOT, i.e. what satellite can
observe, to estimate the surface concentration of PM2.5 (criteria pollutant) Chu et al., (2003), Wang & Christopher (2003), Engel-
Cox (2004), Al-Saadi et al., (2005),…, Hoff & Christopher (2009)