Air quality expert group - Fine particulate matter (PM2.5) in ... - Defra

PM2.5 in the UK
152
Model
50
45
40
35
30
25
20
15
10
5
PM2.5 JAN 2005 (HAR)
0
0 5 10 15 20 25 30 35 40 40 50
Observation
Model
50
45
40
35
30
25
20
15
10
5
PM2.5 JUL 2005 (HAR)
0
0 5 10 15 20 25 30 35 40 40 50
Observation
Figure A2.2.3: Scatter plots of 24-hour means of PM2.5 concentrations for Harwell
for January and July 2005. The red dashed line represents 1:1 line, the purple
dashed line represents 2:1 line and the blue dashed line represents 1:2 line.
Table A2.2.1: Statistical model performance measures for 2006 and 2005 (January and July)
PM2.5 concentrations at Harwell (HAR) and London North Kensington (LNK) sites.
FACT2 (%) RMSE BIAS
HAR (2006) 45 7.0 -5.0
LNK (2006) 33 14.5 -10.3
HAR (January 2005) 69 8.2 2.6
HAR (July 2005) 58 4.6 -4.0
A2.3: WRF/CMAQ applications at King’s College London
Analysis of CMAQ PM predictions for 2008
Overview
11. It is important not only to look at the total modelled and measured
concentration of PM but to assess the performance of the model for each
component, as this is a well established way of finding weaknesses in the
modelling approach be they associated with model chemistry, dispersion
or emissions. In this example we have followed this approach and present
predictions of total PM2.5 as well as the performance of the model components,
nitrate (NO3 - ), sulphate (SO4 2- ), elemental carbon (EC), ammonium (NH4 + )
organic carbon (OC), primary organic aerosol (POA), secondary organic
aerosol (SOA), chloride (Cl - ), sodium (Na + ), particle bound water and “other”
particles (principally metals and minerals). The evaluation of the model includes
components that exist mainly in the coarse (PM10-PM2.5) mode but have a
proportion in the fine mode.
12. The evaluation has followed the availability of measurements of PM2.5 and PM10
species in 2008 and, as such, some comparisons were for hourly PM2.5, some