AeroCom model experiments for HTAP
As discussed during the 5th AeroCom workshop in Virginia Beach, October 2006, one of the
activities in the second phase of AeroCom is to participate in the internationally coordinated
multi-model studies of the Hemispheric Transport of Atmospheric Pollutants (HTAP). For
background information, overview, and comprehensive description of the initial model
experiments please go to http://aqm.jrc.it/HTAP. Here we focus on the sub-sets of experiments
that are particularly relevant to the AeroCom models in addressing the issues of long-range
transport of particulate matters (PM) and their impact on regional air quality.
1. Planned model experiments
FIRST SET OF HTAP EXPERIMENTS: The initial HTAP experiments, set up in coordination
with AeroCom, consist of two source-receptor experiments, SR1 (base run) and SR6
(perturbation run with 20% anthropogenic emissions in defined regions), and, as recommended
addition one tracer experiment, TP1 (CO tracer). These experiments are described at the HTAP
website. Registration is urgent and the experiments SR6 are expected for mid January. See for
requirements http://aqm.jrc.it/HTAP. AeroCom suggests that biomass burning and wild fire
emissions are not considered as anthropogenic for the purpose of setting up experiment SR6.
ADDITIONAL SET OF HTAP-AEROCOM EXPERIMENTS: In addition to the HTAP defined runs,
AeroCom recommends three more perturbation runs. The first one is SR6z, in which
anthropogenic emissions in specified pollution regions are turned off, put to zero, in order to
assess the maximum impact of hemispheric transport of aerosols on regional air quality. (Note:
a 20% reduction of anthropogenic emission specified in HTAP is most appropriate for ozone
runs since the highly non-linear chemistry in ozone production would make the results from
zeroing-out emission runs difficult to interpret.) AeroCom again suggests that biomass burning
and wild fire emissions are not considered as anthropogenic for the purpose of setting up
experiment SR6z.
The second one is SR6d, in which the dust emissions from major dust source region are turned
off in order to estimate the impact of long-range transport of dust from a particular source region
on air quality over land and on eco- system. Given the fact that long-range transport of dust is
the most important mechanism for aerosol transport and the most visible from satellite data, this
experiment is particularly relevant to HTAP even though most dust is from natural sources.
The third experiment is SR6b, in which emissions due to wild fires and biomass burning in the
Northern Hemisphere are set to zero in three regions. The purpose of this experiment is to
establish the contribution to background aerosol levels from natural and anthropogenic wild fires.
Fire produced aerosols have particular potential of being long range transported.
We suggest as a deadline for submitting the additional experiments the 15th of April. Table 1
summarizes all experiments (high-lighted are the additional experiments).
For the purpose of HTAP study, anthropogenic emissions are defined as all fossil and biofuel
combustion, industrial, residential/commercial activities (including aircraft and shipping
emissions), and agriculture activities. Wild fire and biomass burning emissions should at best
correspond to the actual fire situation in the year of simulation. Note that modelers are
encouraged to use the emissions of their choice.
Table 1. Planned AeroCom experiments for HTAP.
Experiment
Description
SR1
Base case simulation for year 2001. Each model
uses own “best estimated” anthropogenic and
natural emissions.
SR6_EA,
Reducing anthropogenic emissions of SO2, BC,
SR6_SA,
POM (and other aerosol precursors such as NOx,
SR6_EU,
VOC, NH3 if capable) by 20% for regions East Asia
SR6_NA
(EA), Europe (EU), North America (NA), and South
Asia (SA)
SR6z_EA,
No anthropogenic emissions in EA, EU, NA, and
SR6z_SA,
SA
SR6z_EU,
SR6z_NA
SR6d_AF,
No dust emissions in Africa (AF), Middle East (ME),
SR6d_ME,
and Asia (AS)
SR6d_AS
SR6b_NE,
No biomass burning emissions in northeast (NE,
SR6b_NW,
boreal regions in Asia and Europe), northwest (NW,
SR6b_SE,
boreal in North America), southeast (SE, tropical
SR6b_SW
and mid-latitudes in Asia, Europe, and northern
Africa), and southwest (SW, North, central and
South America in the NH)
TP1
CO tracer experiment using common surface
sources, simple parameterization for chemical
sources from CH4 and NMVOC, 25-day global
lifetime (see HTAP document).
Purpose
Reference/verification
Analyzing the effects of limiting
oxidant effects on sulfate
formation and transport;
significance of emission
reduction
Analyzing maximum impact of
long-range transport
Assessing maximum impact of
long-range transport of dust
Assessing maximum impact of
regional and long-range
transport of biomass burning
aerosol
Characterizing model transport
2. General guidelines
All model simulations shall be performed for the whole year 2001 with 6-month spin-up time.
Meteorological data used in the model should be consistent with the 2001 condition. Models
should have a horizontal resolution no coarser than 4x5 and at least 10 layers between surface
and 30 hPa, covering at least the Northern Hemisphere.
2.1. Region definitions:
HTAP defines four regions that are of similar size and emission totals (Table 2a):
Table 2a. Anthropogenic source regions.
Name
EA
SA
EU
NA
Region
East Asia
South Asia
Europe + North Africa
North America
Longitude
95E – 160E
50E – 95E
10W – 50E
125W – 60W
Latitude
15N – 50N
5N – 35N
25N – 65N
15N – 55N
AeroCom defines three dust regions and four wild fire regions in NH (Table 2b,2c):
Table 2b. Dust source regions.
Name
AS
ME
AF
Region
Asia
Middle East
Africa
Longitude
75E – 135E
40E – 75E
20W – 40E
Latitude
30N – 50N
10N – 50N
10N – 36N
Table 2c. Biomass burning source regions.
Name
NE
Region
Boreal regions in Asia and
Europe
Boreal regions in North
America
Tropical and mid-lat
regions in Asia, Europe,
and northern Africa)
Tropical and mid-lat
regions in North America
and South America in NH)
NW
SE
SW
Longitude
20W – 180E
Latitude
45N – 70N
180W – 50W
45N – 70N
20W – 180E
180W – 50W
0 – 45N
0 – 45N
2.2. Standard diagnostics:
To obtain maximum logistic synergy between HTAP and AeroCom it is requested for all these
experiments to follow the formatting and diagnostic specifications which are to be found and
updated on the HTAP website (http://aqm.jrc.it/HTAP/out_ES1.html) (file names, explanations,
links to tools)
The reference for which variables should be reported is to be found in the excel file, which is
accessible via the HTAP website (http://aqm.jrc.it/HTAP/HTAP_variables.xls). Please note that
for the netCDF files both the variable names and the attribute standard_name are prescribed. See
below the output files requested for the aerosol analysis part of HTAP/AeroCom experiments.
The excel file contains also info on which variable belongs into which file.
For the aerosol part just one file per file category and year of simulation and experiment is
requested. It is highly recommended to try to use the CMOR formatting package. Note that the
additional experiments are not yet mentioned on the HTAP website and are not included in the
HTAP tables for the CMOR formatting package.
3. Detailed description of experiments
3.1. Experiment SR1 – base run
The SR1 experiment is to establish a reference against the perturbation runs (SR6). The output
of SR1 will be used to evaluate the models with observations and to verify the emission data.
All models will be run in their own configurations with their preferred emission data sets for the
conditions of 2001 (or a close year). Details are listed in Table 4.
Table 3. Analysis tasks and output definition for experiment SR1.
Task no.
Task
SR1.1
Establish the mean model concentrations,
check consistency of model output and
Output
files
aerosolm
metm
Output frequency
monthly
compare with literature
SR1.2
SR1.3
Evaluate surface concentrations
Evaluate aerosol mass and AOD distributions
SR1.4
Evaluate budgets, and depositions
emim
depm
budgetm
sfc
aerosolm
aerosolaod
depm
budgetm
daily
monthly
(aod=daily)
monthly
3.2. Experiment SR6 – perturbation run
The SR6 experiments is to evaluate the effects of anthropogenic emission reduction in a
particular region on surface air quality in all regions. The experiment should be performed the
same as SR1, except that the anthropogenic emissions in a particular region (EA, SA, EU, NA)
should be reduced uniformly by 20%. Only one region is perturbed at one time.
In addition to the HTAP defined experiments, AeroCom recommends three source-receptor
experiments to assess the maximum impact of pollution and dust transport: SR6z, in which the
anthropogenic emissions in the four specified regions are turned off; SR6d, in which the dust
emissions in three major source regions are turned off; SR6b, in which wild fires are turned off.
Table 4. Analysis tasks and output definition for the three experiments in SR6.
Task no.
Task
SR6.1
Evaluate the response of global and regional
aerosol burdens to changes of anthropogenic
aerosol and precursor emissions in specific
regions (EA, SA, EU, NA)
Evaluate the change in surface PM1, PM2.5,
PM10 and aerosol species concentrations in
response to changes of anthropogenic
emission in specific regions
Evaluate regional contributions to PM and
AOD
Evaluate maximum contributions of PM and
AOD from regional emission and hemispheric
transport from other regions (EA, SA, EU,
NA)
Evaluate deposition of PM from own regional
emissions and hemispheric transport
Evaluate maximum contributions of dust from
major dust source regions (AS, ME, AF) to
the PM and AOD in NH
Evaluate deposition of dust emitted from
major source regions to other regions and to
the ocean
Evaluate maximum contributions of biomass
burning aerosols from each Northern
Hemisphere continent to PM and AOD
Evaluate pathways of biomass burning
aerosol from different continents (Arctic,
local, circumpolar)
SR6.2
SR6.3
SR6z.1
SR6z.2
SR6d.1
SR6d.2
SR6b.1
SR6b.2
Output
files
aerosolm
budgetm
emim
depm
sfc
Output frequency
aerosolm
aerosolaod
aerosolm
aerosolaod
monthly
(aod=daily)
Monthly
Daily
depm
Monthly
aerosolm
emim
Monthly
depm
Monthly
aerosolm
aerosolaod
Monthly
aod=daily
Depm,
aerosolm
Monthly
Monthly
Daily
Monthly
3.3. Experiment TP1 – base and perturbation run (option)
Description of model set-up: A simple passive tracer with prescribed surface emissions
(CO_direct) and a fixed, globally uniform lifetime of 25 days shall be introduced into the model.
Surface emissions and common parameterizations shall be adopted from the common data sets
provided on the HTAP website. Four additional tracers shall be defined to label “CO” from
sources in East Asia, South Asia, Europe, and North America (CO_EA, CO_SA, CO_EU, and
CO_NA). Where possible, another five additional tracers to simulate anthropogenic and
biogenic NMVOC emissions (aVOC and bVOC) and the CO produced from their oxidation
(CO_aVOC, CO_bVOC) and from the oxidation of methane (CO_CH4) should also be defined. A
sample FORTRAN subroutine implementing this set-up into the ECHAM model will be provided
on the HTAP web pages. If not all tracers can be defined in your model, we ask you to at least
participate in this experiment with the simulation of the global CO tracer from direct emissions.
Table 4. Analysis tasks and output definition for experiments in TP1.
Task no.
Task
TP1.1
Evaluate the global CO distribution from
direct CO emissions in specific regions (EA,
EU, NA, SA)
Evaluate the source-receptor relationships
for regional CO emissions in specific regions
(EA, EU, NA, SA)
Evaluate the regional contributions of the
different chemical sources to the CO burden
TP1.2
TP1.3
Output
files
tracem
Output frequency
tracem
Monthly
tracem
Monthly
Monthly