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During the last decade a new field of atmospheric modelling - the chemical weather forecasting (CWF) - is quickly developing and growing. However, in the most of the current studies and publications, this field is considered in a simplified concept of the o -line running chemical transport models with operational numerical weather prediction (NWP) data as a driver. A new concept and methodology considering the chem- ical weather as two-way interacting meteorological weather and chemical composition of the atmosphere is suggested and discussed. The on-line integration of mesometeorological models and atmospheric aerosol and chemical transport models gives a possibility to utilize all meteorological 3-D fields in the chemical transport model at each time step and to consider feedbacks of air pollution (e.g. urban aerosols) on meteorological processes/climate forcing and then on the atmospheric chemical composition. This very promising way for future atmospheric simulation systems (as a part of and a step to Earth System Modelling) will lead to a new generation of models for meteorological, environmental and chemical weather forecasting. The methodology how to realise the suggested integrated CWF concept is demonstrated on the example of the European Enviro- HIRLAM integrated system. The importance of di erent feedback mechanisms for CWF is also discussed in the paper.
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9th EMS Annual Meeting and 9th European Conference on Applications of Meteorology 2009
Chemical weather forecasting:
a new concept of integrated modelling
A. Baklanov
Danish Meteorological Institute, Lyngbyvej 100, 2100 Copenhagen, Denmark
Received: 23 December 2009 – Revised: 14 March 2010 – Accepted: 24 March 2010 – Published: 26 March 2010
Abstract. During the last decade a new field of atmospheric modelling the chemical weather forecasting
(CWF) – is quickly developing and growing. However, in the most of the current studies and publications, this
field is considered in a simplified concept of the o-line running chemical transport models with operational
numerical weather prediction (NWP) data as a driver. A new concept and methodology considering the chem-
ical weather as two-way interacting meteorological weather and chemical composition of the atmosphere is
suggested and discussed. The on-line integration of mesometeorological models and atmospheric aerosol and
chemical transport models gives a possibility to utilize all meteorological 3-D fields in the chemical transport
model at each time step and to consider feedbacks of air pollution (e.g. urban aerosols) on meteorological
processes/climate forcing and then on the atmospheric chemical composition. This very promising way for
future atmospheric simulation systems (as a part of and a step to Earth System Modelling) will lead to a new
generation of models for meteorological, environmental and chemical weather forecasting. The methodology
how to realise the suggested integrated CWF concept is demonstrated on the example of the European Enviro-
HIRLAM integrated system. The importance of dierent feedback mechanisms for CWF is also discussed in
the paper.
1 Introduction
During the last decade a new field of atmospheric modelling
the chemical weather forecasting (CWF) is quickly de-
veloping and growing (Lawrence et al., 2005). This was pos-
sible mostly due to the quickly growing supercomputer ca-
pability and operationally available high-resolution numer-
ical weather prediction (NWP) data for atmospheric chem-
ical transport models (ACTMs). However, in the most of
the current systems, studies and publications this new di-
rection is considered in a simplified concept. It includes
only operational air quality forecast for the main pollutants
significant for health eects and uses numerical ACTMs
with operational NWP data as a driver (see e.g. the COST
Action ES0602: Towards a European Network on Chemi-
cal Weather Forecasting and Information Systems, website:
http://www.chemicalweather.eu/, leader Prof. J. Kukkonen).
Such an approach has limitations due to the o-line way
of coupling the ACTMs with NWP or mesometeorological
models (MMMs) (which are running fully independently and
NWP does not get any benefits from the ACTM) without a
Correspondence to: A. Baklanov
(alb@dmi.dk)
possibility to consider any feedback mechanisms. Many ex-
perimental studies (Rosenfeld, 2000; Bellouin et al., 2005;
Ramanathan and Carmichael, 2008) and numerical research
simulations (Jacobson, 2002; Grell et al., 2004; Schulz et
al., 2006) show that atmospheric processes (meteorological
weather, including the precipitation, thunderstorms, radia-
tion budget, cloud processes and planetary boundary-layer
(PBL) structure) depend on concentrations of chemical com-
ponents in the atmosphere.
Chemical species influencing weather and atmospheric
processes include greenhouse gases which warm near-
surface air and aerosols such as sea salt, dust, primary
and secondary particles of anthropogenic and natural origin.
Some aerosol particle components (black carbon, iron, alu-
minium, polycyclic and nitrated aromatic compounds) warm
the air by absorbing solar and thermal-infrared radiation,
while others (water, sulphate, nitrate, most of organic com-
pounds) cool the air by backscattering incident short-wave
radiation to space. The aerosols, beside the above men-
tioned direct eect (via radiation), include many other dier-
ent mechanisms of aerosol-chemistry-cloud-radiation-PBL-
emission interactions, in particular the semi-direct, first and
second indirect eects.
Published by Copernicus Publications.
24 A. Baklanov: Chemical weather forecasting: a new concept of integrated modelling
Therefore ACTMs have to be run together with NWP
models on the same computational grid and with the same
time step using online coupling and considering two-way in-
teraction between the meteorological processes, from one
side, and chemical transformation and aerosol dynamics,
from the other side.
2 Concept and methodology for integrated CWF
modeling
Proceeding from the above mentioned limitations, a newcon-
cept and methodology considering the chemical weather as
two-way interacting physical and chemical weather is sug-
gested. The CWF should include not only health-eecting
pollutants (air quality components) but also green-house
gases and aerosols eecting climate, meteorological pro-
cesses, etc. Such a concept of CWF requests a strategy of a
new generation integrated meteorology and ACT modelling
systems for predicting atmospheric composition, meteorol-
ogy and climate change. The on-line integration of meteoro-
logical or NWP models and atmospheric aerosol and chem-
ical transport models gives a possibility to utilise all meteo-
rological 3-D fields in ACTM at each time step and to con-
sider feedbacks of atmospheric aerosols on meteorological
processes and climate forcing, and further on the chemical
composition (as a chain of dependent nonlinear processes).
This promising way for future atmospheric simulation sys-
tems will lead to a new generation of integrated models for
meteorological, environmental and chemical weather fore-
casting.
The current COST728 Action “Enhancing meso-scale
meteorological modelling capabilities for air pollution and
dispersion applications” (
http://www.cost728.org, leader
Prof. R. Sokhi) addresses key issues concerning the devel-
opment of meso-scale models for atmospheric environmental
problems and, in particular, it encourages the advancementof
science in terms of integration methodologies and strategies
in Europe. The final integration strategy will not be focused
around any particular model, instead it will be possible to
consider an open integrated system with a fixed architecture
(module interface structure) and with a possibility of incor-
porating dierent ACTMs and MMMs/NWP models. Such
a strategy may only be realised through jointly agreed speci-
fications of module structure for easy-to-use interfacing and
integration.
The overall aim of COST728 working group 2 (WG2),
“Integrated systems of MMM and ACTM: strategy, inter-
faces and module unification”, is to identify the require-
ments for the unification of MMM and ACTM modules and
to propose recommendations for a European strategy for in-
tegrated meso-scale modelling capabilities. The first report
of WG2 (COST-WMO, 2007) compiles the existing state-of-
the-art methodologies, approaches, models and practices for
building integrated (oine and online) meso-scale systems
in dierent, mostly European, countries. The report also in-
cludes an overview and a summary of the existing integrated
models and their characteristics as they are presently used.
The model contributions were compiled using COST mem-
ber contributions, each focusing on national model systems.
The modern strategy for integrating MMMs and ACTMs
is suggested to consider air quality modelling as a combi-
nation of (at least) the following factors: air pollution, re-
gional/urban climate/meteorological conditions and popula-
tion exposure. This combination is reasonable due to the fol-
lowing facts: meteorology is the main source of uncertainty
in air pollution and emergency preparedness models; meteo-
rological and pollution components have complex and com-
bined eects on human health (e.g., the Paris deadly heat
wave in July–August 2003 was caused by dierent com-
bined risk factors: high temperature, ozone concentrations,
etc.); pollutants, especially aerosols, influence climate forc-
ing and meteorological events (radiation, precipitation, thun-
derstorms, etc.).
The integration/coupling of the NWP/MMM and ACT
models can be realized by dierent ways using the online
and oine modelling approaches. In more details the defi-
nition and specifics of the approaches, as well as the advan-
tages and disadvantages of the online and oine modelling
are described by Baklanov and Korsholm (2007) and in the
COST-WMO report (2007). It can be realized using the fol-
lowing possible variants (see Fig. 1):
One-way integration (oine coupling):
1. MMM (or any other regional climate or NWP model)
meteorological fields used to drive ACTM (this way
is traditionally used by many air pollution modellers)
();
2. ACTM chemical composition fields as a driver for re-
gional climate modelling or for NWP (e.g. for aerosol
forcing on meteo-processes) (99K).
Two-way integration:
1. Driver and partial feedbacks, for ACTM or for NWP
(data exchange via an interface with a limited time pe-
riod: oine or online access coupling) (⇐⇒);
2. ACTM built inside MMM or NWP model with full
feedbacks included on each time step (online coupling)
().
In this context, several levels of MMM and ACTM
coupling/integration can be considered:
o-line:
separate ACTMs driven by meteorological input data
from meteo-preprocessors, measurements or diagnostic
models,
Adv. Sci. Res., 4, 23–27, 2010 www.adv-sci-res.net/4/23/2010/
A. Baklanov: Chemical weather forecasting: a new concept of integrated modelling 25
Figure 1. Schematic diagram of different approaches for the integration of meteorological/climate and
atmospheric chemical transport models with one- or two-way interactions. Online coupling can be achieved
through the use of various available coupling tools or through directly inlining the chemical and aerosol
modules into the NWP models.
In this context, several levels of MMM and ACTM coupling/integration can be considered:
off-line
:
o separate ACTMs driven by meteorological input data from meteo-preprocessors, measurements or
diagnostic models,
o separate ACTMs driven by analysed or forecasted meteorological data from NWP archives or datasets,
o separate ACTMs reading output-files from operational NWP models or specific MMMs at limited time
intervals (e.g. 1, 3, 6 hours).
on-line
:
o on-line access models, when meteorological data are available at each time-step (possibly via a model
interface as well),
o on-line integration of ACTM into MMM, where two-way feedbacks may be considered. We will use this
definition for on-line coupled/integrated modelling.
The last level of the on-line integration with two-way feedbacks can consider the full chain of feedbacks and
is recommended as the main strategy for integrated CWF models. These methodologies of the integrated
CWF have been realised by several of the COST action partners such as the Danish Meteorological Institute
(DMI), with the Enviro-HIRLAM model (Baklanov et al., 2008a; Korsholm et al., 2008; Korsholm, 2009)
and the COSMO consortium with the Lokal Modell (Vogel et al., 2006, Wolke et al., 2003), as well as the
American WRF-Chem (Grell et al., 2004, 2005) integrated system. These model developments for chemical
weather forecasting are an activity of increasing importance which is due to be supported by the ongoing
COST action ES0602.
The Enviro-HIRLAM integrated system, recently developed by DMI and other collaborators
1
(Chenevez et
al., 2004; Baklanov et al., 2008a; Korsholm et al., 2008, Korsholm, 2009), is an online coupled model for
research and forecasting of both meteorological and chemical weather. It includes two-way feedbacks
between air-pollutants and meteorological processes. Atmospheric chemical transport equations are
implemented inside the meteorological corner on each time step (Chenevez et al., 2004). To make the model
suitable for CWF in urban areas, where most of the population is concentrated, the meteorological part is
improved by the implementation of urban sublayer modules and parameterisations (Baklanov et al., 2008b).
The aerosol module in Enviro-HIRLAM comprises a thermodynamic equilibrium model and the aerosol
dynamics model CAC (Gross and Baklanov, 2004) based on the modal approach. Parameterisations of the
aerosol feedback mechanisms in the Enviro-HIRLAM model are described in Korsholm et al. (2008) and
Korsholm (2009). Several chemical mechanisms can be chosen depending on the specific tasks.
Model validation and sensitivity tests of the on-line versus off-line integrated versions (Grell et al., 2004,
2005; Korsholm et al., 2009) show that the online coupling improves the modelling results. Grell et al. (2005)
show improved predictions of average ozone concentrations when using the online version of WRF-Chem.
Korsholm et al. (2009) using the online Enviro-HIRLAM for the ETEX-1 experiment release show that the
off-line coupling interval increase leads to considerable error and a false peak (not found in the observations),
which almost disappears in the online version that resolves meso-scale influences during plume development.
1
At the current stage the Enviro-HIRLAM model is used as the baseline system for the HIRLAM chemical brunch, and additionally to
the HIRLAM community the following groups join the development team: University of Copenhagen, Tartu University (Estonia),
Russian State Hydro-Meteorological University, Bilbao University (Spain), Odessa State Environmental University (Ukraine), etc.
Aerosol Dynamics
Model
Transport &
Chemistry Models
Atmospheric
Dynamics /
Climate Model
Ocean and
Ecosystem Models
Atmospheric
Contamination Models
Climate /
Meteorological Models
Interface / Cou
p
ler
Figure 1. Schematic diagram of dierent approaches for the inte-
gration of meteorological/climate and atmospheric chemical trans-
port models with one- or two-way interactions. Online coupling can
be achieved through the use of various available coupling tools or
through directly inlining the chemical and aerosol modules into the
NWP models.
separate ACTMs driven by analysed or forecasted me-
teorological data from NWP archives or datasets,
separate ACTMs reading output-files from operational
NWP models or specific MMMs at limited time inter-
vals (e.g. 1, 3, 6 h).
on-line:
on-line access models, when meteorological data are
available at each time-step (possibly via a model inter-
face as well),
on-line integration of ACTM into MMM, where two-
way feedbacks may be considered. We will use this
definition for on-line coupled/integrated modelling.
The last levelof the on-line integration with two-wayfeed-
backs can consider the full chain of feedbacks and is rec-
ommended as the main strategy for integrated CWF mod-
els. These methodologies of the integrated CWF have been
realised by several of the COST action partners such as
the Danish Meteorological Institute (DMI), with the Enviro-
HIRLAM model (Baklanov et al., 2008a; Korsholm et al.,
2008; Korsholm, 2009) and the COSMO consortium with
the Lokal Modell (Vogel et al., 2006; Wolke et al., 2003), as
well as the American WRF-Chem (Grell et al., 2004, 2005)
integrated system. These model developments for chemical
weather forecasting are an activity of increasing importance
which is due to be supported by the ongoing COST action
ES0602.
The Enviro-HIRLAM integrated system, recently devel-
oped by DMI and other collaborators
1
(Chenevez et al.,
2004; Baklanov et al., 2008a; Korsholm et al., 2008, Kor-
sholm, 2009), is an online coupled model for research and
forecasting of both meteorological and chemical weather.
It includes two-way feedbacks between air-pollutants and
meteorological processes. Atmospheric chemical transport
equations are implemented inside the meteorological corner
on each time step (Chenevez et al., 2004). To make the model
suitable for CWF in urban areas, where most of the popu-
lation is concentrated, the meteorological part is improved
by the implementation of urban sublayer modules and pa-
rameterisations (Baklanov et al., 2008b). The aerosol mod-
ule in Enviro-HIRLAM comprises a thermodynamic equilib-
rium model and the aerosol dynamics model CAC(Grossand
Baklanov, 2004) based on the modal approach. Parameteri-
sations of the aerosol feedback mechanisms in the Enviro-
HIRLAM model are described in Korsholm et al. (2008) and
Korsholm (2009). Several chemical mechanisms can be cho-
sen depending on the specific tasks.
Model validation and sensitivity tests of the on-line versus
o-line integrated versions (Grell et al., 2004, 2005; Kor-
sholm et al., 2009) show that the online coupling improves
the modelling results. Grell et al. (2005) show improved pre-
dictions of average ozone concentrations when using the on-
line version of WRF-Chem. Korsholm et al. (2009) using
the online Enviro-HIRLAM for the ETEX-1 experiment re-
lease show that the o-line coupling interval increase leads
to considerable error and a false peak (not found in the obser-
vations), which almost disappears in the online version that
resolves meso-scale influences during plume development.
In the case study by Zhang (2008) it was shown that in-
cluding only the direct aerosol eects leads to a tempera-
ture change about 0.2
C and the water vapor mixing ratio
increases more than 3% at/near surface. The eects of urban
aerosols on the urban boundary layer height, can be of the
same order of magnitude as the eects of the urban heat is-
land (h is up to 100–200m for stable boundary layer) (Bak-
lanov et al., 2008a). Korsholm et al. (2009) show that aerosol
feedbacks through the second indirect eect induce consid-
erable changes in meteorological fields and large changes in
chemical composition, in particular NO
2
, in a case of con-
vective cloud cover and little precipitation.
1
At the current stage the Enviro-HIRLAM model is used as the
baseline system for the HIRLAM chemical branch, and additionally
to the HIRLAM community the following groups join the develop-
ment team: University of Copenhagen, Tartu University (Estonia),
Russian State Hydro-Meteorological University, Bilbao University
(Spain), Odessa State Environmental University (Ukraine), etc.
www.adv-sci-res.net/4/23/2010/ Adv. Sci. Res., 4, 23–27, 2010
26 A. Baklanov: Chemical weather forecasting: a new concept of integrated modelling
3 Discussion and conclusions
The new concept and methodology considering the chemical
weather as two-way interacting meteorological weather and
chemical composition of the atmosphere is suggested for fu-
ture chemical weather forecasting systems.
These on-line coupled model developments will lead to a
new generation of integrated models not only for the chem-
ical weather forecasting, but also for improved meteorologi-
cal weather forecasting (e.g., in urban areas, severe weather
events, fog and visibility, UV-radiation and solar energy,
etc.), bio-meteorological forecasting, climate change mod-
elling, air quality analysis and mitigations, long-term assess-
ment chemical composition.
Main advantages of the on-line modelling approach in-
clude: (i) Only one grid for MMM and ACTM, no interpo-
lation in space and time, (ii) Physical parameterizations and
numerical schemes are the same, no inconsistencies; (iii) All
3-D meteorological variables are available at the right time
at each time step; (iv) No restriction in variability of meteo-
rological fields; (v) Possibility to consider two-way feedback
mechanisms; (vi) No need for meteo- pre/post-processors.
However, for specific tasks the o-line approach can also
be useful and includes the following advantages in separate
cases, e.g. for risk assessments: (i) Possibility of independent
parameterizations; (ii) More suitable for ensemble activities;
(iii) Easier to use for the inverse modelling and adjoint prob-
lem; (iv) Independence of atmospheric pollution model runs
on meteorological model computations; (v) More flexible
grid construction and generation for ACTMs, (vi) Suitable
for emission scenarios analysis and air quality management.
The COST-WMO (2007) and further COST-NetFAM
(2008) overviews show a quite surprising number of on-
line coupled MMM and ACTM model systems already being
used in Europe. However, many of the on-line coupled mod-
els are not built for the mesometeorological scale, and they
(e.g. GME, ECMWF GEMS, MESSy) are global-scale mod-
elling systems and first of all designed for climate change
modelling. Besides, at the current stage most of the on-
line coupled models do not consider feedback mechanisms
or include only direct eects of aerosols on meteorologi-
cal processes (like COSMO LM-ART and MCCM). Only
two meso-scale on-line integrated modelling systems (WRF-
Chem and Enviro-HIRLAM) consider feedbacks with indi-
rect eects of aerosols.
It is necessary to highlight that the interactions of aerosols
and other chemical species with meteorological processes
have many dierent pathways and they have to be priori-
tised and considered in on-line coupled modelling systems
for CWF. Further sensitivity studies are needed to understand
the relative importance of dierent feedback mechanisms for
dierent species, scales and conditions relevant to air quality
and meteorology interactions. A concerted action to mobilise
and coordinate European research in this area is needed.
Acknowledgements. This study was supported by the COST
Actions 728 and ES0602, NetFAM, EC FP7 Project MEGAPOLI
and the Copenhagen Global Change Initiative (COGCI). The
author is grateful to a number of COST728, FUMAPEX, Enviro-
HIRLAM, MEGAPOLI and DMI colleagues, who participated
in the above-mentioned projects, for productive collaboration
and discussions. Especial thanks are to my former PhD student
Ulrik Korsholm (DMI) who realised most of the Enviro-HIRLAM
model coding, simulation runs and studies of the aerosol indirect
eects.
Edited by: M. Piringer
Reviewed by: two anonymous referees
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www.adv-sci-res.net/4/23/2010/ Adv. Sci. Res., 4, 23–27, 2010
... There are two main modelling approaches used within the Eulerian models-offline and online systems (Baklanov 2010;Baklanov et al. 2014). The online integration of meteorological models and chemical transport models (CTMs) provides an opportunity to use 3D meteorological fields in CTM at each time step. ...
... The offline approach is more computationally efficient compared to the online approach-one simulation with the meteorological model can provide input data to many simulations with chemical transport models. A list of the advantages of both the online and offline approaches is given by Baklanov (2010). The application of Eulerian models for pollen modelling within the last 10 years included both offline approach, e.g. with SILAM (Sofiev et al. 2015;Galán et al. 2017;Sofiev 2019) and online approach, e.g. with COSMO-ART (Pauling et al. 2012;Zink et al. 2013) and Enviro-HIRLAM (Kurganskiy et al. 2020). ...
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In recent years, allergies due to airborne pollen allergens have shown an increasing trend, along with the severity of allergic symptoms in most industrialized countries, while synergism with other common atmospheric pollutants has also been identified as affecting the overall quality of citizenly life. In this study, we propose the state-of-the-art WRF-Chem model, which is a complex Eulerian meteorological model integrated on-line with atmospheric chemistry. We used a combination of the WRF-Chem extended towards birch pollen, and the emission module based on heating degree days, which has not been tested before. The simulations were run for the moderate season in terms of birch pollen concentrations (year 2015) and high season (year 2016) over Central Europe, which were validated against 11 observational stations located in Poland. The results show that there is a big difference in the model’s performance for the two modelled years. In general, the model overestimates birch pollen concentrations for the moderate season and highly underestimates birch pollen concentrations for the year 2016. The model was able to predict birch pollen concentrations for first allergy symptoms (above 20 pollen m ⁻³ ) as well as for severe symptoms (above 90 pollen m ⁻³ ) with probability of detection at 0.78 and 0.68 and success ratio at 0.75 and 0.57, respectively for the year 2015. However, the model failed to reproduce these parameters for the year 2016. The results indicate the potential role of correcting the total seasonal pollen emission in improving the model’s performance, especially for specific years in terms of pollen productivity. The application of chemical transport models such as WRF-Chem for pollen modelling provides a great opportunity for simultaneous simulations of chemical air pollution and allergic pollen with one goal, which is a step forward for studying and understanding the co-exposure of these particles in the air.
... It is possible to consider feedbacks of air pollution on meteorological processes and on the atmospheric chemical composition by using online integrated models. This type of simulation will lead to a new generation of models for meteorological, environmental and chemical weather forecasting (Baklanov 2010;Baklanov et al. 2014). Recently, a number of online CTMs, which can be used for operational and researching purposes, were developed. ...
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A short-term forecast of the city “chemical weather” requires real daily data on pollutant emissions. For operational daily forecasts of pollutant concentrations, usually long-term emission averages are used which may differ significantly from real values for a certain day, especially in big cities with intense and variable human activities. The online coupled atmospheric chemical transport model COSMO-ART was implemented for the Moscow region, Russia. A method for calculation of pollutant emissions for short-term forecasting was suggested. In this method, “actual” emissions for a certain day are obtained from measurements of air pollutant concentrations. It is assumed that the pollutant concentration reflects the spatially averaged intensity of emission sources. We used the observational data of pollutant concentrations from the network of the State Ecological Monitoring System of Moscow City. In order to get a more homogeneous field of data, “virtual” stations (so-called "bogus data") were added within the areas not covered with observations. The proposed method allows a transformation of the hourly measurements of air pollutant concentration to emission values just after the measurements are completed. We showed the application of this method for carbon monoxide. Verification of COSMO-ART results demonstrates that the forecasts based on emissions calculated by the new method are better than the ones based on climate mean emissions. The approach suggested in the study provides a possibility to issue more detailed operational short-term forecasts of pollutant concentrations for megacities depending on the real air pollution of the previous day. The main limitation of this methodology is that it can be applied to the chemical species that have longer chemical life-time compared to the frequency of concentration measurements.
... The two models are coupled using an offline coupling technique defined by Baklanov (2010). CAMx is driven independently from RegCM and no feedbacks from the simulated species concentration on RegCM radiation/cloud processes are considered. ...
Article
The regional climate model RegCM4.4, including the surface model CLM4.5, was offline coupled to the chemistry transport model CAMx version 6.30 in order to investigate the impact of the urban canopy induced meteorological changes on the longterm summer photochemistry over central Europe for the 2001–2005 period. First, the urban canopy impact on the meteorological conditions was calculated performing a reference experiment without urban landsurface considered and an experiment with urban surfaces modeled with the urban parameterization within the CLM4.5 model. In accordance with expectations, strong increases of urban surface temperatures (up to 2–3 K), decreases of wind speed (up to −1 ms⁻¹) and increases of vertical turbulent diffusion coefficient (up to 60–70 m²s⁻¹) were found. For the impact on chemistry, these three components were considered. Additionally, we accounted for the effect of temperature enhanced biogenic emission increase. Several experiments were performed by adding these effects one-by-one to the total impact: i.e., first, only the urban temperature impact was considered driving the chemistry model; secondly, the wind impact was added and so on. We found that the impact on biogenic emission account for minor changes in the concentrations of ozone (O3), oxides of nitrogen NOx = NO + NO2 and nitric acid (HNO3). On the other hand, the dominating component acting is the increased vertical mixing, resulting in up to 5 ppbv increase of urban ozone concentrations while causing −2 to −3 ppbv decreases and around 1 ppbv increases of NOx and HNO3 surface concentrations, respectively. The temperature impact alone results in reduction of ozone, increase in NO, decrease in NO2 and increases of HNO3. The wind impact leads, over urban areas, to ozone decreases, increases of NOx and a slight increase in HNO3. The overall impact is similar to the impact of increased vertical mixing alone. The Process Analysis (PA) technique implemented in CAMx was adopted to investigate the causes of the modeled impacts in more details. It showed that the main process contributing to the temperature impact on ozone is a dry-deposition enhancement, while the dominating process controlling the wind impact on ozone over cities is the advection reduction. In case of the impact of enhanced turbulence, PA suggests that ozone increases are, again as assumed, the result of increased downward vertical mixing supported by reduced chemical loss. Comparing the model concentrations with measurements over urban areas, a slight improvement of the model performance was achieved during afternoon hours if urban canopy forcing on chemistry via meteorology was accounted for. The study demonstrates that disregarding the urban canopy induced meteorological effects in air-quality oriented modeling studies can lead to erroneous results in the calculated species concentrations. However, it also shows that the individual components are not equally important: urban canopy induced turbulence effects dominate while the wind-speed and temperature related ones are of considerably smaller magnitude.
... However, in most of the current studies, this field is still considered in a simplified concept of the offline running of atmospheric chemical trans-port (ACT) models with operational numerical weather prediction (NWP) data as a driver (Lawrence at al., 2005). A new concept and methodology considering the "chemical weather" as two-way interacting nonlinear meteorological and chemical/aerosol dynamics processes of the atmosphere have been recently suggested (Grell et al., 2005;Baklanov and Korsholm, 2008;Baklanov, 2010;Grell and Baklanov, 2011). First attempts at building online coupled meteorology and air pollution models for environmental applications were done in the 1980s; see Baklanov (1988), Schlünzen and Pahl (1992), Jacobson (1994). ...
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The Environment – High Resolution Limited Area Model (Enviro-HIRLAM) is developed as a fully online integrated numerical weather prediction (NWP) and atmospheric chemical transport (ACT) model for research and forecasting of joint meteorological, chemical and biological weather. The integrated modelling system is developed by the Danish Meteorological Institute (DMI) in collaboration with several European universities. It is the baseline system in the HIRLAM Chemical Branch and used in several countries and different applications. The development was initiated at DMI more than 15 years ago. The model is based on the HIRLAM NWP model with online integrated pollutant transport and dispersion, chemistry, aerosol dynamics, deposition and atmospheric composition feedbacks. To make the model suitable for chemical weather forecasting in urban areas, the meteorological part was improved by implementation of urban parameterisations. The dynamical core was improved by implementing a locally mass-conserving semi-Lagrangian numerical advection scheme, which improves forecast accuracy and model performance. The current version (7.2), in comparison with previous versions, has a more advanced and cost-efficient chemistry, aerosol multi-compound approach, aerosol feedbacks (direct and semi-direct) on radiation and (first and second indirect effects) on cloud microphysics. Since 2004, the Enviro-HIRLAM has been used for different studies, including operational pollen forecasting for Denmark since 2009 and operational forecasting atmospheric composition with downscaling for China since 2017. Following the main research and development strategy, further model developments will be extended towards the new NWP platform – HARMONIE. Different aspects of online coupling methodology, research strategy and possible applications of the modelling system, and fit-for-purpose model configurations for the meteorological and air quality communities are discussed.
... However, in most of the current studies this field is stil considered in a simplified concept of the 39 off-line running of atmospheric chemical transport (ACT) models with operational numerical weather prediction (NWP) data 40 as a driver (Lawrence at al., 2005). A new concept and methodology considering the " chemical weather " as two-way 41 interacting nonlinear meteorological and chemical/aerosol dynamics processes of the atmosphere have been recently 42 suggested (Grell et al., 2005; Baklanov and Korsholm, 2008; Baklanov, 2010; Grell and Baklanov, 2011). The current 43 experience in the online integrated meteorology-chemistry modelling, importance of different chains of feedback (Baklanov et al., 2014) models. ...
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The Environment – HIgh Resolution Limited Area Model (Enviro-HIRLAM) is developed as a fully online integrated numerical weather prediction (NWP) and atmospheric chemical transport (ACT) model for research and forecasting of joint meteorological, chemical and biological weather. The integrated modelling system is developed by DMI in collaboration with several European universities. It is the baseline system in the HIRLAM Chemical Branch and used in several countries and different applications. The development was initiated at DMI more than 15 years ago. The first version was based on the DMI-HIRLAM NWP model with online integrated passive pollutant transport and dispersion, chemistry, aerosol dynamics, deposition and indirect effects. To make the model suitable for chemical weather forecasting (CWF) in urban areas the meteorological part was improved by implementation of urban parameterizations. The dynamical core was improved by implementing a locally mass conserving semi-Lagrangian numerical advection scheme, which improves forecast accuracy and model performance. The latest developing version is based on HIRLAM reference v7.2 with a more advanced and effective chemistry, aerosol multi-compound approach, aerosol feedbacks (direct and semi-direct) on radiation and (first and second indirect effects) on cloud microphysics. Since 2004 the Enviro-HIRLAM is used for different studies, including operational pollen forecasting for Denmark since 2009. Following main research and development strategy the further model developments will be extended towards the new NWP platform – HARMONIE. Different aspects of online coupling methodology, research strategy and possible applications of the modelling system, and fit-for-purpose model configurations for the meteorological and air quality communities are discussed.
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The importance of and interest to research and investigations of atmospheric composition and its modeling for different applications are substantially increased. Air quality forecast (AQF) and assessment systems help decision makers to improve air quality and public health, mitigate the occurrence of acute air pollution episodes, particularly in urban areas, and reduce the associated impacts on agriculture, ecosystems and climate. Advanced approaches in AQF combine an ensemble of state-of-the-art models, high-resolution emission inventories, satellite observations, and surface measurements of most relevant chemical species to provide hindcasts, analyses, and forecasts from global to regional air pollution and downscaling for selected countries, regions, and urban areas. Based on published reviews and recent analyses, the article discusses main gaps, challenges, applications and advances, main trends and research needs in further advancements of atmospheric composition and air quality modeling and forecasting.
Article
In the framework of the EC FP7 MACC project (http://www.gmes-atmosphere.eu) two possible suites/ examples of multi-scale modelling demonstrated how downscaling from the European MACC ensemble to local-scale air quality forecast can be carried out. The first example (from DMI) illustrated downscaling capabilities for the city of Copenhagen (Denmark) whereas the second example (from NMA) focused on the city of Bucharest (Romania). Multi-scale modelling with one-way nesting for model downscaling from the regional MACC R-Ens to city-scale by the Enviro-HIRLAM/CAMx and to street-scale by the obstacle-resolved M2UE model was suggested for Copenhagen. The MOCAGE in a 3 domain configuration coupled with global ARPEGE and ALARO meso-scale numerical weather prediction model was proposed for Bucharest. The realised chain of models of different scales with nesting of high resolution models for urban areas into larger scale lower resolution models using the European MACC ensemble regional air quality forecast R-Ens gave a possibility to improve the urban air quality forecast considering the urban increment by the city-scale models and the street increment by the micro-scale model. Detailed analysis showed that the developed MACC modelling chain allows downscaling of weather and air quality forecasting on the city-scale and up to the street-scale not only for Copenhagen, but also for any other city. It was found that the street level concentration of traffic induced gases could be up to 5 times or much higher than concentration at roof-top of buildings. High uncertainty of local emissions at the street level has been also observed. It should be noted that online coupling of different scale models could give a better fit of modelling results to observations. The present configuration of the MACC R-Ens adds very valuable information on chemical species compared to just having our own model system. However, if to be used for making additional downscaled runs for operational urban AQ forecasting some modifications seems to be necessary. The suggested recommendations to improve the MACC R-Ens output for downscaling of weather and air quality forecasting on the city-scale (and up to the street-scale) include the following: - Additional chemical species and levels for boundary conditions. Further studies over a not too short period based on an extended data set from the RAQ ensemble system need to be made to see which ones. - A more complete set of chemical species and levels than for boundary conditions for the analysis time to be used for initial conditions for downscaling runs. It might be possible to have a better impact in the places of interest from the MACC ensemble by having different initial conditions for the downscaling run than just for boundary conditions. Again further studies over a not too short period based on an extended data set from the RAQ ensemble need to be made to see which ones. Such a dataset has not yet been available to make such tests. For operational usage (beyond plots and point extraction data) such as initial conditions and boundary conditions for making downscaling run the following should be considered: - No more than 6 hours delay from nominal time. - Twice per day. - Additional fields and levels for boundary and initial field conditions. Further studies need to be made to see which ones. The potential for downscaling of European air quality forecasts, based on the MACC/GEMES core service (R-Ens, etc.), by operating urban and street-level forecast models was demonstrated on examples of Copenhagen and Bucharest as a prototype for future downstream applications. The benefits of the refined forecasts vs. “raw” European ensemble forecast was evaluated and showed good possibilities to improve urban AQ forecast by such downstream service based on the MACC products. This will bring a strong support for continuous improvement of the regional forecast modelling systems for air quality in Europe, and underline clear perspectives for the future regional air quality core-downstream services for end-users.
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Citation: Jacobson, M. Z., Reply to comment by J. Feichter et al. on ''Control of fossil-fuel particulate black carbon and organic matter, possibly the most effective method of slowing global warming,'' J. Geophys. Res., 108(D24), 4768, doi:10.1029/2002JD003299, 2003.
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Chemical weather is a field of increasing popularity and several institutes, such as Environment Canada and NOAA, currently forecast both chemical and meteorological weather. Following a definition (Lawrence et al., 2005), chemical weather may be given as local, regional and global distributions of trace gases and aerosols with corresponding variability ranging from minutes to days. Two modeling paradigms exist for forecasting chemical weather; the online approach and the offline approach (Baklanov and Korsholm, 2008, Baklanov, et al., 2008). The use of the terms online and offline in this context has been ambiguous, but a formal definition may be given as follows: offline models are separate chemical transport models (CTM's) forced by output from meteorological models, analyzed or forecasted meteorological data from archives or data sets, pre-processed meteorological data, measurements or output from diagnostic models; online models comprise online access models in which the meteorological forcing fields are available at each time step of the meteorological driver and online coupled models in which the CTM has been integrated into the meteorological driver and feedbacks between meteorological and chemical and aerosol fields are possible. In this definition it is possible to generate an online access model by employing an offline model with a very high coupling frequency e.g every 10 minutes, for example using a coupler such as OASIS4 or US-ESMF (COST-NetFAM, 2007, Dickinson, 2002), to exchange chemical and meteorological fields each time step. However, the handling of high resolution data in this manner is highly cumbersome and time consuming and therefore, not suited for operational chemical weather forecasting. Alternatively, an online coupled model may be generated by integrating a CTM in the meteorological driver, thereby, reducing the external data handling to a minimum. This should be done in such a way that all transport, dispersion and transformation of the chemical and aerosol species are done on the grid used by the meteorological model using the same numerical solution methods. We believe that this approach contains a number of advantages that makes it convenient. These include the use of the same parameterizations and numerical solution schemes for the chemical and aerosol species and the meteorological driving fields eliminating this type of inconsistency as well as the removal of spatial and temporal interpolation of the meteorological forcing fields. Comparing to offline models the online approach takes full advantage of the variability of the meteorological fields, it may include feedbacks and has shorter execution time. One might say that when using an offline model the computational resources are spread out over a longer time span, since, the meteorological forecast, the pre-processing (spatial and temporal interpolation) of the driving fields and the execution of the CTM are done separately, whereas with an online model, as advocated above, it is all done in during one run. It should be noted that, if it is assumed that feedbacks are not of importance, offline models have advantages in other disciplines such as sensitivity studies, including air quality impact studies, where meteorology is kept constant and emissions are varied. According to the definition given above chemical weather forecasting is not a new discipline, since offline air quality models have been used for several decades. However, if one wishes to simulate the short term variability (below one hour), present in chemical and aerosol fields, which is important for feedbacks (see Feedback section later) online coupled models are needed.
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Integrated Systems of Meso-Meteorological and Chemical Transport Models front & content look at: http://www.springer.com/la/book/9783642139796 Provides overall view of the current situation with the on-line and off-line coupling of meteorological and air quality models around the word as well as discussing advantages and disadvantages. This book, as the outcome of the COST-728/NetFAM workshop, focuses on the follow­ing main topics: 1) on-line coupled meteorology-chemistry modelling with two-way feedbacks, 2) off-line coupled modelling and interfaces, 3) validation and case studies including air quality related episodes, and 4) integration of atmospheric chemical transport (ACT) models with numerical weather prediction (NWP). This book is one of the first attempts to give an overall look on such integrated meso-meteorology and chemistry modelling approach. It reviews the current situation with the on-line and off-line coupling of mesoscale meteorological and ACT models worldwide as well as discusses advantages and shortcomings, best practices, and gives recommendations for on-line and off-line coupling of NWP and ACT models, implementation strategy for different feedback mechanisms, direct and indirect effects of aerosols and advanced interfaces between both types of models. The book is oriented towards numerical weather prediction and air quality modelling communities.
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Nine different global models with detailed aerosol modules have independently produced instantaneous direct radiative forcing due to anthropogenic aerosols. The anthropogenic impact is derived from the difference of two model simulations with identically prescribed aerosol emissions, one for present-day and one for pre-industrial conditions. The difference in the energy budget at the top of the atmosphere (ToA) yields a new harmonized estimate for the aerosol direct radiative forcing (RF) under all-sky conditions. On a global annual basis RF is –0.2 Wm^-2, with a standard deviation of ±0.2 Wm^-2. Anthropogenic nitrate and dust are not included in this estimate. No model shows a significant positive all-sky RF. The corresponding clear-sky RF is –0.6 Wm^-2. The cloud-sky RF was derived based on all-sky and clear-sky RF and modelled cloud cover. It was significantly different from zero and ranged between –0.16 and +0.34 Wm^-2. A sensitivity analysis shows that the total aerosol RF is influenced by considerable diversity in simulated residence times, mass extinction coefficients and most importantly forcing efficiencies (forcing per unit optical depth). Forcing efficiency differences among models explain most of the variability, mainly because all-sky forcing estimates require proper representation of cloud fields and the correct relative altitude placement between absorbing aerosol and clouds. The analysis of the sulphate RF shows that differences in sulphate residence times are compensated by opposite mass extinction coefficients. This is explained by more sulphate particle humidity growth and thus higher extinction in models with short-lived sulphate present at lower altitude and vice versa. Solar absorption within the atmospheric column is estimated at +0.85 Wm^-2. The local annual average maxima of atmospheric forcing exceed +5 Wm^-2 confirming the regional character of aerosol impacts on climate. The annual average surface forcing is –1.03 Wm^-2.
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It has been postulated that dimethyl sulphide (DMS) emissions from the oceans can produce new condensation nuclei and eventually cloud condensation nuclei. Thus, DMS may have a significant influence on the Earth's radiation budget. A study of this postulate has been conducted for marine boundary layer conditions using a newly developed chemistry–aerosol–cloud (CAC) modelling system. The CAC modelling system is a variable heterogeneous chemistry model including aerosol physics using the modal concept. A series of simulations describing the clean marine atmosphere with variations of DMS emissions are presented. These simulations show that DMS can increase the particle number concentration of non sea-salt sulphate in accumulation mode from 10% to 25% under clean marine atmospheric conditions, and the total production of accumulation mode particles from 5% to 15%. Furthermore, the importance of including a DMS loss to the liquid-phase aerosols is shown. If this link is not included then the number of particles in the accumulation mode can be increased by a factor up to 8.
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The increased resolution of numerical weather prediction models allows nowadays addressing more realistically urban meteorology and air pollution processes. This has triggered new interest in modelling and describing experimentally the specific features and processes of urban areas. Recent developments and results performed within the EU-funded project FUMAPEX on integrated systems for forecasting urban meteorology and air pollution are reported here. Sensitivity studies with respect to optimum resolution, parametrisation of urban roughness and surface exchange fluxes and the role of urban soil layers are carried out with advanced meso- or sub-meso meteorological models. They show that sensible improvements can be achieved by higher model resolution that is accompanied with better description of urban surface features. Recommendations, especially with respect to advanced urban air quality forecasting and information systems, are given together with an assessment of the needed further research and data. www.atmos-chem-phys.net/8/523/2008/
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Air quality models base on mass balances described by systems of time-dependent, three-dimensional advection-diffusion-reaction equations. The solution of such systems is numerically expensive in terms of computing time. This requires the use of fast parallel computers. Multiblock grid techniques and implicit-explicit (IMEX) time integration schemes are suited to take benefit from the parallel architecture. A parallel version of the multiscale chemistry-transport code MUSCAT (MUiltiScale Chemistry Aerosol Transport) is presented which is based on these techniques (Wolke and Knoth, 2000).
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The term 'chemical weather,' the short-term variability of the atmospheric chemical composition, has come into widespread use in the field of atmospheric sciences. Chemical weather results from the strong influence of meteorological variability, chemical complexity, and regionally and temporally varying emissions. Chemical weather can be seen as analogous to the meteorological weather, and can be contrasted with the chemical climate, which denotes the mean trace gas and aerosol distributions on timescales of months to decades. Both climate models and observations are crucial to the study of the chemical weather, particularly their joint usage in tasks such as interpretation of data, evaluation of models, making forecasts to guide measurements, and assimilation of observations to improve model simulations. The most evident direct link of the chemical weather to other disciplines is that with numerical weather prediction (NWP), and also to the study of climate change. Key applications of the study of chemical weather include human health, and effects of trace gases and aerosols on agriculture and ecosystems. The chemical weather simulations and forecasts will need to be carefully assessed in terms of the ability of data assimilation algorithms and their routine application to help improve the forecast skill.
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We applied a parameterization for the emission of mineral dust particles which takes into account the relevant processes such as saltation and combines previous, physically based parameterizations. The size distribution of the soil particles is taken into account to describe the saltation. The emitted particles are described by three log-normal distributions with fixed standard deviations. A comparison of the results of a stand alone version of our parameterization with observations shows that despite tuning of model parameters there are still differences. Finally, we included the parameterization within our three-dimensional mesoscale model system for the area of the Dead Sea. The channelling effect of the Jordan Valley and stable stratification during the day modifies the horizontal distribution of the dust particles. At greater distances the size and the mass distributions of the particles is shifted towards smaller diameters due to sedimentation which is important for radiative feedback mechanisms. Sensitivity runs show the advantage of the parameterization which allows a time dependent ratio of the saltation and the emission flux at each grid point.
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Computational advances now allow air quality forecast models to fully couple the meteorology with chemical constituents within a unified modeling system - online - that allows two-way interactions. The more common approach is the offline system, which only allows one-way coupling from the meteorology - sampled at fixed time intervals - to the chemistry. To study the information loss between online and offline numerical forecasts, a next-generation nonhydrostatic air quality modeling system has been developed that can be used both offline or online. First, a control online air quality simulation is conducted and the meteorology and chemical data are saved at a 10 s time interval. Subsequently, three offline simulations are conducted with meteorological data updates at 10, 30, and 60 min time intervals. Analysis of the wind velocity power spectrum and chemical profiles indicate that the offline simulations are susceptible to large errors in the vertical mass distribution.