139 research outputs found
A multi-model case study on aerosol-meteorology interactions with regional online coupled chemistry-meteorology models
Regional effects of atmospheric aerosols on temperature: An evaluation of an ensemble of online coupled models
The climate effect of atmospheric aerosols is associated with their
influence on the radiative budget of the Earth due to the direct
aerosol–radiation interactions (ARIs) and indirect effects, resulting from
aerosol–cloud–radiation interactions (ACIs). Online coupled
meteorology–chemistry models permit the description of these effects on the
basis of simulated atmospheric aerosol concentrations, although there is
still some uncertainty associated with the use of these models. Thus,
the objective of this work is to assess whether the inclusion of atmospheric
aerosol radiative feedbacks of an ensemble of online coupled models improves
the simulation results for maximum, mean and minimum temperature at 2 m over
Europe. The evaluated models outputs originate from EuMetChem COST Action
ES1004 simulations for Europe, differing in the inclusion (or omission) of
ARI and ACI in the various models. The cases studies cover two important
atmospheric aerosol episodes over Europe in the year 2010: (i) a heat wave event
and a forest fire episode (July–August 2010) and (ii) a more humid episode
including a Saharan desert dust outbreak in October 2010. The simulation
results are evaluated against observational data from the E-OBS gridded database.
The results indicate that, although there is only a slight improvement in the
bias of the simulation results when including the radiative feedbacks, the
spatiotemporal variability and correlation coefficients are improved for the
cases under study when atmospheric aerosol radiative effects are included
An assessment of aerosol optical properties from remote-sensing observations and regional chemistry–climate coupled models over Europe
Atmospheric aerosols modify the radiative budget
of the Earth due to their optical, microphysical and chemical properties, and
are considered one of the most uncertain climate forcing agents. In order to
characterise the uncertainties associated with satellite and modelling
approaches to represent aerosol optical properties, mainly aerosol optical
depth (AOD) and Ångström exponent (AE), their representation by
different remote-sensing sensors and regional online coupled
chemistry–climate models over Europe are evaluated. This work also
characterises whether the inclusion of aerosol–radiation (ARI) or/and
aerosol–cloud interactions (ACI) help improve the skills of modelling
outputs.Two case studies were selected within the EuMetChem COST Action ES1004
framework when important aerosol episodes in 2010 all over Europe took
place: a Russian wildfire episode and a Saharan desert dust outbreak that
covered most of the Mediterranean Sea. The model data came from different
regional air-quality–climate simulations performed by working group 2 of
EuMetChem, which differed according to whether ARI or ACI was included or
not. The remote-sensing data came from three different sensors: MODIS, OMI
and SeaWIFS. The evaluation used classical statistical metrics to first
compare satellite data versus the ground-based instrument network (AERONET)
and then to evaluate model versus the observational data (both satellite and
ground-based data).Regarding the uncertainty in the satellite representation of AOD, MODIS
presented the best agreement with the AERONET observations compared to other
satellite AOD observations. The differences found between remote-sensing
sensors highlighted the uncertainty in the observations, which have to be
taken into account when evaluating models. When modelling results were
considered, a common trend for underestimating high AOD levels was observed.
For the AE, models tended to underestimate its variability, except when
considering a sectional approach in the aerosol representation. The modelling
results showed better skills when ARI+ACI interactions were included; hence
this improvement in the representation of AOD (above 30 % in the model error)
and AE (between 20 and 75 %) is important to provide a better description of
aerosol–radiation–cloud interactions in regional climate models
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Assessment of the MACC reanalysis and its influence as chemical boundary conditions for regional air quality modeling in AQMEII-2
The Air Quality Model Evaluation International Initiative (AQMEII) has now reached its second phase which is dedicated to the evaluation of online coupled chemistry-meteorology models. Sixteen modeling groups from Europe and five from North America have run regional air quality models to simulate the year 2010 over one European and one North American domain. The MACC re-analysis has been used as chemical initial (IC) and boundary conditions (BC) by all participating regional models in AQMEII-2. The aim of the present work is to evaluate the MACC re-analysis along with the participating regional models against a set of ground-based measurements (O3, CO, NO, NO2, SO2, SO42−) and vertical profiles (O3 and CO). Results indicate different degrees of agreement between the measurements and the MACC re-analysis, with an overall better performance over the North American domain. The influence of BC on regional air quality simulations is analyzed in a qualitative way by contrasting model performance for the MACC re-analysis with that for the regional models. This approach complements more quantitative approaches documented in the literature that often have involved sensitivity simulations but typically were limited to only one or only a few regional scale models. Results suggest an important influence of the BC on ozone for which the underestimation in winter in the MACC re-analysis is mimicked by the regional models. For CO, it is found that background concentrations near the domain boundaries are rather close to observations while those over the interior of the two continents are underpredicted by both MACC and the regional models over Europe but only by MACC over North America. This indicates that emission differences between the MACC re-analysis and the regional models can have a profound impact on model performance and points to the need for harmonization of inputs in future linked global/regional modeling studies
A systems approach to risk and resilience analysis in the woody-biomass sector: A case study of the failure of the South African wood pellet industry
© 2017 Elsevier Ltd Currently more than 600 million of the 800 million people in SSA are without electricity, and it is estimated that an additional 2500 GW of power is required by 2030. Although the woody-biomass market in the developed world is relatively mature, only four woody-biomass plants in SSA have been established, all of which were closed by 2013. With its affordable labour, favourable climate and well-established forestry and agricultural sectors, South Africa appears to have the potential for a successful woody-biomass industry. This paper documents a first attempt at analysing why these plants failed. It aims to contextualise the potential role of a sustainable woody-biomass sector in South Africa, through firstly developing a SES-based analytical framework and secondly, using this to undertake a retrospective resilience-based risk assessment of the four former woody-biomass pellet plants in order to identify strategies for increasing the resilience of the industry. The SES-based framework advances previous theory, which usually focuses on natural resources and their supply, by introducing a production process (with inputs and outputs), internal business dynamics and ecological variable interactions. The risk assessment can be used at a broad level to highlight important aspects which should be considered during feasibility assessments for new plants. Further work is proposed to focus on splitting the social-ecological system at different scales for further analysis, and to investigate the long-term ecological impacts of woody-biomass utilisation
Insights into the deterministic skill of air quality ensembles from the analysis of AQMEII data
© 2016. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited. Ioannis Kioutsioukis, et al, ‘Insights into the deterministic skill of air quality ensembles from the analysis of AQMEII data’, Atmospheric Chemistry and Physics, Vol 16(24): 15629-15652, published 20 December 2016, the version of record is available at doi:10.5194/acp-16-15629-2016 Published by Copernicus Publications on behalf of the European Geosciences Union.Simulations from chemical weather models are subject to uncertainties in the input data (e.g. emission inventory, initial and boundary conditions) as well as those intrinsic to the model (e.g. physical parameterization, chemical mechanism). Multi-model ensembles can improve the forecast skill, provided that certain mathematical conditions are fulfilled. In this work, four ensemble methods were applied to two different datasets, and their performance was compared for ozone (O3), nitrogen dioxide (NO2) and particulate matter (PM10). Apart from the unconditional ensemble average, the approach behind the other three methods relies on adding optimum weights to members or constraining the ensemble to those members that meet certain conditions in time or frequency domain. The two different datasets were created for the first and second phase of the Air Quality Model Evaluation International Initiative (AQMEII). The methods are evaluated against ground level observations collected from the EMEP (European Monitoring and Evaluation Programme) and AirBase databases. The goal of the study is to quantify to what extent we can extract predictable signals from an ensemble with superior skill over the single models and the ensemble mean. Verification statistics show that the deterministic models simulate better O3 than NO2 and PM10, linked to different levels of complexity in the represented processes. The unconditional ensemble mean achieves higher skill compared to each station's best deterministic model at no more than 60 % of the sites, indicating a combination of members with unbalanced skill difference and error dependence for the rest. The promotion of the right amount of accuracy and diversity within the ensemble results in an average additional skill of up to 31 % compared to using the full ensemble in an unconditional way. The skill improvements were higher for O3 and lower for PM10, associated with the extent of potential changes in the joint distribution of accuracy and diversity in the ensembles. The skill enhancement was superior using the weighting scheme, but the training period required to acquire representative weights was longer compared to the sub-selecting schemes. Further development of the method is discussed in the conclusion.Peer reviewedFinal Published versio
Case studies on aerosol feedback effects in online coupled chemistry-meteorology models during the 2010 Russian fire event
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