Global aerosol simulations using NICAM.16 on a 14 km grid spacing for a climate study: improved and remaining issues  relative to a lower-resolution model

Abstract. High-performance computing resources allow us to conduct numerical simulations with a horizontal grid spacing that is sufficiently high to resolve cloud systems on a global scale, and high-resolution models (HRMs) generally provide better simulation performance than low-resolution models (LRMs). In this study, we execute a next-generation model that is capable of simulating global aerosols using version 16 of the Nonhydrostatic Icosahedral Atmospheric Model (NICAM.16). The simulated aerosol distributions are obtained for 3 years with an HRM using a global 14 km grid spacing, an unprecedentedly high horizontal resolution and long integration period. For comparison, a NICAM with a 56 km grid spacing is also run as an LRM, although this horizontal resolution is still high among current global aerosol climate models. The comparison elucidated that the differences in the various variables of meteorological fields, including the wind speed, precipitation, clouds, radiation fluxes and total aerosols, are generally within 10 % of their annual averages, but most of the variables related to aerosols simulated by the HRM are slightly closer to the observations than are those simulated by the LRM. Upon investigating the aerosol components, the differences in the water-insoluble black carbon and sulfate concentrations between the HRM and LRM are large (up to 32 %), even in the annual averages. This finding is attributed to the differences in the aerosol wet deposition flux, which is determined by the conversion rate of cloud to precipitation, and the difference between the HRM and LRM is approximately 20 %. Additionally, the differences in the simulated aerosol concentrations at polluted sites during polluted months between the HRM and LRM are estimated with normalized mean biases of −19 % for black carbon (BC), −5 % for sulfate and −3 % for the aerosol optical thickness (AOT). These findings indicate that the impacts of higher horizontal grid spacings on model performance for secondary products such as sulfate, and complex products such as the AOT, are weaker than those for primary products, such as BC. On a global scale, the subgrid variabilities in the simulated AOT and cloud optical thickness (COT) in the 1∘×1∘ domain using 6-hourly data are estimated to be 28.5 % and 80.0 %, respectively, in the HRM, whereas the corresponding differences are 16.6 % and 22.9 % in the LRM. Over the Arctic, both the HRM and the LRM generally reproduce the observed aerosols, but the largest difference in the surface BC mass concentrations between the HRM and LRM reaches 30 % in spring (the HRM-simulated results are closer to the observations). The vertical distributions of the HRM- and LRM-simulated aerosols are generally close to the measurements, but the differences between the HRM and LRM results are large above a height of approximately 3 km, mainly due to differences in the wet deposition of aerosols. The global annual averages of the effective radiative forcings due to aerosol–radiation and aerosol–cloud interactions (ERFari and ERFaci) attributed to anthropogenic aerosols in the HRM are estimated to be -0.293±0.001 and -0.919±0.004 W m−2, respectively, whereas those in the LRM are -0.239±0.002 and -1.101±0.013 W m−2. The differences in the ERFari between the HRM and LRM are primarily caused by those in the aerosol burden, whereas the differences in the ERFaci are primarily caused by those in the cloud expression and performance, which are attributed to the grid spacing. The analysis of interannual variability revealed that the difference in reproducibility of both sulfate and carbonaceous aerosols at different horizontal resolution is greater than their interannual variability over 3 years, but those of dust and sea salt AOT and possibly clouds were the opposite. Because at least 10 times the computer resources are required for the HRM (14 km grid) compared to the LRM (56 km grid), these findings in this study help modelers decide whether the objectives can be achieved using such higher resolution or not under the limitation of available computational resources.

Download Full-text

Global aerosol simulations using NICAM.16 on a 14-km grid spacing for a climate study: Improved and remaining issues relative to a lower-resolution model

10.5194/gmd-2020-34 ◽

2020 ◽

Author(s):

Daisuke Goto ◽

Yousuke Sato ◽

Hisashi Yashiro ◽

Kentaroh Suzuki ◽

Eiji Oikawa ◽

...

Keyword(s):

Wet Deposition ◽

Global Scale ◽

Horizontal Resolution ◽

Global Climate Models ◽

The Arctic ◽

Generation Model ◽

Grid Spacing ◽

Anthropogenic Aerosols ◽

Hourly Data ◽

Horizontal Grid

Abstract. High-performance computing resources allow us to conduct numerical simulations with a horizontal grid spacing that is sufficiently high to resolve cloud systems on a global scale, and high-resolution models (HRMs) generally provide better simulation performances than low-resolution models (LRMs). In this study, we execute a next-generation model that is capable of simulating global aerosols on a nonhydrostatic icosahedral atmospheric model version 16 (NICAM.16). The simulated aerosol distributions are obtained for 3 years with a HRM in a global 14-km grid spacing, an unprecedentedly high horizontal resolution and long integration period. For comparison, a NICAM with a 56-km grid spacing is also run as an LRM, although this horizontal resolution is still high among current global climate models. The comparison elucidated that the differences in the various variables of meteorological fields, including the wind speed, precipitation, clouds, radiation fluxes and total aerosols, are generally within 10 % of their annual averages, but most of the variables related to aerosols simulated by the HRM are slightly closer to the observations than are those simulated by the LRM. Upon investigating the aerosol components, the differences in the water-insoluble black carbon (WIBC) and sulfate concentrations between the HRM and LRM are large (up to 32 %), even in the annual averages. This finding is attributed to the differences in the column burden of the aerosol wet deposition, which is determined by a conversion rate of precipitation to cloud and the difference between the HRM and LRM is approximately 20 %. Additionally, the differences in the simulated aerosol concentrations at polluted sites during polluted months between the HRM and LRM are estimated with medians of −23 % (−63 % to −2.5 %) for BC, −4 % (−91 % to +18 %) for sulfate and −1 % (−49 % to +223 %) for the aerosol optical thickness (AOT). These findings indicate that the differences in the secondary and tertiary products, such as the AOT, between the different horizontal grid spacings are not explained simply by the grid size. On a global scale, the subgrid variabilities in the simulated AOT and COT in the 1°×1° domain using 6-hourly data are estimated to be 28.5 % and 80.0 %, respectively, in the HRM, whereas the corresponding differences are 16.6 % and 22.9 % in the LRM. Over the Arctic, both the HRM and the LRM generally reproduce the observed aerosols, but the largest difference in the surface BC mass concentrations between the HRM and LRM reaches 30 % in spring (the HRM-simulated results are closer to the observations). The vertical distributions of the HRM- and LRM-simulated aerosols are generally close to the measurements, but the differences between the HRM and LRM results are large above a height of approximately 3 km, mainly due to differences in the wet deposition of the aerosols. The global annual averages of the direct and indirect aerosol radiative forcings (ARFs) attributed to anthropogenic aerosols in the HRM are estimated to be −0.29 Wm−2 and −0.93 Wm−2, respectively, whereas those in the LRM are −0.24 Wm−2 and −1.10 Wm−2. The differences in the direct ARF between the HRM and LRM are primarily caused by those in the aerosol burden, whereas the differences in the indirect ARF are primarily caused by those in the cloud expression and performance, which are attributed to the grid spacing. Because one-tenth of the computer resources are required for the LRM (56-km grid) compared to the HRM (14-km grid), we recommend that the various tuning parameters associated with the aerosol distributions using the LRM can be applicable to those using the HRM under the limitation of the available computational resources or before the HRM integration.

Download Full-text

Relationships between interannual variability of glacier mass balance and climate

Journal of Glaciology ◽

10.1017/s0022143000001313 ◽

1999 ◽

Vol 45 (151) ◽

pp. 456-462 ◽

Cited By ~ 21

Author(s):

Roger J. Braithwaite ◽

Yu Zhang

Keyword(s):

Standard Deviation ◽

Mass Balance ◽

Interannual Variability ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

The Arctic ◽

Glacier Mass Balance ◽

Strongly Correlated ◽

Calculated Mass ◽

The Difference

AbstractThe interannual variability of glacier mass balance is expressed by the standard deviation of net balance, which varies from about ±0.1 to ±1.4 m a−1for a sample of 115 glaciers with at least 5 years of record. The standard deviation of net balance is strongly correlated with the mass-balance amplitude (half the difference between winter and summer balances) for 60 glaciers, so the amplitude can be estimated from net balance standard deviation for the other 55 glaciers where winter and summer balances are unavailable. The observed and calculated mass-balance amplitudes for the 115 glaciers show contrasts between the Arctic and lower latitudes, and between maritime and continental regions. The interannual variability of mass balance means that balances must be measured for at least a few years to determine a statistically reliable mean balance for any glacier. The net balance of the Greenland ice sheet is still not accurately known, but its standard deviation is here estimated to be about ±0.24 m a−1, in agreement with other Arctic glaciers. Mass-balance variability of this magnitude implies that the ice sheet can thicken or thin by several metres over 20–30 years without giving statistically significant evidence of non-zero balance under present climate.

Download Full-text

Simulation of the Summer Monsoon Rainfall over East Asia Using the NCEP GFS Cumulus Parameterization at Different Horizontal Resolutions

Weather and Forecasting ◽

10.1175/waf-d-13-00143.1 ◽

2014 ◽

Vol 29 (5) ◽

pp. 1143-1154 ◽

Cited By ~ 25

Author(s):

Kyo-Sun Sunny Lim ◽

Song-You Hong ◽

Jin-Ho Yoon ◽

Jongil Han

Keyword(s):

Summer Monsoon ◽

Monsoon Rainfall ◽

Asian Summer Monsoon ◽

Monsoon Season ◽

Wrf Model ◽

Horizontal Resolution ◽

Cumulus Parameterization ◽

Grid Spacing ◽

Simulated Precipitation ◽

Horizontal Grid

Abstract The most recent version of the simplified Arakawa–Schubert (SAS) cumulus scheme in the National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) (GFS SAS) is implemented in the Weather Research and Forecasting (WRF) Model with a modification of the triggering condition and the convective mass flux in order to make it dependent on the model’s horizontal grid spacing. The East Asian summer monsoon season of 2006 is selected in order to evaluate the performance of the modified GFS SAS scheme. In comparison to the original GFS SAS scheme, the modified GFS SAS scheme shows overall better agreement with the observations in terms of the simulated monsoon rainfall. The simulated precipitation from the original GFS SAS scheme is insensitive to the model’s horizontal grid spacing, which is counterintuitive because the portion of the resolved clouds in a grid box should increase as the model grid spacing decreases. This behavior of the original GFS SAS scheme is alleviated by the modified GFS SAS scheme. In addition, three different cumulus schemes (Grell and Freitas, Kain and Fritsch, and Betts–Miller–Janjić) are chosen to investigate the role of a horizontal resolution on the simulated monsoon rainfall. Although the forecast skill of the surface rainfall does not always improve as the spatial resolution increases, the improvement of the probability density function of the rain rate with the smaller grid spacing is robust regardless of the cumulus parameterization scheme.

Download Full-text

Sensitivity of aerosol optical thickness and aerosol direct radiative effect to relative humidity

Atmospheric Chemistry and Physics ◽

10.5194/acp-9-2375-2009 ◽

2009 ◽

Vol 9 (7) ◽

pp. 2375-2386 ◽

Cited By ~ 63

Author(s):

H. Bian ◽

M. Chin ◽

J. M. Rodriguez ◽

H. Yu ◽

J. E. Penner ◽

...

Keyword(s):

Relative Humidity ◽

Temporal Resolution ◽

Optical Thickness ◽

Sensitivity Study ◽

Horizontal Resolution ◽

Aerosol Optical Thickness ◽

Observation System ◽

Anthropogenic Aerosol ◽

The Difference ◽

The Many

Abstract. We present a sensitivity study of the effects of spatial and temporal resolution of atmospheric relative humidity (RH) on calculated aerosol optical thickness (AOT) and the aerosol direct radiative effects (DRE) in a global model. We carry out different modeling experiments using the same aerosol fields simulated in the Global Modeling Initiative (GMI) model at a resolution of 2° latitude by 2.5° longitude, using time-averaged fields archived every three hours by the Goddard Earth Observation System Version 4 (GEOS-4), but we change the horizontal and temporal resolution of the relative humidity fields. We find that, on a global average, the AOT calculated using RH at a 1°×1.25° horizontal resolution is 11% higher than that using RH at a 2°×2.5° resolution, and the corresponding DRE at the top of the atmosphere is 8–9% and 15% more negative (i.e., more cooling) for total aerosols and anthropogenic aerosol alone, respectively, in the finer spatial resolution case. The difference is largest over surface escarpment regions (e.g. >200% over the Andes Mountains) where RH varies substantially with surface terrain. The largest zonal mean AOT difference occurs at 50–60° N (16–21%), where AOT is also relatively larger. A similar impact is also found when the time resolution of RH is increased. This increase of AOT and aerosol cooling with the increase of model resolution is due to the highly non-linear relationship between RH and the aerosol mass extinction efficiency (MEE) at high RH (>80%). Our study is a specific example of the uncertainty in model results highlighted by multi-model comparisons such as AeroCom, and points out one of the many inter-model differences that can contribute to the overall spread among models.

Download Full-text

Sensitivity of Fine-Scale Structure in Tropical Cyclone Boundary Layer to Model Horizontal Resolution at Sub-Kilometer Grid Spacing

Frontiers in Earth Science ◽

10.3389/feart.2021.707274 ◽

2021 ◽

Vol 9 ◽

Author(s):

Hongxiong Xu ◽

Yuqing Wang

Keyword(s):

Boundary Layer ◽

Tropical Cyclone ◽

Inner Core ◽

Mesoscale Model ◽

Horizontal Resolution ◽

Scale Structure ◽

Fine Scale ◽

Grid Spacing ◽

Large Eddies ◽

Horizontal Grid

In view of the increasing interest in the explicit simulation of fine-scale features in the tropical cyclone (TC) boundary layer (TCBL), the effects of horizontal grid spacing on a 7–10 h simulation of an idealized TC are examined using the Weather Research and Forecast (ARW-WRF) mesoscale model with one-way moving nests and the nonlinear backscatter with anisotropy (NBA) sub-grid-scale (SGS) scheme. In general, reducing the horizontal grid spacing from 2 km to 500 m tends to produce a stronger TC with lower minimum sea level pressure (MSLP), stronger surface winds, and smaller TC inner core size. However, large eddies cannot be resolved at these grid spacings. In contrast, reducing the horizontal grid spacing from 500 to 166 m and further to 55 m leads to a decrease in TC intensity and an increase in the inner-core TC size. Moreover, although the 166-m grid spacing starts to resolve large eddies in terms of TCBL horizontal rolls and tornado-scale vortex, the use of the finest grid spacing of 55 m tends to produce shorter wavelengths in the turbulent motion and stronger multi-scale turbulence interaction. It is concluded that a grid spacing of sub-100-meters is desirable to produce more detailed and fine-scale structure of TCBL horizontal rolls and tornado-scale vortices, while the relatively coarse sub-kilometer grid spacing (e.g., 500 m) is more cost-effective and feasible for research that is not interested in the turbulence processes and for real-time operational TC forecasting in the near future.

Download Full-text

Deposition of ionic species and black carbon to the Arctic snow pack: Combining snow pit observations with modeling

10.5194/acp-2019-215 ◽

2019 ◽

Author(s):

Hans-Werner Jacobi ◽

Friedrich Obleitner ◽

Sophie Da Costa ◽

Patrick Ginot ◽

Kostas Eleftheriadis ◽

...

Keyword(s):

Black Carbon ◽

Atmospheric Aerosols ◽

Wet Deposition ◽

Regional Climate ◽

Ionic Species ◽

Sea Salt ◽

The Arctic ◽

Winter Period ◽

Snow Pack ◽

Aerosol Formation

Abstract. Although aerosols in the Arctic have multiple and complex impacts on the regional climate, their removal due to deposition is still not well quantified. We combined meteorological, aerosol, precipitation, and snow pack observations with simulations to derive information about the deposition of sea salt components and black carbon (BC) from November 2011 to April 2012 to the Arctic snow pack at two locations close to Ny-Ålesund, Svalbard. The dominating role of sea salt and the contribution of dust for the composition of atmospheric aerosols were reflected in the seasonal composition of the snow pack. The strong alignment of the concentrations of the major sea salt components in the aerosols, the precipitation, and the snow pack is linked to the importance of wet deposition for the transfer from the atmosphere to the snow pack. This agreement was less strong for monthly snow budgets and deposition indicating important relocation of the impurities inside the snow pack after deposition. Wet deposition was less important for the transfer of nitrate, non sea salt-sulfate, and BC to the snow during the winter period. The average BC concentration in the snow pack remains small with a limited impact on snow albedo and melting. Nevertheless, the observations also indicate an important redistribution of BC in the snowpack leading to layers with enhanced concentrations. The complex behavior of bromide due to modifications during the sea salt aerosol formation and remobilization in the atmosphere and in the snow were not resolved due to the lack of measurements in aerosols and precipitation.

Download Full-text

Influence of cloud microphysical processes on black carbon wet removal, global distributions, and radiative forcing

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-1587-2019 ◽

2019 ◽

Vol 19 (3) ◽

pp. 1587-1603 ◽

Cited By ~ 4

Author(s):

Jiayu Xu ◽

Jiachen Zhang ◽

Junfeng Liu ◽

Kan Yi ◽

Songlin Xiang ◽

...

Keyword(s):

Black Carbon ◽

Wet Deposition ◽

Radiative Forcing ◽

Cloud Water ◽

Ice Nucleation ◽

The Arctic ◽

Cloud Microphysical Processes ◽

Vertical Distributions ◽

Microphysical Processes ◽

Wet Removal

Abstract. Parameterizations that impact wet removal of black carbon (BC) remain uncertain in global climate models. In this study, we enhance the default wet deposition scheme for BC in the Community Earth System Model (CESM) to (a) add relevant physical processes that were not resolved in the default model and (b) facilitate understanding of the relative importance of various cloud processes on BC distributions. We find that the enhanced scheme greatly improves model performance against HIPPO observations relative to the default scheme. We find that convection scavenging, aerosol activation, ice nucleation, evaporation of rain or snow, and below-cloud scavenging dominate wet deposition of BC. BC conversion rates for processes related to in-cloud water–ice conversion (i.e., riming, the Bergeron process, and evaporation of cloud water sedimentation) are relatively smaller, but have large seasonal variations. We also conduct sensitivity simulations that turn off each cloud process one at a time to quantify the influence of cloud processes on BC distributions and radiative forcing. Convective scavenging is found to have the largest impact on BC concentrations at mid-altitudes over the tropics and even globally. In addition, BC is sensitive to all cloud processes over the Northern Hemisphere at high latitudes. As for BC vertical distributions, convective scavenging greatly influences BC fractions at different altitudes. Suppressing BC droplet activation in clouds mainly decreases the fraction of column BC below 5 km, whereas suppressing BC ice nucleation increases that above 10 km. During wintertime, the Bergeron process also significantly increases BC concentrations at lower altitudes over the Arctic. Our simulation yields a global BC burden of 85 Gg; corresponding direct radiative forcing (DRF) of BC estimated using the Parallel Offline Radiative Transfer (PORT) is 0.13 W m−2, much lower than previous studies. The range of DRF derived from sensitivity simulations is large, 0.09–0.33 W m−2, corresponding to BC burdens varying from 73 to 151 Gg. Due to differences in BC vertical distributions among each sensitivity simulation, fractional changes in DRF (relative to the baseline simulation) are always higher than fractional changes in BC burdens; this occurs because relocating BC in the vertical influences the radiative forcing per BC mass. Our results highlight the influences of cloud microphysical processes on BC concentrations and radiative forcing.

Download Full-text

Relationships between interannual variability of glacier mass balance and climate

Journal of Glaciology ◽

10.3189/s0022143000001313 ◽

1999 ◽

Vol 45 (151) ◽

pp. 456-462 ◽

Cited By ~ 4

Author(s):

Roger J. Braithwaite ◽

Yu Zhang

Keyword(s):

Standard Deviation ◽

Mass Balance ◽

Interannual Variability ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

The Arctic ◽

Glacier Mass Balance ◽

Strongly Correlated ◽

Calculated Mass ◽

The Difference

AbstractThe interannual variability of glacier mass balance is expressed by the standard deviation of net balance, which varies from about ±0.1 to ±1.4 m a−1 for a sample of 115 glaciers with at least 5 years of record. The standard deviation of net balance is strongly correlated with the mass-balance amplitude (half the difference between winter and summer balances) for 60 glaciers, so the amplitude can be estimated from net balance standard deviation for the other 55 glaciers where winter and summer balances are unavailable. The observed and calculated mass-balance amplitudes for the 115 glaciers show contrasts between the Arctic and lower latitudes, and between maritime and continental regions. The interannual variability of mass balance means that balances must be measured for at least a few years to determine a statistically reliable mean balance for any glacier. The net balance of the Greenland ice sheet is still not accurately known, but its standard deviation is here estimated to be about ±0.24 m a−1, in agreement with other Arctic glaciers. Mass-balance variability of this magnitude implies that the ice sheet can thicken or thin by several metres over 20–30 years without giving statistically significant evidence of non-zero balance under present climate.

Download Full-text

A multi-resolution assessment of the Community Multiscale Air Quality (CMAQ) Model v4.7 wet deposition estimates for 2002–2006

Geoscientific Model Development Discussions ◽

10.5194/gmdd-3-2315-2010 ◽

2010 ◽

Vol 3 (4) ◽

pp. 2315-2360 ◽

Cited By ~ 6

Author(s):

K. W. Appel ◽

K. M. Foley ◽

J. O. Bash ◽

R. W. Pinder ◽

R. L. Dennis ◽

...

Keyword(s):

Air Quality ◽

Wet Deposition ◽

Model Performance ◽

Grid Spacing ◽

Model Simulations ◽

Western Us ◽

Primary Focus ◽

National Trends ◽

Horizontal Grid ◽

No Emissions

Abstract. This paper examines the operational performance of the Community Multiscale Air Quality (CMAQ) model simulations for 2002–2006 using both 36-km and 12-km horizontal grid spacing with a primary focus on the performance of the CMAQ model in predicting wet deposition of sulfate (SO4=), ammonium (NH4+) and nitrate (NO3−). Performance of the wet deposition species is determined by comparing CMAQ predicted concentrations to concentrations measured by the National Acid Deposition Program (NADP), specifically the National Trends Network (NTN). For SO4= wet deposition, the CMAQ model estimates were generally comparable between the 36-km and 12-km simulations for the eastern US, with the 12-km simulation giving slightly higher estimates of SO4= wet deposition than the 36-km simulation on average. The normalized mean bias (NMB) was slightly higher for the 12-km simulation, however, both simulations had annual biases that were less than ±15% for each of the five years. The model estimated SO4= wet deposition values improved when they were adjusted to account for biases in the model estimated precipitation. The CMAQ model underestimates NH4+ wet deposition over the eastern US using both the 36-km and 12-km horizontal grid spacing, with a slightly larger underestimation in the 36-km simulation. The largest underestimations occur during the winter and spring periods, while the summer and fall have slightly smaller underestimations of NH4+ wet deposition. Annually, the NMB generally ranges between −10% and −16% for the 12-km simulation and −12% to −18% for the 36-km simulation over the five-year period for the eastern US. The underestimation in NH4+ wet deposition is likely due, in part, to the poor temporal and spatial representation of ammonia (NH3) emissions, particularly those emissions associated with fertilizer applications and NH3 bi-directional exchange. The model performance for estimates of NO3− wet deposition are mixed throughout the year, with the model largely underestimating NO3− wet deposition in the spring and summer in the eastern US, while the model has a relatively small bias in the fall and winter. Model estimates of NO3− wet deposition tend to be slightly lower for the 36-km simulation as compared to the 12-km simulation, particularly in the spring. Annually for the eastern US, the NMB ranges from roughly −12% to −20% for the 12-km simulation and −18% to −26% for the 36-km simulation. The underestimation of NO3− wet deposition in the spring and summer is due, in part, to a lack of lightning generated NO emissions in the upper troposphere, which can be a large source of NO in the spring and summer when lightning activity is the high. CMAQ model simulations that include the production of NO from lightning show a significant improvement in the NO3− wet deposition estimates in the eastern US in the summer. Model performance for the western US was generally not as good as that for the eastern US for all three wet deposition species.

Download Full-text

Cross-polar transport and scavenging of Siberian aerosols containing black carbon during the 2012 ACCESS summer campaign

10.5194/acp-2016-1023 ◽

2017 ◽

Author(s):

Jean-Christophe Raut ◽

Louis Marelle ◽

Jerome D. Fast ◽

Jennie L. Thomas ◽

Bernadett Weinzierl ◽

...

Keyword(s):

Black Carbon ◽

Biomass Burning ◽

Forest Fires ◽

Large Scale ◽

Large Fraction ◽

Arctic Region ◽

Horizontal Resolution ◽

The Arctic ◽

Svalbard Archipelago ◽

Wet Removal

Abstract. During the ACCESS airborne campaign in July 2012, extensive boreal forest ﬁres resulted in significant aerosol transport to the Arctic. A 10 day episode combining intense biomass burning over Siberia and low-pressure systems over the Arctic Ocean resulted in efficient transport of plumes containing black carbon (BC) towards the Arctic, mostly in the upper troposphere (6–8 km). A combination of in situ observations (DLR Falcon aircraft), satellite analysis and WRF-Chem simulations are used to understand the vertical and horizontal transport mechanisms of BC with a focus on the role of wet removal. Between the northwestern Norwegian coast and the Svalbard archipelago, the Falcon aircraft sampled plumes with enhanced CO concentrations up to 200 ppbv and BC mixing ratios up to 25 ng kg−1 . During transport to the Arctic region, a large fraction of BC particles are scavenged by two wet deposition processes, namely wet removal by large-scale precipitation and removal in wet convective updrafts, with both processes contributing almost equally to the total accumulated deposition of BC. Our results underline that applying a ﬁner horizontal resolution (40 instead of 100 km) improves the model performance, as it significantly reduces the overestimation of BC levels observed at a coarser resolution in the mid-troposphere. According to the simulations at 40 km, the transport efficiency of BC (TEBC ) in biomass burning plumes is about 60 %, which is impacted by small accumulated precipitation along trajectory (APT) (1 mm). In contrast TEBC is very small (

Download Full-text