scholarly journals The impact of secondary ice production on Arctic stratocumulus

2020 ◽  
Vol 20 (3) ◽  
pp. 1301-1316
Author(s):  
Georgia Sotiropoulou ◽  
Sylvia Sullivan ◽  
Julien Savre ◽  
Gary Lloyd ◽  
Thomas Lachlan-Cope ◽  
...  
Keyword(s):  
Large Scale ◽  
Cloud Condensation Nuclei ◽  
The Arctic ◽  
Computationally Efficient ◽  
Eddy Simulation ◽  
Scale Models ◽  
Break Up ◽  
Ice Production ◽  
Low Sensitivity ◽  
The Impact

Abstract. In situ measurements of Arctic clouds frequently show that ice crystal number concentrations (ICNCs) are much higher than the number of available ice-nucleating particles (INPs), suggesting that secondary ice production (SIP) may be active. Here we use a Lagrangian parcel model (LPM) and a large-eddy simulation (LES) to investigate the impact of three SIP mechanisms (rime splintering, break-up from ice–ice collisions and drop shattering) on a summer Arctic stratocumulus case observed during the Aerosol-Cloud Coupling And Climate Interactions in the Arctic (ACCACIA) campaign. Primary ice alone cannot explain the observed ICNCs, and drop shattering is ineffective in the examined conditions. Only the combination of both rime splintering (RS) and collisional break-up (BR) can explain the observed ICNCs, since both of these mechanisms are weak when activated alone. In contrast to RS, BR is currently not represented in large-scale models; however our results indicate that this may also be a critical ice-multiplication mechanism. In general, low sensitivity of the ICNCs to the assumed INP, to the cloud condensation nuclei (CCN) conditions and also to the choice of BR parameterization is found. Finally, we show that a simplified treatment of SIP, using a LPM constrained by a LES and/or observations, provides a realistic yet computationally efficient way to study SIP effects on clouds. This method can eventually serve as a way to parameterize SIP processes in large-scale models.

scholarly journals The impact of Secondary Ice Production on Arctic Stratocumulus

2019 ◽  
Author(s):  
Georgia Sotiropoulou ◽  
Sylvia Sullivan ◽  
Julien Savre ◽  
Gary Lloyd ◽  
Thomas Lachlan-Cope ◽  
...  
Keyword(s):  
Large Scale ◽  
Cloud Condensation Nuclei ◽  
The Arctic ◽  
Computationally Efficient ◽  
Scale Models ◽  
Break Up ◽  
Ice Production ◽  
Low Sensitivity ◽  
Droplet Shattering ◽  
The Impact

Abstract. In-situ measurements of Arctic clouds frequently show that ice crystal number concentrations (ICNCs) are much higher than the available ice-nucleating particles (INPs), suggesting that Secondary Ice Production (SIP) may be active. Here we use a Lagrangian Parcel Model and a Large Eddy Simulation to investigate the impact of three SIP mechanisms (rime-splintering, break-up from ice-ice collisions and droplet-shattering) on a summer Arctic stratocumulus case observed during the Cloud Coupling And Climate Interactions in the Arctic (ACCACIA) campaign. Primary ice alone cannot explain the observed ICNCs, and droplet-shattering is an ineffective SIP mechanism for the conditions considered. Rime-splintering, a mechanism that usually dominates within the studied temperature range, is also weak owing to the lack of large droplets to initiate this process. In contrast, break-up enhances ICNCs by 1–1.5 orders of magnitude, bringing simulations in good agreement with observations. Combining both processes can further explain some of the largest ICNCs observed. The main conclusions of this study show low sensitivity to the assumed INP and Cloud Condensation Nuclei (CCN) conditions. Our results indicate that collisional break-up may be an important ice-multiplication mechanism that is currently not represented in large-scale models. Finally, we also show that a simplified treatment of SIP, using a LPM constrained by a LES and/or observations, provides a realistic yet computationally efficient description of SIP effects that can eventually serve as an efficient way to parameterize this process in large-scale models.

Secondary Ice Production in Antarctic Clouds: a process neglected in large-scale models

2020 ◽  
Author(s):  
Georgia Sotiropoulou ◽  
Etienne Vignon ◽  
Gillian Young ◽  
Thomas Lachlan-Cope ◽  
Alexis Berne ◽  
...  
Keyword(s):  
Large Scale ◽  
Climate Models ◽  
Weather Prediction ◽  
Wrf Model ◽  
Weddell Sea ◽  
Microphysics Scheme ◽  
Ice Multiplication ◽  
Ice Production ◽  
Low Sensitivity ◽  
The Impact

<p>In-situ measurements of Antarctic clouds frequently show that ice crystal number concentrations  are much higher than the available ice-nucleating particles, suggesting that Secondary Ice Production (SIP) may be active. Here we investigate the impact of two SIP mechanisms, Hallett-Mossop (H-M)and collisional break-up (BR), on a case from the Microphysics of Antarctic Clouds (MAC) campaign in Weddell Sea using the Weather and Research Forecasting (WRF) model. H-M is already included in the default version of the Morrison microphysics scheme in WRF; for BR we implement different parameterizations and compare their performance. H-M alone is not effective enough to reproduce the observed concentrations. In contrast, BR can result in realistic ice multiplication, independently of whether H-M is active or not. In particular, the Phillips parameterization results in very good agreement with observations, but its performance depends on the prescribed rimed fraction of the colliding ice particles. Finally, our results show low sensitivity to primary ice nucleation, as long as there are enough primary ice crystals to initiate ice-ice collisions. Our findings suggest that BR is a potentially important SIP mechanism in the pristine Antarctic atmosphere that is currently not represented in weather-prediction and climate models.</p>

scholarly journals A parameterization of sub-grid particle formation in sulfur-rich plumes for global- and regional-scale models

2013 ◽  
Vol 13 (23) ◽  
pp. 12117-12133 ◽  
Author(s):  
R. G. Stevens ◽  
J. R. Pierce
Keyword(s):  
Power Plants ◽  
Large Scale ◽  
Regional Scale ◽  
Particle Formation ◽  
Computationally Efficient ◽  
Boundary Layer Height ◽  
Eddy Simulation ◽  
Scale Models ◽  
Physically Based ◽  
Cloud Resolving Model

Abstract. New-particle formation in the plumes of coal-fired power plants and other anthropogenic sulfur sources may be an important source of particles in the atmosphere. It remains unclear, however, how best to reproduce this formation in global and regional aerosol models with grid-box lengths that are tens of kilometres and larger. Based on the results of the System for Atmospheric Modelling (SAM), a large-eddy simulation/cloud-resolving model (LES/CRM) with online two-moment aerosol sectional (TOMAS) microphysics, we have developed a computationally efficient, but physically based, parameterization that predicts the characteristics of aerosol formed within sulfur-rich plumes based on parameters commonly available in global- and regional-scale models. Given large-scale mean meteorological parameters ((1) wind speed, (2) boundary-layer height and (3) downward shortwave radiative flux), (4) emissions of SO2 and (5) NOx from the source, (6) mean background condensation sink, (7) background SO2 and (8) NOx concentrations, and (9) the desired distance from the source, the parameterization will predict (1) the fraction of the emitted SO2 that is oxidized to H2SO4, (2) the fraction of that H2SO4 that forms new particles instead of condensing onto pre-existing particles, (3) the mean mass per particle of the newly formed particles, and (4) the number of newly formed particles per kilogram SO2 emitted. The parameterization we describe here should allow for more accurate predictions of aerosol size distributions and a greater confidence in the effects of aerosols in climate and health studies.

scholarly journals A parameterization of sub-grid particle formation in sulphur-rich plumes for global and regional-scale models

2013 ◽  
Vol 13 (7) ◽  
pp. 19583-19623 ◽  
Author(s):  
R. G. Stevens ◽  
J. R. Pierce
Keyword(s):  
Power Plants ◽  
Large Scale ◽  
Regional Scale ◽  
Particle Formation ◽  
Computationally Efficient ◽  
Boundary Layer Height ◽  
Eddy Simulation ◽  
Scale Models ◽  
Physically Based ◽  
Cloud Resolving Model

Abstract. New-particle formation in the plumes of coal-fired power plants and other anthropogenic sulphur sources may be an important source of particles in the atmosphere. It remains unclear, however, how best to reproduce this formation in global and regional aerosol models with grid-box lengths that are tens of kilometres and larger. Based on the results of the System for Atmospheric Modelling (SAM), a Large-Eddy Simulation/Cloud-Resolving Model (LES/CRM) with online TwO Moment Aerosol Sectional (TOMAS) microphysics, we have developed a computationally efficient, but physically based, parameterization that predicts the characteristics of aerosol formed within sulphur-rich plumes based on parameters commonly available in global- and regional-scale models. Given large-scale mean meteorological parameters ((1) wind speed, (2) boundary-layer height and (3) downward shortwave radiative flux), (4) emissions of SO2 and (5) NOx from the source, (6) mean background condensation sink, (7) background SO2 and (8) NOx concentrations, and (9) the desired distance from the source; the parameterization will predict: (1) the fraction of the emitted SO2 that is oxidized to H2SO4, (2) the fraction of that H2SO4 that forms new particles instead of condensing onto preexisting particles, (3) the mean mass per particle of the newly formed particles, and (4) the number of newly formed particles per kilogram SO2 emitted. The parameterization we describe here should allow for more accurate predictions of aerosol size distributions and a greater confidence in the effects of aerosols in climate and health studies.

scholarly journals Cryospheric Impacts of Soviet River Diversion Schemes

1984 ◽  
Vol 5 ◽  
pp. 61-68 ◽  
Author(s):  
T. Holt ◽  
P. M. Kelly ◽  
B. S. G. Cherry
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
River Discharge ◽  
Large Scale ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Sea Ice Concentration ◽  
Ice Concentration ◽  
The Arctic Ocean ◽  
The Impact

Soviet plans to divert water from rivers flowing into the Arctic Ocean have led to research into the impact of a reduction in discharge on Arctic sea ice. We consider the mechanisms by which discharge reductions might affect sea-ice cover and then test various hypotheses related to these mechanisms. We find several large areas over which sea-ice concentration correlates significantly with variations in river discharge, supporting two particular hypotheses. The first hypothesis concerns the area where the initial impacts are likely to which is the Kara Sea. Reduced riverflow is associated occur, with decreased sea-ice concentration in October, at the time of ice formation. This is believed to be the result of decreased freshening of the surface layer. The second hypothesis concerns possible effects on the large-scale current system of the Arctic Ocean and, in particular, on the inflow of Atlantic and Pacific water. These effects occur as a result of changes in the strength of northward-flowing gradient currents associated with variations in river discharge. Although it is still not certain that substantial transfers of riverflow will take place, it is concluded that the possibility of significant cryospheric effects and, hence, large-scale climate impact should not be neglected.

scholarly journals Can the Impact of Aerosols on Deep Convection be Isolated from Meteorological Effects in Atmospheric Observations?

2018 ◽  
Vol 75 (10) ◽  
pp. 3347-3363 ◽  
Author(s):  
Wojciech W. Grabowski
Keyword(s):  
Numerical Simulations ◽  
Large Scale ◽  
Cloud Condensation Nuclei ◽  
Deep Convection ◽  
Surface Fluxes ◽  
Phase Iii ◽  
Moist Convection ◽  
Atmospheric Measurements ◽  
The Impact ◽  
Meteorological Effects

Influence of pollution on dynamics of deep convection continues to be a controversial topic. Arguably, only carefully designed numerical simulations can clearly separate the impact of aerosols from the effects of meteorological factors that affect moist convection. This paper argues that such a separation is virtually impossible using observations because of the insufficient accuracy of atmospheric measurements and the fundamental nature of the interaction between deep convection and its environment. To support this conjecture, results from numerical simulations are presented that apply modeling methodology previously developed by the author. The simulations consider small modifications, difficult to detect in observations, of the initial sounding, surface fluxes, and large-scale forcing tendencies. All these represent variations of meteorological conditions that affect deep convective dynamics independently of aerosols. The setup follows the case of daytime convective development over land based on observations during the Large-Scale Biosphere–Atmosphere (LBA) field project in Amazonia. The simulated observable macroscopic changes of convection, such as the surface precipitation and upper-tropospheric cloudiness, are similar to or larger than those resulting from changes of cloud condensation nuclei from pristine to polluted conditions studied previously using the same modeling case. Observations from Phase III of the Global Atmospheric Research Program Atlantic Tropical Experiment (GATE) are also used to support the argument concerning the impact of the large-scale forcing. The simulations suggest that the aerosol impacts on dynamics of deep convection cannot be isolated from meteorological effects, at least for the daytime development of unorganized deep convection considered in this study.

New Earth-space infrastructures enable full-scale monitoring capability

2021 ◽  
Author(s):  
Eija Tanskanen ◽  
Tero Raita ◽  
Joni Tammi ◽  
Jouni Pulliainen ◽  
Hannu Koivula ◽  
...  
Keyword(s):  
Large Scale ◽  
Situational Awareness ◽  
Full Scale ◽  
The Arctic ◽  
Environment Change ◽  
Earth Space ◽  
Earth Environment ◽  
Internal Sources ◽  
Space Environments ◽  
The Impact

<p>The near-Earth environment is continuously changing by disturbances from external and internal sources. A combined research ecosystem is needed to be able to monitor short- and long-term changes and mitigate their societal effects. Observatories and large-scale infrastructures are the best way to guarantee continuous 24/7 observations and full-scale monitoring capability. Sodankylä Geophysical Observatory takes care of continuous geoenvironmental monitoring in Finland and together with national infrastructures such as FIN-EPOS and E2S enable extending and expanding the monitoring capability. European Plate Observing System of Finland (FIN-EPOS) and flexible instrument network of FIN-EPOS (FLEX-EPOS) will create a national pool of instruments including geophysical instruments targeted for solving topical questions of solid Earth physics. Scientific and new hardware building by FLEX-EPOS is essential in order to identify and reduce the impact of seismic, magnetic and geodetic hazards and understand the underlying processes.</p><p> </p><p>New national infrastructure Earth-Space Research Ecosystem (E2S) will combine measurements from atmosphere to near-Earth and distant space. This combined infrastructure will enable resolving how the Arctic environment change over the seasons, years, decades and centuries. We target our joint efforts to improve the situational awareness in the near-Earth and space environments, and in the Arctic for enhancing safety on ground and in space. This presentation will give details on the large-scale Earth-space infrastructures and research ecosystems and will give examples on how they can improve the safety of society.</p>

scholarly journals Nitrification of the lowermost stratosphere during the exceptionally cold Arctic winter 2015–2016

2019 ◽  
Vol 19 (21) ◽  
pp. 13681-13699 ◽  
Author(s):  
Marleen Braun ◽  
Jens-Uwe Grooß ◽  
Wolfgang Woiwode ◽  
Sören Johansson ◽  
Michael Höpfner ◽  
...  
Keyword(s):  
Nitric Acid ◽  
Cross Sections ◽  
Large Scale ◽  
Potential Temperature ◽  
Lagrangian Model ◽  
The Arctic ◽  
Small Scale ◽  
Mixing Ratios ◽  
Fine Structures ◽  
The Impact

Abstract. The Arctic winter 2015–2016 was characterized by exceptionally low stratospheric temperatures, favouring the formation of polar stratospheric clouds (PSCs) from mid-December until the end of February down to low stratospheric altitudes. Observations by GLORIA (Gimballed Limb Observer for Radiance Imaging of the Atmosphere) on HALO (High Altitude and LOng range research aircraft) during the PGS (POLSTRACC–GW-LCYCLE II–SALSA) campaign from December 2015 to March 2016 allow the investigation of the influence of denitrification on the lowermost stratosphere (LMS) with a high spatial resolution. Two-dimensional vertical cross sections of nitric acid (HNO3) along the flight track and tracer–tracer correlations derived from the GLORIA observations document detailed pictures of wide-spread nitrification of the Arctic LMS during the course of an entire winter. GLORIA observations show large-scale structures and local fine structures with enhanced absolute HNO3 volume mixing ratios reaching up to 11 ppbv at altitudes of 13 km in January and nitrified filaments persisting until the middle of March. Narrow coherent structures tilted with altitude of enhanced HNO3, observed in mid-January, are interpreted as regions recently nitrified by sublimating HNO3-containing particles. Overall, extensive nitrification of the LMS between 5.0 and 7.0 ppbv at potential temperature levels between 350 and 380 K is estimated. The GLORIA observations are compared with CLaMS (Chemical Lagrangian Model of the Stratosphere) simulations. The fundamental structures observed by GLORIA are well reproduced, but differences in the fine structures are diagnosed. Further, CLaMS predominantly underestimates the spatial extent of HNO3 maxima derived from the GLORIA observations as well as the overall nitrification of the LMS. Sensitivity simulations with CLaMS including (i) enhanced sedimentation rates in case of ice supersaturation (to resemble ice nucleation on nitric acid trihydrate (NAT)), (ii) a global temperature offset, (iii) modified growth rates (to resemble aspherical particles with larger surfaces) and (iv) temperature fluctuations (to resemble the impact of small-scale mountain waves) slightly improved the agreement with the GLORIA observations of individual flights. However, no parameter could be isolated which resulted in a general improvement for all flights. Still, the sensitivity simulations suggest that details of particle microphysics play a significant role for simulated LMS nitrification in January, while air subsidence, transport and mixing become increasingly important for the simulated HNO3 distributions towards the end of the winter.

scholarly journals Simple measures of ozone depletion in the polar stratosphere

2008 ◽  
Vol 8 (2) ◽  
pp. 251-264 ◽  
Author(s):  
R. Müller ◽  
J.-U. Grooß ◽  
C. Lemmen ◽  
D. Heinze ◽  
M. Dameris ◽  
...  
Keyword(s):  
Total Ozone ◽  
Climate Model ◽  
The Arctic ◽  
Total Column Ozone ◽  
Ozone Loss ◽  
Break Up ◽  
Column Ozone ◽  
The Impact ◽  
Polar Ozone ◽  
Daily Total

Abstract. We investigate the extent to which quantities that are based on total column ozone are applicable as measures of ozone loss in the polar vortices. Such quantities have been used frequently in ozone assessments by the World Meteorological Organization (WMO) and also to assess the performance of chemistry-climate models. The most commonly considered quantities are March and October mean column ozone poleward of geometric latitude 63° and the spring minimum of daily total ozone minima poleward of a given latitude. Particularly in the Arctic, the former measure is affected by vortex variability and vortex break-up in spring. The minimum of daily total ozone minima poleward of a particular latitude is debatable, insofar as it relies on one single measurement or model grid point. We find that, for Arctic conditions, this minimum value often occurs in air outside the polar vortex, both in the observations and in a chemistry-climate model. Neither of the two measures shows a good correlation with chemical ozone loss in the vortex deduced from observations. We recommend that the minimum of daily minima should no longer be used when comparing polar ozone loss in observations and models. As an alternative to the March and October mean column polar ozone we suggest considering the minimum of daily average total ozone poleward of 63° equivalent latitude in spring (except for winters with an early vortex break-up). Such a definition both obviates relying on one single data point and reduces the impact of year-to-year variability in the Arctic vortex break-up on ozone loss measures. Further, this measure shows a reasonable correlation (r=–0.75) with observed chemical ozone loss. Nonetheless, simple measures of polar ozone loss must be used with caution; if possible, it is preferable to use more sophisticated measures that include additional information to disentangle the impact of transport and chemistry on ozone.

scholarly journals Nitrification of the lowermost stratosphere during the exceptionally cold Arctic winter 2015/16

2019 ◽  
Author(s):  
Marleen Braun ◽  
Jens-Uwe Grooß ◽  
Wolfgang Woiwode ◽  
Sören Johansson ◽  
Michael Höpfner ◽  
...  
Keyword(s):  
Cross Sections ◽  
Large Scale ◽  
Potential Temperature ◽  
Lagrangian Model ◽  
The Arctic ◽  
Small Scale ◽  
Mountain Waves ◽  
Mixing Ratios ◽  
Fine Structures ◽  
The Impact

Abstract. The Arctic winter 2015/16 was characterized by exceptionally cold stratospheric temperatures, favouring the formation of polar stratospheric clouds (PSCs) from mid-December until the end of February down to low stratospheric altitudes. Observations by GLORIA (Gimballed Limb Observer for Radiance Imaging of the Atmosphere) on HALO (High Altitude and LOng range research aircraft) during the PGS (POLSTRACC/GW-LCYLCE II/SALSA) campaign from December 2015 to March 2016 allow an investigation of the influence of denitrification on the lowermost stratosphere (LMS) with a high spatial resolution. For the first time vertical cross-sections of nitric acid (HNO3) along the flight track and tracer-tracer correlations derived from the GLORIA observations document detailed pictures of wide-spread nitrification of the Arctic LMS during the course of an entire winter. GLORIA observations show large-scale structures and local fine structures with strongly enhanced absolute HNO3 volume mixing ratios reaching up to 11 ppbv at altitudes of 11 km in January and nitrified filaments persisting until the middle of March. Narrow streaks of enhanced HNO3, observed in mid-January, are interpreted as regions recently nitrified by sublimating HNO3-containing particles. Overall, a nitrification of the LMS between 5.0 ppbv and 7.0 ppbv at potential temperature levels between 350 and 380 K is estimated. This extent of nitrification has never been observed before in the Arctic lowermost stratosphere. The GLORIA observations are compared with CLaMS (Chemical Lagrangian Model of the Stratosphere) simulations. The fundamental structures observed by GLORIA are well reproduced, but differences in the fine structures are diagnosed. Further, CLaMS predominantly underestimates the spatial extent of maximum HNO3 mixing ratios derived from the GLORIA observations as well as the enhancement at lower altitudes. Sensitivity simulations with CLaMS including (i) enhanced sedimentation rates in case of ice supersaturation (to resemble ice nucleation on NAT), (ii) a global temperature offset, (iii) modified growth rates (to resemble aspherical particles with larger surfaces) and (iv) temperature fluctuations (to resemble the impact of small-scale mountain waves) mostly improve the agreement with the GLORIA observations. The sensitivity simulations suggest that details of particle microphysics play a significant role for simulated LMS nitrification in January, while air subsidence, transport and mixing become increasingly important towards the end of the winter.

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