Sensitivity of Lake-Effect Cloud Microphysical Processes to Ice Crystal Habit and Nucleation during OWLeS IOP4

Abstract Ice crystal habit significantly impacts ice crystal processes such as growth by vapor deposition. Despite this, most bulk microphysical models disregard this natural shape effect and assume ice to grow spherically. This paper focuses on how the evolution of ice crystal shape and choice of ice nucleation parameterization in the adaptive habit microphysics model (AHM) influence the lake-effect storm that occurred during intensive observing period 4 (IOP4) of the Ontario Winter Lake-effect Systems (OWLeS) field campaign. This localized snowstorm produced total accumulated liquid-equivalent precipitation amounts up to 17.92 mm during a 16-h time period, providing a natural laboratory to investigate the ice–liquid partitioning within the cloud, various microphysical process rates, the accumulated precipitation magnitude, and its associated spatial distribution. Two nucleation parameterizations were implemented, and aerosol data from a size-resolved advanced particle microphysics (APM) model were ingested into the AHM for use in parameterizing ice and cloud condensation nuclei. Simulations allowing ice crystals to grow nonspherically produced 1.6%–2.3% greater precipitation while altering the nucleation parameterization changed the type of accumulating hydrometeors. In addition, all simulations were highly sensitive to the domain resolution and the source of initial and boundary conditions. These findings form the foundational understanding of relationships among ice crystal habit, nucleation parameterizations, and resultant cold-season mesoscale precipitation within detailed bulk microphysical models allowing adaptive habit.

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Exploring the Diabatic Role of Ice Microphysical Processes in Two North Atlantic Summer Cyclones

Monthly Weather Review ◽

10.1175/mwr-d-15-0253.1 ◽

2016 ◽

Vol 144 (4) ◽

pp. 1249-1272 ◽

Cited By ~ 20

Author(s):

C. Dearden ◽

G. Vaughan ◽

T. Tsai ◽

J.-P. Chen

Keyword(s):

Crystal Habit ◽

Ice Crystal ◽

Heating And Cooling ◽

First Case ◽

Storm Evolution ◽

In Situ Observations ◽

Microphysical Processes ◽

Ice Production ◽

The Impact

Abstract Numerical simulations are performed with the Weather Research and Forecasting Model to elucidate the diabatic effects of ice phase microphysical processes on the dynamics of two slow-moving summer cyclones that affected the United Kingdom during the summer of 2012. The first case is representative of a typical midlatitude storm for the time of year, while the second case is unusually deep. Sensitivity tests are performed with 5-km horizontal grid spacing and at lead times between 1 and 2 days using three different microphysics schemes, one of which is a new scheme whose development was informed by the latest in situ observations of midlatitude weather systems. The effects of latent heating and cooling associated with deposition growth, sublimation, and melting of ice are assessed in terms of the impact on both the synoptic scale and the frontal scale. The results show that, of these diabatic processes, deposition growth was the most important in both cases, affecting the depth and position of each of the low pressure systems and influencing the spatial distribution of the frontal precipitation. Cooling associated with sublimation and melting also played a role in determining the cyclone depth, but mainly in the more intense cyclone case. The effects of ice crystal habit and secondary ice production are also explored in the simulations, based on insight from in situ observations. However in these two cases, the ability to predict changes in crystal habit did not significantly impact the storm evolution, and the authors found no obvious need to parameterize secondary ice crystal production at the model resolutions considered.

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Cold cloud microphysical process rates in a global chemistry–climate model

Atmospheric Chemistry and Physics ◽

10.5194/acp-21-1485-2021 ◽

2021 ◽

Vol 21 (3) ◽

pp. 1485-1505

Author(s):

Sara Bacer ◽

Sylvia C. Sullivan ◽

Odran Sourdeval ◽

Holger Tost ◽

Jos Lelieveld ◽

...

Keyword(s):

Atmospheric Chemistry ◽

Climate Models ◽

Climate Model ◽

Ice Nucleation ◽

Ice Crystals ◽

Ice Crystal ◽

Microphysical Process ◽

Future Global Warming ◽

Microphysical Processes ◽

Ice Production

Abstract. Microphysical processes in cold clouds which act as sources or sinks of hydrometeors below 0 ∘C control the ice crystal number concentrations (ICNCs) and in turn the cloud radiative effects. Estimating the relative importance of the cold cloud microphysical process rates is of fundamental importance to underpin the development of cloud parameterizations for weather, atmospheric chemistry, and climate models and to compare the output with observations at different temporal resolutions. This study quantifies and investigates the ICNC rates of cold cloud microphysical processes by means of the chemistry–climate model EMAC (ECHAM/MESSy Atmospheric Chemistry) and defines the hierarchy of sources and sinks of ice crystals. Both microphysical process rates, such as ice nucleation, aggregation, and secondary ice production, and unphysical correction terms are presented. Model ICNCs are also compared against a satellite climatology. We found that model ICNCs are in overall agreement with satellite observations in terms of spatial distribution, although the values are overestimated, especially around high mountains. The analysis of ice crystal rates is carried out both at global and at regional scales. We found that globally the freezing of cloud droplets and convective detrainment over tropical land masses are the dominant sources of ice crystals, while aggregation and accretion act as the largest sinks. In general, all processes are characterized by highly skewed distributions. Moreover, the influence of (a) different ice nucleation parameterizations and (b) a future global warming scenario on the rates has been analysed in two sensitivity studies. In the first, we found that the application of different parameterizations for ice nucleation changes the hierarchy of ice crystal sources only slightly. In the second, all microphysical processes follow an upward shift in altitude and an increase by up to 10 % in the upper troposphere towards the end of the 21st century.

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Cold cloud microphysical process rates in a global chemistry-climate model

10.5194/acp-2020-365 ◽

2020 ◽

Author(s):

Sara Bacer ◽

Sylvia C. Sullivan ◽

Holger Tost ◽

Jos Lelieveld ◽

Andrea Pozzer

Keyword(s):

Atmospheric Chemistry ◽

Climate Models ◽

Climate Model ◽

Ice Nucleation ◽

Skewed Distribution ◽

Ice Crystals ◽

Ice Crystal ◽

Microphysical Process ◽

Future Global Warming ◽

Microphysical Processes

Abstract. Microphysical processes in cold clouds which act as sources or sinks of hydrometeors below 0 °C control the ice crystal number concentrations (ICNCs) and in turn the cloud radiative effects. Estimating the relative importance of the cold cloud microphysical process rates is of fundamental importance to underpin the development of cloud parameterizations for weather, atmospheric chemistry and climate models and compare the output with observations at different temporal resolutions. This study quantifies and investigates the cold cloud microphysical process rates by means of the chemistry-climate model EMAC and defines the hierarchy of sources and sinks of ice crystals. The analysis is carried out both at global and at regional scales. We found that globally the freezing of cloud droplets, along with convective detrainment over tropical land masses, are the dominant sources of ice crystals, while aggregation and accretion act as the largest sinks. In general, all processes are characterised by highly skewed distribution. Moreover, the influence of (a) different ice nucleation parameterizations and (b) a future global warming scenario on the rates has been analysed in two sensitivity studies. In the first, we found that the application of different parameterizations for ice nucleation changed only slightly the hierarchy of ice crystal sources. In the second, all microphysical processes followed an upward shift (in altitude) and an increase by up to 10 % in the upper troposphere towards the end of the 21st century. This increase could have important feedbacks, such as leading to enhanced longwave warming of the uppermost atmosphere.

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Lake-to-Lake Cloud Bands: Frequencies and Locations

Monthly Weather Review ◽

10.1175/2007mwr1960.1 ◽

2007 ◽

Vol 135 (12) ◽

pp. 4202-4213 ◽

Cited By ~ 24

Author(s):

Yarice Rodriguez ◽

David A. R. Kristovich ◽

Mark R. Hjelmfelt

Keyword(s):

High Resolution ◽

Great Lakes ◽

Satellite Imagery ◽

Lake Superior ◽

Great Lakes Region ◽

Lake Effect ◽

Time Period ◽

High Resolution Satellite Imagery

Abstract Premodification of the atmosphere by upwind lakes is known to influence lake-effect snowstorm intensity and locations over downwind lakes. This study highlights perhaps the most visible manifestation of the link between convection over two or more of the Great Lakes lake-to-lake (L2L) cloud bands. Emphasis is placed on L2L cloud bands observed in high-resolution satellite imagery on 2 December 2003. These L2L cloud bands developed over Lake Superior and were modified as they passed over Lakes Michigan and Erie and intervening land areas. This event is put into a longer-term context through documentation of the frequency with which lake-effect and, particularly, L2L cloud bands occurred over a 5-yr time period over different areas of the Great Lakes region.

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Impact of Graupel Parameterization Schemes on Idealized Bow Echo Simulations

Monthly Weather Review ◽

10.1175/mwr-d-12-00064.1 ◽

2013 ◽

Vol 141 (4) ◽

pp. 1241-1262 ◽

Cited By ~ 43

Author(s):

Rebecca D. Adams-Selin ◽

Susan C. van den Heever ◽

Richard H. Johnson

Keyword(s):

Complete Removal ◽

Cold Pool ◽

Size Distributions ◽

Pressure Gradients ◽

Cooling Rates ◽

Cold Pools ◽

Highly Sensitive ◽

Bow Echo ◽

Mean Size ◽

Microphysical Processes

Abstract The effect of changes in microphysical cooling rates on bow echo development and longevity are examined through changes to graupel parameterization in the Advanced Research Weather Research and Forecasting Model (ARW-WRF). Multiple simulations are performed that test the sensitivity to different graupel size distributions as well as the complete removal of graupel. It is found that size distributions with larger and denser, but fewer, graupel hydrometeors result in a weaker cold pool due to reduced microphysical cooling rates. This yields weaker midlevel (3–6 km) buoyancy and pressure perturbations, a later onset of more elevated rear inflow, and a weaker convective updraft. The convective updraft is also slower to tilt rearward, and thus bowing occurs later. Graupel size distributions with more numerous, smaller, and lighter hydrometeors result in larger microphysical cooling rates, stronger cold pools, more intense midlevel buoyancy and pressure gradients, and earlier onset of surface-based rear inflow; these systems develop bowing segments earlier. A sensitivity test with fast-falling but small graupel hydrometeors revealed that small mean size and slow fall speed both contribute to the strong cooling rates. Simulations entirely without graupel are initially weaker, because of limited contributions from cooling by melting of the slowly falling snow. However, over the next hour increased rates of melting snow result in an increasingly more intense system with new bowing. Results of the study indicate that the development of a bow echo is highly sensitive to microphysical processes, which presents a challenge to the prediction of these severe weather phenomena.

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A Coupled Cloud Physics–Radiation Parameterization of the Bulk Optical Properties of Cirrus and Its Impact on the Met Office Unified Model Global Atmosphere 5.0 Configuration

Journal of Climate ◽

10.1175/jcli-d-13-00700.1 ◽

2014 ◽

Vol 27 (20) ◽

pp. 7725-7752 ◽

Cited By ~ 36

Author(s):

Anthony J. Baran ◽

Peter Hill ◽

Kalli Furtado ◽

Paul Field ◽

James Manners

Keyword(s):

Optical Properties ◽

Atmospheric Temperature ◽

Unified Model ◽

Crystal Habit ◽

Temperature Structure ◽

Ice Crystal ◽

Cloud Physics ◽

Shape Distribution ◽

Temperature Bias ◽

Ice Water

Abstract A new coupled cloud physics–radiation parameterization of the bulk optical properties of ice clouds is presented. The parameterization is consistent with assumptions in the cloud physics scheme regarding particle size distributions (PSDs) and mass–dimensional relationships. The parameterization is based on a weighted ice crystal habit mixture model, and its bulk optical properties are parameterized as simple functions of wavelength and ice water content (IWC). This approach directly couples IWC to the bulk optical properties, negating the need for diagnosed variables, such as the ice crystal effective dimension. The parameterization is implemented into the Met Office Unified Model Global Atmosphere 5.0 (GA5) configuration. The GA5 configuration is used to simulate the annual 20-yr shortwave (SW) and longwave (LW) fluxes at the top of the atmosphere (TOA), as well as the temperature structure of the atmosphere, under various microphysical assumptions. The coupled parameterization is directly compared against the current operational radiation parameterization, while maintaining the same cloud physics assumptions. In this experiment, the impacts of the two parameterizations on the SW and LW radiative effects at TOA are also investigated and compared against observations. The 20-yr simulations are compared against the latest observations of the atmospheric temperature and radiative fluxes at TOA. The comparisons demonstrate that the choice of PSD and the assumed ice crystal shape distribution are as important as each other. Moreover, the consistent radiation parameterization removes a long-standing tropical troposphere cold temperature bias but slightly warms the southern midlatitudes by about 0.5 K.

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Automatic identification of the dominant microphysical processes in snowfall over the Antarctic coast using polarimetric radar observations

10.5194/egusphere-egu2020-21653 ◽

2020 ◽

Author(s):

Noémie Planat ◽

Josué Gehring ◽

Etienne Vignon ◽

Alexis Berne

Keyword(s):

Vapor Deposition ◽

Radar Signal ◽

Polar Regions ◽

Atmospheric Models ◽

Altitudinal Distribution ◽

Microphysical Process ◽

Microphysical Processes ◽

Differential Reflectivity ◽

The Antarctic ◽

Expected Increase

Microphysical processes in cold precipitating clouds are not fully understood and their parametrization in atmospheric models remains challenging&#160;. In particular the lack of evaluation and validation of the microphysical parameterizations in polar regions questions the reliability of the ice sheet surface mass balance assessments. Recently, strong&#160;discrepancies have been found in the precipitation structure between simulations with different microphysical parameterizations over the Antarctic coast.The dissimilarities between simulations seem to be due to different treatments of the riming, aggregation and sublimation processes.&#160;Evaluating the representation of a particular microphysical process in a model is delicate, especially because it is difficult to obtain in situ estimations, even qualitative, of a given microphysical process. In this study, we developed a method to identify&#160;the&#160;regions in radar scans where either aggregation and riming, vapor deposition or sublimation are the dominant microphysical processes.This method is based on the vertical (downward) gradients of reflectivity and differential reflectivity computed over columns extracted from range height indicator scans. Because of the expected increase in size and decrease in oblateness of the particles, aggregation and riming are identified as regions with positive gradients of reflectivity and negative gradients of differential reflectivity. Because of the expected increase in size and oblateness, vapor deposition is identified as regions with positive gradients of reflectivity and positive gradients of differential reflectivity. Because of the expected decrease in size and in concentration, snowflake sublimation, and possibly snowflake breakup, are defined as regions with negative gradients of reflectivity.&#160;The method was employed on two frontal precipitation events, which took place during the austral summer APRES3 campaign (2015-2016) in Dumont d&#8217;Urville (DDU) station, Antarctic coast. Significant differences appear&#160;in&#160;the mean altitudinal distribution where each process takes place.&#160;Given that the radar signal extends up to 4500 m a.g.l., we could show that crystal growth dominates around 2800 m while aggregation and riming prevail around 1500 m. Sublimation mostly occurs below 900 m, concurring with previous studies stating that snowflakes preferentially sublimate in the relatively dry katabatic boundary layer.Moreover the&#160;statistical&#160;distributions of different radar variables provides quantitative information to further characterize the microphysical processes of interest.This method could be further used to assess the ability of atmospheric models to reproduce the correct microphysical processes at the correct locations.

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Lagrangian stochastic microphysics at unresolved scales in turbulent cloud simulations

10.5194/egusphere-egu2020-20398 ◽

2020 ◽

Author(s):

Gustavo Abade ◽

Marta Waclawczyk ◽

Wojciech W. Grabowski ◽

Hanna Pawlowska

Keyword(s):

Droplet Size ◽

Cloud Condensation Nuclei ◽

Droplet Size Distribution ◽

Cloud Microphysics ◽

Cloud Droplets ◽

Adiabatic Cooling ◽

Subgrid Scales ◽

The Mean ◽

Microphysical Processes ◽

Droplet Size Distributions

Turbulent clouds are challenging to model and simulate due to uncertainties in microphysical processes occurring at unresolved subgrid scales (SGS). These processes include the transport of cloud particles, supersaturation fluctuations, turbulent mixing, and the resulting stochastic droplet activation and growth by condensation. In this work, we apply two different Lagrangian stochastic schemes to model SGS cloud microphysics. Collision and coalescence of droplets are not considered. Cloud droplets and unactivated cloud condensation nuclei (CCN) are described by Lagrangian particles (superdroplets). The first microphysical scheme directly models the supersaturation fluctuations experienced by each Lagrangian superdroplet as it moves with the air flow. Supersaturation fluctuations are driven by turbulent fluctuations of the droplet vertical velocity through the adiabatic cooling/warming effect. The second, more elaborate scheme uses both temperature and vapor mixing ratio as stochastic attributes attached to each superdroplet. It is based on the probability density function formalism that provides a consistent Eulerian-Lagrangian formulation of scalar transport in a turbulent flow. Both stochastic microphysical schemes are tested in a synthetic turbulent-like cloud flow that mimics a stratocumulus topped boundary layer. It is shown that SGS turbulence plays a key role in broadening the droplet-size distribution towards larger sizes. Also, the feedback on water vapor of stochastically activated droplets buffers the variations of the mean supersaturation driven the resolved transport. This extends the distance over which entrained CNN are activated inside the cloud layer and produces multimodal droplet-size distributions.

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A Classification of Ice Crystal Habits Using Combined Lidar and Scanning Polarimeter Observations during the SEAC4RS Campaign

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-20-0037.1 ◽

2020 ◽

Vol 37 (12) ◽

pp. 2185-2196

Author(s):

Natalie Midzak ◽

John E. Yorks ◽

Jianglong Zhang ◽

Bastiaan van Diedenhoven ◽

Sarah Woods ◽

...

Keyword(s):

Atmospheric Composition ◽

Crystal Habit ◽

Ice Crystal ◽

Cloud Physics ◽

Cloud Particle ◽

Clustering Technique ◽

Ice Crystal Habits

AbstractUsing collocated NASA Cloud Physics Lidar (CPL) and Research Scanning Polarimeter (RSP) data from the Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) campaign, a new observational-based method was developed which uses a K-means clustering technique to classify ice crystal habit types into seven categories: column, plates, rosettes, spheroids, and three different type of irregulars. Intercompared with the collocated SPEC, Inc., Cloud Particle Imager (CPI) data, the frequency of the detected ice crystal habits from the proposed method presented in the study agrees within 5% with the CPI-reported values for columns, irregulars, rosettes, and spheroids, with more disagreement for plates. This study suggests that a detailed ice crystal habit retrieval could be applied to combined space-based lidar and polarimeter observations such as CALIPSO and POLDER in addition to future missions such as the Aerosols, Clouds, Convection, and Precipitation (A-CCP).

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