Simulating Mixed Phase Arctic Stratus Clouds

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Simulating Mixed-phase Arctic Stratus Clouds

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ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (727 download)

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Book Synopsis Simulating Mixed-phase Arctic Stratus Clouds by :

Download or read book Simulating Mixed-phase Arctic Stratus Clouds written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The importance of Arctic mixed-phase clouds on radiation and the Arctic climate is well known. However, the development of mixed-phase cloud parameterization for use in large scale models is limited by lack of both related observations and numerical studies using multidimensional models with advanced microphysics that provide the basis for understanding the relative importance of different microphysical processes that take place in mixed-phase clouds. To improve the representation of mixed-phase cloud processes in the GISS GCM we use the GISS single-column model coupled to a bin resolved microphysics (BRM) scheme that was specially designed to simulate mixed-phase clouds and aerosol-cloud interactions. Using this model with the microphysical measurements obtained from the DOE ARM Mixed-Phase Arctic Cloud Experiment (MPACE) campaign in October 2004 at the North Slope of Alaska, we investigate the effect of ice initiation processes and Bergeron-Findeisen process (BFP) on glaciation time and longevity of single-layer stratiform mixed-phase clouds. We focus on observations taken during 9th-10th October, which indicated the presence of a single-layer mixed-phase clouds. We performed several sets of 12-h simulations to examine model sensitivity to different ice initiation mechanisms and evaluate model output (hydrometeors concentrations, contents, effective radii, precipitation fluxes, and radar reflectivity) against measurements from the MPACE Intensive Observing Period. Overall, the model qualitatively simulates ice crystal concentration and hydrometeors content, but it fails to predict quantitatively the effective radii of ice particles and their vertical profiles. In particular, the ice effective radii are overestimated by at least 50%. However, using the same definition as used for observations, the effective radii simulated and that observed were more comparable. We find that for the single-layer stratiform mixed-phase clouds simulated, process of ice phase initiation due to freezing of supercooled water in both saturated and undersaturated (w.r.t. water) environments is as important as primary ice crystal origination from water vapor. We also find that the BFP is a process mainly responsible for the rates of glaciation of simulated clouds. These glaciation rates cannot be adequately represented by a water-ice saturation adjustment scheme that only depends on temperature and liquid and solid hydrometeors contents as is widely used in bulk microphysics schemes and are better represented by processes that also account for supersaturation changes as the hydrometeors grow.

Simulating Mixed-phase Arctic Stratus Clouds

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ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (727 download)

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Book Synopsis Simulating Mixed-phase Arctic Stratus Clouds by :

Download or read book Simulating Mixed-phase Arctic Stratus Clouds written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The importance of Arctic mixed-phase clouds on radiation and the Arctic climate is well known. However, the development of mixed-phase cloud parameterization for use in large scale models is limited by lack of both related observations and numerical studies using multidimensional models with advanced microphysics that provide the basis for understanding the relative importance of different microphysical processes that take place in mixed-phase clouds. To improve the representation of mixed-phase cloud processes in the GISS GCM we use the GISS single-column model coupled to a bin resolved microphysics (BRM) scheme that was specially designed to simulate mixed-phase clouds and aerosol-cloud interactions. Using this model with the microphysical measurements obtained from the DOE ARM Mixed-Phase Arctic Cloud Experiment (MPACE) campaign in October 2004 at the North Slope of Alaska, we investigate the effect of ice initiation processes and Bergeron-Findeisen process (BFP) on glaciation time and longevity of single-layer stratiform mixed-phase clouds. We focus on observations taken during October 9th-10th, which indicated the presence of a single-layer mixed-phase clouds. We performed several sets of 12-hour simulations to examine model sensitivity to different ice initiation mechanisms and evaluate model output (hydrometeors concentrations, contents, effective radii, precipitation fluxes, and radar reflectivity) against measurements from the MPACE Intensive Observing Period. Overall, the model qualitatively simulates ice crystal concentration and hydrometeors content, but it fails to predict quantitatively the effective radii of ice particles and their vertical profiles. In particular, the ice effective radii are overestimated by at least 50%. However, using the same definition as used for observations, the effective radii simulated and that observed were more comparable. We find that for the single-layer stratiform mixed-phase clouds simulated, process of ice phase initiation due to freezing of supercooled water in both saturated and subsaturated (w.r.t. water) environments is as important as primary ice crystal origination from water vapor. We also find that the BFP is a process mainly responsible for the rates of glaciation of simulated clouds. These glaciation rates cannot be adequately represented by a water-ice saturation adjustment scheme that only depends on temperature and liquid and solid hydrometeors contents as is widely used in bulk microphysics schemes and are better represented by processes that also account for supersaturation changes as the hydrometeors grow.

Arctic mixed-phase clouds : Macro- and microphysical insights with a numerical model

Author : Loewe, Katharina
Publisher : KIT Scientific Publishing
ISBN 13 : 3731506866
Total Pages : 174 pages
Book Rating : 4.7/5 (315 download)

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Book Synopsis Arctic mixed-phase clouds : Macro- and microphysical insights with a numerical model by : Loewe, Katharina

Download or read book Arctic mixed-phase clouds : Macro- and microphysical insights with a numerical model written by Loewe, Katharina and published by KIT Scientific Publishing. This book was released on 2017-09-15 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work provides new insights into macro- and microphysical properties of Arctic mixed-phase clouds: first, by comparing semi-idealized large eddy simulations with observations; second, by dissecting the influences of different surface types and boundary layer structures on Arctic mixed- phase clouds; third, by elucidating the dissipation process; and finally by analyzing the main microphysical processes inside Arctic mixed-phase clouds.

Mixed-Phase Clouds

Author : Constantin Andronache
Publisher : Elsevier
ISBN 13 : 012810550X
Total Pages : 302 pages
Book Rating : 4.1/5 (281 download)

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Book Synopsis Mixed-Phase Clouds by : Constantin Andronache

Download or read book Mixed-Phase Clouds written by Constantin Andronache and published by Elsevier. This book was released on 2017-09-28 with total page 302 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mixed-Phase Clouds: Observations and Modeling presents advanced research topics on mixed-phase clouds. As the societal impacts of extreme weather and its forecasting grow, there is a continuous need to refine atmospheric observations, techniques and numerical models. Understanding the role of clouds in the atmosphere is increasingly vital for current applications, such as prediction and prevention of aircraft icing, weather modification, and the assessment of the effects of cloud phase partition in climate models. This book provides the essential information needed to address these problems with a focus on current observations, simulations and applications. Provides in-depth knowledge and simulation of mixed-phase clouds over many regions of Earth, explaining their role in weather and climate Features current research examples and case studies, including those on advanced research methods from authors with experience in both academia and the industry Discusses the latest advances in this subject area, providing the reader with access to best practices for remote sensing and numerical modeling

Intercomparison of Model Simulations of Mixed-phase Clouds Observed During the ARM Mixed-Phase Arctic Cloud Experiment. Part I

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ISBN 13 :
Total Pages : 80 pages
Book Rating : 4.:/5 (727 download)

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Book Synopsis Intercomparison of Model Simulations of Mixed-phase Clouds Observed During the ARM Mixed-Phase Arctic Cloud Experiment. Part I by :

Download or read book Intercomparison of Model Simulations of Mixed-phase Clouds Observed During the ARM Mixed-Phase Arctic Cloud Experiment. Part I written by and published by . This book was released on 2008 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt: Results are presented from an intercomparison of single-column and cloud-resolving model simulations of a cold-air outbreak mixed-phase stratocumulus cloud observed during the Atmospheric Radiation Measurement (ARM) program's Mixed-Phase Arctic Cloud Experiment. The observed cloud occurred in a well-mixed boundary layer with a cloud top temperature of -15 C. The observed liquid water path of around 160 g m−2 was about two-thirds of the adiabatic value and much greater than the mass of ice crystal precipitation which when integrated from the surface to cloud top was around 15 g m−2. The simulations were performed by seventeen single-column models (SCMs) and nine cloud-resolving models (CRMs). While the simulated ice water path is generally consistent with the observed values, the median SCM and CRM liquid water path is a factor of three smaller than observed. Results from a sensitivity study in which models removed ice microphysics indicate that in many models the interaction between liquid and ice-phase microphysics is responsible for the large model underestimate of liquid water path. Despite this general underestimate, the simulated liquid and ice water paths of several models are consistent with the observed values. Furthermore, there is some evidence that models with more sophisticated microphysics simulate liquid and ice water paths that are in better agreement with the observed values, although considerable scatter is also present. Although no single factor guarantees a good simulation, these results emphasize the need for improvement in the model representation of mixed-phase microphysics. This case study, which has been well observed from both aircraft and ground-based remote sensors, could be a benchmark for model simulations of mixed-phase clouds.

Simulations of Arctic Mixed-phase Clouds in Forecasts with CAM3 and AM2 for M-PACE.

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Publisher :
ISBN 13 :
Total Pages : 45 pages
Book Rating : 4.:/5 (958 download)

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Book Synopsis Simulations of Arctic Mixed-phase Clouds in Forecasts with CAM3 and AM2 for M-PACE. by :

Download or read book Simulations of Arctic Mixed-phase Clouds in Forecasts with CAM3 and AM2 for M-PACE. written by and published by . This book was released on 2008 with total page 45 pages. Available in PDF, EPUB and Kindle. Book excerpt: [1] Simulations of mixed-phase clouds in forecasts with the NCAR Atmosphere Model version 3 (CAM3) and the GFDL Atmospheric Model version 2 (AM2) for the Mixed-Phase Arctic Cloud Experiment (M-PACE) are performed using analysis data from numerical weather prediction centers. CAM3 significantly underestimates the observed boundary layer mixed-phase cloud fraction and cannot realistically simulate the variations of liquid water fraction with temperature and cloud height due to its oversimplified cloud microphysical scheme. In contrast, AM2 reasonably reproduces the observed boundary layer cloud fraction while its clouds contain much less cloud condensate than CAM3 and the observations. The simulation of the boundary layer mixed-phase clouds and their microphysical properties is considerably improved in CAM3 when a new physically based cloud microphysical scheme is used (CAM3LIU). The new scheme also leads to an improved simulation of the surface and top of the atmosphere longwave radiative fluxes. Sensitivity tests show that these results are not sensitive to the analysis data used for model initialization. Increasing model horizontal resolution helps capture the subgrid-scale features in Arctic frontal clouds but does not help improve the simulation of the single-layer boundary layer clouds. AM2 simulated cloud fraction and LWP are sensitive to the change in cloud ice number concentrations used in the Wegener-Bergeron-Findeisen process while CAM3LIU only shows moderate sensitivity in its cloud fields to this change. Furthermore, this paper shows that the Wegener-Bergeron-Findeisen process is important for these models to correctly simulate the observed features of mixed-phase clouds.

Intercomparison of Model Simulations of Mixed-phase Clouds Observed During the ARM Mixed-Phase Arctic Cloud Experiment. Part II

Author :
Publisher :
ISBN 13 :
Total Pages : 65 pages
Book Rating : 4.:/5 (727 download)

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Book Synopsis Intercomparison of Model Simulations of Mixed-phase Clouds Observed During the ARM Mixed-Phase Arctic Cloud Experiment. Part II by :

Download or read book Intercomparison of Model Simulations of Mixed-phase Clouds Observed During the ARM Mixed-Phase Arctic Cloud Experiment. Part II written by and published by . This book was released on 2008 with total page 65 pages. Available in PDF, EPUB and Kindle. Book excerpt: Results are presented from an intercomparison of single-column and cloud-resolving model simulations of a deep, multi-layered, mixed-phase cloud system observed during the ARM Mixed-Phase Arctic Cloud Experiment. This cloud system was associated with strong surface turbulent sensible and latent heat fluxes as cold air flowed over the open Arctic Ocean, combined with a low pressure system that supplied moisture at mid-level. The simulations, performed by 13 single-column and 4 cloud-resolving models, generally overestimate the liquid water path and strongly underestimate the ice water path, although there is a large spread among the models. This finding is in contrast with results for the single-layer, low-level mixed-phase stratocumulus case in Part I of this study, as well as previous studies of shallow mixed-phase Arctic clouds, that showed an underprediction of liquid water path. The overestimate of liquid water path and underestimate of ice water path occur primarily when deeper mixed-phase clouds extending into the mid-troposphere were observed. These results suggest important differences in the ability of models to simulate Arctic mixed-phase clouds that are deep and multi-layered versus shallow and single-layered. In general, models with a more sophisticated, two-moment treatment of the cloud microphysics produce a somewhat smaller liquid water path that is closer to observations. The cloud-resolving models tend to produce a larger cloud fraction than the single-column models. The liquid water path and especially the cloud fraction have a large impact on the cloud radiative forcing at the surface, which is dominated by the longwave flux for this case.

Simulating Arctic Mixed-phase Clouds and Their Sensitivity to Ice Nucleation

Author : Marco Paukert
Publisher :
ISBN 13 :
Total Pages : 99 pages
Book Rating : 4.:/5 (17 download)

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Book Synopsis Simulating Arctic Mixed-phase Clouds and Their Sensitivity to Ice Nucleation by : Marco Paukert

Download or read book Simulating Arctic Mixed-phase Clouds and Their Sensitivity to Ice Nucleation written by Marco Paukert and published by . This book was released on 2013 with total page 99 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Ice Particle Habit Effects On The Resilience Of Arctic Mixed-Phase Stratus Clouds In One-Dimensional Model Simulations

Author : Abhisek Das
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (14 download)

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Book Synopsis Ice Particle Habit Effects On The Resilience Of Arctic Mixed-Phase Stratus Clouds In One-Dimensional Model Simulations by : Abhisek Das

Download or read book Ice Particle Habit Effects On The Resilience Of Arctic Mixed-Phase Stratus Clouds In One-Dimensional Model Simulations written by Abhisek Das and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Arctic single layer mixed-phase clouds were studied using a one-dimensional model that incorporated the adaptive habit growth model for ice microphysics. The base case was from the Indirect and Semi-Direct Aerosol Campaign, and it was perturbed over a range of cloud temperatures, ice nuclei concentrations, and large-scale subsidence velocities, quantities upon which mixed-phase cloud glaciation timescales are dependent. The focus of the study was quantifying mixed-phase cloud glaciation timescale dependence on these three parameters. To this end, a metric of liquid cloud evolution based on liquid water path changes was developed and used to characterize mixed-phase cloud evolution towards glaciation. Dependence of the metric on cloud temperatures from -30°C to -5°C, ice nuclei concentrations from 0.10 L-1 to 30 L-1 in a diagnostic nucleation scheme, and strong to moderate (observed) to no subsidence, with both spherical and habit-dependent ice crystal growth, was investigated. Spherical and habit-dependent ice crystal growth led to different relationships between critical ice nuclei concentration, the ice nuclei concentration above which a mixed-phase cloud glaciates, and cloud average temperature and subsidence strength. For spherical ice crystal growth, the relationship between critical ice nuclei concentration and cloud average temperature is monotonic, with the critical ice nuclei concentration decreasing with decreasing cloud average temperature. With strengthening subsidence, the critical ice nuclei concentration decreases for every cloud average temperature. For habit-dependent ice crystal growth, the relationship with cloud average temperature is not monotonic because ice crystals develop dendritic and columnar habits near -15°C and -7°C, respectively. At these two temperatures ice crystals grow faster and deplete more supercooled liquid water, leading to deep local minima in critical ice nuclei concentrations around these two temperatures. As for spherical growth, critical ice nuclei concentrations decrease with increasing subsidence for habit-dependent ice crystal growth. Habit-dependent ice crystal growth coupled with cloud average temperature, critical ice nuclei concentration, and subsidence strength lead to significant changes in Arctic mixed-phase cloud lifetimes.

Arctic Mixed-phase Clouds

Author : Katharina Loewe
Publisher :
ISBN 13 : 9781013281211
Total Pages : 160 pages
Book Rating : 4.2/5 (812 download)

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Book Synopsis Arctic Mixed-phase Clouds by : Katharina Loewe

Download or read book Arctic Mixed-phase Clouds written by Katharina Loewe and published by . This book was released on 2020-10-09 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work provides new insights into macro- and microphysical properties of Arctic mixed-phase clouds: first, by comparing semi-idealized large eddy simulations with observations; second, by dissecting the influences of different surface types and boundary layer structures on Arctic mixed- phase clouds; third, by elucidating the dissipation process; and finally by analyzing the main microphysical processes inside Arctic mixed-phase clouds. This work was published by Saint Philip Street Press pursuant to a Creative Commons license permitting commercial use. All rights not granted by the work's license are retained by the author or authors.

Numerical Modeling of Arctic Mixed-phase Layered Clouds

Author : Yaosheng Chen
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (15 download)

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Book Synopsis Numerical Modeling of Arctic Mixed-phase Layered Clouds by : Yaosheng Chen

Download or read book Numerical Modeling of Arctic Mixed-phase Layered Clouds written by Yaosheng Chen and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Arctic mixed-phase clouds are often multi-layered. Different cloud layers interact through radiation as well as ice precipitation falling from upper layer clouds into the lower layer clouds. The evolution of an Arctic mixed-phase stratiform cloud under prescribed perturbations from an overlaying cloud in the form of downwelling longwave radiation and ice precipitation was simulated and documented. The perturbations created regions with heterogeneous properties in the horizontal direction within the lower level cloud, the consequence of which was the development of a mesoscale circulation that propagated the perturbations well beyond the location of the initial perturbed region.In a separate study, we forward modeled radar Doppler spectra based on a large-eddy simulation (LES) model simulation of a single layer Arctic mixed-phase cloud and compared the modeled quantities with those retrieved from the observations. We show that there was a significant contribution from the microphysical broadening to the cloud radar Doppler spectral width in Arctic mixed-phase clouds. LES simulations configured with different ice particle characteristics captured different aspects of the observations in the simulated case, where a mixture of ice particles of different properties were likely present. The dynamics of the LES simulations, characterized with the total turbulent kinetic energy dissipation rate, agreed fairly well with the values retrieved from the observations. Due to significant numerical dissipation in the model for the case evaluated here, the TKE dissipation rate from the subgrid-scale model did not represent the dissipation rate in the model.

Evaluation of Mixed-Phase Cloud Microphysics Parameterizations with the NCAR Single Column Climate Model (SCAM) and ARM Observations

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ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (873 download)

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Book Synopsis Evaluation of Mixed-Phase Cloud Microphysics Parameterizations with the NCAR Single Column Climate Model (SCAM) and ARM Observations by :

Download or read book Evaluation of Mixed-Phase Cloud Microphysics Parameterizations with the NCAR Single Column Climate Model (SCAM) and ARM Observations written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Mixed-phase stratus clouds are ubiquitous in the Arctic and play an important role in climate in this region. However, climate models have generally proven unsuccessful at simulating the partitioning of condensed water into liquid droplets and ice crystals in these Arctic clouds, which affect modeled cloud phase, cloud lifetime and radiative properties. An ice nucleation parameterization and a vapor deposition scheme were developed that together provide a physically-consistent treatment of mixed-phase clouds in global climate models. These schemes have been implemented in the National Center for Atmospheric Research (NCAR) Community Atmospheric Model Version 3 (CAM3). This report documents the performance of these schemes against ARM Mixed-phase Arctic Cloud Experiment (M-PACE) observations using the CAM single column model version (SCAM). SCAM with our new schemes has a more realistic simulation of the cloud phase structure and the partitioning of condensed water into liquid droplets against observations during the M-PACE than the standard CAM simulations.

The Arctic Clouds from Model Simulations and Long-term Observations at Barrow, Alaska

Author : Ming Zhao
Publisher :
ISBN 13 : 9781303050398
Total Pages : 93 pages
Book Rating : 4.0/5 (53 download)

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Book Synopsis The Arctic Clouds from Model Simulations and Long-term Observations at Barrow, Alaska by : Ming Zhao

Download or read book The Arctic Clouds from Model Simulations and Long-term Observations at Barrow, Alaska written by Ming Zhao and published by . This book was released on 2012 with total page 93 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Arctic is a region that is very sensitive to global climate change while also experiencing significant changes in its surface air temperature, sea-ice cover, atmospheric circulation, precipitation, snowfall, biogeochemical cycling, and land surface. Although previous studies have shown that the arctic clouds play an important role in the arctic climate changes, the arctic clouds are poorly understood and simulated in climate model due to limited observations. Furthermore, most of the studies were based on short-term experiments and typically only cover the warm seasons, which do not provide a full understanding of the seasonal cycle of arctic clouds. To address the above concerns and to improve our understanding of arctic clouds, six years of observational and retrieval data from 1999 to 2004 at the Atmospheric Radiation Management (ARM) Climate Research Facility (ACRF) North Slope of Alaska (NSA) Barrow site are used to understand the arctic clouds and related radiative processes. In particular, we focus on the liquid-ice mass partition in the mixed-phase cloud layer. Statistical results show that aerosol type and concentration are important factors that impact the mixed-phase stratus (MPS) cloud microphysical properties: liquid water path (LWP) and liquid water fraction (LWF) decrease with the increase of cloud condensation nuclei (CCN) number concentration; the high dust loading and dust occurrence in the spring are possible reasons for the much lower LWF than the other seasons. The importance of liquid-ice mass partition on surface radiation budgets was analyzed by comparing cloud longwave radiative forcings under the same LWP but different ice water path (IWP) ranges. Results show the ice phase enhance the surface cloud longwave (LW) forcing by 8~9 W m−2 in the moderately thin MPS. This result provides an observational evidence on the aerosol glaciation effect in the moderately thin MPS, which is largely unknown so far. The above new insights are important to guide the model parameterizations of liquid-ice mass partition in arctic mixed-phase clouds, and are served as a test bed to cloud models and cloud microphysical schemes. The observational data between 1999 and 2007 are used to assess the performance of the European Center for Medium-Range Weather Forecasts (ECMWF) model in the Arctic region. The ECMWF model-simulated near-surface humidity had seasonal dependent biases as large as 20%, while also experiencing difficulty representing boundary layer (BL) temperature inversion height and strength during the transition seasons. Although the ECMWF model captured the seasonal variation of surface heat fluxes, it had sensible heat flux biases over 20 W m−2 in most of the cold months. Furthermore, even though the model captured the general seasonal variations of low-level cloud fraction (LCF) and LWP, it still overestimated the LCF by 20% or more and underestimated the LWP over 50% in the cold season. On average, the ECMWF model underestimated LWP by ~30 g m−2 but more accurately predicted ice water path for BL clouds. For BL mixed-phase clouds, the model predicted water-ice mass partition was significantly lower than the observations, largely due to the temperature dependence of water-ice mass partition used in the model. The new cloud and BL schemes of the ECMWF model that were implemented after 2003 only resulted in minor improvements in BL cloud simulations in summer. These results indicate that significant improvements in cold season BL and mixed-phase cloud processes in the model are needed. In this study, single-layer MPS clouds were simulated by the Weather Research and Forecasting (WRF) model under different microphysical schemes and different ice nuclei (IN) number concentrations. Results show that by using proper IN concentration, the WRF model incorporated with Morrison microphysical scheme can reasonably capture the observed seasonal differences in temperature dependent liquid-ice mass partition. However, WRF simulations underestimate both LWP and IWP indicating its deficiency in capturing the radiative impacts of arctic MPS clouds.

Mesoscale Modeling During Mixed-Phase Arctic Cloud Experiment

Author :
Publisher :
ISBN 13 :
Total Pages : 5 pages
Book Rating : 4.:/5 (685 download)

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Book Synopsis Mesoscale Modeling During Mixed-Phase Arctic Cloud Experiment by :

Download or read book Mesoscale Modeling During Mixed-Phase Arctic Cloud Experiment written by and published by . This book was released on 2005 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mixed-phase arctic stratus clouds are the predominant cloud type in the Arctic (Curry et al. 2000) and through various feedback mechanisms exert a strong influence on the Arctic climate. Perhaps one of the most intriguing of their features is that they tend to have liquid tops that precipitate ice. Despite the fact that this situation is colloidally unstable, these cloud systems are quite long lived - from a few days to over a couple of weeks. It has been hypothesized that mixed-phase clouds are maintained through a balance between liquid water condensation resulting from the cloud-top radiative cooling and ice removal by precipitation (Pinto 1998; Harrington et al. 1999). In their modeling study Harrington et al. (1999) found that the maintenance of this balance depends strongly on the ambient concentration of ice forming nucleus (IFN). In a follow-up study, Jiang et al. (2002), using only 30% of IFN concentration predicted by Meyers et al. (1992) IFN parameterization were able to obtain results similar to the observations reported by Pinto (1998). The IFN concentration measurements collected during the Mixed-Phase Arctic Cloud Experiment (M-PACE), conducted in October 2004 over the North Slope of Alaska and the Beaufort Sea (Verlinde et al. 2005), also showed much lower values then those predicted (Prenne, pers. comm.) by currently accepted ice nucleation parameterizations (e.g. Meyers et al. 1992). The goal of this study is to use the extensive IFN data taken during M-PACE to examine what effects low IFN concentrations have on mesoscale cloud structure and coastal dynamics.

Simulations of Aerosol, Microphysical and Coastal Influences on Arctic Mixed-phase Clouds

Author : Alexander Elkov Avramov
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (476 download)

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Book Synopsis Simulations of Aerosol, Microphysical and Coastal Influences on Arctic Mixed-phase Clouds by : Alexander Elkov Avramov

Download or read book Simulations of Aerosol, Microphysical and Coastal Influences on Arctic Mixed-phase Clouds written by Alexander Elkov Avramov and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

LES Simulations of Roll Clouds Observed During Mixed- Phase Arctic Cloud Experiment

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ISBN 13 :
Total Pages : 5 pages
Book Rating : 4.:/5 (685 download)

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Book Synopsis LES Simulations of Roll Clouds Observed During Mixed- Phase Arctic Cloud Experiment by :

Download or read book LES Simulations of Roll Clouds Observed During Mixed- Phase Arctic Cloud Experiment written by and published by . This book was released on 2005 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: Roll clouds, and associated roll convection, are fairly common features of the atmospheric boundary layer. While these organized cumuliform clouds are found over many regions of the planet, they are quite ubiquitous near the edge of the polar ice sheets. In particular, during periods of off-ice flow, when cold polar air flows from the ice pack over the relatively warm ocean water, strong boundary layer convection develops along with frequent rolls. According to Bruemmer and Pohlman (2000), most of the total cloud cover in the Arctic is due to roll clouds. In an effort to examine the influences of mixed-phase microphysics on the boundary layer evolution of roll clouds during off-ice flow, Olsson and Harrington (2000) used a 2D mesoscale model coupled to a bulk microphysical scheme (see Section 2). Their results showed that mixed-phase clouds produced more shallow boundary layers with weaker turbulence than liquid-phase cases. Furthermore, their results showed that because of th e reduced turbulent drag on the atmosphere in the mixed-phase case, regions of mesoscale divergence in the marginal ice-zone were significantly affected. A follow-up 2D study (Harrington and Olsson 2001) showed that the reduced turbulent intensity in mixed-phase cases was due to precipitation. Ice precipitation caused downdraft stabilization which fed back and caused a reduction in the surface heat fluxes. In this work, we extend the work of Olsson and Harrington (2000) and Harrington and Olsson (2001) by examining the impacts of ice microphysics on roll convection. We will present results that illustrate how microphysics alters roll cloud structure and dynamics.

Formation of Arctic Mixed-phase Stratocumulus Clouds in Advecting Air Masses

Author : Lucien Simpfendoerfer
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (15 download)

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Book Synopsis Formation of Arctic Mixed-phase Stratocumulus Clouds in Advecting Air Masses by : Lucien Simpfendoerfer

Download or read book Formation of Arctic Mixed-phase Stratocumulus Clouds in Advecting Air Masses written by Lucien Simpfendoerfer and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Remote sensing observations across the Arctic indicate that Arctic stratocumuli must form through the cooling of advecting air masses during all seasons, not only in summer as was previously proposed. In this study, radiative transfer calculations and single column model simulations are used to investigate Arctic stratocumuli formation processes and their sensitivities. First, a radiative transfer model and clear-sky radiosonde observations from near Barrow, Alaska, are used to learn about the processes that drive and inhibit cooling within advecting air masses in the Arctic. Next, a single column model simulation is used to investigate how Arctic stratocumuli form when ice precipitation is involved in the formation process. Finally, sets of single column simulations are used to investigate formation processes sensitivities to the availability of moisture, the background static stability, and the ice precipitation rate. Radiative transfer calculations show that Arctic stratocumuli may form through radiative cooling and/or synoptic-scale lifting, and that subsidence is more effective than solar heating in inhibiting cloud formation. The single column model simulations show that ice inhibits the growth of liquid during the formation process and that the outcome of the formation process is extremely sensitive to the environment in which the process occurs. Arctic stratocumuli that form in moist environments with low concentrations of ice forming nuclei are likely to become optically thick and exert a large radiative forcing on the surface. Conversely, Arctic stratocumuli that form in dry environments or in environments with high concentrations of ice forming nuclei are likely to become optically thin or dissipate and exert a small radiative forcing on the surface. Static stability affects the formation process by modifying entrainment rates and therefore modifying the processes sensitivities to the availability of moisture above and below. The results highlight the importance of precipitation-radiative-dynamical interactions in simulating Arctic stratocumuli in larger-scale models.