Assessment of a Microphysical Ensemble Used to Investigate the OWLeS IOP4 Lake-Effect Storm

2021 ◽  
Author(s):  
Lauriana C. Gaudet ◽  
Kara J. Sulia ◽  
Tzu-Chin Tsai ◽  
Jen-Ping Chen ◽  
Jessica P. Blair
Keyword(s):  
Liquid Water Content ◽  
Weather Research And Forecasting ◽  
Microphysics Scheme ◽  
Convective Clouds ◽  
Cloud Properties ◽  
Ice Nuclei ◽  
Lake Effect ◽  
Microphysical Processes ◽  
Snow And Ice

AbstractMicrophysical processes within mixed-phase convective clouds can have cascading impacts on cloud properties and resultant precipitation. This paper investigates the role of microphysics in the lake-effect storm (LES) observed during intensive observing period 4 of the Ontario Winter Lake-effect Systems field campaign. A microphysical ensemble is composed of 24 simulations that differ in the microphysics scheme used (e.g., Weather Research and Forecasting Model microphysics options or a choice of two bulk adaptive habit models) along with changes in the representation of aerosol and potential ice nuclei concentrations, ice nucleation parameterizations, rain and ice fall speeds, spectral indices, ice habit assumptions, and the number of moments used for modeling ice-phase hydrometeors in each adaptive habit model. Each of these changes to microphysics resulted in varied precipitation types at the surface; 15 members forecast a mixture of snow, ice, and graupel, seven members forecast only snow and ice, and the remaining two members forecast a combination of snow, ice, graupel, and rain. Observations from an optical disdrometer positioned to the south of the LES core indicate that 92% of the observed particles were snow and ice, 5% were graupel, and 3% were rain and drizzle. Analysis of observations spanning more than a point location, such as polarimetric radar observations and aircraft measurements of liquid water content, provides insight into cloud composition and processes leading to the differences at the surface. Ensemble spread is controlled by hydrometeor type differences spurred by processes or parameters (e.g., ice fall speed) that affect graupel mass.

Development of convection in a mesoscale cloud system and its effect on the microphysics over the tropical Atlantic Ocean

2020 ◽  
Author(s):  
Zhiqiang Cui ◽  
Alan Blyth ◽  
Steven Abel ◽  
Paul Barrett ◽  
Hamish Gordon
Keyword(s):  
Climate Models ◽  
Transitional Zone ◽  
Liquid Water Content ◽  
Cloud Microphysics ◽  
Cloud System ◽  
Main Layer ◽  
Convective Clouds ◽  
Cloud Properties ◽  
Low Clouds ◽  
Microphysical Processes

<p>Climate models have large uncertainty to represent the low clouds in the transitional zone from stratocumulus to cumulus clouds. This talk presents an observational study of a mesoscale cloud system near Ascension Island during the CLouds and Aerosol Radiative Impacts and Forcing (CLARIFY) field campaign. Extensive aircraft measurements were made to investigate the cloud microphysics when convection developed in a stratiform cloud system. The aircraft penetrated the clouds at levels below, within, and above the main layer. In-cloud penetrations show that the development of convections increased the drop number concentration, the effective radius of drops, the size of drizzle drops, and liquid water content. In the process of convection development, the morphology of the cloud changed from an overcast stratocumulus system to organised convective clouds. The wind shear and the compensating subsidence associated with the convections seemed to be responsible for the appearance of the system. The results indicate that the convective clouds significantly affected the stratocumulus cloud properties in the transition. Our study of the microphysical processes in the transitional zone helps to improve the representation and evolution of low clouds in models. </p><p> </p>

scholarly journals Analytical Investigation of the Role of Lateral Mixing in the Evolution of Nonprecipitating Cumulus. Part II: Dissolving Stage

2020 ◽  
Vol 77 (3) ◽  
pp. 911-924
Author(s):  
M. Pinsky ◽  
A. Khain
Keyword(s):  
Turbulent Mixing ◽  
Liquid Water Content ◽  
Analytical Investigation ◽  
Cloud Environment ◽  
Potential Evaporation ◽  
Cumulus Clouds ◽  
Convective Clouds ◽  
Cloud Characteristics ◽  
Lateral Mixing

Abstract A minimalistic analytical model allowing analysis of the dissolving stage of nonprecipitating convective clouds is proposed. The model takes into account two mechanisms: turbulent mixing with a dry environment and cloud volume settling. The temporal changes in the spatial structure of a cloud and in its immediate environment in the course of cloud dissolving are analyzed. The comparison of the effects of a temperature increase in the course of cloud descent and mixing with dry surrounding air shows that the descent is a dominating factor determining a decrease in the liquid water content (LWC), while mixing has a stronger effect on the cloud shape. Narrowing/broadening of clouds due to lateral mixing with dry air during cloud dissolving is determined by the potential evaporation parameter proportional to the ratio of the saturation deficit in the cloud environment to LWC. An equation for cloud dissolving time is obtained. After a cloud totally dissolves, it leaves behind an area with humidity exceeding that of the environment. The main parameter determining the dissolving time is the downdraft velocity. It should exceed 50 cm s−1 in order to provide reasonable dissolving time. The turbulent intensity, LWC, and humidity of the environment air also have an impact on dissolving time: the lower the LWC and the humidity of environment air, the faster cloud dissolving is. The simple solution presented in this paper can be useful for evaluation of cloud characteristics at the dissolving stage and can be included in procedures of parameterization of cloud cover formed by nonprecipitating or slightly precipitating cumulus clouds (Cu). Values of the environment humidity and temperature, LWC at cloud top, cloud width, vertical velocity of downdraft, and the turbulent coefficient should be parameters of this parameterization.

scholarly journals Numerical Simulation of the Effect of Cloud Condensation Nuclei Concentration on the Microphysical Processes in Typhoon Usagi

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Xiying Ye ◽  
Qimin Cao ◽  
Baolin Jiang ◽  
Wenshi Lin
Keyword(s):  
Latent Heat ◽  
Cloud Condensation Nuclei ◽  
Cloud Water ◽  
Weather Research And Forecasting ◽  
Forecasting Model ◽  
Condensation Nuclei ◽  
Microphysics Scheme ◽  
Sensitivity Tests ◽  
Microphysical Processes ◽  
Heat Released

The Weather Research and Forecasting model version 3.2.1 with the Lin microphysics scheme was used herein to simulate super typhoon Usagi, which occurred in 2013. To investigate the effect of the concentration of cloud condensation nuclei (CCN) on the development of typhoon Usagi, a control simulation was performed with a CCN concentration of 100 cm−3, together with two sensitivity tests: C10 and C1000, having CCN concentrations of 10 cm−3 and 1000 cm−3, respectively. The path, intensity, precipitation, microphysical processes, and the release of latent heat resulting from the typhoon in all three simulations were analyzed to show that an increase in CCN concentration leads to decreases in intensity and precipitation, an increase of the cloudless area in the eye of the typhoon, a more disordered cloud system, and less latent heat released through microphysical processes, especially the automatic conversion of cloud water into rainwater. Overall, an increase in CCN concentration reduces the total latent heat released during the typhoon suggesting that typhoon modification by aerosol injection may be optimized using numerical simulations to ensure the strongest release of latent heat within the typhoon.

scholarly journals Ice Nucleation Parameterization and Relative Humidity Distribution in Idealized Squall-Line Simulations

2017 ◽  
Vol 74 (9) ◽  
pp. 2761-2787 ◽  
Author(s):  
Minghui Diao ◽  
George H. Bryan ◽  
Hugh Morrison ◽  
Jorgen B. Jensen
Keyword(s):  
Relative Humidity ◽  
Ice Nucleation ◽  
Squall Line ◽  
Microphysics Scheme ◽  
Convective Clouds ◽  
Microphysical Properties ◽  
Double Moment ◽  
Microphysical Processes ◽  
Almost All ◽  
Cloud Evolution

Abstract Output from idealized simulations of a squall line are compared with in situ aircraft-based observations from the Deep Convective Clouds and Chemistry campaign. Relative humidity distributions around convection are compared between 1-Hz aircraft observations (≈250-m horizontal scale) and simulations using a double-moment bulk microphysics scheme at three horizontal grid spacings: Δx = 0.25, 1, and 4 km. The comparisons focus on the horizontal extent of ice supersaturated regions (ISSRs), the maximum and average relative humidity with respect to ice (RHi) in ISSRs, and the ice microphysical properties during cirrus cloud evolution, with simulations at 0.25 and 1 km providing better results than the 4-km simulation. Within the ISSRs, all the simulations represent the dominant contributions of water vapor horizontal heterogeneities to ISSR formation on average, but with larger variabilities in such contributions than the observations. The best results are produced by a Δx = 0.25-km simulation with the RHi threshold for initiating ice nucleation increased to 130%, which improves almost all the ISSR characteristics and allows for larger magnitude and frequency of ice supersaturation (ISS) > 8%. This simulation also allows more occurrences of clear-sky ISSRs and a higher spatial fraction of ISS for in-cloud conditions, which are consistent with the observations. These improvements are not reproduced by modifying other ice microphysical processes, such as a factor-of-2 reduction in the ice nuclei concentration; a factor-of-10 reduction in the vapor deposition rate; turning off heterogeneous contact and immersion freezing; or turning off homogeneous freezing of liquid water.

Examination of Aerosol-Induced Convective Invigoration Using Idealized Simulations

2021 ◽  
Vol 78 (1) ◽  
pp. 287-298
Author(s):  
William R. Cotton ◽  
Robert Walko
Keyword(s):  
Atmospheric Chemistry ◽  
Convective Cloud ◽  
Liquid Water Content ◽  
South Florida ◽  
Relative Role ◽  
Anthropogenic Aerosol ◽  
Convective Clouds ◽  
Large Eddy ◽  
Precipitation Enhancement

AbstractIdealized large-eddy simulations (LESs) are performed of deep convective clouds over south Florida to examine the relative role of aerosol-induced condensational versus mixed-phase invigoration to convective intensity and rainfall. Aerosol concentrations and chemistry are represented by using output from the GEOS-Chem global atmospheric chemistry model run with and without anthropogenic aerosol sources. The results clearly show that higher aerosol concentrations result in enhanced precipitation, larger amounts of cloud liquid water content, enhanced updraft velocities during the latter part of the simulation, and a modest enhancement of the latent heating of condensation. Overall, our results are consistent with the concept that convective cloud invigoration is mainly due to condensational invigoration and not primarily to mixed-phase invigoration. Furthermore, our results suggest that condensational invigoration can result in appreciable precipitation enhancement of ordinary warm-based convective clouds such as are common in locations like south Florida.

scholarly journals Aerosol effects on deep convection: the propagation of aerosol perturbations through convective cloud microphysics

2019 ◽  
Vol 19 (4) ◽  
pp. 2601-2627 ◽  
Author(s):  
Max Heikenfeld ◽  
Bethan White ◽  
Laurent Labbouz ◽  
Philip Stier
Keyword(s):  
Latent Heat ◽  
Cloud Condensation Nuclei ◽  
Cloud Microphysics ◽  
Latent Heating ◽  
Microphysics Scheme ◽  
Convective Clouds ◽  
Wide Range ◽  
Microphysical Processes ◽  
Aerosol Effects ◽  
The Impact

Abstract. The impact of aerosols on ice- and mixed-phase processes in deep convective clouds remains highly uncertain, and the wide range of interacting microphysical processes is still poorly understood. To understand these processes, we analyse diagnostic output of all individual microphysical process rates for two bulk microphysics schemes in the Weather and Research Forecasting model (WRF). We investigate the response of individual processes to changes in aerosol conditions and the propagation of perturbations through the microphysics all the way to the macrophysical development of the convective clouds. We perform simulations for two different cases of idealised supercells using two double-moment bulk microphysics schemes and a bin microphysics scheme. The simulations cover a comprehensive range of values for cloud droplet number concentration (CDNC) and cloud condensation nuclei (CCN) concentration as a proxy for aerosol effects on convective clouds. We have developed a new cloud tracking algorithm to analyse the morphology and time evolution of individually tracked convective cells in the simulations and their response to the aerosol perturbations. This analysis confirms an expected decrease in warm rain formation processes due to autoconversion and accretion for more polluted conditions. There is no evidence of a significant increase in the total amount of latent heat, as changes to the individual components of the integrated latent heating in the cloud compensate each other. The latent heating from freezing and riming processes is shifted to a higher altitude in the cloud, but there is no significant change to the integrated latent heat from freezing. Different choices in the treatment of deposition and sublimation processes between the microphysics schemes lead to strong differences including feedbacks onto condensation and evaporation. These changes in the microphysical processes explain some of the response in cloud mass and the altitude of the cloud centre of gravity. However, there remain some contrasts in the development of the bulk cloud parameters between the microphysics schemes and the two simulated cases.

scholarly journals Comment on "Clouds and the Faint Young Sun Paradox" by Goldblatt and Zahnle (2011)

2012 ◽  
Vol 8 (2) ◽  
pp. 701-703 ◽  
Author(s):  
R. Rondanelli ◽  
R. S. Lindzen
Keyword(s):  
Radiative Forcing ◽  
Cirrus Clouds ◽  
Climate Feedback ◽  
Cloud Radiative Forcing ◽  
Convective Clouds ◽  
Cloud Properties ◽  
Deep Convective Clouds ◽  
The Tropics ◽  
High Clouds

Abstract. Goldblatt and Zahnle (2011) raise a number of issues related to the possibility that cirrus clouds can provide a solution to the faint young sun paradox. Here, we argue that: (1) climates having a lower than present mean surface temperature cannot be discarded as solutions to the faint young sun paradox, (2) the detrainment from deep convective clouds in the tropics is a well-established physical mechanism for the formation of high clouds that have a positive radiative forcing (even if the possible role of these clouds as a negative climate feedback remains controversial) and (3) even if some cloud properties are not mutually consistent with observations in radiative transfer parameterizations, the most relevant consistency (for the purpose of hypothesis testing) is with observations of the cloud radiative forcing. Therefore, we maintain that cirrus clouds, as observed in the current climate and covering a large region of the tropics, can provide a solution to the faint young sun paradox, or at least ease the amount of CO2 or other greenhouse substances needed to provide temperatures above freezing during the Archean.

scholarly journals Effects of Aerosols as Ice Nuclei on the Dynamics, Microphysics and Precipitation of Severe Storm Clouds

Atmosphere ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 783
Author(s):  
Huiling Yang ◽  
Hui Xiao ◽  
Chunwei Guo
Keyword(s):  
Northern China ◽  
Atmospheric Modeling ◽  
Cloud Droplets ◽  
Severe Storm ◽  
Mixing Ratios ◽  
Convective Clouds ◽  
Ice Nuclei ◽  
High Concentrations ◽  
Regional Atmospheric Modeling

The Regional Atmospheric Modeling System (RAMS) is used to investigate the effect of aerosols acting as ice nuclei (IN) on the formation and growth of hydrometeor particles as well as on the dynamics and precipitation of a severe storm in Northern China. The focus of this study is to determine how the overall dynamics and microphysical structure of deep convective clouds are influenced if IN concentrations are somehow altered in a storm environment that is otherwise unchanged. Ice mixing ratios tend to increase and liquid mixing ratios tend to decrease with increasing IN concentrations. High concentrations of IN reduce the mean hail diameter and hail particles with smaller diameters melt more easily, which leads to a decrease in ground hailfall and an increase in surface rainfall. Liquid water plays a more important role in the process of hail formation, while the role of ice particles in the process of hail formation decreases with higher IN concentrations. The role of small cloud droplets in the formation of raindrops is increased and the role of hail melting in the process of raindrops formation is weakened with enhanced IN concentrations. Both latent heat release and absorption significantly increase with increasing IN concentrations. Increasing the concentration of IN by an appropriate amount is beneficial for increasing the total water content and strengthening the updraft, leading to enhancement of a storm, but excessive IN concentrations will inhibit the development of a storm.

scholarly journals Observations and WRF simulations of fog events at the Spanish Northern Plateau

2012 ◽  
Vol 8 (1) ◽  
pp. 11-18 ◽  
Author(s):  
C. Román-Cascón ◽  
C. Yagüe ◽  
M. Sastre ◽  
G. Maqueda ◽  
F. Salamanca ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Surface Layer ◽  
Weather Prediction ◽  
Liquid Water Content ◽  
Weather Research And Forecasting ◽  
Mean Square ◽  
Gravitational Settling ◽  
Pbl Scheme ◽  
Pbl Parameterization

Abstract. The prediction of fogs is one of the processes not well reproduced by the Numerical Weather Prediction (NWP) models. In particular, the role of turbulence in the formation or dissipation of fogs is one of the physical processed not well understood, and therefore, not well parameterized by the NWP models. Observational analysis of three different periods with fogs at the Spanish Northern Plateau has been carried out. These periods have also been simulated with the Weather Research and Forecasting (WRF) numerical model and their results have been compared to observations. The study includes a comparison of the skill of different planetary boundary layer (PBL) parameterizations, surface layer schemes and a test of the gravitational settling of clouds/fogs droplets option. A statistical analysis of this comparison has been evaluated in order to study differences between the periods and between the various parameterizations used. The model results for each PBL parameterization were different, depending on the studied period, due to differences in the features of each fog. This fact made it difficult to obtain generalized conclusions, but allowed us to determine which parameterization performed better for each case. In general, judging from the models results of liquid water content (LWC), none of the PBL schemes were able to correctly simulate the fogs, being Mellor-Yamada Nakanishi and Niino (MYNN) 2.5 level PBL scheme the best one in most of the cases. This conclusion is also supported by the root mean square error (RMSE) calculated for different meteorological variables.

scholarly journals The Use of Partial Cloudiness in a Bulk Cloud Microphysics Scheme: Concept and 2D Results

2018 ◽  
Vol 75 (8) ◽  
pp. 2711-2719 ◽  
Author(s):  
So-Young Kim ◽  
Song-You Hong
Keyword(s):  
Cloud Microphysics ◽  
Cloud Fraction ◽  
Weather Research And Forecasting ◽  
Statistical Relationship ◽  
Microphysics Scheme ◽  
Underlying Assumption ◽  
Alternative Concept ◽  
Single Moment ◽  
Microphysical Processes ◽  
Source And Sink

The source and sink terms of microphysical processes vary nonlinearly with cloud condensate amount. Therefore, partial cloudiness is one of the important factors to be considered in a cloud microphysics scheme given that in-cloud condensate amount depends on the cloud fraction of the grid box. An alternative concept to represent the partial cloudiness effect on the microphysical processes of a bulk microphysics scheme is proposed. Based on the statistical relationship between cloud condensate and cloudiness, all hydrometeors in the microphysical processes are treated after converting them to in-cloud values by dividing the amount by estimated cloudiness and multiplying it after the computation of all microphysics terms. The underlying assumption is that all the microphysical processes occur in a cloudy part of the grid box. In a 2D idealized storm case, the Weather Research and Forecasting (WRF) single-moment 5-class (WSM5) microphysics scheme with the proposed approach increases the amount of snow and rain through enhanced autoconversion/accretion and increases precipitation reaching the surface.

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