A Double‐Moment SBU‐YLIN Cloud Microphysics Scheme and its Impact on a Squall Line Simulation

Abstract A semi-Lagrangian advection scheme is developed for falling hydrometeors in hopes of replacing the conventional Eulerian scheme that has been widely used in the cloud microphysics scheme of numerical atmospheric models. This semi-Lagrangian scheme uses a forward advection method to determine the advection path with or without iteration, and advected mass in a two-time-level algorithm with mass conservation. Monotonicity is considered in mass-conserving interpolation between Lagrangian grids and model Eulerian grids, thus making it a positive definite advection scheme. For mass-conserving interpolation between the two grid systems, the piecewise constant method (PCM), piecewise linear method (PLM), and piecewise parabolic method (PPM) are proposed. The falling velocity at the bottom cell edge is modified to avoid unphysical deformation by scanning from the top layer to the bottom of the model, which enables the use of a large time step with reasonable accuracy. The scheme is implemented and tested in the Weather Research and Forecasting (WRF) Single-Moment 3-Class Microphysics Scheme (WSM3). In a theoretical test bed with constant terminal velocity, the proposed semi-Lagrangian algorithm shows that the higher-order interpolation scheme produces less diffusive features at maximal precipitation. Results from another idealized test bed with mass-weighted terminal velocity demonstrate that the accuracy of the proposed scheme is still satisfactory even with a time step of 120 s when the mean terminal velocity averaged at the departure and arrival points is employed. A two-dimensional (2D) squall-line test using the WSM3 scheme shows that the control run with the Eulerian advection scheme and the semi-Lagrangian run with the PCM method reveal similar results, whereas behaviors using the PLM and PPM are similar with higher-resolution features, such as mammatus-like clouds.

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Improvement in Global Cloud-System-Resolving Simulations by Using a Double-Moment Bulk Cloud Microphysics Scheme

Journal of Climate ◽

10.1175/jcli-d-14-00241.1 ◽

2015 ◽

Vol 28 (6) ◽

pp. 2405-2419 ◽

Cited By ~ 24

Author(s):

Tatsuya Seiki ◽

Chihiro Kodama ◽

Akira T. Noda ◽

Masaki Satoh

Keyword(s):

Radiative Forcing ◽

Atmospheric Temperature ◽

Cloud Microphysics ◽

Radiative Heating ◽

Cloud System ◽

Microphysics Scheme ◽

Climate Simulations ◽

Double Moment ◽

Cloud Ice ◽

The Impact

Abstract This study examines the impact of an alteration of a cloud microphysics scheme on the representation of longwave cloud radiative forcing (LWCRF) and its impact on the atmosphere in global cloud-system-resolving simulations. A new double-moment bulk cloud microphysics scheme is used, and the simulated results are compared with those of a previous study. It is demonstrated that improvements within the new cloud microphysics scheme have the potential to substantially improve climate simulations. The new cloud microphysics scheme represents a realistic spatial distribution of the cloud fraction and LWCRF, particularly near the tropopause. The improvement in the cirrus cloud-top height by the new cloud microphysics scheme substantially reduces the warm bias in atmospheric temperature from the previous simulation via LWCRF by the cirrus clouds. The conversion rate of cloud ice to snow and gravitational sedimentation of cloud ice are the most important parameters for determining the strength of the radiative heating near the tropopause and its impact on atmospheric temperature.

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A Comparative Study of Bin and Bulk Cloud Microphysics Schemes in Simulating a Heavy Precipitation Case

Atmosphere ◽

10.3390/atmos9120475 ◽

2018 ◽

Vol 9 (12) ◽

pp. 475 ◽

Cited By ~ 2

Author(s):

Hyunho Lee ◽

Jong-Jin Baik

Keyword(s):

Heat Release ◽

Latent Heat ◽

Wrf Model ◽

Heavy Precipitation ◽

Cloud Microphysics ◽

Latent Heat Release ◽

Microphysics Scheme ◽

Surface Precipitation ◽

Double Moment ◽

Bin Microphysics

Comparisons between bin and bulk cloud microphysics schemes are conducted by simulating a heavy precipitation case using a bin microphysics scheme and four double-moment bulk microphysics schemes in the Weather Research and Forecasting (WRF) model. For this, we implemented an updated bin microphysics scheme in the WRF model. All of the microphysics schemes underestimate observed strong precipitation, but the bin microphysics scheme yields the result that is closest to observations. The differences among the schemes are more pronounced in terms of hydrometeor number concentration than in terms of hydrometeor mixing ratio. In this case, the bin scheme exhibits remarkably more latent heat release by deposition and riming than the bulk schemes. This causes stronger updrafts and more upward transport of water vapor, which leads to more deposition, and again, increases the latent heat release. An additional simulation using the bin scheme but excluding the riming of cloud droplets on ice crystals, which is not or poorly treated in the examined bulk schemes, shows that surface precipitation is slightly weakened and moved farther downwind compared to that of the control simulation. This implies that the more appropriate representation of microphysical processes in the bin microphysics scheme contributes to the more accurate prediction of precipitation in this case.

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Parameterization of Cloud Microphysics Based on the Prediction of Bulk Ice Particle Properties. Part I: Scheme Description and Idealized Tests

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-14-0065.1 ◽

2015 ◽

Vol 72 (1) ◽

pp. 287-311 ◽

Cited By ~ 176

Author(s):

Hugh Morrison ◽

Jason A. Milbrandt

Keyword(s):

Degrees Of Freedom ◽

Cloud Microphysics ◽

Squall Line ◽

Microphysics Scheme ◽

Particle Properties ◽

Wide Range ◽

Single Category ◽

Ratio Variables ◽

Cloud Ice ◽

Ice Phase

Abstract A method for the parameterization of ice-phase microphysics is proposed and used to develop a new bulk microphysics scheme. All ice-phase particles are represented by several physical properties that evolve freely in time and space. The scheme prognoses four ice mixing ratio variables, total mass, rime mass, rime volume, and number, allowing 4 degrees of freedom for representing the particle properties using a single category. This approach represents a significant departure from traditional microphysics schemes in which ice-phase hydrometeors are partitioned into various predefined categories (e.g., cloud ice, snow, and graupel) with prescribed characteristics. The liquid-phase component of the new scheme uses a standard two-moment, two-category approach. The proposed method and a complete description of the new predicted particle properties (P3) scheme are provided. Results from idealized model simulations of a two-dimensional squall line are presented that illustrate overall behavior of the scheme. Despite its use of a single ice-phase category, the scheme simulates a realistically wide range of particle characteristics in different regions of the squall line, consistent with observed ice particles in real squall lines. Sensitivity tests show that both the prediction of the rime mass fraction and the rime density are important for the simulation of the squall-line structure and precipitation.

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Multimoment Ice Bulk Microphysics Scheme with Consideration for Particle Shape and Apparent Density. Part I: Methodology and Idealized Simulation

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-19-0125.1 ◽

2020 ◽

Vol 77 (5) ◽

pp. 1821-1850 ◽

Cited By ~ 2

Author(s):

Tzu-Chin Tsai ◽

Jen-Ping Chen

Keyword(s):

Solid Phase ◽

Smooth Transition ◽

Squall Line ◽

Diffusional Growth ◽

Microphysics Scheme ◽

Line System ◽

Vertical Distributions ◽

Double Moment ◽

Dimensional Simulation ◽

Moment Approach

Abstract To improve the parameterization of ice-phase microphysics in regional meteorological models, this study developed a triple-moment bulk scheme, which also tracks the variations in the shape and density of several hydrometeors. Solid-phase hydrometeors are classified into pristine ice, snow aggregates, rimed ice, and hailstones based on their physical mechanisms. The new scheme has been incorporated into the Weather Research and Forecasting Model and tested with an idealized two-dimensional simulation of a squall-line system. The simulation successfully revealed the smooth transition from the convective core to the stratiform anvil as well as the alternating pattern in the hydrometeor vertical distributions, as was similarly demonstrated in other similar studies. A few sensitivity tests were performed to reveal the importance of including shape and density variations, which strongly affect the mean particle size by up to 50% and fall speed by as much as 100% for individual hydrometeor categories. Furthermore, the inclusion of a third moment could enhance the diffusional growth rate of small crystals and reduce the ventilation effect of large particles compared with the conventional double-moment approach. These factors have a significant influence on cloud structure and precipitation amounts.

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Aerosol effects on the development of a supercell storm in a double-moment bulk-cloud microphysics scheme

Journal of Geophysical Research Atmospheres ◽

10.1029/2010jd014128 ◽

2011 ◽

Vol 116 (D2) ◽

Cited By ~ 10

Author(s):

Kyo-Sun Sunny Lim ◽

Song-You Hong ◽

Seong Soo Yum ◽

Jimy Dudhia ◽

Joseph B. Klemp

Keyword(s):

Cloud Microphysics ◽

Microphysics Scheme ◽

Supercell Storm ◽

Double Moment ◽

Aerosol Effects

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Advection of Coupled Hydrometeor Quantities in Bulk Cloud Microphysics Schemes

Monthly Weather Review ◽

10.1175/mwr-d-15-0368.1 ◽

2016 ◽

Vol 144 (8) ◽

pp. 2809-2829 ◽

Cited By ~ 10

Author(s):

Hugh Morrison ◽

Anders A. Jensen ◽

Jerry Y. Harrington ◽

Jason A. Milbrandt

Keyword(s):

Traditional Approach ◽

Computational Cost ◽

Cloud Microphysics ◽

Squall Line ◽

Bulk Property ◽

Property A ◽

Microphysics Scheme ◽

Mixing Ratios ◽

Advection Schemes ◽

Vector Transport

Abstract This paper discusses the advection of coupled hydrometeor quantities by air motion in atmospheric models. It is shown that any bulk property derived from a set of advected microphysical variables must meet certain conditions in order to be preserved during transport using linear or semilinear advection schemes when the property is initially uniform, with implications for physical consistency of the property. A new, efficient flux-based method for calculating hydrometeor advection, similar to vector transport applied previously in aerosol modeling, is also presented. In this method, called scaled flux vector transport (SFVT), lead scalars (the mass mixing ratios) are advected using the host model’s unmodified advection scheme and secondary scalars (e.g., number mixing ratios) are advected by appropriately scaling the lead scalar fluxes. By design, SFVT retains linear relationships between the advected scalars. Analytic tests reveal that mean errors using SFVT are similar to those incurred using the traditional approach of separately advecting each variable. SFVT is applied to the multimoment predicted particle properties bulk microphysics scheme in idealized two-dimensional squall-line simulations using the Weather Research and Forecasting Model. The computational cost in total wall clock run time is reduced by 10%–15% while producing solutions similar to the traditional approach. Thus, SFVT can reduce the overall cost of using multimoment bulk microphysics schemes, making them competitive with simpler schemes having fewer prognostic variables.

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Development of aerosol activation in the double-moment Unified Model and evaluation with CLARIFY measurements

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-10997-2020 ◽

2020 ◽

Vol 20 (18) ◽

pp. 10997-11024

Author(s):

Hamish Gordon ◽

Paul R. Field ◽

Steven J. Abel ◽

Paul Barrett ◽

Keith Bower ◽

...

Keyword(s):

Weather Prediction ◽

Aerosol Particles ◽

Cloud Microphysics ◽

Unified Model ◽

Radiation Balance ◽

Air Quality Model ◽

Quality Model ◽

Microphysics Scheme ◽

Modest Improvement ◽

Double Moment

Abstract. Representing the number and mass of cloud and aerosol particles independently in a climate, weather prediction or air quality model is important in order to simulate aerosol direct and indirect effects on radiation balance. Here we introduce the first configuration of the UK Met Office Unified Model in which both cloud and aerosol particles have “double-moment” representations with prognostic number and mass. The GLObal Model of Aerosol Processes (GLOMAP) aerosol microphysics scheme, already used in the Hadley Centre Global Environmental Model version 3 (HadGEM3) climate configuration, is coupled to the Cloud AeroSol Interacting Microphysics (CASIM) cloud microphysics scheme. We demonstrate the performance of the new configuration in high-resolution simulations of a case study defined from the CLARIFY aircraft campaign in 2017 near Ascension Island in the tropical southern Atlantic. We improve the physical basis of the activation scheme by representing the effect of existing cloud droplets on the activation of new aerosol, and we also discuss the effect of unresolved vertical velocities. We show that neglect of these two competing effects in previous studies led to compensating errors but realistic droplet concentrations. While these changes lead only to a modest improvement in model performance, they reinforce our confidence in the ability of the model microphysics code to simulate the aerosol–cloud microphysical interactions it was designed to represent. Capturing these interactions accurately is critical to simulating aerosol effects on climate.

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

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-16-0356.1 ◽

2017 ◽

Vol 74 (9) ◽

pp. 2761-2787 ◽

Cited By ~ 5

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.

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Numerical Investigations of Atmospheric Rivers and the Rain Shadow over the Santa Clara Valley

Atmosphere ◽

10.3390/atmos10030114 ◽

2019 ◽

Vol 10 (3) ◽

pp. 114 ◽

Cited By ~ 2

Author(s):

Dalton Behringer ◽

Sen Chiao

Keyword(s):

San Francisco ◽

Wrf Model ◽

Cloud Microphysics ◽

The Other ◽

Microphysics Scheme ◽

Atmospheric Rivers ◽

Bright Band ◽

Warm Rain ◽

Double Moment ◽

Warm Rain Process

This study investigated precipitation distribution patterns in association with atmospheric rivers (ARs). The Weather Research and Forecasting (WRF) model was employed to simulate two strong atmospheric river events. The precipitation forecasts were highly sensitive to cloud microphysics parameterization schemes. Thus, radar observed and simulated Z H and Z D R were evaluated to provide information about the drop-size distribution (DSD). Four microphysics schemes (WSM-5, WSM-6, Thompson, and WDM-6) with nested simulations (3 km, 1 km, and 1/3 km) were conducted. One of the events mostly contained bright-band (BB) rainfall and lasted less than 24 h, while the other contained both BB and non-bright-band (NBB) rainfall, and lasted about 27 h. For each event, there was no clear improvement in the 1/3 km model, over the 1 km model. Overall, the WDM-6 microphysics scheme best represented the rainfall and the DSD. It appears that this scheme performed well, due to its relative simplicity in ice and mixed-phase microphysics, while providing double-moment predictions of warm rain microphysics (i.e., cloud and rain mixing ratio and number concentration). The other schemes tested either provided single-moment predictions of all classes or double-moment predictions of ice and rain (Thompson). Considering the shallow nature of precipitation in atmospheric rivers and the high-frequency of the orographic effect enhancing the warm rain process, these assumptions appear to be applicable over the southern San Francisco Bay Area.

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