scholarly journals Spectral (Bin) Microphysics Coupled with a Mesoscale Model (MM5). Part II: Simulation of a CaPE Rain Event with a Squall Line

2005 ◽  
Vol 133 (1) ◽  
pp. 59-71 ◽  
Author(s):  
Barry H. Lynn ◽  
Alexander P. Khain ◽  
Jimy Dudhia ◽  
Daniel Rosenfeld ◽  
Andrei Pokrovsky ◽  
...  
Keyword(s):  
Mesoscale Model ◽  
Three Dimensional ◽  
Aerosol Concentration ◽  
Squall Line ◽  
Rain Event ◽  
Maximum Rainfall ◽  
Cloud Structure ◽  
Sensing Applications ◽  
Rate Versus ◽  
Bin Microphysics

Abstract Spectral (bin) microphysics (SBM) has been implemented into the three-dimensional fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5). The new model was used to simulate a squall line that developed over Florida on 27 July 1991. It is shown that SBM reproduces precipitation rate, rain amounts, and location, radar reflectivity, and cloud structure much better than bulk parameterizations currently implemented in MM5. Sensitivity tests show the importance of (i) raindrop breakup, (ii) in-cloud turbulence, (iii) different aerosol concentrations, and (iv) inclusion of scavenging of aerosols. Breakup decreases average and maximum rainfall. In-cloud turbulence enhances particle drop collision rates and increases rain rates. A “continental” aerosol concentration produces a much larger maximum rainfall rate versus that obtained with “maritime” aerosol concentration. At the same time accumulated rain is larger with maritime aerosol concentration. The scavenging of aerosols by nucleating water droplets strongly affected the concentration of aerosols in the atmosphere. The spectral (bin) microphysics mesoscale model can potentially be used for studies of specific phenomena such as severe storms, winter storms, tropical cyclones, etc. The more realistic reproduction of cloud structure than that obtained with bulk parameterization implies that the model will be more useful for remote sensing applications and in the development of advanced rain retrieval algorithms. The model can also simulate the effect of cloud seeding on rain production.

scholarly journals Spectral (Bin) Microphysics Coupled with a Mesoscale Model (MM5). Part I: Model Description and First Results

2005 ◽  
Vol 133 (1) ◽  
pp. 44-58 ◽  
Author(s):  
Barry H. Lynn ◽  
Alexander P. Khain ◽  
Jimy Dudhia ◽  
Daniel Rosenfeld ◽  
Andrei Pokrovsky ◽  
...  
Keyword(s):  
Mesoscale Model ◽  
Precipitation Amount ◽  
Three Dimensional ◽  
Distribution Functions ◽  
Aerosol Concentration ◽  
Model Description ◽  
Atmospheric Models ◽  
Diffusional Growth ◽  
Initial Development ◽  
Bin Microphysics

Abstract Considerable research investments have been made to improve the accuracy of forecasting precipitation systems in cloud-resolving, mesoscale atmospheric models. Yet, despite a significant improvement in model grid resolution and a decrease in initial condition uncertainty, the accurate prediction of precipitation amount and distribution still remains a difficult problem. Now, the development of a fast version of spectral (bin) microphysics (SBM Fast) offers significant potential for improving the description of precipitation-forming processes in mesoscale atmospheric models. The SBM Fast is based on solving a system of equations for size distribution functions for water drops and three types of ice crystals (plates, columns, and dendrites), as well as snowflakes, graupel, and hail/frozen drops. Ice processes are represented by three size distributions, instead of six in the original SBM code. The SBM uses first principles to simulate microphysical processes such as diffusional growth and collision. A budget for aerosols is used to obtain the spectrum of condensation nuclei, which is used to obtain the initial drop spectrum. Hence, SBM allows one to take into account aerosol effects on precipitation, and corresponding cloud effects on the atmospheric aerosol concentration and distribution. SBM Fast has been coupled with the three-dimensional fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5), which allows SBM Fast to simulate microphysics within a realistic, time-varying mesoscale environment. This paper describes the first three-dimensional SBM mesoscale model and presents results using 1-km resolution to simulate initial development of a cloud system over Florida on 27 July 1991. The focus is on initial cloud development along the west coast, just prior to sea-breeze formation. The results indicate that the aerosol concentration had a very important impact on cloud dynamics, microphysics, and rainfall. Vertical cross sections of clouds obtained using SBM Fast are compared to those from a version of the “Reisner2” bulk-parameterization scheme that uses the Kessler autoconversion formula. The results show that this version of “Reisner2” produced vertically upright clouds that progressed very quickly from initial cloud formation to raindrop formation. In contrast, clouds obtained using SBM were relatively long lasting with greater production of stratiform clouds.

scholarly journals LIMA (v1.0): a two-moment microphysical scheme driven by a multimodal population of cloud condensation and ice freezing nuclei

2015 ◽  
Vol 8 (9) ◽  
pp. 7767-7820 ◽  
Author(s):  
B. Vié ◽  
J.-P. Pinty ◽  
S. Berthet ◽  
M. Leriche
Keyword(s):  
Mesoscale Model ◽  
Cloud Condensation Nuclei ◽  
Three Dimensional ◽  
Single Equation ◽  
Ice Crystals ◽  
Growth Mode ◽  
Squall Line ◽  
Complex Nature ◽  
Cloud Droplets ◽  
Ice Clouds

Abstract. The paper describes the 2-moment microphysical scheme LIMA (Liquid Ice Multiple Aerosols), which relies on the prognostic evolution of a three-dimensional (3-D) aerosol population, and the careful description of the nucleating properties that enable cloud droplets and pristine ice crystals to form. LIMA uses the aerosol nucleating properties to form cloud droplets and pristine ice crystals. Several modes of Cloud Condensation Nuclei (CCN) and Ice Freezing Nuclei (IFN) are considered individually. A special class of partially soluble IFN is also introduced. These "aged" IFN act first as CCN and then as IFN by immersion nucleation at low temperatures. All the CCN modes are in competition with each other, as expressed by the single equation of maximum supersaturation. The IFN are insoluble aerosols that nucleate ice in several ways (condensation, deposition and immersion freezing) assuming the singular hypothesis. The scheme also includes the homogeneous freezing of cloud droplets, the Hallett–Mossop ice multiplication process and the freezing of haze at very low temperature. LIMA assumes that water vapour is in thermodynamic equilibrium with the population of cloud droplets (adjustment to saturation in warm clouds). In ice clouds, the prediction of the number concentration of the pristine ice crystals is used to compute explicit deposition and sublimation rates (leading to free under/supersaturation over ice). The formation of hydrometeors is standard. The autoconversion, accretion and self-collection processes shape the raindrop spectra. The initiation of the large crystals and aggregates category is the result of the depositional growth of large crystals beyond a critical size. Aggregation and riming are computed explicitly. Heavily rimed crystals (graupel) can experience a dry or wet growth mode. An advanced version of the scheme includes a separate hail category of particles forming and growing exclusively in the wet growth mode. The sedimentation of all particle types is included. The LIMA scheme is inserted in the cloud-resolving mesoscale model Meso-NH. The flexibility of LIMA is illustrated by two 2-D experiments. The first one highlights the sensitivity of orographic ice clouds to IFN types and IFN concentrations. Then a squall line case discusses the microstructure of a mixed-phase cloud and the impacts of pure CCN and IFN polluting plumes. The experiments show that LIMA captures the complex nature of aerosol-cloud interactions leading to different pathways for cloud and precipitation formation.

scholarly journals Idealized Simulations of a Squall Line from the MC3E Field Campaign Applying Three Bin Microphysics Schemes: Dynamic and Thermodynamic Structure

2017 ◽  
Vol 145 (12) ◽  
pp. 4789-4812 ◽  
Author(s):  
Lulin Xue ◽  
Jiwen Fan ◽  
Zachary J. Lebo ◽  
Wei Wu ◽  
Hugh Morrison ◽  
...  
Keyword(s):  
Mass Density ◽  
Three Dimensional ◽  
Wrf Model ◽  
Terminal Velocity ◽  
Squall Line ◽  
Cold Pool ◽  
Field Campaign ◽  
Thermodynamic Structure ◽  
Bin Microphysics ◽  
The Impact

The squall-line event on 20 May 2011, during the Midlatitude Continental Convective Clouds (MC3E) field campaign has been simulated by three bin (spectral) microphysics schemes coupled into the Weather Research and Forecasting (WRF) Model. Semi-idealized three-dimensional simulations driven by temperature and moisture profiles acquired by a radiosonde released in the preconvection environment at 1200 UTC in Morris, Oklahoma, show that each scheme produced a squall line with features broadly consistent with the observed storm characteristics. However, substantial differences in the details of the simulated dynamic and thermodynamic structure are evident. These differences are attributed to different algorithms and numerical representations of microphysical processes, assumptions of the hydrometeor processes and properties, especially ice particle mass, density, and terminal velocity relationships with size, and the resulting interactions between the microphysics, cold pool, and dynamics. This study shows that different bin microphysics schemes, designed to be conceptually more realistic and thus arguably more accurate than bulk microphysics schemes, still simulate a wide spread of microphysical, thermodynamic, and dynamic characteristics of a squall line, qualitatively similar to the spread of squall-line characteristics using various bulk schemes. Future work may focus on improving the representation of ice particle properties in bin schemes to reduce this uncertainty and using the similar assumptions for all schemes to isolate the impact of physics from numerics.

scholarly journals Rapid Growth of TiO2 Nanoflowers via Low-Temperature Solution Process: Photovoltaic and Sensing Applications

Materials ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 566 ◽  
Author(s):  
M. Akhtar ◽  
Ahmad Umar ◽  
Swati Sood ◽  
InSung Jung ◽  
H. Hegazy ◽  
...  
Keyword(s):  
Low Temperature ◽  
Anatase Phase ◽  
Three Dimensional ◽  
Solution Process ◽  
Dye Sensitized Solar Cell ◽  
Sensor Applications ◽  
Dye Sensitized ◽  
Sensing Applications ◽  
Density Growth ◽  
Temperature Solution

This paper reports the rapid synthesis, characterization, and photovoltaic and sensing applications of TiO2 nanoflowers prepared by a facile low-temperature solution process. The morphological characterizations clearly reveal the high-density growth of a three-dimensional flower-shaped structure composed of small petal-like rods. The detailed properties confirmed that the synthesized nanoflowers exhibited high crystallinity with anatase phase and possessed an energy bandgap of 3.2 eV. The synthesized TiO2 nanoflowers were utilized as photo-anode and electron-mediating materials to fabricate dye-sensitized solar cell (DSSC) and liquid nitroaniline sensor applications. The fabricated DSSC demonstrated a moderate conversion efficiency of ~3.64% with a maximum incident photon to current efficiency (IPCE) of ~41% at 540 nm. The fabricated liquid nitroaniline sensor demonstrated a good sensitivity of ~268.9 μA mM−1 cm−2 with a low detection limit of 1.05 mM in a short response time of 10 s.

scholarly journals Parameterizing the impact of vegetated urban canopies on wind and temperature fields by using a simple nudging method

2021 ◽  
Author(s):  
Ge Cheng ◽  
David Grawe ◽  
K. Heinke Schlünzen
Keyword(s):  
Mesoscale Model ◽  
Three Dimensional ◽  
Urban Canopy ◽  
Temperature Fields ◽  
Simple Method ◽  
Local Climate ◽  
Local Climate Zones ◽  
Urban Canopy Parameterizations ◽  
The Impact ◽  
Nudging Method

<p>Nudging is a simple method that aims to dynamically adjust the model toward the observations by including an additional feedback term in the model governing equation. This method is widely applied in data assimilation due to its simple implementation and reasonable model results. The basic concept of nudging is similar to that of urban canopy parameterization, in which additional terms are usually added in the conservation equations of momentum and energy aiming to simulate the canopy effects. However, few studies have investigated the implementation of nudging methods in urban canopy parameterizations. In this study we developed a multi-layer urban canopy parameterization (UCP) by using a nudging approach to represent the impacts of vegetated urban canopies on temperatures and winds in mesoscale models.</p><p>The difficulty of developing UCP by using a nudging method lies in defining appropriate values for the nudging coefficients and the forcing fields (e.g. indoor temperature fields for temperature nudging). To determine nudging coefficients, we use three major urban canopy morphological parameters: building height, frontal area density and building density. The ranges of these parameters are taken from the values for the Local Climate Zones datasets, in our case for the city of Hamburg. The UCP is employed in the three -dimensional atmospheric mesoscale model METRAS. Results show that this UCP can well simulate wind-blocking effects induced from obstacles as buildings and trees and urban heat island phenomenon for cities. Thus, nudging is an efficient and effective method that can be used for urban canopy parameterizations. However, as well known for nudging, it is not conserving energy. Therefore, we investigated the energy loss by tracking the reduced kinetic energy and internal energy. The UCP and model results will be presented.</p>

scholarly journals Characteristics of Correlation Statistics between Droplet Radius and Optical Thickness of Warm Clouds Simulated by a Three-Dimensional Regional-Scale Spectral Bin Microphysics Cloud Model

2012 ◽  
Vol 69 (2) ◽  
pp. 484-503 ◽  
Author(s):  
Yousuke Sato ◽  
Kentaroh Suzuki ◽  
Takamichi Iguchi ◽  
In-Jin Choi ◽  
Hiroyuki Kadowaki ◽  
...  
Keyword(s):  
Optical Thickness ◽  
Cloud Model ◽  
Regional Scale ◽  
Atmospheric Stability ◽  
Three Dimensional ◽  
Droplet Radius ◽  
Cloud Particle ◽  
Sbm Model ◽  
Bin Microphysics ◽  
Correlation Statistics

Abstract Three-dimensional downscaling simulations using a spectral bin microphysics (SBM) model were conducted to investigate the effects of aerosol amount and dynamical stabilities of the atmosphere on the correlation statistics between cloud droplet effective radius (RE) and cloud optical thickness (COT) of warm clouds off the coast of California. The regeneration process of aerosols was implemented into the SBM and was found to be necessary for simulating the satellite-observed microphysical properties of warm clouds by the SBM model used in this study. The results showed that the aerosol amount changed the correlation statistics in a way that changes the cloud particle number concentration, whereas the inversion height of the boundary layer, which is related to the atmospheric stability and the cloud-top height, changed the correlation statistics in a way that changes the liquid water path. These results showed that the dominant mechanisms that control the correlation statistics are similar to those suggested by previous modeling studies based on two-dimensional idealized simulations. On the other hand, the present three-dimensional modeling was also able to simulate some realistic patterns of the correlation statistics, namely, mixtures of characteristic patterns and the “high-heeled” pattern as observed by satellite remote sensing.

scholarly journals Mode Analysis of Pt/LGS Surface Acoustic Wave Devices

Sensors ◽  
2020 ◽  
Vol 20 (24) ◽  
pp. 7111
Author(s):  
Hongsheng Xu ◽  
Hao Jin ◽  
Shurong Dong ◽  
Xinyu Song ◽  
Jinkai Chen ◽  
...  
Keyword(s):  
Acoustic Wave ◽  
Surface Acoustic Wave ◽  
Three Dimensional ◽  
Euler Angle ◽  
Mode Analysis ◽  
Single Chip ◽  
Leaky Waves ◽  
Pt Electrode ◽  
Sensing Applications ◽  
Saw Devices

Platinum (Pt) gratings on langasite (LGS) substrates are a widely used structures in high temperature surface acoustic wave (SAW) devices. Multiple modes can be excited in Pt/LGS SAW devices owing to the heavy weight of the Pt electrode and leaky waves in the LGS substrate. In this work, we report on a detailed mode analysis of Pt/LGS SAW devices, where three commonly used LGS cuts are considered. A three-dimensional (3D) finite element method (FEM) numerical model was developed, and the simulation and experiment results were compared. The experiment and simulation results showed that there are two modes excited in the Pt/LGS SAW devices with Euler angle (0°, 138.5°, 27°) and (0°, 138.5°, 117°), which are Rayleigh-type SAW and SH-type leaky wave, respectively. Only the Rayleigh-type mode was observed in the Pt/LGS SAW devices with Euler angle (0°, 138.5°, 72°). It was found that the acoustic velocities are dependent on the wavelength, which is attributed to the change of wave penetration depth in interdigital transducers (IDTs) and the velocity dispersion can be modulated by the thickness of the Pt electrode. We also demonstrated that addition of an Al2O3 passivation layer has no effect on the wave modes, but can increase the resonant frequencies. This paper provides a better understanding of the acoustic modes of Pt/LGS SAW devices, as well as useful guidance for device design. It is believed that the Rayleigh-type SAW and SH-type leaky waves are potentially useful for dual-mode sensing applications in harsh environments, to achieve multi-parameter monitoring or temperature-compensation on a single chip.

scholarly journals Use of a Radar Simulator on the Output Fields from a Numerical Mesoscale Model to Analyze X-Band Rain Estimators

2008 ◽  
Vol 25 (3) ◽  
pp. 341-367 ◽  
Author(s):  
E-P. Zahiri ◽  
M. Gosset ◽  
J-P. Lafore ◽  
V. Gouget
Keyword(s):  
Measurement Uncertainty ◽  
Size Distribution ◽  
Mesoscale Model ◽  
Squall Line ◽  
Model Case ◽  
Differential Phase Shift ◽  
Drop Shape ◽  
X Band ◽  
Radar Simulator ◽  
Rain Rates

Abstract A full radar simulator, which works with the 3D output fields from a numerical mesoscale model, has been developed. This simulator uses a T-matrix code to calculate synthetic radar measurements, accounts for both backscattering and propagation effects, and includes polarimetric variables. The tool is modular to allow several options in the derivation of the synthetic radar variables. A measurement uncertainty can be taken into account on both the simulated reflectivities and the differential phase shift. A scheme can also be switched on to allow for the gate-to-gate variability of the rain drops size distribution or, also, their oblateness. This work was done in the framework of the installation in West Africa of a polarimetric X-band radar for the observation of tropical rain. Accordingly, the first objective pursued with this simulation setup is a detailed analysis of X-band polarimetric rain retrieval algorithms. Two retrieval schemes, a simple R–KDP formula and a profiler that uses both reflectivity and ϕDP, are tested. For that purpose the simulator is run on a model case study of an African squall line, then the two schemes are used to retrieve the rain rates from the synthetic radar variables and compare them to the original. The scores of the schemes are discussed and compared. The authors analyze the sensitivity of the results to the measurement uncertainty and also to several aspects of drop size distribution and drop shape variability.

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