Aerosol effects on electrification and lightning discharges in a multicell thunderstorm simulated by the WRF-ELEC model

Abstract. To investigate the effects of aerosols on lightning activity, the Weather Research and Forecasting (WRF) Model with a two-moment bulk microphysical scheme and bulk lightning model was employed to simulate a multicell thunderstorm that occurred in the metropolitan Beijing area. The results suggest that under polluted conditions lightning activity is significantly enhanced during the developing and mature stages. Electrification and lightning discharges within the thunderstorm show characteristics distinguished by different aerosol conditions through microphysical processes. Elevated aerosol loading increases the cloud droplets numbers, the latent heat release, updraft and ice-phase particle number concentrations. More charges in the upper level are carried by ice particles and enhance the electrification process. A larger mean-mass radius of graupel particles further increases non-inductive charging due to more effective collisions. In the continental case where aerosol concentrations are low, less latent heat is released in the upper parts and, as a consequence, the updraft speed is weaker, leading to smaller concentrations of ice particles, lower charging rates and fewer lightning discharges.

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Aerosol Effects on Electrification and Lightning Discharges in a Multicell Thunderstorm Simulated by the WRF-ELEC Model

10.5194/acp-2020-1284 ◽

2021 ◽

Author(s):

Mengyu Sun ◽

Dongxia Liu ◽

Xiushu Qie ◽

Edward R. Mansell ◽

Yoav Yair ◽

...

Keyword(s):

Latent Heat ◽

Phase Particle ◽

Lightning Discharge ◽

Wrf Model ◽

Lightning Activity ◽

Cloud Droplets ◽

Beijing Area ◽

Ice Particles ◽

Lightning Discharges ◽

Upper Level

Abstract. To investigate the effects of aerosol on lightning activity, the Weather Research and Forecasting (WRF) Model with a two-moment bulk microphysical scheme and bulk lightning model was employed to simulate a multicell thunderstorm that occurred in the metropolitan Beijing area. The results suggest that under polluted condition lightning activity is significantly enhanced during the developing and mature stages, while it is being delayed at the initial stage. Electrification and lightning discharges within the thunderstorm show distinguish characteristics by different aerosol conditions through microphysical processes. Elevated aerosol loading increases the cloud droplets numbers, the latent heat release, updraft and ice-phase particle number concentrations. More negative charges in the upper level are carried by ice particles and enhance the electrification process. A larger effective radius of graupel particles further increases non-inductive charging due to more effective collisions. The first lightning discharge was delayed at the beginning of polluted thunderstorm, coincident with the delayed occurrence of graupel and ice particles, which are responsible for charge generation through the non-inductive mechanism. In the continental case where aerosol concentrations are low, less latent heat releases in the upper parts of the cloud and as a consequence, the updraft speed is weaker leading to smaller concentrations of ice particles, lower charging rates and less lightning discharges.

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A New Bulk Microphysical Scheme That Includes Riming Intensity and Temperature-Dependent Ice Characteristics

Monthly Weather Review ◽

10.1175/2010mwr3293.1 ◽

2011 ◽

Vol 139 (3) ◽

pp. 1013-1035 ◽

Cited By ~ 87

Author(s):

Yanluan Lin ◽

Brian A. Colle

Keyword(s):

Wrf Model ◽

Computationally Efficient ◽

Fall Velocity ◽

Surface Precipitation ◽

Ice Particles ◽

Microphysical Processes ◽

Empirical Coefficients ◽

Oregon Cascades ◽

Microphysical Parameterization ◽

Ice Water

Abstract A new bulk microphysical parameterization (BMP) scheme is presented that includes a diagnosed riming intensity and its impact on ice characteristics. As a result, the new scheme represents a continuous spectrum from pristine ice particles to heavily rimed particles and graupel using one prognostic variable [precipitating ice (PI)] rather than two separate variables (snow and graupel). In contrast to most existing parameterization schemes that use fixed empirical relationships to describe ice particles, general formulations are proposed to consider the influences of riming intensity and temperature on the projected area, mass, and fall velocity of PI particles. The proposed formulations are able to cover the variations of empirical coefficients found in previous observational studies. The new scheme also reduces the number of parameterized microphysical processes by ∼50% as compared to conventional six-category BMPs and thus it is more computationally efficient. The new scheme (called SBU-YLIN) has been implemented in the Weather Research and Forecasting (WRF) model and compared with three other schemes for two events during the Improvement of Microphysical Parameterization through Observational Verification Experiment (IMPROVE-2) over the central Oregon Cascades. The new scheme produces surface precipitation forecasts comparable to more complicated BMPs. The new scheme reduces the snow amounts aloft as compared to other WRF schemes and compares better with observations, especially for an event with moderate riming aloft. Sensitivity tests suggest both reduced snow depositional growth rate and more efficient fallout due to the contribution of riming to the reduction of ice water content aloft in the new scheme, with a larger impact from the partially rimed snow and fallout.

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Different effects of latent heat in planetary boundary layer and cloud microphysical processes on Typhoon Sarika (2016)

Geofizika ◽

10.15233/gfz.2020.37.4 ◽

2020 ◽

Vol 37 (1) ◽

pp. 45-66 ◽

Cited By ~ 1

Author(s):

Jiangnan Li ◽

Youlong Chen ◽

Wenshi Lin ◽

Fangzhou Li ◽

Chenghui Ding

Keyword(s):

Boundary Layer ◽

Latent Heat ◽

Planetary Boundary Layer ◽

Wrf Model ◽

Critical Factor ◽

Cloud Microphysics ◽

Mature Stage ◽

Microphysical Process ◽

Cloud Microphysical Processes ◽

Microphysical Processes

Three simulation experiments were conducted on Typhoon (TC) “Sarika” (2016) using the WRF model, different effects of the latent heat in planetary boundary layer and cloud microphysical process on the TC were investigated. The control experiment well simulated the changes in TC track and intensity. The latent heat in planetary boundary layer or cloud microphysics process can affect the TC track and moving speed. Latent heat affects the TC strength by affecting the TC structure. Compared with the CTL experiment, both the NBL experiment and the NMP experiment show weakening in dynamics and thermodynamics characteristics of TC. Without the effect of latent heat, the TC cannot develop upwards and thus weakens in its intensity and reduces in precipitation; this weakening effect appears to be more obvious in the case of closing the latent heat in planetary boundary layer. The latent heat in planetary boundary layer mainly influences the generation and development of TC during the beginning stage, whereas the latent heat in cloud microphysical process is conducive to the strengthen and maintenance of TC in the mature stage. The latent heat energy of the cloud microphysical process in the TC core region is an order of magnitude larger than the surface enthalpy. But the latent heat release of cloud microphysical processes is not the most critical factor for TC enhancement, while the energy transfer of boundary layer processes is more important.

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Predicting lightning activity in Greece with the Weather Research and Forecasting (WRF) model

Atmospheric Research ◽

10.1016/j.atmosres.2014.12.009 ◽

2015 ◽

Vol 156 ◽

pp. 1-13 ◽

Cited By ~ 25

Author(s):

Theodore M. Giannaros ◽

Vassiliki Kotroni ◽

Konstantinos Lagouvardos

Keyword(s):

Wrf Model ◽

Lightning Activity ◽

Weather Research And Forecasting ◽

Weather Research

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Intercomparison of Spatial Forecast Verification Methods: Identifying Skillful Spatial Scales Using the Fractions Skill Score

Weather and Forecasting ◽

10.1175/2009waf2222260.1 ◽

2010 ◽

Vol 25 (1) ◽

pp. 343-354 ◽

Cited By ~ 100

Author(s):

Marion Mittermaier ◽

Nigel Roberts

Keyword(s):

Spatial Scales ◽

Wrf Model ◽

Skill Score ◽

Area Ratio ◽

Forecast Verification ◽

Care Needs ◽

Forecast Performance ◽

Verification Methods ◽

Upper Level ◽

Formed Part

Abstract The fractions skill score (FSS) was one of the measures that formed part of the Intercomparison of Spatial Forecast Verification Methods project. The FSS was used to assess a common dataset that consisted of real and perturbed Weather Research and Forecasting (WRF) model precipitation forecasts, as well as geometric cases. These datasets are all based on the NCEP 240 grid, which translates to approximately 4-km resolution over the contiguous United States. The geometric cases showed that the FSS can provide a truthful assessment of displacement errors and forecast skill. In addition, the FSS can be used to determine the scale at which an acceptable level of skill is reached and this usage is perhaps more helpful than interpreting the actual FSS value. This spatial-scale approach is becoming more popular for monitoring operational forecast performance. The study also shows how the FSS responds to forecast bias. A more biased forecast always gives lower FSS values at large scales and usually at smaller scales. It is possible, however, for a more biased forecast to give a higher score at smaller scales, when additional rain overlaps the observed rain. However, given a sufficiently large sample of forecasts, a more biased forecast system will score lower. The use of percentile thresholds can remove the impacts of the bias. When the proportion of the domain that is “wet” (the wet-area ratio) is small, subtle differences introduced through near-threshold misses can lead to large changes in FSS magnitude in individual cases (primarily because the bias is changed). Reliable statistics for small wet-area ratios require a larger sample of forecasts. Care needs to be taken in the choice of verification domain. For high-resolution models, the domain should be large enough to encompass the length scale of the typical mesoscale forcing (e.g., upper-level troughs or squall lines). If the domain is too large, the wet-area ratios will always be small. If the domain is too small, fluctuations in the wet-area ratio can be large and larger spatial errors may be missed. The FSS is a good measure of the spatial accuracy of precipitation forecasts. Different methods are needed to determine other patterns of behavior.

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Pathways to the Production of Precipitating Hydrometeors and Tropical Cyclone Development

Monthly Weather Review ◽

10.1175/mwr-d-15-0363.1 ◽

2016 ◽

Vol 144 (6) ◽

pp. 2395-2420 ◽

Cited By ~ 5

Author(s):

J.-W. Bao ◽

S. A. Michelson ◽

E. D. Grell

Keyword(s):

Tropical Cyclone ◽

Wrf Model ◽

Cloud Microphysics ◽

Weather Research And Forecasting ◽

Rapid Intensification ◽

Latent Heating ◽

Vertical Distributions ◽

Double Moment ◽

Microphysical Processes ◽

Definition Of

Abstract Pathways to the production of precipitation in two cloud microphysics schemes available in the Weather Research and Forecasting (WRF) Model are investigated in a scenario of tropical cyclone intensification. Comparisons of the results from the WRF Model simulations indicate that the variation in the simulated initial rapid intensification of an idealized tropical cyclone is due to the differences between the two cloud microphysics schemes in their representations of pathways to the formation and growth of precipitating hydrometeors. Diagnoses of the source and sink terms of the hydrometeor budget equations indicate that the major differences in the production of hydrometeors between the schemes are in the spectral definition of individual hydrometeor categories and spectrum-dependent microphysical processes, such as accretion growth and sedimentation. These differences lead to different horizontally averaged vertical profiles of net latent heating rate associated with significantly different horizontally averaged vertical distributions and production rates of hydrometeors in the simulated clouds. Results from this study also highlight the possibility that the advantage of double-moment formulations can be overshadowed by the uncertainties in the spectral definition of individual hydrometeor categories and spectrum-dependent microphysical processes.

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The sensitivity of atmospheric blocking to changes in upstream latent heating – numerical experiments

10.5194/wcd-2020-5 ◽

2020 ◽

Cited By ~ 1

Author(s):

Daniel Steinfeld ◽

Maxi Boettcher ◽

Richard Forbes ◽

Stephan Pfahl

Keyword(s):

Causal Relationship ◽

Climate Models ◽

Weather Prediction ◽

Conveyor Belt ◽

Cloud Formation ◽

Latent Heating ◽

Atmospheric Blocking ◽

Tropospheric Circulation ◽

Upper Level ◽

Microphysical Processes

Abstract. Recent climatological studies based on trajectory calculations have pointed to an important role of latent heating during cloud formation for the dynamics of anticyclonic circulation anomalies such as atmospheric blocking. However, the causal relationship between latent heating and blocking formation has not yet been fully elucidated. To explicitly study this causal relationship, we perform sensitivity simulations of five selected blocking events with a global weather prediction model in which we artificially eliminate latent heating in clouds upstream of the blocking anticyclones. This elimination has substantial effects on the upper-tropospheric circulation in all case studies, but there is also significant case-to-case variability: some blocking systems do not develop at all without upstream latent heating, while for others the amplitude of the blocking anticyclones is merely reduced. This strong influence of latent heating on the jet stream is due to the injection of air masses with low potential vorticity (PV) into the upper troposphere in strongly ascending warm conveyor belt airstreams, and the interaction of the associated divergent outflow with the upper-level PV structure. The important influence of diabatic heating demonstrated with these experiments suggests that an accurate parameterization of microphysical processes in weather prediction and climate models is crucial for adequately representing blocking dynamics.

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Effects of Air Pollutants on Summer Precipitation in Different Regions of Beijing

Atmosphere ◽

10.3390/atmos13010141 ◽

2022 ◽

Vol 13 (1) ◽

pp. 141

Author(s):

Yan Yang ◽

Wei Zhou ◽

Qian Gao ◽

Delong Zhao ◽

Xiange Liu ◽

...

Keyword(s):

Air Pollutants ◽

Summer Precipitation ◽

Weather Research And Forecasting ◽

Mountainous Areas ◽

Cloud Droplets ◽

Beijing Area ◽

Pollution Levels ◽

Mountainous Regions ◽

Effective Particle ◽

Air Layers

Many studies have shown that air pollutants have complex impacts on urban precipitation. Meteorological weather station and satellite Aerosol Optical Depth (AOD) product data from the last 20 years, combined with simulation results from the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem), this paper focuses on the effects of air pollutants on summer precipitation in different regions of Beijing. These results showed that air pollution intensity during the summer affected the precipitation contribution rate (PCR) of plains and mountainous regions in the Beijing area, especially in the plains. Over the past 20 years, plains PCR increased by ~10% when the AOD augmented by 0.15, whereas it decreased with lower pollution levels. In contrast, PCR in mountainous areas decreased with higher pollution levels and increased with lower pollution levels. Our analysis from model results indicated that aerosol increases reduce the effective particle size of cloud droplets and raindrops. Smaller cloud raindrops more readily transport to high air layers and participate in the generation of ice-phase substances in the clouds, increasing the total amount of cloud water in the air in a certain time, which ultimately enhanced precipitation intensity on the plains. The removal of pollutants caused by increased precipitation in the plains decreased rainfall levels in mountainous areas.

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Microphysical Processes in Cirrus and Their Impact on Radiation: A Mesoscale Modeling Perspective

Cirrus ◽

10.1093/oso/9780195130720.003.0023 ◽

2002 ◽

Author(s):

Vitaly I. Khvorostyanov ◽

Kenneth Sassen

Keyword(s):

Optical Properties ◽

General Circulation ◽

Climate Models ◽

Cooling Effect ◽

Climatic Impact ◽

Positive Feedbacks ◽

Cloud Forcing ◽

Two Factors ◽

Upper Level ◽

Microphysical Processes

The impact of cloudiness on the global radiative budget and its climatic consequences have been widely discussed during the last three decades. It was gradually recognized that the climatic effect of cloudiness depends on its height: low- and middle-level cloudiness have a total cooling effect on the Earth climatic system, while the upper-level clouds, cirrus, may have mostly a warming effect (IPCC 1995). The net effect of cirrus (i.e., warming or cooling), is much less clear because neither their microphysical and optical properties, nor the processes that govern their formation, are well understood and parameterized in climate models. These uncertainties have stimulated several major field projects performed within the International Satellite Cloud Climatology Project (ISCCP; Rossow and Schiffer 1991) with subsequent data analysis reports [e.g., FIRE IFO-I (1990), FIRE IFO-II (1995), and EUCREX (Raschke et al. 1996)]. The relevant theoretical works, and even the simplest climate models, indicate that the climatic impact of cirrus depends on their microstructure: clouds composed of small crystals with effective radii less than about 16 μm have a total cooling effect, but clouds of larger crystals have a warming effect (Stephens et al. 1990). It was shown that the total cloud forcing at the top of the atmosphere (TOA) is positive from a few to a few tens of watts per square meter for the large crystals and decreases with decreasing crystal radius (Fu and Liou 1993). Most of the previous theoretical studies of cirrus radiative properties, after choosing some model of microphysics and some values for the mass extinction and absorption coefficients, then prescribed them to the whole cloud, neglecting any vertical variations. Simulations with general circulation models (GCMs) showed that cirrus clouds with their optical properties parameterized in such a way (i.e., constant with height) have a total warming effect and positive feedbacks with respect to greenhouse gas-induced global warming (e.g., Ramanathan et al. 1983; Wetherald and Manabe 1988). Today, the estimation of the warming/cooling effect of cirrus has become even more complicated due to two factors. First, for many years the usual in situ probes allowed the measurement of ice crystals with radii only larger than 25-50 μm, so the smallest and most optically and radiatively active crystals were unresolved.

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Polar Winds: Airborne Doppler Wind Lidar Missions in the Arctic for Atmospheric Observations and Numerical Model Comparisons

Atmosphere ◽

10.3390/atmos11111141 ◽

2020 ◽

Vol 11 (11) ◽

pp. 1141

Author(s):

Steven Greco ◽

George D. Emmitt ◽

Alice DuVivier ◽

Keith Hines ◽

Michael Kavaya

Keyword(s):

Wrf Model ◽

The Arctic ◽

Weather Research And Forecasting ◽

Dynamic Features ◽

Wind Retrieval ◽

Atmospheric Observations ◽

Wind Lidar ◽

Upper Level ◽

Upper Level Jet ◽

Doppler Wind Lidar

During October–November 2014 and May 2015, NASA sponsored and conducted a pair of airborne campaigns called Polar Winds to investigate atmospheric circulations, particularly in the boundary layer, over the Arctic using NASA’s Doppler Aerosol WiNd (DAWN) lidar. A description of the campaigns, the DAWN instrument, wind retrieval methods and data processing is provided. During the campaigns, the DAWN instrument faced backscatter sensitivity issues in the low aerosol conditions that were fairly frequent in the 2–6 km altitude range. However, when DAWN was able to make measurements, comparisons with dropsondes show good agreement and very low bias and supports the use of an airborne Doppler wind lidar such as DAWN that can provide profiles with high velocity precision, ~65 m vertical resolution and horizontal spacing as fine as 3–7 km. Case study analyses of a Greenland tip jet, barrier winds and an upper level jet are presented and show how, despite sensitivity issues, DAWN data can be confidently used in diagnostic studies of dynamic features in the Arctic. Comparisons with both an operational and research Weather Research and Forecasting (WRF) model for these events also show the potential for utilization in model validation. The sensitivity issues of the DAWN laser have since been corrected.

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