Possible Aerosol Effects on Lightning Activity and Structure of Hurricanes

Abstract According to observations of hurricanes located relatively close to the land, intense and persistent lightning takes place within a 250–300-km radius ring around the hurricane center, whereas the lightning activity in the eyewall takes place only during comparatively short periods usually attributed to eyewall replacement. The mechanism responsible for the formation of the maximum flash density at the tropical cyclone (TC) periphery is not well understood as yet. In this study it is hypothesized that lightning at the TC periphery arises under the influence of small continental aerosol particles (APs), which affect the microphysics and the dynamics of clouds at the TC periphery. To show that aerosols change the cloud microstructure and the dynamics to foster lightning formation, the authors use a 2D mixed-phase cloud model with spectral microphysics. It is shown that aerosols that penetrate the cloud base of maritime clouds dramatically increase the amount of supercooled water, as well as the ice contents and vertical velocities. As a result, in clouds developing in the air with high AP concentration, ice crystals, graupel, frozen drops and/or hail, and supercooled water can coexist within a single cloud zone, which allows collisions and charge separation. The simulation of possible aerosol effects on the landfalling tropical cyclone has been carried out using a 3-km-resolution Weather Research and Forecast (WRF) mesoscale model. It is shown that aerosols change the cloud microstructure in a way that permits the attribution of the observed lightning structure to the effects of continental aerosols. It is also shown that aerosols, which invigorate clouds at 250–300 km from the TC center, decrease the convection intensity in the TC center, leading to some TC weakening. The results suggest that aerosols change the intensity and the spatial distribution of precipitation in landfalling TCs and can possibly contribute to the weekly cycle of the intensity and precipitation of landfalling TCs. More detailed investigations of the TC–aerosol interaction are required.

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Opinion: Cloud-phase climate feedback and the importance of ice-nucleating particles

10.5194/acp-2020-852 ◽

2020 ◽

Cited By ~ 1

Author(s):

Benjamin J. Murray ◽

Kenneth S. Carslaw ◽

Paul R. Field

Keyword(s):

Climate Models ◽

Research Effort ◽

Aerosol Particles ◽

Supercooled Water ◽

Ice Crystals ◽

Climate Feedback ◽

Seasonal Cycles ◽

Predictive Capability ◽

Shallow Clouds ◽

Warming World

Abstract. Shallow clouds covering vast areas of the world's mid- and high-latitude oceans play a key role in dampening the global temperature rise associated with CO2. These clouds, which contain both ice and supercooled water, respond to a warming world by transitioning to a state with more liquid water and a greater albedo, resulting in a negative cloud-phase climate feedback component. Here we argue that the magnitude of the negative cloud-phase feedback component depends on the amount and nature of the small fraction of aerosol particles that can nucleate ice crystals. We propose that a concerted research effort is required to reduce substantial and important uncertainties related to the poorly understood sources, concentration, seasonal cycles and nature of these ice-nucleating particles (INPs) and their rudimentary treatment in climate models. The topic is important because many climate models may have overestimated the magnitude of the cloud-phase feedback, and those with better representation of shallow oceanic clouds predict a substantially larger climate warming. We make the case that understanding the present-day INP population in shallow clouds in the cold-sector of cyclone systems is particularly critical for defining present-day cloud phase and therefore how the clouds respond to warming. We also need to develop a predictive capability for future INP emissions in a warmer world with less ice and snow and potentially stronger INP sources.

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Opinion: Cloud-phase climate feedback and the importance of ice-nucleating particles

Atmospheric Chemistry and Physics ◽

10.5194/acp-21-665-2021 ◽

2021 ◽

Vol 21 (2) ◽

pp. 665-679

Author(s):

Benjamin J. Murray ◽

Kenneth S. Carslaw ◽

Paul R. Field

Keyword(s):

Climate Models ◽

Research Effort ◽

Aerosol Particles ◽

Supercooled Water ◽

Ice Crystals ◽

Climate Feedback ◽

Seasonal Cycles ◽

Predictive Capability ◽

Shallow Clouds ◽

Warming World

Abstract. Shallow clouds covering vast areas of the world's middle- and high-latitude oceans play a key role in dampening the global temperature rise associated with CO2. These clouds, which contain both ice and supercooled water, respond to a warming world by transitioning to a state with more liquid water and a greater albedo, resulting in a negative “cloud-phase” climate feedback component. Here we argue that the magnitude of the negative cloud-phase feedback component depends on the amount and nature of the small fraction of aerosol particles that can nucleate ice crystals. We propose that a concerted research effort is required to reduce substantial uncertainties related to the poorly understood sources, concentration, seasonal cycles and nature of these ice-nucleating particles (INPs) and their rudimentary treatment in climate models. The topic is important because many climate models may have overestimated the magnitude of the cloud-phase feedback, and those with better representation of shallow oceanic clouds predict a substantially larger climate warming. We make the case that understanding the present-day INP population in shallow clouds in the cold sector of cyclone systems is particularly critical for defining present-day cloud phase and therefore how the clouds respond to warming. We also need to develop a predictive capability for future INP emissions and sinks in a warmer world with less ice and snow and potentially stronger INP sources.

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The Role of Small Soluble Aerosols in the Microphysics of Deep Maritime Clouds

Journal of the Atmospheric Sciences ◽

10.1175/2011jas3649.1 ◽

2012 ◽

Vol 69 (9) ◽

pp. 2787-2807 ◽

Cited By ~ 47

Author(s):

A. P. Khain ◽

V. Phillips ◽

N. Benmoshe ◽

A. Pokrovsky

Keyword(s):

Vertical Velocity ◽

Cloud Condensation Nuclei ◽

Synergetic Effect ◽

Supercooled Water ◽

Ice Crystals ◽

Cloud Base ◽

Droplet Concentration ◽

High Concentrations ◽

Drop Size Distributions

Abstract Some observational evidence—such as bimodal drop size distributions, comparatively high concentrations of supercooled drops at upper levels, high concentrations of small ice crystals in cloud anvils leading to high optical depth, and lightning in the eyewalls of hurricanes—indicates that the traditional view of the microphysics of deep tropical maritime clouds requires, possibly, some revisions. In the present study it is shown that the observed phenomena listed above can be attributed to the presence of small cloud condensation nuclei (CCN) with diameters less than about 0.05 μm. An increase in vertical velocity above cloud base can lead to an increase in supersaturation and to activation of the smallest CCN, resulting in production of new droplets several kilometers above the cloud base. A significant increase in supersaturation can be also caused by a decrease in droplet concentration during intense warm rain formation accompanied by an intense vertical velocity. This increase in supersaturation also can trigger in-cloud nucleation and formation of small droplets. Another reason for an increase in supersaturation and in-cloud nucleation can be riming, resulting in a decrease in droplet concentration. It has been shown that successive growth of new nucleated droplets increases supercooled water content and leads to significant ice crystal concentrations aloft. The analysis of the synergetic effect of the smallest CCN and giant CCN on production of supercooled water and ice crystals in cloud anvils allows reconsideration of the role of giant CCN. Significant effects of small aerosols on precipitation and cloud updrafts have been found. The possible role of these small aerosols as well as small aerosols with combination of giant CCN in creating conditions favorable for lightning in deep maritime clouds is discussed.

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Explicitly Simulated Electrification and Lightning within a Tropical Cyclone Based on the Environment of Hurricane Isaac (2012)

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-14-0374.1 ◽

2015 ◽

Vol 72 (11) ◽

pp. 4167-4193 ◽

Cited By ~ 20

Author(s):

Alexandre O. Fierro ◽

Edward R. Mansell ◽

Conrad L. Ziegler ◽

Donald R. MacGorman

Keyword(s):

Tropical Cyclone ◽

Negative Charge ◽

Lightning Activity ◽

Ice Crystals ◽

Weather Research And Forecasting ◽

The Earth ◽

Ice Water Path ◽

Total Lightning ◽

Ice Water ◽

Positively Charged

Abstract This work analyzes a high-resolution 350-m simulation of the electrification processes within a hurricane in conjunction with available total lightning observations to augment the general understanding of some of the key cloud-scale electrification processes within these systems. The general environment and trends of Hurricane Isaac (2012), whose lightning activity was observed by the Earth Networks Total Lightning Network, were utilized to produce a reasonable tropical cyclone simulation. The numerical model in this work employs explicit electrification and lightning parameterizations within the Weather Research and Forecasting Model. Overall, simulated storm-total flash origin density rates remain comparable to the observations. Because simulated reflectivities were larger and echo tops were higher in the eyewall than observed, the model consistently overestimated lightning rates there. The gross vertical charge structure in the eyewall resembled a normal tripole or a positive dipole, depending on the location. The negative charge at middle levels and positive at upper levels arose primarily from noninductive charging between graupel and ice crystals/snow. As some graupel melted into rain, the main midlevel negative charge region extended down to the surface in some places. The large volume of positively charged snow aloft caused a radially extensive negative screening layer to form on the lighter ice crystals above it. Akin to continental storms and tropical convection, lightning activity in the eyewall was well correlated with the ice water path (r > 0.7) followed by the graupel + hail path (r ≈ 0.7) and composite reflectivity at temperatures less than −10°C and the snow + ice path (r ≈ 0.5). Relative maxima in updraft volume, graupel volume, and total lightning rates in the eyewall all were coincident with the end of an intensification phase.

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Measurements of Ice Nucleating Particles and Ice Residuals

Meteorological Monographs ◽

10.1175/amsmonographs-d-16-0008.1 ◽

2017 ◽

Vol 58 ◽

pp. 8.1-8.13 ◽

Cited By ~ 25

Author(s):

Daniel J. Cziczo ◽

Luis Ladino ◽

Yvonne Boose ◽

Zamin A. Kanji ◽

Piotr Kupiszewski ◽

...

Keyword(s):

Electron Microscope ◽

Condensed Phase ◽

Atmospheric Aerosols ◽

Aerosol Particles ◽

Ice Crystals ◽

Ice Formation ◽

Similar Amount ◽

Residual Material ◽

History Of ◽

Phase Water

Abstract It has been known that aerosol particles act as nuclei for ice formation for over a century and a half (see Dufour). Initial attempts to understand the nature of these ice nucleating particles were optical and electron microscope inspection of inclusions at the center of a crystal (see Isono; Kumai). Only within the last few decades has instrumentation to extract ice crystals from clouds and analyze the residual material after sublimation of condensed-phase water been available (see Cziczo and Froyd). Techniques to ascertain the ice nucleating potential of atmospheric aerosols have only been in place for a similar amount of time (see DeMott et al.). In this chapter the history of measurements of ice nucleating particles, both in the field and complementary studies in the laboratory, are reviewed. Remaining uncertainties and artifacts associated with measurements are described and suggestions for future areas of improvement are made.

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Simulating the influence of primary biological aerosol particles on clouds by heterogeneous ice nucleation

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-15437-2018 ◽

2018 ◽

Vol 18 (20) ◽

pp. 15437-15450 ◽

Cited By ~ 4

Author(s):

Matthias Hummel ◽

Corinna Hoose ◽

Bernhard Pummer ◽

Caroline Schaupp ◽

Janine Fröhlich-Nowoisky ◽

...

Keyword(s):

Pseudomonas Syringae ◽

Aerosol Particles ◽

Fungal Spores ◽

Ice Nucleation ◽

Ice Crystals ◽

Atmospheric Measurements ◽

Cloud Ice ◽

Biological Aerosol Particles ◽

Ice Phase ◽

Heterogeneous Ice Nucleation

Abstract. Primary ice formation, which is an important process for mixed-phase clouds with an impact on their lifetime, radiative balance, and hence the climate, strongly depends on the availability of ice-nucleating particles (INPs). Supercooled droplets within these clouds remain liquid until an INP immersed in or colliding with the droplet reaches its activation temperature. Only a few aerosol particles are acting as INPs and the freezing efficiency varies among them. Thus, the fraction of supercooled water in the cloud depends on the specific properties and concentrations of the INPs. Primary biological aerosol particles (PBAPs) have been identified as very efficient INPs at high subzero temperatures, but their very low atmospheric concentrations make it difficult to quantify their impact on clouds. Here we use the regional atmospheric model COSMO–ART to simulate the heterogeneous ice nucleation by PBAPs during a 1-week case study on a domain covering Europe. We focus on three highly ice-nucleation-active PBAP species, Pseudomonas syringae bacteria cells and spores from the fungi Cladosporium sp. and Mortierella alpina. PBAP emissions are parameterized in order to represent the entirety of bacteria and fungal spores in the atmosphere. Thus, only parts of the simulated PBAPs are assumed to act as INPs. The ice nucleation parameterizations are specific for the three selected species and are based on a deterministic approach. The PBAP concentrations simulated in this study are within the range of previously reported results from other modeling studies and atmospheric measurements. Two regimes of PBAP INP concentrations are identified: a temperature-limited and a PBAP-limited regime, which occur at temperatures above and below a maximal concentration at around −10 ∘C, respectively. In an ensemble of control and disturbed simulations, the change in the average ice crystal concentration by biological INPs is not statistically significant, suggesting that PBAPs have no significant influence on the average state of the cloud ice phase. However, if the cloud top temperature is below −15 ∘C, PBAP can influence the cloud ice phase and produce ice crystals in the absence of other INPs. Nevertheless, the number of produced ice crystals is very low and it has no influence on the modeled number of cloud droplets and hence the cloud structure.

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MU Radar and Lidar Observations of Clear-Air Turbulence underneath Cirrus

Monthly Weather Review ◽

10.1175/2009mwr2927.1 ◽

2010 ◽

Vol 138 (2) ◽

pp. 438-452 ◽

Cited By ~ 18

Author(s):

Hubert Luce ◽

Takuji Nakamura ◽

Masayuki K. Yamamoto ◽

Mamoru Yamamoto ◽

Shoichiro Fukao

Keyword(s):

Convective Instability ◽

Radar Data ◽

Ice Crystals ◽

Shear Instability ◽

Cloud Base ◽

Doppler Spectrum ◽

Cirrus Cloud ◽

Air Turbulence ◽

Mu Radar ◽

Generation Mechanisms

Abstract Turbulence generation mechanisms prevalent in the atmosphere are mainly shear instabilities, breaking of internal buoyancy waves, and convective instabilities such as thermal convection due to heating of the ground. In the present work, clear-air turbulence underneath a cirrus cloud base is described owing to coincident observations from the VHF (46.5 MHz) middle and upper atmosphere (MU) radar, a Rayleigh–Mie–Raman (RMR) lidar, and a balloon radiosonde on 7–8 June 2006 (at Shigaraki, Japan; 34.85°N, 136.10°E). Time–height cross section of lidar backscatter ratio obtained at 2206 LT 7 June 2006 showed the presence of a cirrus layer between 8.0 and 12.5 km MSL. Downward-penetrating structures of ice crystals with horizontal and vertical extents of 1.0–4.0 km and 200–800 m, respectively, have been detected at the cirrus cloud base for about 35 min. At the same time, the MU radar data revealed clear-air turbulence layers developing downward from the cloud base in the environment of the protuberances detected by the RMR lidar. Their maximum depth was about 2.0 km for about 1.5 h. They were associated with oscillatory vertical wind perturbations of up to ±1.5 m s−1 and variances of Doppler spectrum of 0.2–1.5 m−2 s−2. Analysis of the data suggests that the turbulence and the downward penetration of cloudy air were possibly the consequence of a convective instability (rather than a dynamical shear instability) that was likely due to sublimation of ice crystals in the subcloud region. Downward clear-air motions measured by the MU radar were associated with the descending protuberances, and updrafts were observed between them. These observations suggest that the cloudy air might have been pushed down by the downdrafts of the convective instability and pushed up by the updrafts to form the observed protuberances at the cloud base. These structures may be virga or perhaps more likely mamma as reported by recent observations of cirrus mamma with similar instruments and by numerical simulations.

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Impact of Four-Dimensional Variational Data Assimilation of Atmospheric Motion Vectors on Tropical Cyclone Track Forecasts

Weather and Forecasting ◽

10.1175/waf940.1 ◽

2006 ◽

Vol 21 (4) ◽

pp. 663-669 ◽

Cited By ~ 11

Author(s):

Dongliang Wang ◽

Xudong Liang ◽

Yihong Duan ◽

Johnny C. L. Chan

Keyword(s):

Tropical Cyclone ◽

Data Assimilation ◽

Mesoscale Model ◽

State University ◽

Motion Vectors ◽

Geostationary Meteorological Satellite ◽

Atmospheric Motion ◽

Atmospheric Motion Vectors ◽

Data Assimilation Technique ◽

The Impact

Abstract The fifth-generation Pennsylvania State University–National Center for Atmospheric Research nonhydrostatic Mesoscale Model is employed to evaluate the impact of the Geostationary Meteorological Satellite-5 water vapor and infrared atmospheric motion vectors (AMVs), incorporated with the four-dimensional variational (4DVAR) data assimilation technique, on tropical cyclone (TC) track predictions. Twenty-two cases from eight different TCs over the western North Pacific in 2002 have been examined. The 4DVAR assimilation of these satellite-derived wind observations leads to appreciable improvements in the track forecasts, with average reductions in track error of ∼5% at 12 h, 12% at 24 h, 10% at 36 h, and 7% at 48 h. Preliminary results suggest that the improvement depends on the quantity of the AMV data available for assimilation.

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