scholarly journals Aircraft Observations of Ice Particle Properties in Stratiform Precipitating Clouds

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Tuanjie Hou ◽  
Hengchi Lei ◽  
Zhaoxia Hu ◽  
Jun Zhou
Keyword(s):  
Particle Size ◽  
Northern China ◽  
Size Spectrum ◽  
Airborne Measurements ◽  
Particle Properties ◽  
Stratiform Clouds ◽  
Convective Cells ◽  
Parameter Values ◽  
Ice Water ◽  
Precipitating Clouds

This study presented airborne measurements of ice particle properties in three stratiform precipitating clouds over northern China. By using horizontal observations at selected altitudes, the distributions of ice water content (IWC), particle habits, and particle size spectrum parameters were investigated. The cloud cases were characterized by high IWC values due to the existence of embedded convective cells. Liquid water contents were rather low with the maxima of less than 0.3 g m−3and the general values of less than 0.1 g m−3. The occurrence of large dendritic crystals as well as rimed capped columns and branched crystals indicated that ice seeding from the above cloud layer (6 km altitude or above) contributed significantly to both high ice crystal number concentrations and IWCs. Horizontal observations at selected levels suggested the general decreasing trend of IWC with decreasing temperature only in part of the cloud layers but not throughout the cold layer of the multilayered stratiform clouds. Both exponential and gamma functions were used to characterize the particle size spectrum parameters. The slope parameter values of exponential distributions were primarily in the range of 103–104 m−1. In comparison, slope values of the gamma distribution fits spanned more and a relationship was found between the dispersion and slope values.

The Size Distribution and Mass-Weighted Terminal Velocity of Low-Latitude Tropopause Cirrus Crystal Populations

2009 ◽  
Vol 66 (7) ◽  
pp. 2013-2028 ◽  
Author(s):  
C. G. Schmitt ◽  
A. J. Heymsfield
Keyword(s):  
Particle Size ◽  
Size Distribution ◽  
Terminal Velocity ◽  
Range Data ◽  
Regional Study ◽  
Low Latitude ◽  
Particle Properties ◽  
Validation Experiment ◽  
Using Data ◽  
Ice Water

Abstract Ice crystal terminal velocities govern the lifetime of radiatively complex, climatologically important, low-latitude tropopause cirrus clouds. To better understand cloud lifetimes, the terminal velocities of low-latitude tropopause cirrus cloud particles have been estimated using data from aircraft field campaigns. Data used in this study were collected during the Cirrus Regional Study of Tropical Anvils and Cirrus Layers–Florida Area Cirrus Experiment (CRYSTAL-FACE) and the Pre-Aura Validation Experiment (Pre-AVE). Particle properties were measured with the NCAR video ice particle sampler (VIPS) probe, thus providing information about particles in a poorly understood size range. Data used in this study were limited to high-altitude nonconvective thin clouds with temperatures between −56° and −86°C. Realistic particle terminal velocity estimates require accurate values of particle projected area and mass. Exponential functions were used to predict the dimensional properties of ice particles smaller than 200 microns and were found to predict ice water content measurements well when compared to power-law representations. The shapes of the particle size distributions were found to be monomodal and were well represented by exponential or gamma functions. Incorporating these findings into terminal velocity calculations led to lower values of mass-weighted terminal velocities for particle populations than are currently predicted for low-latitude ice clouds. New parameterizations for individual particle properties as well as particle size distribution properties are presented and compared to commonly used parameterizations. Results from this study are appropriate for use in estimating the properties of low-latitude thin and subvisible cirrus at temperatures lower than −56°C.

Airborne measurements of dust layer properties, particle size distribution and mixing state of Saharan dust during SAMUM 2006

Tellus B ◽  
2009 ◽  
Vol 61 (1) ◽  
Author(s):  
Bernadett Weinzierl ◽  
Andreas Petzold ◽  
Michael Esselborn ◽  
Martin Wirth ◽  
Katharina Rasp ◽  
...  
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Saharan Dust ◽  
Mixing State ◽  
Dust Layer ◽  
Airborne Measurements

scholarly journals On microphysical processes of noctilucent clouds (NLC): observations and modeling of mean and width of the particle size-distribution

2010 ◽  
Vol 10 (2) ◽  
pp. 3605-3625
Author(s):  
G. Baumgarten ◽  
J. Fiedler ◽  
M. Rapp
Keyword(s):  
Particle Size ◽  
Linear Relationship ◽  
Size Distribution ◽  
Eddy Diffusion ◽  
Particle Sizes ◽  
Noctilucent Clouds ◽  
Atmospheric Variability ◽  
Distribution Width ◽  
Particle Properties ◽  
Microphysical Processes

Abstract. Noctilucent clouds (NLC) in the polar summer mesopause region have been observed in Norway (69° N, 16° E) between 1998 and 2009 by 3-color lidar technique. Assuming a mono-modal Gaussian size distribution we deduce mean and width of the particle sizes throughout the clouds. We observe a quasi linear relationship between distribution width and mean of the particle size at the top of the clouds and a deviation from this behavior for particle sizes larger than 40 nm, most often in the lower part of the layer. The vertically integrated particle properties show that 65% of the data follows the linear relationship with a slope of 0.42±0.02. For the vertically resolved particle properties (Δz=0.15 km) the slope is smaller and only 0.39±0.03. We compare our observations to microphysical modeling of noctilucent clouds and find that the distribution width depends on turbulence, the time that turbulence can act (cloud age), and the sampling volume/time (atmospheric variability). The model results nicely reproduce the measurements and show that the observed slope can be explained by eddy diffusion profiles as observed from rocket measurements.

scholarly journals A review of biomass burning emissions, part II: Intensive physical properties of biomass burning particles

2004 ◽  
Vol 4 (5) ◽  
pp. 5135-5200 ◽  
Author(s):  
J. S. Reid ◽  
R. Koppmann ◽  
T. F. Eck ◽  
D. P. Eleuterio
Keyword(s):  
Particle Size ◽  
Biomass Burning ◽  
Measurement Techniques ◽  
Emission Factors ◽  
Future Research ◽  
Data Set ◽  
Particle Properties ◽  
In Situ Experiments ◽  
Literature Base ◽  
Biomass Burning Particles

Abstract. The last decade has seen tremendous advances in atmospheric aerosol particle research that is often performed in the context of climate and global change science. Biomass burning, one of the largest sources of accumulation mode particles globally, has been closely studied for its radiative, geochemical, and dynamic impacts. These studies have taken many forms including laboratory burns, in situ experiments, remote sensing, and modeling. While the differing perspectives of these studies have ultimately improved our qualitative understanding of biomass burning issues, the varied nature of the work make inter-comparisons and resolutions of some specific issues difficult. In short, the literature base has become a milieu of small pieces of the biomass-burning puzzle. This manuscript, the second part of four, examines the properties of biomass-burning particle emissions. Here we review and discuss the literature concerning the measurement of smoke particle size, chemistry, thermodynamic properties, and emission factors. Where appropriate, critiques of measurement techniques are presented. We show that very large differences in measured particle properties have appeared in the literature, in particular with regards to particle carbon budgets. We investigate emissions uncertainties using scale analyses, which shows that while emission factors for grass and brush are relatively well known, very large uncertainties still exist in emission factors of boreal, temperate and some tropical forests. Based on an uncertainty analysis of the community data set of biomass burning measurements, we present simplified models for particle size and emission factors. We close this review paper with a discussion of the community experimental data, point to lapses in the data set, and prioritize future research topics.

scholarly journals Stability and Charging Characteristics of the Comma Head Region of Continental Winter Cyclones

2014 ◽  
Vol 71 (5) ◽  
pp. 1559-1582 ◽  
Author(s):  
Robert M. Rauber ◽  
Joseph Wegman ◽  
David M. Plummer ◽  
Andrew A. Rosenow ◽  
Melissa Peterson ◽  
...  
Keyword(s):  
Convective Available Potential Energy ◽  
Spectral Width ◽  
Head Region ◽  
Stratiform Clouds ◽  
Southern Side ◽  
Northern Zone ◽  
Cutoff Low ◽  
Deep Cyclone ◽  
Convective Cells

Abstract This paper presents analyses of the finescale structure of convection in the comma head of two continental winter cyclones and a 16-storm climatology analyzing the distribution of lightning within the comma head. A case study of a deep cyclone is presented illustrating how upper-tropospheric dry air associated with the dry slot can intrude over moist Gulf air, creating two zones of precipitation within the comma head: a northern zone characterized by deep stratiform clouds topped by generating cells and a southern zone marked by elevated convection. Lightning, when it occurred, originated from the elevated convection. A second case study of a cutoff low is presented to examine the relationship between lightning flashes and wintertime convection. Updrafts within convective cells in both storms approached 6–8 m s−1, and convective available potential energy in the cell environment reached approximately 50–250 J kg−1. Radar measurements obtained in convective updraft regions showed enhanced spectral width within the temperature range from −10° to −20°C, while microphysical measurements showed the simultaneous presence of graupel, ice particles, and supercooled water at the same temperatures, together supporting noninductive charging as an important charging mechanism in these storms. A climatology of lightning flashes across the comma head of 16 winter cyclones shows that lightning flashes commonly occur on the southern side of the comma head where dry-slot air is more likely to overrun lower-level moist air. Over 90% of the cloud-to-ground flashes had negative polarity, suggesting the cells were not strongly sheared aloft. About 55% of the flashes were associated with cloud-to-ground flashes while 45% were in-cloud flashes.

Effect of the Algal Length/Aperture Length Ratio on Coulter Analyses of Lake Seston

1981 ◽  
Vol 38 (8) ◽  
pp. 912-916 ◽  
Author(s):  
H. A. Vanderploeg
Keyword(s):  
Particle Size ◽  
Particle Size Analysis ◽  
Coulter Counter ◽  
Length Ratio ◽  
Size Analysis ◽  
Size Spectrum ◽  
Major Difficulty ◽  
Best Estimate ◽  
Continuous Particle

Experiments on sizing seston and nylon rods in Coulter apertures of different sizes showed that a major difficulty in obtaining a continuous particle-size spectrum for lake seston is the presence of long, thin algae which are significantly undersized unless their lengths are shorter than aperture length. These fibers affect not only the choice of the largest aperture tube required but also the combination of aperture tubes necessary to obtain a continuous particle-size spectrum. Methods are given for selecting aperture tubes and blending the data obtained from them to give a best estimate of the continuous particle-size spectrum.Key words: Coulter counter, multitube technique, lake seston, particle-size analysis, aperture tube selection

scholarly journals Physical Properties of High-Level Cloud over Land and Ocean from CloudSat–CALIPSO Data

2014 ◽  
Vol 27 (23) ◽  
pp. 8966-8978 ◽  
Author(s):  
Juan Huo ◽  
Daren Lu
Keyword(s):  
Linear Relationship ◽  
Water Content ◽  
Northern China ◽  
Occurrence Frequency ◽  
Radiative Energy ◽  
Cloud Base ◽  
The Pacific ◽  
Ice Water Content ◽  
High Level ◽  
Ice Water

Abstract Unlike other cloud types, high-level clouds play an important role, often imposing a warming effect, in the earth–atmosphere radiative energy budget. In this paper, macro- and microphysical characteristics of cirrus clouds, such as their occurrence frequency, geometric scale, water content, and particle size, over northern China (land area, herein called the L area) and the Pacific Ocean (ocean area, herein the O area) are analyzed and compared based on CloudSat and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) products from 1 January 2007 to 31 December 2010. Over both areas, statistical analysis shows that cirrus occurrence approached 33% in summer whereas it was only ~10% in winter, >50% of cirrus cloud thicknesses were in the range of ~(0.25–1.5) km, there were >98% ice particles in high-level clouds, and temperature had a closer linear relationship with ice effective radius (IER) than height. Also, the seasonal difference of this linear relationship is minor over both land and ocean. Comparisons reveal that the mean occurrence frequency, mean cloud thickness, range of cloud-base and cloud-top height, IER, and ice water content of cirrus in summer were generally greater in winter, and greater over the O area than over the L area. However, the relationship between IER and temperature over land is close to that over ocean.

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