Evaluation of the Lidar–Radar Cloud Ice Water Content Retrievals Using Collocated in Situ Measurements

AbstractRemote sensing and in situ measurements made during the Colorado Airborne Multiphase Cloud Study, 2010–2011 (CAMPS) with instruments aboard the University of Wyoming King Air aircraft are used to evaluate lidar–radar-retrieved cloud ice water content (IWC). The collocated remote sensing and in situ measurements provide a unique dataset for evaluation studies. Near-flight-level IWC retrieval is compared with an in situ probe: the Colorado closed-path tunable diode laser hygrometer (CLH). Statistical analysis showed that the mean radar–lidar IWC is within 26% of the mean in situ measurements for pure ice clouds and within 9% for liquid-topped mixed-phase clouds. Considering their different measurement techniques and different sample volumes, the comparison shows a statistically good agreement and is close to the measurement uncertainty of the CLH, which is around 20%. It is shown that ice cloud microphysics including ice crystal shape and orientation has a significant impact on IWC retrievals. These results indicate that the vertical profile of the retrieved lidar–radar IWC can be reliably combined with the flight-level measurements made by the in situ probes to provide a more complete picture of the cloud microphysics.

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Comparisons of in situ measurements of cirrus cloud ice water content

Journal of Geophysical Research Atmospheres ◽

10.1029/2006jd008214 ◽

2007 ◽

Vol 112 (D10) ◽

Cited By ~ 31

Author(s):

Sean M. Davis ◽

Linnea M. Avallone ◽

Elliot M. Weinstock ◽

Cynthia H. Twohy ◽

Jessica B. Smith ◽

...

Keyword(s):

Water Content ◽

In Situ Measurements ◽

Cirrus Cloud ◽

Ice Water Content ◽

Cloud Ice ◽

Ice Water

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Diagnosing the average spatio-temporal impact of convective systems – Part 1: A methodology for evaluating climate models

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-12043-2013 ◽

2013 ◽

Vol 13 (23) ◽

pp. 12043-12058 ◽

Cited By ~ 2

Author(s):

M. S. Johnston ◽

S. Eliasson ◽

P. Eriksson ◽

R. M. Forbes ◽

K. Wyser ◽

...

Keyword(s):

Water Content ◽

Outgoing Longwave Radiation ◽

Longwave Radiation ◽

Cloud Fraction ◽

Convective Systems ◽

Ice Water Content ◽

The Mean ◽

Spatio Temporal ◽

Cloud Ice ◽

Ice Water

Abstract. An earlier method to determine the mean response of upper-tropospheric water to localised deep convective systems (DC systems) is improved and applied to the EC-Earth climate model. Following Zelinka and Hartmann (2009), several fields related to moist processes and radiation from various satellites are composited with respect to the local maxima in rain rate to determine their spatio-temporal evolution with deep convection in the central Pacific Ocean. Major improvements to the earlier study are the isolation of DC systems in time so as to prevent multiple sampling of the same event, and a revised definition of the mean background state that allows for better characterisation of the DC-system-induced anomalies. The observed DC systems in this study propagate westward at ~4 m s−1. Both the upper-tropospheric relative humidity and the outgoing longwave radiation are substantially perturbed over a broad horizontal extent and for periods >30 h. The cloud fraction anomaly is fairly constant with height but small maximum can be seen around 200 hPa. The cloud ice water content anomaly is mostly confined to pressures greater than 150 hPa and reaches its maximum around 450 hPa, a few hours after the peak convection. Consistent with the large increase in upper-tropospheric cloud ice water content, albedo increases dramatically and persists about 30 h after peak convection. Applying the compositing technique to EC-Earth allows an assessment of the model representation of DC systems. The model captures the large-scale responses, most notably for outgoing longwave radiation, but there are a number of important differences. DC systems appear to propagate eastward in the model, suggesting a strong link to Kelvin waves instead of equatorial Rossby waves. The diurnal cycle in the model is more pronounced and appears to trigger new convection further to the west each time. Finally, the modelled ice water content anomaly peaks at pressures greater than 500 hPa and in the upper troposphere between 250 hPa and 500 hPa, there is less ice than the observations and it does not persist as long after peak convection. The modelled upper-tropospheric cloud fraction anomaly, however, is of a comparable magnitude and exhibits a similar longevity as the observations.

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UARS/MLS Cloud Ice Measurements: Implications for H2O Transport near the Tropopause

Journal of the Atmospheric Sciences ◽

10.1175/jas-3382.1 ◽

2005 ◽

Vol 62 (2) ◽

pp. 518-530 ◽

Cited By ~ 40

Author(s):

D. L. Wu ◽

W. G. Read ◽

A. E. Dessler ◽

S. C. Sherwood ◽

J. H. Jiang

Keyword(s):

Water Content ◽

Total Water ◽

Ice Clouds ◽

Clear Sky ◽

Ice Water Content ◽

Satellite Microwave ◽

Cold Point ◽

Cloud Ice ◽

Ice Water

Abstract A technique for detecting large hydrometeors at high altitudes is described here and applied to the Upper Atmosphere Research Satellite/Microwave Limb Sounder (UARS/MLS) 203-GHz radiance measurements at tangent pressures between 200 and 46 hPa. At these tangent pressures the radiances remain optically thin and cloudy-sky radiances are brighter than normal clear-sky cases. Unlike infrared/visible cloud observations, the 203-GHz radiances can penetrate most ice clouds and are sensitive to ice crystals of convective origin. Rough ice water content (IWC) retrievals are made near the tropopause using estimated size distributions from in situ convective studies. The seasonal mean IWC observed at 100 hPa reaches vapor-equivalent 20 ppmv or more over convective centers, dominating the total water content. Convectively lofted ice, therefore, appears to be hydrologically significant at the tropical cold point. IWC is well correlated spatially with relative humidity with respect to ice (RHi) at 100 hPa during both the dry (January–March) and moist (July–September) periods.

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In-situ measurements of tropical cloud properties in the West African monsoon: upper tropospheric ice clouds, mesoscale convective system outflow, and subvisual cirrus

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-11-745-2011 ◽

2011 ◽

Vol 11 (1) ◽

pp. 745-812 ◽

Cited By ~ 4

Author(s):

W. Frey ◽

S. Borrmann ◽

D. Kunkel ◽

R. Weigel ◽

M. de Reus ◽

...

Keyword(s):

Water Content ◽

Potential Temperature ◽

In Situ Measurements ◽

Size Distributions ◽

Ice Crystal ◽

Cloud Particle ◽

Ice Particles ◽

Ice Water Content ◽

Ice Water

Abstract. In-situ measurements of ice crystal size distributions in tropical upper troposphere/lower stratosphere (UT/LS) clouds were performed during the SCOUT-AMMA campaign over West Africa in August 2006. The cloud properties were measured with a Forward Scattering Spectrometer Probe (FSSP-100) and a Cloud Imaging Probe (CIP) operated aboard the Russian high altitude research aircraft M-55 ''Geophysica'' with the mission base in Ouagadougou, Burkina Faso. A total of 117 ice particle size distributions were obtained from the measurements in the vicinity of Mesoscale Convective Systems (MCS). Two or three modal lognormal size distributions were fitted to the average size distributions for different potential temperature bins. The measurements showed proportionate more large ice particles compared to former measurements above maritime regions. With the help of trace gas measurements of NO, NOy, CO2, CO, and O3, and satellite images clouds in young and aged MCS outflow were identified. These events were observed at altitudes of 11.0 km to 14.2 km corresponding to potential temperature levels of 346 K to 356 K. In a young outflow (developing MCS) ice crystal number concentrations of up to 8.3 cm−3 and rimed ice particles with maximum dimensions exceeding 1.5 mm were found. A maximum ice water content of 0.05 g m−3 was observed and an effective radius of about 90 μm. In contrast the aged outflow events were more diluted and showed a maximum number concentration of 0.03 cm−3, an ice water content of 2.3 × 10−4 g m−3, an effective radius of about 18 μm, while the largest particles had a maximum dimension of 61 μm. Close to the tropopause subvisual cirrus were encountered four times at altitudes of 15 km to 16.4 km. The mean ice particle number concentration of these encounters was 0.01 cm−3 with maximum particle sizes of 130 μm, and the mean ice water content was about 1.4 × 10−4 g m−3. All known in-situ measurements of subvisual tropopause cirrus are compared and an exponential fit on the size distributions is established in order to give a parameterisation for modelling. A comparison of aerosol to ice crystal number concentrations, in order to obtain an estimate on how many ice particles result from activation of the present aerosol, yielded low activation ratios for the subvisual cirrus cases of roughly one cloud particle per 30 000 aerosol particles, while for the MCS outflow cases this resulted in a high ratio of one cloud particle per 300 aerosol particles.

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Development of a Method to Detect High Ice Water Content Environments Using Machine Learning

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-19-0179.1 ◽

2020 ◽

Vol 37 (4) ◽

pp. 641-663

Author(s):

Julie A. Haggerty ◽

Allyson Rugg ◽

Rodney Potts ◽

Alain Protat ◽

J. Walter Strapp ◽

...

Keyword(s):

Machine Learning ◽

False Alarm ◽

Water Content ◽

Field Experiments ◽

Weather Prediction ◽

In Situ Measurements ◽

Probability Of Detection ◽

Ice Water Content ◽

Ice Water

AbstractThis paper describes development of a method for discriminating high ice water content (HIWC) conditions that can disrupt jet-engine performance in commuter and large transport aircraft. Using input data from satellites, numerical weather prediction models, and ground-based radar, this effort employs machine learning to determine optimal combinations of available information using fuzzy logic. Airborne in situ measurements of ice water content (IWC) from a series of field experiments that sampled HIWC conditions serve as training data in the machine-learning process. The resulting method, known as the Algorithm for Prediction of HIWC Areas (ALPHA), estimates the likelihood of HIWC conditions over a three-dimensional domain. Performance statistics calculated from an independent subset of data reserved for verification indicate that the ALPHA has skill for detecting HIWC conditions, albeit with significant false alarm rates. Probability of detection (POD), probability of false detection (POFD), and false alarm ratio (FAR) are 86%, 29% (60% when IWC below 0.1 g m−3 are omitted), and 51%, respectively, for one set of detection thresholds using in situ measurements. Corresponding receiver operating characteristic (ROC) curves give an area under the curve of 0.85 when considering all data and 0.69 for only points with IWC of at least 0.1 g m−3. Monte Carlo simulations suggest that aircraft sampling biases resulted in a positive POD bias and the actual probability of detection is between 78.5% and 83.1% (95% confidence interval). Analysis of individual case studies shows that the ALPHA output product generally tracks variation in the measured IWC.

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In situ measurements of tropical cloud properties in the West African Monsoon: upper tropospheric ice clouds, Mesoscale Convective System outflow, and subvisual cirrus

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-5569-2011 ◽

2011 ◽

Vol 11 (12) ◽

pp. 5569-5590 ◽

Cited By ~ 44

Author(s):

W. Frey ◽

S. Borrmann ◽

D. Kunkel ◽

R. Weigel ◽

M. de Reus ◽

...

Keyword(s):

Water Content ◽

Potential Temperature ◽

In Situ Measurements ◽

Size Distributions ◽

Ice Crystal ◽

Cloud Particle ◽

Ice Particles ◽

Ice Water Content ◽

Ice Water

Abstract. In situ measurements of ice crystal size distributions in tropical upper troposphere/lower stratosphere (UT/LS) clouds were performed during the SCOUT-AMMA campaign over West Africa in August 2006. The cloud properties were measured with a Forward Scattering Spectrometer Probe (FSSP-100) and a Cloud Imaging Probe (CIP) operated aboard the Russian high altitude research aircraft M-55 Geophysica with the mission base in Ouagadougou, Burkina Faso. A total of 117 ice particle size distributions were obtained from the measurements in the vicinity of Mesoscale Convective Systems (MCS). Two to four modal lognormal size distributions were fitted to the average size distributions for different potential temperature bins. The measurements showed proportionately more large ice particles compared to former measurements above maritime regions. With the help of trace gas measurements of NO, NOy, CO2, CO, and O3 and satellite images, clouds in young and aged MCS outflow were identified. These events were observed at altitudes of 11.0 km to 14.2 km corresponding to potential temperature levels of 346 K to 356 K. In a young outflow from a developing MCS ice crystal number concentrations of up to (8.3 ± 1.6) cm−3 and rimed ice particles with maximum dimensions exceeding 1.5 mm were found. A maximum ice water content of 0.05 g m−3 was observed and an effective radius of about 90 μm. In contrast the aged outflow events were more diluted and showed a maximum number concentration of 0.03 cm−3, an ice water content of 2.3 × 10−4 g m−3, an effective radius of about 18 μm, while the largest particles had a maximum dimension of 61 μm. Close to the tropopause subvisual cirrus were encountered four times at altitudes of 15 km to 16.4 km. The mean ice particle number concentration of these encounters was 0.01 cm−3 with maximum particle sizes of 130 μm, and the mean ice water content was about 1.4 × 10−4 g m−3. All known in situ measurements of subvisual tropopause cirrus are compared and an exponential fit on the size distributions is established for modelling purposes. A comparison of aerosol to ice crystal number concentrations, in order to obtain an estimate on how many ice particles may result from activation of the present aerosol, yielded low ratios for the subvisual cirrus cases of roughly one cloud particle per 30 000 aerosol particles, while for the MCS outflow cases this resulted in a high ratio of one cloud particle per 300 aerosol particles.

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Diagnosing the average spatio-temporal impact of convective systems – Part 1: A methodology for evaluating climate models

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-13-13653-2013 ◽

2013 ◽

Vol 13 (5) ◽

pp. 13653-13684

Author(s):

M. S. Johnston ◽

P. Eriksson ◽

S. Eliasson ◽

M. D. Zelinka ◽

R. M. Forbes ◽

...

Keyword(s):

Water Content ◽

Outgoing Longwave Radiation ◽

Deep Convection ◽

Longwave Radiation ◽

Cloud Fraction ◽

Ice Water Content ◽

The Mean ◽

Spatio Temporal ◽

Cloud Ice ◽

Ice Water

Abstract. A~method to determine the mean response of upper tropospheric water to localised deep convective (DC) events is improved and applied to the EC-Earth climate model. Following Zelinka and Hartmann (2009), several fields related to moist processes and radiation are composited with respect to local maxima in rain rate to determine their spatio-temporal evolution with deep convection in the central Pacific Ocean. Major improvements to the above study are the isolation of DC events in time so as to prevent multiple sampling of the same event, and a revised definition of the mean background state that allows for better characterization of the DC-induced anomalies. The DC events observed in this study propagate westward at ~ 4 m s−1. Both the upper tropospheric relative humidity and outgoing longwave radiation are substantially perturbed over a broad horizontal extent during peak convection and for long periods of time. Cloud fraction anomaly increases throughout the upper troposphere, especially in the 200–250 hPa layer, reaching peak coverage following deep convection. Cloud ice water content anomaly confined to pressures greater than about 250 hPa and peaks near 450 hPa within a few hours of the DC event but remain enhanced following the DC event. Consistent with the large increase in upper tropospheric cloud ice, albedo increases dramatically and persists for sometime following the DC event. Applying the method to the model demonstrates that it is able to capture the large-scale responses to DC events, most notably for outgoing longwave radiation, but there are a number of important differences. For example, the DC signature of upper tropospheric humidity consistently covers a broader horizontal area than what is observed. In addition, the DC events move eastward in the model, but westward in the observations, and exhibit an unrealistic 24 h repeat cycle. Moreover, the modeled upper tropospheric cloud fraction anomalies – despite being of comparable magnitude and exhibiting similar longevity – are confined to a thinner layer that is closer to the tropopause and peak earlier than in observations. Finally, the modeled ice water content anomalies at pressures greater than about 350 hPa are about twice as large as in the observations and do not persist as long after peak convection.

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Variability of Microphysical Parameters in High-Altitude Ice Clouds: Results of the Remote Sensing Method

Journal of Applied Meteorology ◽

10.1175/1520-0450-36.6.633 ◽

1997 ◽

Vol 36 (6) ◽

pp. 633-648 ◽

Cited By ~ 36

Author(s):

Sergey Y. Matrosov

Keyword(s):

Remote Sensing ◽

Water Content ◽

Cloud Microphysics ◽

Cloud Base ◽

Particle Sizes ◽

Ice Clouds ◽

Cloud Parameters ◽

Microphysical Parameters ◽

Ice Water Content ◽

Ice Water

Abstract The remote sensing method for retrieving vertical profiles of microphysical parameters in ice clouds from ground-based measurements taken by the Doppler radar and IR radiometer was applied to several cloud cases observed during different field experiments including FIRE-II, ASTEX, and the Arizona Program. The measurements were performed with the NOAA Environmental Technology Laboratory instrumentation. The observed ice clouds were mostly cirrus clouds located in the upper troposphere above 5.6 km. Their geometrical thicknesses varied from a few hundred meters to 3 km. Characteristic cloud particle sizes expressed in median mass diameters of equal-volume spheres varied from about 25 μm to more than 400 μm. Typically, characteristic particle sizes were increasing toward the cloud base, with the exception of the lowest range gates where particles were quickly sublimating. Highest particle concentrations were usually observed near the cloud tops. The vertical variability of particle sizes inside an individual cloud could reach one order of magnitude. The standard deviation of the mean profile for a typical cloud is usually factor of 2 or 3 smaller than mean values of particle characteristic size. Typical values of retrieved cloud ice water content varied from 1 to 100 mg m−3; however, individual variations were as high as four orders of magnitude. There was no consistent pattern in the vertical distribution of ice water content except for the rapid decrease in the vicinity of the cloud base. The relationships between retrieved cloud parameters and measured radar reflectivities were considered. The uncertainty of estimating cloud parameters from the power-law regressions is discussed. The parameters of these regressions varied from cloud to cloud and were comparable to the parameters in corresponding regressions obtained from direct particle sampling in other experiments. Relationships between cloud microphysical parameters and reflectivity can vary even for the same observational case. The variability diminishes if stronger reflectivities are considered. A procedure of “tuning” cloud microphysics–reflectivity regressions for individual profiles is suggested. Such a procedure can simplify the radar–radiometer method and make it applicable for a broader range of clouds.

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Ice Crystal Sizes in High Ice Water Content Clouds. Part I: On the Computation of Median Mass Diameter from In Situ Measurements

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-15-0151.1 ◽

2016 ◽

Vol 33 (11) ◽

pp. 2461-2476 ◽

Cited By ~ 17

Author(s):

D. Leroy ◽

E. Fontaine ◽

A. Schwarzenboeck ◽

J. W. Strapp

Keyword(s):

Water Content ◽

Image Data ◽

In Situ Measurements ◽

Ice Crystals ◽

Commercial Aircraft ◽

Mass Distributions ◽

Ice Water Content ◽

Definition Of ◽

Ice Water

AbstractEngine and air data probe manufacturers, as well as aviation agencies, are interested in better characterization of high ice water content (HIWC) areas close to thunderstorms, since HIWC conditions are suspected to cause in-service engine power loss and air data events on commercial aircraft. In this context, a collaborative field campaign has been conducted by high-altitude ice crystals (HAIC) and HIWC projects in order to provide ice water content and median mass diameter (MMD) of ice crystals in the HIWC environment.The computation of MMD from in situ measurements relies mainly on the definition of the crystal dimension D and on the relationship, which is used to convert number into mass distributions. The first part of this study shows that MMD can significantly deviate when using different mass–size relationships from the literature. Sensitivity tests demonstrate that MMD is significantly impacted by the choice of β. However, the larger contributor to MMD differences seems to be the choice of the size definition D itself.Since MMDs are quite sensitive to β, this study suggests a generic method for deducing β solely from optical array probes (OAPs) image data for various size definitions. The method is based on simulations of 3D crystal objects projected onto a 2D plane, thereby relating crystal mass to 2D area (projection) and perimeter. The MMD values calculated for different size definitions are quite similar, at least much closer than MMDs derived from different m(D) relationships in the literature.

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