scholarly journals Evaluation of differential absorption radars in the 183 GHz band for profiling water vapour in ice clouds

2019 ◽  
Vol 12 (6) ◽  
pp. 3335-3349 ◽  
Author(s):  
Alessandro Battaglia ◽  
Pavlos Kollias
Keyword(s):  
Relative Humidity ◽  
Water Vapour ◽  
Vertical Resolution ◽  
Ice Crystal ◽  
Differential Absorption ◽  
Ice Clouds ◽  
Microphysical Properties ◽  
W Band ◽  
Vapour Density ◽  
Water Vapour Absorption

Abstract. Relative humidity (RH) measurements in ice clouds are essential for determining ice crystal growth processes and rates. A differential absorption radar (DAR) system with several frequency channels within the 183.3 GHz water vapour absorption band is proposed for measuring RH within ice clouds. Here, the performance of a DAR system is evaluated by applying a DAR simulator to A-Train observations in combination with co-located European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis. Observations from the CloudSat W-band radar and from the CALIPSO lidar are converted first into ice microphysical properties and then coupled with ECMWF temperature and relative humidity profiles in order to compute scattering properties at any frequency within the 183.3 GHz band. A self-similar Rayleigh–Gans approximation is used to model the ice crystal scattering properties. The radar reflectivities are computed both for a space-borne and airborne and a ground-based DAR system by using appropriate radar receiver characteristics. Sets of multi-frequency synthetic observation of attenuated reflectivities are then exploited to retrieve profiles of water vapour density by fitting the line shape at different levels. A total of 10 d of A-Train observations are used to test the measurement technique performance for different combinations of tones when sampling ice clouds globally. Results show that water vapour densities can be derived at the level that can enable ice process studies (i.e. better than 3 %), both from a ground-based system (at the minute temporal scale and with circa 100 m vertical resolution) and from a space-borne system (at 500 m vertical resolution and with circa 5 km integration lengths) with four tones in the upper wing of the absorption line. Deploying ground-based DAR system at high latitudes and high altitudes is highly recommended to test the findings of this work in the field.

scholarly journals Evaluation of differential absorption radars in the 183 GHz band for profiling water vapour in ice clouds

2019 ◽  
Author(s):  
Alessandro Battaglia ◽  
Pavlos Kollias
Keyword(s):  
Relative Humidity ◽  
Water Vapour ◽  
Vertical Resolution ◽  
Differential Absorption ◽  
Ice Clouds ◽  
Microphysical Properties ◽  
W Band ◽  
Vapour Density ◽  
Water Vapour Absorption ◽  
The Right

Abstract. Relative humidity (RH) measurements in ice clouds are essential for determining the ice crystals growth processes and rates. A differential absorption radar (DAR) system with several frequency channels within the 183.3 GHz water vapour absorption band is proposed for measuring RH within ice clouds. Here, the performance of a DAR system is evaluated by applying a DAR simulator to A-Train observations in combination with collocated European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis. Observations from the CloudSat W-band radar and from the CALIPSO lidar are converted first into ice microphysical properties and then coupled with ECMWF temperature and relative humidity profiles in order to compute scattering properties at any frequency within the 183.3 GHz band. Self-similar Rayleigh Gans approximation is used to model the ice crystal scattering properties. The radar reflectivities are computed both for a space-borne and a ground-based DAR system by using appropriate radar receiver characteristics. Sets of multi-frequency synthetic observation of attenuated reflectivities are then used to retrieve profile of water vapour density by fitting the line shape at different levels. 10 days of A-Train observations are used to test the measurement technique performance for different combination of tones when sampling ice clouds globally. Results show that that water vapour densities can be derived with accuracies that can enable ice process studies (i.e. better than 3 %) both from a ground-based system (at the minute temporal scale and with circa 100 m vertical resolution) and from a space/airborne system (at 500 m vertical resolution and with circa 5 km integration lengths) with four tones in the right wing of the absorption line. A ground-based DAR system to be deployed at high latitude/high altitudes is highly recommended to test the findings of this work in the field.

scholarly journals Direct comparisons of ice cloud macro- and microphysical properties simulated by the Community Atmosphere Model version 5 with HIPPO aircraft observations

2017 ◽  
Vol 17 (7) ◽  
pp. 4731-4749 ◽  
Author(s):  
Chenglai Wu ◽  
Xiaohong Liu ◽  
Minghui Diao ◽  
Kai Zhang ◽  
Andrew Gettelman ◽  
...  
Keyword(s):  
Nucleation And Growth ◽  
Ice Nucleation ◽  
Ice Crystal ◽  
Ice Clouds ◽  
Model Version ◽  
Microphysical Properties ◽  
Cloud Properties ◽  
Community Atmosphere Model ◽  
Atmosphere Model ◽  
Ice Water

Abstract. In this study we evaluate cloud properties simulated by the Community Atmosphere Model version 5 (CAM5) using in situ measurements from the HIAPER Pole-to-Pole Observations (HIPPO) campaign for the period of 2009 to 2011. The modeled wind and temperature are nudged towards reanalysis. Model results collocated with HIPPO flight tracks are directly compared with the observations, and model sensitivities to the representations of ice nucleation and growth are also examined. Generally, CAM5 is able to capture specific cloud systems in terms of vertical configuration and horizontal extension. In total, the model reproduces 79.8 % of observed cloud occurrences inside model grid boxes and even higher (94.3 %) for ice clouds (T ≤ −40 °C). The missing cloud occurrences in the model are primarily ascribed to the fact that the model cannot account for the high spatial variability of observed relative humidity (RH). Furthermore, model RH biases are mostly attributed to the discrepancies in water vapor, rather than temperature. At the micro-scale of ice clouds, the model captures the observed increase of ice crystal mean sizes with temperature, albeit with smaller sizes than the observations. The model underestimates the observed ice number concentration (Ni) and ice water content (IWC) for ice crystals larger than 75 µm in diameter. Modeled IWC and Ni are more sensitive to the threshold diameter for autoconversion of cloud ice to snow (Dcs), while simulated ice crystal mean size is more sensitive to ice nucleation parameterizations than to Dcs. Our results highlight the need for further improvements to the sub-grid RH variability and ice nucleation and growth in the model.

scholarly journals Statistical downscaling of water vapour satellite measurements from profiles of tropical ice clouds

2020 ◽  
Vol 12 (1) ◽  
pp. 1-20 ◽  
Author(s):  
Giulia Carella ◽  
Mathieu Vrac ◽  
Hélène Brogniez ◽  
Pascal Yiou ◽  
Hélène Chepfer
Keyword(s):  
Relative Humidity ◽  
Water Vapour ◽  
Water Cycle ◽  
Skill Score ◽  
Horizontal Resolution ◽  
Coefficient Of Determination ◽  
Climate Projections ◽  
Ice Clouds ◽  
Multi Scale ◽  
Scattering Ratio

Abstract. Multi-scale interactions between the main players of the atmospheric water cycle are poorly understood, even in the present-day climate, and represent one of the main sources of uncertainty among future climate projections. Here, we present a method to downscale observations of relative humidity available from the Sondeur Atmosphérique du Profil d'Humidité Intertropical par Radiométrie (SAPHIR) passive microwave sounder at a nominal horizontal resolution of 10 km to the finer resolution of 90 m using scattering ratio profiles from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) lidar. With the scattering ratio profiles as covariates, an iterative approach applied to a non-parametric regression model based on a quantile random forest is used. This allows us to effectively incorporate into the predicted relative humidity structure the high-resolution variability from cloud profiles. The finer-scale water vapour structure is hereby deduced from the indirect physical correlation between relative humidity and the lidar observations. Results are presented for tropical ice clouds over the ocean: based on the coefficient of determination (with respect to the observed relative humidity) and the continuous rank probability skill score (with respect to the climatology), we conclude that we are able to successfully predict, at the resolution of cloud measurements, the relative humidity along the whole troposphere, yet ensure the best possible coherence with the values observed by SAPHIR. By providing a method to generate pseudo-observations of relative humidity (at high spatial resolution) from simultaneous co-located cloud profiles, this work will help revisit some of the current key barriers in atmospheric science. A sample dataset of simultaneous co-located scattering ratio profiles of tropical ice clouds and observations of relative humidity downscaled at the resolution of cloud measurements is available at https://doi.org/10.14768/20181022001.1 (Carella et al., 2019).

OSMOLALITY AND ELECTROLYTE COMPOSITION OF PLEON FLUID IN PORCELLIO SCABER (CRUSTACEA, ISOPQDA, ONISCIDEA): IMPLICATIONS FOR WATER VAPOUR ABSORPTION

1992 ◽  
Vol 164 (1) ◽  
pp. 189-203 ◽  
Author(s):  
JONATHAN C. WRIGHT ◽  
MICHAEL J. O'DONNELL
Keyword(s):  
Relative Humidity ◽  
Water Vapour ◽  
Fluid Secretion ◽  
Electrolyte Composition ◽  
Fluid Volume ◽  
Ambient Water ◽  
Porcellio Scaber ◽  
Endogenous Production ◽  
Water Vapour Absorption ◽  
Microelectrode Measurements

Active water vapour absorption in Porcellio scaber is associated with the endogenous production of strongly hyperosmotic fluid in the pleoventral chamber (pleoventralraum; PV). Pre-desiccated animals show increased pleon fluid secretion within 1–2 min of transfer to suprathreshold humidities (>87 % relative humidity). The conspicuous increase in fluid volume is accompanied by a rise in osmolality from isosmotic (approximately 750mosmolkg−1) up to as much as 8.2osmolkg−1. Vapour absorption is marked by the onset of metachronal pleopodal ventilation and a subsequent decline in fluid osmolality as uptake fluid approaches equilibrium with ambient water activities. The effects of sealing of the PV by the margins of the depressed pleopods, along with the observation that animals ventilate even when PV fluid activities are somewhat below ambient, suggest that resultant pressure increases may elevate humidity within the PV and thereby augment vapour uptake. Ion-selective microelectrode measurements of Na+, K+, Ca2+ and Cl− concentrations in nanolitre samples of isolated pleon fluid identify Na+ and Cl− as the major osmolytes. Possible preadaptions favouring evolution of vapour absorption in the Oniscidea are discussed

Microphysical Properties of Ice Crystal Precipitation and Surface-Generated Ice Crystals in a High Alpine Environment in Switzerland

2017 ◽  
Vol 56 (2) ◽  
pp. 433-453 ◽  
Author(s):  
Oliver Schlenczek ◽  
Jacob P. Fugal ◽  
Gary Lloyd ◽  
Keith N. Bower ◽  
Thomas W. Choularton ◽  
...  
Keyword(s):  
Ice Crystals ◽  
Crystal Habit ◽  
The Arctic ◽  
Spatial And Temporal Variability ◽  
Research Station ◽  
Size Distributions ◽  
Ice Crystal ◽  
Ice Clouds ◽  
Microphysical Properties ◽  
The Individual

AbstractDuring the Cloud and Aerosol Characterization Experiment (CLACE) 2013 field campaign at the High Altitude Research Station Jungfraujoch, Switzerland, optically thin pure ice clouds and ice crystal precipitation were measured using holographic and other in situ particle instruments. For cloud particles, particle images, positions in space, concentrations, and size distributions were obtained, allowing one to extract size distributions classified by ice crystal habit. Small ice crystals occurring under conditions with a vertically thin cloud layer above and a stratocumulus layer approximately 1 km below exhibit similar properties in size and crystal habits as Antarctic/Arctic diamond dust. Also, ice crystal precipitation stemming from midlevel clouds subsequent to the diamond dust event was observed with a larger fraction of ice crystal aggregates when compared with the diamond dust. In another event, particle size distributions could be derived from mostly irregular ice crystals and aggregates, which likely originated from surface processes. These particles show a high spatial and temporal variability, and it is noted that size and habit distributions have only a weak dependence on the particle number concentration. Larger ice crystal aggregates and rosette shapes of some hundred microns in maximum dimension could be sampled as a precipitating cirrostratus cloud passed the site. The individual size distributions for each habit agree well with lognormal distributions. Fitted parameters to the size distributions are presented along with the area-derived ice water content, and the size distributions are compared with other measurements of pure ice clouds made in the Arctic and Antarctic.

scholarly journals Bulk microphysical properties of semi transparent cirrus from AIRS: a six years global climatology and statistical analysis in synergy with CALIPSO and CloudSat

2011 ◽  
Vol 11 (9) ◽  
pp. 24671-24725
Author(s):  
A. Guignard ◽  
C. J. Stubenrauch ◽  
A. J. Baran ◽  
R. Armante
Keyword(s):  
Statistical Analysis ◽  
General Circulation ◽  
General Circulation Models ◽  
Single Scattering ◽  
Ice Crystals ◽  
Effective Diameter ◽  
Ice Crystal ◽  
Ice Clouds ◽  
Microphysical Properties ◽  
Ice Water

Abstract. This article presents a retrieval method and a statistical analysis of the bulk micropysical properties of semi-transparent ice clouds using the Atmospheric Infrared Sounder (AIRS). Global and long-term coverage provides information on the effective diameter (De) and habits of ice crystals in relation with their environment, ice water path (IWP) and temperature. The method relies on spectral absorption differences between 8 and 12 μm that depend on ice crystal properties. Using single scattering properties for column-like or aggregate-like ice crystals, the method is sensitive to De of up to 85 μm and IWP of up to 120 g m−2. Uncertainties due to the hypotheses on atmospheric parameters and ice crystal single scattering properties as well as horizontal heterogeneities have been demonstrated to be small. The behaviour of bulk microphysical properties as a function of temperature demonstrates that pure ice clouds only occur when Tcld<230 K. On a global scale, these clouds represent practically 25 % of all high clouds and are mainly encountered in the mid-latitudes during winter and in the tropics. Colocated Radar-Lidar Geometrical Profiling (GEOPROF) data reveal an increase in the vertical extent of these cloud layers during mid-latitude winter but which does not significantly impact ice crystal characteristics. A comparative study with bulk microphysical properties from the TIROS-N Operational Vertical Sounder (TOVS) reveals improvements, especially for optically thin and thick semi-transparent ice clouds. Finally, we investigated parametrizations of De as a function of IWP or Ice Water Content (IWC), which could be useful for modelling cirrus in General Circulation Models.

An Effective Radius Retrieval for Thick Ice Clouds Using GOES

2008 ◽  
Vol 47 (4) ◽  
pp. 1222-1231 ◽  
Author(s):  
Daniel T. Lindsey ◽  
Louie Grasso
Keyword(s):  
Crystal Size ◽  
Difficult Problem ◽  
Effective Radius ◽  
Ice Crystal ◽  
Ice Clouds ◽  
Ice Cloud ◽  
Satellite Retrieval ◽  
Microphysical Properties ◽  
Ice Crystal Size ◽  
Shortwave Infrared

Abstract Satellite retrieval of cirrus cloud microphysical properties is an important but difficult problem because of uncertainties in ice-scattering characteristics. Most methods have been developed for instruments aboard polar-orbiting satellites, which have better spatial and spectral resolution than geostationary sensors. The Geostationary Operational Environmental Satellite (GOES) series has the advantage of excellent temporal resolution, so that the evolution of thunderstorm-cloud-top properties can be monitored. In this paper, the authors discuss the development of a simple ice cloud effective radius retrieval for thick ice clouds using three bands from the GOES imager: one each in the visible, shortwave infrared, and window infrared portion of the spectrum. It is shown that this retrieval compares favorably to the MODIS effective radius algorithm. In addition, a comparison of the retrieval for clouds viewed simultaneously from GOES-East and GOES-West reveals that the assumed ice-scattering properties perform very well. The algorithm is then used to produce maps of mean ice cloud effective radius over the continental United States. A real-time version of this retrieval is currently running and may be used to study the evolution of thunderstorm-top ice crystal size in rapidly evolving convection.

scholarly journals Classification of Ice Crystal Shapes in Midlatitude Ice Clouds from Three Years of Lidar Observations over the SIRTA Observatory

2006 ◽  
Vol 63 (11) ◽  
pp. 2978-2991 ◽  
Author(s):  
Vincent Noel ◽  
Helene Chepfer ◽  
Martial Haeffelin ◽  
Yohann Morille
Keyword(s):  
Relative Concentration ◽  
Strong Dependence ◽  
Depolarization Ratio ◽  
Ice Crystal ◽  
Jet Streams ◽  
Ice Clouds ◽  
Wind Speeds ◽  
Crystal Shapes ◽  
Microphysical Properties ◽  
Aspect Ratios

Abstract This paper presents a study of ice crystal shapes in midlatitude ice clouds inferred from a technique based on the comparison of ray-tracing simulations with lidar depolarization ratio measured at 532 nm. This technique is applied to three years of lidar depolarization ratio observations from the Site Instrumental de Recherche par Télédétection Atmosphérique (SIRTA) observatory in Palaiseau, France, amounting to 322 different days of ice cloud observations. Particles in clouds are classified in three major groups: plates, columns, and irregular shapes with aspect ratios close to unity. Retrieved shapes are correlated with radiosounding observations from a close-by meteorological station: temperature, relative humidity, wind speed, and direction. Results show a strong dependence of the relative concentration of different crystal shapes to most atmospheric variables, such as the temperature, with a clear successive dominance by platelike (temperature above −20°C), irregular (temperatures between −60° and −40°C), and columnlike shapes (temperatures below −60°C). Particle shapes are almost exclusively columnlike below −75°C. This is in sharp contrast with previous results of the same classification applied to tropical clouds, and highlights the high geographic variability of the ice clouds distribution of microphysical properties. Results also suggest that ice clouds created by jet streams (identified by high wind speeds) are strongly dominated by columnlike shapes, while front-created ice clouds (identified by lower wind speeds) show a much more variable mix of shapes, with the dominant shapes depending on other factors. Results also suggest different microphysical properties according to the average direction source of air masses and winds. Following these results, a possible parameterization of ice crystal shapes in midlatitude ice clouds as a function of temperature is provided.

scholarly journals Direct comparisons of ice cloud macro- and microphysical properties simulated by the Community Atmosphere Model version 5 with HIPPO aircraft observations

2017 ◽  
Author(s):  
Chenglai Wu ◽  
Xiaohong Liu ◽  
Minghui Diao ◽  
Kai Zhang ◽  
Andrew Gettelman ◽  
...  
Keyword(s):  
Nucleation And Growth ◽  
Ice Nucleation ◽  
Ice Crystal ◽  
Ice Clouds ◽  
Model Version ◽  
Microphysical Properties ◽  
Cloud Properties ◽  
Community Atmosphere Model ◽  
Atmosphere Model ◽  
Ice Water

Abstract. In this study we evaluate cloud properties simulated by the Community Atmosphere Model Version 5 (CAM5) using in-situ measurements from the HIAPER Pole-to-Pole Observations (HIPPO) for the period of 2009 to 2011. The modeled wind and temperature are nudged towards reanalysis. Model results collocated with HIPPO flight tracks are directly compared with the observations, and model sensitivities to the representations of ice nucleation and growth are also examined. Generally, CAM5 is able to capture specific cloud systems in terms of vertical configuration and horizontal extension. In total, the model reproduces 79.8 % of observed cloud occurrences inside model grid boxes, and even higher (94.3 %) for ice clouds (T ≤ −40 °C). The missing cloud occurrences in the model are primarily ascribed to the fact that the model cannot account for the high spatial variability of observed relative humidity (RH). Furthermore, model RH biases are mostly attributed to the discrepancies in water vapor, rather than temperature. At the micro-scale of ice clouds, the model captures the observed increase of ice crystal mean sizes with temperature, albeit with smaller sizes than the observations. The model underestimates the observed ice number concentration (Ni) and ice water content (IWC) for ice crystals larger than 75 μm in diameter. Modeled IWC and Ni are more sensitive to the threshold diameter for autoconversion of cloud ice to snow (Dcs), while simulated ice crystal mean size is more sensitive to ice nucleation parameterizations than to Dcs. Our results highlight the need for further improvements to the sub-grid RH variability and ice nucleation and growth in the model.

scholarly journals The origin of midlatitude ice clouds and the resulting influence on their microphysical properties

2015 ◽  
Vol 15 (23) ◽  
pp. 34243-34281 ◽  
Author(s):  
A. E. Luebke ◽  
A. Afchine ◽  
A. Costa ◽  
J. Meyer ◽  
C. Rolf ◽  
...  
Keyword(s):  
Bimodal Distribution ◽  
Cirrus Clouds ◽  
Ice Crystals ◽  
Radiative Properties ◽  
Ice Crystal ◽  
Ice Clouds ◽  
Microphysical Properties ◽  
Ice Crystal Size ◽  
Ice Water

Abstract. The radiative role of ice clouds in the atmosphere is known to be important, but uncertainties remain concerning the magnitude and net effects. However, through measurements of the microphysical properties of cirrus clouds, we can better characterize them, which can ultimately allow for their radiative properties to be more accurately ascertained. It has recently been proposed that there are two types of cirrus clouds – in situ and liquid origin. In this study, we present observational evidence to show that two distinct types of cirrus do exist. Airborne, in situ measurements of cloud ice water content (IWC), ice crystal concentration (Nice), and ice crystal size from the 2014 ML-CIRRUS campaign provide cloud samples that have been divided according to their origin type. The key features that set liquid origin cirrus apart from the in situ origin cirrus are a higher frequency of high IWC (> 100 ppmv), higher Nice values, and larger ice crystals. A vertical distribution of Nice shows that the in situ origin cirrus clouds exhibit a median value of around 0.1 cm−3, while the liquid origin concentrations are slightly, but notably higher. The median sizes of the crystals contributing the most mass are less than 200 μm for in situ origin cirrus, with some of the largest crystals reaching 550 μm in size. The liquid origin cirrus, on the other hand, were observed to have median diameters greater than 200 μm, and crystals that were up to 750 μm. An examination of these characteristics in relation to each other and their relationship to temperature provides strong evidence that these differences arise from the dynamics and conditions in which the ice crystals formed. Additionally, the existence of these two groups in cirrus cloud populations may explain why a bimodal distribution in the IWC-temperature relationship has been observed. We hypothesize that the low IWC mode is the result of in situ origin cirrus and the high IWC mode is the result of liquid origin cirrus.

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