scholarly journals Vertical Structure of Ice Clouds and Vertical Air Motion from Vertically Pointing Cloud Radar Measurements

2021 ◽  
Vol 13 (21) ◽  
pp. 4349
Author(s):  
Bo-Young Ye ◽  
GyuWon Lee
Keyword(s):  
Vertical Structure ◽  
Cirrus Clouds ◽  
Doppler Velocity ◽  
Upward Motion ◽  
Fall Velocity ◽  
Ice Clouds ◽  
Cloud Radar ◽  
Ice Particles ◽  
Stratiform Clouds ◽  
Air Motion

The vertical structure of ice clouds and vertical air motion (Vair) were investigated using vertically pointing Ka-band cloud radar. The distributions of reflectivity (Z), Doppler velocity (VD), and spectrum width (SW) were analyzed for three ice cloud types, namely, cirrus, anvil, and stratiform clouds. The radar parameters of the cirrus clouds showed narrower distributions than those of the stratiform and anvil clouds. In the vertical structures, the rapid growth of Z and VD occurred in the layer between 8 and 12 km (roughly a layer of −40 °C to −20 °C) for all ice clouds. The prominent feature in the stratiform clouds was an elongated “S” shape in the VD near 7–7.5 km (at approximately −16 °C to −13 °C) due to a significant decrease in an absolute value of VD. The mean terminal fall velocity (Vt) and Vair in the ice clouds were estimated using pre-determined Vt–Z relationships (Vt = aZb) and the observed VD. Although the cirrus clouds demonstrated wide distributions in coefficients a and exponents b depending on cloud heights, they showed a smaller change in Z and Vt values compared to that of the other cloud types. The anvil clouds had a larger exponent than that of the stratiform clouds, indicating that the ice particle density of anvil clouds increases at a faster rate compared with the density of stratiform clouds for the same Z increment. The significant positive Vair appeared at the top of all ice clouds in range up to 0.5 m s−1, and the anvil clouds showed the deepest layer of upward motion. The stratiform and anvil clouds showed a dramatic increase in vertical air motion in the layer of 6–8 km as shown by the rapid decrease of VD. This likely caused increase of supersaturation above. A periodic positive Vair linked with a significant reduction in VD appeared at the height of 7–8 km (approximately −15 °C) dominantly in the stratiform clouds. This layer exhibited a bi-modal power spectrum produced by pre-existing larger ice particles and newly formed numerous smaller ice particles. This result raised a question on the origins of smaller ice particles such as new nucleation due to increased supersaturation by upward motion below or the seeder-feeder effect. In addition, the retrieved Vair with high-resolution data well represented a Kelvin-Helmholtz wave development.

Cirrus Microphysical Properties and Air Motion Statistics Using Cloud Radar Doppler Moments. Part II: Climatology

2008 ◽  
Vol 47 (12) ◽  
pp. 3221-3235 ◽  
Author(s):  
Min Deng ◽  
Gerald G. Mace
Keyword(s):  
Great Plains ◽  
Seasonal Variations ◽  
Radiative Heating ◽  
Ice Clouds ◽  
Cloud Radar ◽  
Microphysical Properties ◽  
Cloud Properties ◽  
Early Afternoon ◽  
Seasonal And Diurnal Variations ◽  
Air Motion

Abstract The algorithm described in Part I has been applied to the millimeter cloud radar observations from January 1999 to December 2005 at the Atmospheric Radiation Measurement Program (ARM) Southern Great Plains (SGP) and Tropical Western Pacific (including Manus and Nauru) sites. Approximately 10 000 cirrus hours from each of these sites were analyzed. Retrieved cloud properties including condensed mass, particle size, optical depth, and in-cloud vertical air motions were analyzed in terms of their geographical, seasonal, and diurnal variations. The analysis shows that tropical ice clouds observed by millimeter radar are very different from ice clouds at SGP, with the tropical clouds having slightly larger particle sizes and greater ice masses and being more likely to be associated with ascending air motions, in addition to being colder and higher in altitude. A positive residual of derived in-cloud air motion found in the tropical data likely provides evidence for lofting of air into the tropopause transition layer as a result of radiative heating. The midlatitude cirrus demonstrate strong seasonal variations with more frequent, thicker clouds occurring during the summer than during the winter. Very subtle seasonal variations are found for tropical ice clouds, and evidence is presented that cirrus properties vary interannually and are correlated with El Niño oscillations. In addition, it is found that tropical cirrus demonstrate a stronger diurnal cycle than cirrus of the midlatitudes, with the in-cloud updrafts peaking in the early afternoon.

scholarly journals Combining cloud radar and radar wind profiler for a value added estimate of vertical air motion and particle terminal velocity within clouds

2018 ◽  
Author(s):  
Martin Radenz ◽  
Johannes Bühl ◽  
Volker Lehmann ◽  
Ulrich Görsdorf ◽  
Ronny Leinweber
Keyword(s):  
Value Added ◽  
Terminal Velocity ◽  
Wind Profiler ◽  
Air Velocity ◽  
Fall Velocity ◽  
Cloud Radar ◽  
A Value ◽  
Direct Measurements ◽  
Air Motion ◽  
Better Than

Abstract. Vertical-stare observations from a 482 MHz radar wind profiler and a 35 GHz cloud radar are combined on the level of individual Doppler spectra to measure vertical air motions in clear air, clouds and precipitation. For this purpose, a separation algorithm is proposed to remove the influence of falling particles from the wind profiler Doppler spectra and to calculate the terminal fall velocity of hydrometeors. The remaining error of both vertical air motion and terminal fall velocity is estimated to be better than 0.1 m s−1 using numerical simulations. This combination of both instruments allows direct measurements of in-cloud vertical air velocity and particle terminal fall velocity by means of ground-based remote sensing. The possibility of providing a profile every 10 s with a height resolution of

scholarly journals Evaluation of gridded scanning ARM cloud radar reflectivity observations and vertical doppler velocity retrievals

2014 ◽  
Vol 7 (4) ◽  
pp. 1089-1103 ◽  
Author(s):  
K. Lamer ◽  
A. Tatarevic ◽  
I. Jo ◽  
P. Kollias
Keyword(s):  
Great Plains ◽  
Spatial Scales ◽  
Domain Size ◽  
Horizontal Wind ◽  
Cape Cod ◽  
Doppler Velocity ◽  
Cloud Radar ◽  
Stratiform Clouds ◽  
Atmospheric Observations ◽  
Atmospheric Radiation Measurement

Abstract. The scanning Atmospheric Radiation Measurement (ARM) cloud radars (SACRs) provide continuous atmospheric observations aspiring to capture the 3-D cloud-scale structure. Sampling clouds in 3-D is challenging due to their temporal–spatial scales, the need to sample the sky at high elevations and cloud radar limitations. Thus, a suggested scan strategy is to repetitively slice the atmosphere from horizon to horizon as clouds advect over the radar (Cross-Wind Range-Height Indicator – CW-RHI). Here, the processing and gridding of the SACR CW-RHI scans are presented. First, the SACR sample observations from the ARM Southern Great Plains and Cape Cod sites are post-processed (detection mask, gaseous attenuation correction, insect filtering and velocity de-aliasing). The resulting radial Doppler moment fields are then mapped to Cartesian coordinates with time as one of the dimensions. Next the Cartesian-gridded Doppler velocity fields are decomposed into the horizontal wind velocity contribution and the vertical Doppler velocity component. For validation purposes, all gridded and retrieved fields are compared to collocated zenith-pointing ARM cloud radar measurements. We consider that the SACR sensitivity loss with range, the cloud type observed and the research purpose should be considered in determining the gridded domain size. Our results also demonstrate that the gridded SACR observations resolve the main features of low and high stratiform clouds. It is established that the CW-RHI observations complemented with processing techniques could lead to robust 3-D cloud dynamical representations up to 25–30 degrees off zenith. The proposed gridded products are expected to advance our understanding of 3-D cloud morphology, dynamics and anisotropy and lead to more realistic 3-D radiative transfer calculations.

scholarly journals Combining cloud radar and radar wind profiler for a value added estimate of vertical air motion and particle terminal velocity within clouds

2018 ◽  
Vol 11 (10) ◽  
pp. 5925-5940 ◽  
Author(s):  
Martin Radenz ◽  
Johannes Bühl ◽  
Volker Lehmann ◽  
Ulrich Görsdorf ◽  
Ronny Leinweber
Keyword(s):  
Value Added ◽  
Terminal Velocity ◽  
Wind Profiler ◽  
Separation Algorithm ◽  
Fall Velocity ◽  
Cloud Radar ◽  
A Value ◽  
Cloud Dynamics ◽  
Direct Measurements ◽  
Air Motion

Abstract. Vertical-stare observations from a 482 MHz radar wind profiler and a 35 GHz cloud radar are combined on the level of individual Doppler spectra to measure vertical air motions in clear air, clouds and precipitation. For this purpose, a separation algorithm is proposed to remove the influence of falling particles from the wind profiler Doppler spectra and to calculate the terminal fall velocity of hydrometeors. The remaining error of both vertical air motion and terminal fall velocity is estimated to be better than 0.1 m s−1 using numerical simulations. This combination of instruments allows direct measurements of in-cloud vertical air velocity and particle terminal fall velocity by means of ground-based remote sensing. The possibility of providing a profile every 10 s with a height resolution of <100 m allows further insight into the process scale of in-cloud dynamics. The results of the separation algorithm are illustrated by two case studies, the first covering a deep frontal cloud and the second featuring a shallow mixed-phase cloud.

Finescale Vertical Structure and Evolution of a Preconvective Dryline on 19 June 2002

2007 ◽  
Vol 135 (6) ◽  
pp. 2111-2134 ◽  
Author(s):  
Benjamin D. Sipprell ◽  
Bart Geerts
Keyword(s):  
Vertical Structure ◽  
Radar Data ◽  
Doppler Velocity ◽  
Convective Boundary ◽  
Convective Initiation ◽  
Depth Difference ◽  
Cloud Radar ◽  
Later Phase ◽  
Total Elimination ◽  
Vertical Transect

Abstract High-resolution airborne cloud radar data and other International H2O Project datasets are used to describe the vertical structure of an unusual prefrontal dryline. This dryline, observed in northwestern Kansas on 19 June 2002, first progressed eastward and tilted toward the west, and later became more stationary and reversed its tilt, toward the moist side. The convective boundary layer (CBL) depth difference also reversed: only in the later phase did the dry-side CBL become deeper than on the moist side. Echo and single/dual-Doppler velocity data in a vertical transect across the dryline suggest a solenoidal circulation dynamically consistent with the observed horizontal buoyancy gradient. Both this gradient and the solenoidal circulation reversed in the later phase. Simultaneously, confluence toward the dryline increased, resulting in an increasing moisture gradient as well as a deepening CBL in the dryline convergence zone. It is speculated that the baroclinically generated horizontal vorticity contributed to this CBL deepening, as the sign of this vorticity was opposite to that of the low-level wind shear on the opposite side of the dryline in both phases. Deep-convective initiation appears to have resulted from this local CBL deepening, leading to a total elimination of convective inhibition near the dryline.

scholarly journals Establishment and preliminary application of forward modeling method for Doppler spectral density of ice particles

2019 ◽  
Author(s):  
Han Ding ◽  
Liping Liu
Keyword(s):  
Particle Size ◽  
Spectral Density ◽  
Cross Section ◽  
Ice Crystals ◽  
Ice Crystal ◽  
Fall Velocity ◽  
Density Data ◽  
Cloud Radar ◽  
Backscattering Cross Section ◽  
Ice Particles

Abstract. Owing to the various shapes of ice particles, the relationships between fall velocity, backscattering cross-section, mass, and particle size are complicated, which affects the application of cloud radar Doppler spectral density data to retrieve the microphysical properties of ice crystals. In this paper, under the assumption of six particle shape types, the relationships between particle mass, fall velocity, backscattering cross-section, and particle size were established based on existing research. Variations of Doppler spectral density with the same particle size distribution (PSD) of different ice particle types are discussed, and the radar-retrieved liquid and ice PSDs, water content, and mean volume-weighted particle diameter are compared with airborne in situ observations in Xingtai, Hebei Province, China, in 2018. The results showed the following: (1) for particles with the same equivalent diameter (De), the fall velocity of aggregates is the largest, followed by hexagonal columns, hexagonal plates, sector plates, and stellar crystals, with ice spheres falling two to three times faster than ice crystals with the same De. Hexagonal columns have the largest backscattering cross-section, followed by stellar crystals and sector plates, and the backscattering cross-sections of hexagonal plates and two kinds of aggregates are very close to those of ice spheres. (2) The width of the simulated radar Doppler spectral density generated by various ice crystal types with the same PSD is mainly affected by particle fall velocity and increased fall velocity rates with increased particle size, as do PSDs retrieved from the same Doppler spectral density data. (3) PSD comparisons showed that each ice crystal type retrieved from the cloud radar corresponded well to aircraft observations within a certain scale range when assuming that only a certain type of ice crystals existed in the cloud, which can fully prove the feasibility of retrieving ice PSDs from reflectivity spectral density.

scholarly journals The Characterization of Ice Cloud Properties from Doppler Radar Measurements

2007 ◽  
Vol 46 (10) ◽  
pp. 1682-1698 ◽  
Author(s):  
Julien Delanoë ◽  
A. Protat ◽  
D. Bouniol ◽  
Andrew Heymsfield ◽  
Aaron Bansemer ◽  
...  
Keyword(s):  
Water Content ◽  
Weather Prediction ◽  
Doppler Velocity ◽  
Fall Velocity ◽  
Ice Cloud ◽  
Cloud Radar ◽  
Cloud Properties ◽  
Ice Water Content ◽  
Radar Measurements ◽  
Ice Water

Abstract The paper describes an original method that is complementary to the radar–lidar algorithm method to characterize ice cloud properties. The method makes use of two measurements from a Doppler cloud radar (35 or 95 GHz), namely, the radar reflectivity and the Doppler velocity, to recover the effective radius of crystals, the terminal fall velocity of hydrometeors, the ice water content, and the visible extinction from which the optical depth can be estimated. This radar method relies on the concept of scaling the ice particle size distribution. An error analysis using an extensive in situ airborne microphysical database shows that the expected errors on ice water content and extinction are around 30%–40% and 60%, respectively, including both a calibration error and a bias on the terminal fall velocity of the particles, which all translate into errors in the retrieval of the density–diameter and area–diameter relationships. Comparisons with the radar–lidar method in areas sampled by the two instruments also demonstrate the accuracy of this new method for retrieval of the cloud properties, with a roughly unbiased estimate of all cloud properties with respect to the radar–lidar method. This method is being systematically applied to the cloud radar measurements collected over the three-instrumented sites of the European Cloudnet project to validate the representation of ice clouds in numerical weather prediction models and to build a cloud climatology.

scholarly journals Establishment and Preliminary Application of the Forward Modeling Method for Doppler Spectral Density of Ice Particles

2020 ◽  
Vol 12 (20) ◽  
pp. 3378
Author(s):  
Han Ding ◽  
Liping Liu
Keyword(s):  
Particle Size ◽  
Spectral Density ◽  
Cross Section ◽  
Ice Crystals ◽  
Doppler Spectrum ◽  
Ice Crystal ◽  
Fall Velocity ◽  
Cloud Radar ◽  
Backscattering Cross Section ◽  
Ice Particles

Owing to the various shapes of ice particles, the relationships between fall velocity, backscattering cross-section, mass, and particle size are complicated. This affects the application of cloud radar Doppler spectral density data in the retrieval of the microphysical properties of ice crystals. In this study, under the assumption of six particle shape types, the relationships between particle mass, fall velocity, backscattering cross-section, and particle size were established based on existing research. Variations of Doppler spectral density with the same particle size distribution (PSD) of different ice particle types are discussed. The radar-retrieved liquid and ice PSDs, water content, and mean volume-weighted particle diameter were compared with airborne in situ observations in the Xingtai, Hebei Province, China, in 2018. The results showed the following. (1) For the particles with the same equivalent diameter (De), the fall velocity of the aggregates was the largest, followed by hexagonal columns, hexagonal plates, sector plates, and stellar crystals, with the ice spheres falling two to three times faster than ice crystals with the same De. Hexagonal columns had the largest backscattering cross-section, followed by stellar crystals and sector plates, and the backscattering cross-sections of hexagonal plates and the two types of aggregates were very close to those of ice spheres. (2) The width of the simulated radar Doppler spectral density generated by various ice crystal types with the same PSD was mainly affected by the particle’s falling velocity, which increased with the particle size. Turbulence had different degrees of influence on the Doppler spectrum of different ice crystals, and it also brought large errors to the PSD retrieval. (3) PSD comparisons showed that each ice crystal type retrieved from the cloud radar corresponded well to aircraft observations within a certain scale range, when assuming that only a certain type of ice crystals existed in the cloud, which could fully prove the feasibility of retrieving ice PSDs from the reflectivity spectral density.

scholarly journals Evaluation of gridded Scanning ARM Cloud Radar reflectivity observations and vertical Doppler velocity retrievals

2013 ◽  
Vol 6 (6) ◽  
pp. 9579-9621 ◽  
Author(s):  
K. Lamer ◽  
A. Tatarevic ◽  
I. Jo ◽  
P. Kollias
Keyword(s):  
Spatial Scales ◽  
Domain Size ◽  
Horizontal Wind ◽  
Cape Cod ◽  
Doppler Velocity ◽  
Cloud Radar ◽  
Stratiform Clouds ◽  
Atmospheric Observations ◽  
Processing Techniques ◽  
High Elevations

Abstract. The Scanning ARM Cloud Radars (SACR's) provide continuous atmospheric observations aspiring to capture the 3-D cloud-scale structure. Sampling clouds in 3-D is challenging due to their temporal-spatial scales, the need to sample the sky at high elevations and cloud radar limitations. Thus, a common scan strategy is to repetitively slice the atmosphere from horizon to horizon as clouds advect over the radar (Cross-Wind Range Height Indicator – CWRHI). Here, the processing and gridding of the SACR CW-RHI scans are presented. First, the SACR sample observations from the ARM Oklahoma (SGP) and Cape-Cod (PVC) sites are post-processed (detection mask, velocity de-aliasing and gaseous attenuation correction). The resulting radial Doppler moment fields are then mapped to Cartesian coordinates with time as one of the dimension. The Cartesian-gridded Doppler velocity fields are next decomposed into the horizontal wind velocity contribution and the vertical Doppler velocity component. For validation purposes, all gridded and retrieved fields are compared to collocated zenith pointing ARM cloud radar measurements. We consider that the SACR sensitivity loss with range, the cloud type observed and the research purpose should be considered in determining the gridded domain size. Our results also demonstrate that the gridded SACR observations resolve the main features of low and high stratiform clouds. It is established that the CW-RHI observations complemented with processing techniques could lead to robust 3-D clouds dynamical representations up to 25–30° off zenith. The proposed gridded products are expected to advance our understanding of 3-D cloud morphology, dynamics, anisotropy and lead to more realistic 3-D radiative transfer calculations.

Sign in / Sign up

Export Citation Format

Share Document