Triple-frequency radar retrieval of microphysical properties of snow

Abstract. An algorithm based on triple-frequency (X, Ka, W) radar measurements that retrieves the size, water content and degree of riming of ice clouds is presented. This study exploits the potential of multi-frequency radar measurements to provide information on bulk snow density that should underpin better estimates of the snow characteristic size and content within the radar volume. The algorithm is based on Bayes' rule with riming parameterised by the “fill-in” model. The radar reflectivities are simulated with a range of scattering models corresponding to realistic snowflake shapes. The algorithm is tested on multi-frequency radar data collected during the ESA-funded Radar Snow Experiment For Future Precipitation Mission. During this campaign, in situ microphysical probes were mounted on the same aeroplane as the radars. This nearly perfectly co-located dataset of the remote and in situ measurements gives an opportunity to derive a combined multi-instrument estimate of snow microphysical properties that is used for a rigorous validation of the radar retrieval. Results suggest that the triple-frequency retrieval performs well in estimating ice water content (IWC) and mean mass-weighted diameters obtaining root-mean-square errors of 0.13 and 0.15, respectively, for log 10IWC and log 10Dm. The retrieval of the degree of riming is more challenging, and only the algorithm that uses Doppler information obtains results that are highly correlated with the in situ data.

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Triple frequency radar retrieval of microphysical properties of snow

10.5194/amt-2021-227 ◽

2021 ◽

Author(s):

Kamil Mroz ◽

Alessandro Battaglia ◽

Cuong Nguyen ◽

Andrew Heymsfield ◽

Alain Protat ◽

...

Keyword(s):

Water Content ◽

Radar Data ◽

Characteristic Size ◽

In Situ Data ◽

Microphysical Properties ◽

Triple Frequency ◽

Radar Measurements ◽

Highly Correlated ◽

Ice Water

Abstract. An algorithm based on triple-frequency (X, Ka, W) radar measurements that retrieves the size, water content and degree of riming of ice clouds is presented. This study exploits the potential of multi-frequency radar measurements to provide information on bulk snow density that should underpin better estimates of the snow characteristic size and content within the radar volume. The algorithm is based on Bayes' rule with riming parameterized by the “fill-in” model. The radar reflectivities are simulated with a range of scattering models corresponding to realistic snowflake shapes. The algorithm is tested on multi-frequency radar data collected during the ESA-funded Radar Snow Experiment. During this campaign in-situ microphysical probes were mounted on the same airplane as the radars. This nearly perfectly collocated dataset of the remote and in-situ measurements gives an opportunity to derive a combined multi-instrument estimate of snow microphysical properties that is used for a rigorous validation of the radar retrieval. Results suggest that the triple-frequency retrieval performs well in estimating ice water content and mean-mass-weighted diameters obtaining root-mean-square-error of 0.13 and 0.15, respectively for log10 IWC and log10 Dm. The retrieval of the degree of riming is more challenging and only the algorithm that uses Doppler information obtains results that are highly correlated with the in-situ data.

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Dependence of the Ice Water Content and Snowfall Rate on Temperature, Globally: Comparison of in Situ Observations, Satellite Active Remote Sensing Retrievals, and Global Climate Model Simulations

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-16-0230.1 ◽

2017 ◽

Vol 56 (1) ◽

pp. 189-215 ◽

Cited By ~ 16

Author(s):

Andrew Heymsfield ◽

Martina Krämer ◽

Norman B. Wood ◽

Andrew Gettelman ◽

Paul R. Field ◽

...

Keyword(s):

Water Content ◽

Global Climate ◽

Global Climate Model ◽

Ice Cloud ◽

In Situ Data ◽

Microphysical Properties ◽

Ice Water Content ◽

In Situ Observations ◽

Ice Water

AbstractCloud ice microphysical properties measured or estimated from in situ aircraft observations are compared with global climate models and satellite active remote sensor retrievals. Two large datasets, with direct measurements of the ice water content (IWC) and encompassing data from polar to tropical regions, are combined to yield a large database of in situ measurements. The intention of this study is to identify strengths and weaknesses of the various methods used to derive ice cloud microphysical properties. The in situ data are measured with total water hygrometers, condensed water probes, and particle spectrometers. Data from polar, midlatitude, and tropical locations are included. The satellite data are retrieved from CloudSat/CALIPSO [the CloudSat Ice Cloud Property Product (2C-ICE) and 2C-SNOW-PROFILE] and Global Precipitation Measurement (GPM) Level2A. Although the 2C-ICE retrieval is for IWC, a method to use the IWC to get snowfall rates S is developed. The GPM retrievals are for snowfall rate only. Model results are derived using the Community Atmosphere Model (CAM5) and the Met Office Unified Model [Global Atmosphere 7 (GA7)]. The retrievals and model results are related to the in situ observations using temperature and are partitioned by geographical region. Specific variables compared between the in situ observations, models, and retrievals are the IWC and S. Satellite-retrieved IWCs are reasonably close in value to the in situ observations, whereas the models’ values are relatively low by comparison. Differences between the in situ IWCs and those from the other methods are compounded when S is considered, leading to model snowfall rates that are considerably lower than those derived from the in situ data. Anomalous trends with temperature are noted in some instances.

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Coincident In-situ and Triple-Frequency Radar Airborne Observations in the Arctic

10.5194/amt-2021-148 ◽

2021 ◽

Author(s):

Cuong M. Nguyen ◽

Mengistu Wolde ◽

Alessandro Battaglia ◽

Leonid Nichman ◽

Natalia Bliankinshtein ◽

...

Keyword(s):

National Research Council ◽

Characteristic Size ◽

The Arctic ◽

Dual Frequency ◽

Microphysical Properties ◽

Triple Frequency ◽

W Band ◽

Modelling Studies ◽

Frequency Ratios

Abstract. This paper describes X-Ka-W-band airborne radar observations and almost perfectly co-located in situ microphysical measurements on board the National Research Council Canada (NRC) Convair-580 aircraft from the Radar Snow Experiment (RadSnowExp). Over 12 hours of flight data with more than 3.4 hours in non-Rayleigh regions for at least one of the radar frequencies provide a unique opportunity for studying the relationship between cloud microphysical properties and radar dual-frequency ratios (DFR). The results from this study are consistent with the main findings of previous modelling studies with specific regions of the DFR plane associated with unique scattering properties of different ice habits, especially in riming conditions. Moreover, the datasets could be used to produce look-up-tables for retrieving cloud bulk density and characteristic size.

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Atmospheric Ice Particle Shape Estimates from Polarimetric Radar Measurements and In Situ Observations

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-17-0111.1 ◽

2017 ◽

Vol 34 (12) ◽

pp. 2569-2587 ◽

Cited By ~ 15

Author(s):

Sergey Y. Matrosov ◽

Carl G. Schmitt ◽

Maximilian Maahn ◽

Gijs de Boer

Keyword(s):

Aspect Ratio ◽

Particle Shape ◽

Characteristic Size ◽

In Situ Measurements ◽

Department Of Energy ◽

Depolarization Ratio ◽

Suggested Approach ◽

Aspect Ratios ◽

Radar Measurements

AbstractA remote sensing approach to retrieve the degree of nonsphericity of ice hydrometeors using scanning polarimetric Ka-band radar measurements from a U.S. Department of Energy Atmospheric Radiation Measurement (ARM) Program cloud radar operated in an alternate transmission–simultaneous reception mode is introduced. Nonsphericity is characterized by aspect ratios representing the ratios of particle minor-to-major dimensions. The approach is based on the use of a circular depolarization ratio (CDR) proxy reconstructed from differential reflectivity ZDR and copolar correlation coefficient ρhυ linear polarization measurements. Essentially combining information contained in ZDR and ρhυ, CDR-based retrievals of aspect ratios are fairly insensitive to hydrometeor orientation if measurements are performed at elevation angles of around 40°–50°. The suggested approach is applied to data collected using the third ARM Mobile Facility (AMF3), deployed to Oliktok Point, Alaska. Aspect ratio retrievals were also performed using ZDR measurements that are more strongly (compared to CDR) influenced by hydrometeor orientation. The results of radar-based retrievals are compared with in situ measurements from the tethered balloon system (TBS)-based video ice particle sampler and the ground-based multiangle snowflake camera. The observed ice hydrometeors were predominantly irregular-shaped ice crystals and aggregates, with aspect ratios varying between approximately 0.3 and 0.8. The retrievals assume that particle bulk density influencing (besides the particle shape) observed polarimetric variables can be deduced from the estimates of particle characteristic size. Uncertainties of CDR-based aspect ratio retrievals are estimated at about 0.1–0.15. Given these uncertainties, radar-based retrievals generally agreed with in situ measurements. The advantages of using the CDR proxy compared to the linear depolarization ratio are discussed.

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Evaluation of Several A-Train Ice Cloud Retrieval Products with In Situ Measurements Collected during the SPARTICUS Campaign

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-12-054.1 ◽

2013 ◽

Vol 52 (4) ◽

pp. 1014-1030 ◽

Cited By ~ 89

Author(s):

Min Deng ◽

Gerald G. Mace ◽

Zhien Wang ◽

R. Paul Lawson

Keyword(s):

Water Content ◽

Detection Threshold ◽

In Situ Measurements ◽

Subtle Difference ◽

Ice Cloud ◽

In Situ Data ◽

Cloud Water Content ◽

Mass Size ◽

Ice Water

AbstractIn this study several ice cloud retrieval products that utilize active and passive A-Train measurements are evaluated using in situ data collected during the Small Particles in Cirrus (SPARTICUS) field campaign. The retrieval datasets include ice water content (IWC), effective radius re, and visible extinction σ from CloudSat level-2C ice cloud property product (2C-ICE), CloudSat level-2B radar-visible optical depth cloud water content product (2B-CWC-RVOD), radar–lidar (DARDAR), and σ from Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). When the discrepancies between the radar reflectivity Ze derived from 2D stereo probe (2D-S) in situ measurements and Ze measured by the CloudSat radar are less than 10 dBZe, the flight mean ratios of the retrieved IWC to the IWC estimated from in situ data are 1.12, 1.59, and 1.02, respectively for 2C-ICE, DARDAR, and 2B-CWC-RVOD. For re, the flight mean ratios are 1.05, 1.18, and 1.61, respectively. For σ, the flight mean ratios for 2C-ICE, DARDAR, and CALIPSO are 1.03, 1.42, and 0.97, respectively. The CloudSat 2C-ICE and DARDAR retrieval products are typically in close agreement. However, the use of parameterized radar signals in ice cloud volumes that are below the detection threshold of the CloudSat radar in the 2C-ICE algorithm provides an extra constraint that leads to slightly better agreement with in situ data. The differences in assumed mass–size and area–size relations between CloudSat 2C-ICE and DARDAR also contribute to some subtle difference between the datasets: re from the 2B-CWC-RVOD dataset is biased more than the other retrieval products and in situ measurements by about 40%. A slight low (negative) bias in CALIPSO σ may be due to 5-km averaging in situations in which the cirrus layers have significant horizontal gradients in σ.

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Comparative assessment of GRASP algorithm for a dust event over Granada (Spain) during ChArMEx-ADRIMED 2013 campaign

Atmospheric Measurement Techniques ◽

10.5194/amt-10-4439-2017 ◽

2017 ◽

Vol 10 (11) ◽

pp. 4439-4457 ◽

Cited By ~ 19

Author(s):

Jose A. Benavent-Oltra ◽

Roberto Román ◽

María J. Granados-Muñoz ◽

Daniel Pérez-Ramírez ◽

Pablo Ortiz-Amezcua ◽

...

Keyword(s):

Aerosol Layer ◽

Horizontal Distance ◽

Lidar System ◽

Dust Layer ◽

Airborne Measurements ◽

In Situ Data ◽

Microphysical Properties ◽

Starting Point ◽

Aerosol Properties

Abstract. In this study, vertical profiles and column-integrated aerosol properties retrieved by the GRASP (Generalized Retrieval of Atmosphere and Surface Properties) algorithm are evaluated with in situ airborne measurements made during the ChArMEx-ADRIMED field campaign in summer 2013. In the framework of this campaign, two different flights took place over Granada (Spain) during a desert dust episode on 16 and 17 June. The GRASP algorithm, which combines lidar and sun–sky photometer data measured at Granada, was used to retrieve aerosol properties. Two sun-photometer datasets are used: one co-located with the lidar system and the other in the Cerro Poyos station, approximately 1200 m higher than the lidar system but at a short horizontal distance. Column-integrated aerosol microphysical properties retrieved by GRASP are compared with AERONET products showing a good agreement. Differences between GRASP retrievals and airborne extinction profiles are in the range of 15 to 30 %, depending on the instrument on board the aircraft used as reference. On 16 June, a case where the dust layer was coupled to the aerosol layer close to surface, the total volume concentration differences between in situ data and GRASP retrieval are 15 and 36 % for Granada and Cerro Poyos retrievals, respectively. In contrast, on 17 June the dust layer was decoupled from the aerosol layer close to the surface, and the differences are around 17 % for both retrievals. In general, all the discrepancies found are within the uncertainly limits, showing the robustness and reliability of the GRASP algorithm. However, the better agreement found for the Cerro Poyos retrieval with the aircraft data and the vertical homogeneity of certain properties retrieved with GRASP, such as the scattering Ångström exponent, for cases with aerosol layers characterized by different aerosol types, shows that uncertainties in the vertical distribution of the aerosol properties have to be considered. The comparison presented here between GRASP and other algorithms (i.e. AERONET and LIRIC) and with airborne in situ measurements shows the potential to retrieve the optical and microphysical profiles of the atmospheric aerosol properties. Also, the advantage of GRASP versus LIRIC is that GRASP does not assume the results of the AERONET inversion as a starting point.

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A Landsat-Era Sierra Nevada Snow Reanalysis (1985–2015)

Journal of Hydrometeorology ◽

10.1175/jhm-d-15-0177.1 ◽

2016 ◽

Vol 17 (4) ◽

pp. 1203-1221 ◽

Cited By ~ 74

Author(s):

Steven A. Margulis ◽

Gonzalo Cortés ◽

Manuela Girotto ◽

Michael Durand

Keyword(s):

Sierra Nevada ◽

Snow Water Equivalent ◽

Reanalysis Dataset ◽

In Situ Data ◽

Snow Covered Area ◽

Covered Area ◽

Snow Water ◽

Fully Bayesian ◽

Mean Square Errors

Abstract A newly developed state-of-the-art snow water equivalent (SWE) reanalysis dataset over the Sierra Nevada (United States) based on the assimilation of remotely sensed fractional snow-covered area data over the Landsat 5–8 record (1985–2015) is presented. The method (fully Bayesian), resolution (daily and 90 m), temporal extent (31 years), and accuracy provide a unique dataset for investigating snow processes. The verified dataset (based on a comparison with over 9000 station years of in situ data) exhibited mean and root-mean-square errors less than 3 and 13 cm, respectively, and correlation greater than 0.95 compared with in situ SWE observations. The reanalysis dataset was used to characterize the peak SWE climatology to provide a basic accounting of the stored snowpack water in the Sierra Nevada over the last 31 years. The pixel-wise peak SWE volume over the domain was found to be 20.0 km3 on average with a range of 4.0–40.6 km3. The ongoing drought in California contains the two lowest snowpack years (water years 2014 and 2015) and three of the four driest years over the examined record. It was found that the basin-average peak SWE, while underestimating the total water storage in snowpack over the year, accurately captures the interannual variability in stored snowpack water. However, the results showed that the assumption that 1 April SWE is representative of the peak SWE can lead to significant underestimation of basin-average peak SWE both on an average (21% across all basins) and on an interannual basis (up to 98% across all basin years).

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Microphysical properties and high ice water content in continental and oceanic Mescoscale Convective Systems and potential implications for commercial aircraft at flight altitude

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-13-22535-2013 ◽

2013 ◽

Vol 13 (8) ◽

pp. 22535-22574

Author(s):

J.-F. Gayet ◽

V. Shcherbakov ◽

L. Bugliaro ◽

A. Protat ◽

J. Delanoë ◽

...

Keyword(s):

Water Content ◽

Convective Cloud ◽

Effective Radius ◽

Convective System ◽

Commercial Aircraft ◽

Microphysical Properties ◽

Maximum Reflectivity ◽

Ice Water Content ◽

Ice Water

Abstract. Two complementary case studies are conducted to analyse convective system properties in the region where strong cloud-top lidar backscatter anomalies are observed as reported by Platt et al. (2011). These anomalies were reported for the first time using in-situ microphysical measurements in an isolated continental convective cloud over Germany during the CIRCLE2 experiment (Gayet et al., 2012). In this case, quasi collocated in situ observations with CALIPSO, CloudSat and Meteosat-9/SEVIRI observations confirm that regions of backscatter anomalies represent the most active and dense convective cloud parts with likely the strongest core updrafts and unusual high values of the particle concentration, extinction and ice water content (IWC), with the occurrence of small ice crystal sizes. Similar spaceborne observations are then analyzed in a maritime mesoscale cloud system (MCS) on 20 June 2008 located off the Brazil coast between 0° and 3° N latitude. Near cloud-top backscatter anomalies are evidenced in a region which corresponds to the coldest temperatures with maximum cloud top altitudes derived from collocated CALIPSO/IIR and Meteosat-9/SEVIRI infrared brightness temperatures. The interpretation of CALIOP data highlights significant differences of microphysical properties from those observed in the continental isolated convective cloud. Indeed, SEVIRI retrievals in the visible confirm much smaller ice particles near-top of the isolated continental convective cloud, i.e. effective radius (Reff) ~15 μm against 22–27 μm in the whole MCS area. 94 GHz Cloud Profiling Radar observations from CloudSat are then used to describe the properties of the most active cloud regions at and below cloud top. The cloud ice water content and effective radius retrieved with the CloudSat 2B-IWC and DARDAR inversion techniques, show that at usual cruise altitudes of commercial aircraft (FL 350 or ~10 700 m level), high IWC (i.e. up to 2 to 4 g m−3) could be identified according to specific IWC-Z relationships. These values correspond to a maximum reflectivity factor of +18 dBZ (at 94 GHz). Near-top cloud properties also indicate signatures of microphysical characteristics according to the cloud-stage evolution as revealed by SEVIRI images to identify the development of new cells within the MCS cluster. It is argued that the availability of real time information of the km-scale cloud top IR brightness temperature decrease with respect to the cloud environment would help identify MCS cloud areas with potentially high ice water content and small particle sizes against which onboard meteorological radar may not be suitable to provide timely warning.

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