Zhien Wang | University of Wyoming (original) (raw)

Papers by Zhien Wang

Research paper thumbnail of A Refined Two-Channel Microwave Radiometer Liquid Water Path Retrieval for Cold Regions by Using Multiple-Sensor Measurements

IEEE Geoscience and Remote Sensing Letters, 2007

Abstract—Traditional two-channel microwave radiometers (MWRs) are widely used to measure cloud li... more Abstract—Traditional two-channel microwave radiometers (MWRs) are widely used to measure cloud liquid water path (LWP); however, the retrieved LWPs are subject to relatively large uncertainties, particularly for low LWP clouds. By reformulating the statistical retrieval ...

Research paper thumbnail of Airborne dust distributions over the Tibetan Plateau and surrounding areas derived from the first year of CALIPSO lidar observations

Atmospheric Chemistry and Physics, 2008

Research paper thumbnail of A height resolved global view of dust aerosols from the first year CALIPSO lidar measurements

Journal of Geophysical Research, 2008

Based on the first year of CALIPSO lidar measurements under cloud-free conditions, a height-resol... more Based on the first year of CALIPSO lidar measurements under cloud-free conditions, a height-resolved global distribution of dust aerosols is presented for the first time. Results indicate that spring is the most active dust season, during which ˜20% and ˜12% of areas between 0 and 60°N are influenced by dust at least 10% and 50% of the time, respectively. In summer within 3-6 km, ˜8.3% of area between 0 and 60°N is impacted by dust at least 50% of the time. Strong seasonal cycles of dust layer vertical extent are observed in major source regions, which are similar to the seasonal variation of the thermally driven boundary layer depth. The arid and semiarid areas in North Africa and the Arabian Peninsula are the most persistent and prolific dust sources. African dust is transported across the Atlantic all yearlong with strong seasonal variation in the transport pathways mainly in the free troposphere in summer and at the low altitudes in winter. However, the trans-Atlantic dust is transported at the low altitudes is important for all seasons, especially transported further cross the ocean. The crossing Atlantic dusty zones are shifted southward from summer to winter, which is accompanied by a similar southward shift of dust-generating areas over North Africa. The Taklimakan and Gobi deserts are two major dust sources in East Asia with long-range transport mainly occurring in spring. The large horizontal and vertical coverage of dust aerosols indicate their importance in the climate system through both direct and indirect aerosol effects.

Research paper thumbnail of Classifying clouds around the globe with the CloudSat radar: 1-year of results

Geophysical Research Letters, 2008

CloudSat supports a 94 GHz cloud profiling radar as part of the innovative A-train formation of s... more CloudSat supports a 94 GHz cloud profiling radar as part of the innovative A-train formation of satellites studying the Earths clouds and atmosphere. Using the vertical profiles of clouds and precipitation, an algorithm has been developed to determine the type of clouds present. ...

Research paper thumbnail of Testing IWC Retrieval Methods Using Radar and Ancillary Measurements with In Situ Data

Journal of Applied Meteorology and Climatology, 2008

Vertical profiles of ice water content (IWC) can now be derived globally from spaceborne cloud sa... more Vertical profiles of ice water content (IWC) can now be derived globally from spaceborne cloud satellite radar (CloudSat) data. Integrating these data with Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) data may further increase accuracy. Evaluations of the ...

Research paper thumbnail of CALIPSO/CALIOP Cloud Phase Discrimination Algorithm

Journal of Atmospheric and Oceanic Technology, 2009

Research paper thumbnail of Association of Antarctic polar stratospheric cloud formation on tropospheric cloud systems

Geophysical Research Letters, 2008

Research paper thumbnail of The Cloudsat Mission and the A-Train

Bulletin of The American Meteorological Society, 2002

CloudSat is a satellite experiment designed to measure the vertical structure of clouds from spac... more CloudSat is a satellite experiment designed to measure the vertical structure of clouds from space. The expected launch of CloudSat is planned for 2004, and once launched, CloudSat will orbit in formation as part of a constellation of satellites (the A-Train) that includes NASA's Aqua and Aura satellites, a NASA-CNES lidar satellite (CALIPSO), and a CNES satellite carrying a polarimeter (PARASOL). A unique feature that CloudSat brings to this constellation is the ability to fly a precise orbit enabling the fields of view of the CloudSat radar to be overlapped with the CALIPSO lidar footprint and the other measurements of the constellation. The precision and near simultaneity of this overlap creates a unique multisatellite observing system for studying the atmospheric processes essential to the hydrological cycle.The vertical profiles of cloud properties provided by CloudSat on the global scale fill a critical gap in the investigation of feedback mechanisms linking clouds to climate. Measuring these profiles requires a combination of active and passive instruments, and this will be achieved by combining the radar data of CloudSat with data from other active and passive sensors of the constellation. This paper describes the underpinning science and general overview of the mission, provides some idea of the expected products and anticipated application of these products, and the potential capability of the A-Train for cloud observations. Notably, the CloudSat mission is expected to stimulate new areas of research on clouds. The mission also provides an important opportunity to demonstrate active sensor technology for future scientific and tactical applications. The CloudSat mission is a partnership between NASA's JPL, the Canadian Space Agency, Colorado State University, the U.S. Air Force, and the U.S. Department of Energy.

Research paper thumbnail of Ozone Destruction in Continental Stratus Clouds: An Aircraft Case Study

Journal of Applied Meteorology, 2000

Research paper thumbnail of Cloud Type and Macrophysical Property Retrieval Using Multiple Remote Sensors

Journal of Applied Meteorology, 2001

A cloud detection algorithm based on ground-based remote sensors has been developed that can diff... more A cloud detection algorithm based on ground-based remote sensors has been developed that can differentiate among various atmospheric targets such as ice and water clouds, virga, precipitation, and aerosol layers. Standard cloud type and macrophysical properties are identified by combining polarization lidar, millimeter-wave radar, infrared radiometer, and dual-channel microwave radiometer measurements. These algorithms are applied to measurements collected during 1998

Research paper thumbnail of Cirrus Cloud Microphysical Property Retrieval Using Lidar and Radar Measurements. Part I: Algorithm Description and Comparison with In Situ Data

Journal of Applied Meteorology, 2002

Research paper thumbnail of Cirrus Cloud Ice Water Content Radar Algorithm Evaluation Using an Explicit Cloud Microphysical Model

Journal of Applied Meteorology, 2002

Research paper thumbnail of THE CLOUDSAT MISSION AND THE A-TRAIN A New Dimension of Space-Based Observations of Clouds and Precipitation

Research paper thumbnail of Studying Altocumulus with Ice Virga Using Ground-Based Active and Passive Remote Sensors

Journal of Applied Meteorology, 2004

Research paper thumbnail of Cloud and Aerosol Research Capabilities at FARS: The Facility for Atmospheric Remote Sensing

Bulletin of The American Meteorological Society, 2001

Since October 1987, the University of Utah Facility for Atmospheric Remote Sensing (FARS) has bee... more Since October 1987, the University of Utah Facility for Atmospheric Remote Sensing (FARS) has been applied to the probing of the atmosphere, concentrating on the study of high-level clouds. Regular FARS measurements, which currently total ~3000 h of ruby lidar ...

Research paper thumbnail of Continental Stratus Clouds: A Case Study Using Coordinated Remote Sensing and Aircraft Measurements

Journal of The Atmospheric Sciences, 1999

A continental stratus cloud layer was studied by advanced ground-based remote sensing instruments... more A continental stratus cloud layer was studied by advanced ground-based remote sensing instruments and aircraft probes on 30 April 1994 from the Cloud and Radiation Testbed site in north-central Oklahoma. The boundary layer structure clearly resembled that of a cloud-topped mixed layer, and the cloud content is shown to be near adiabatic up to the cloud-top entrainment zone. A cloud retrieval algorithm using the radar reflectivity and cloud droplet concentration (either measured in situ or deduced using dual-channel microwave radiometer data) is applied to construct uniquely high-resolution cross sections of liquid water content and mean droplet radius. The combined evidence indicates that the 350-600 m deep, slightly supercooled (2.0° to 2.0°C) cloud, which failed to produce any detectable ice or drizzle particles, contained an average droplet concentration of 347 cm3, and a maximum liquid water content of 0.8 g m3 and mean droplet radius of 9 m near cloud top. Lidar data indicate that the Ka-band radar usually detected the cloud-base height to within 50 m, such that the radar insensitivity to small cloud droplets had a small impact on the findings. Radar-derived liquid water paths ranged from 71 to 259 g m2 as the stratus deck varied, which is in excellent agreement with dual-channel microwave radiometer data, but 20% higher than that measured in situ. This difference appears to be due to the undersampling of the few largest cloud droplets by the aircraft probes. This combination of approaches yields a unique image of the content of a continental stratus cloud, as well as illustrating the utility of modern remote sensing systems for probing nonprecipitating water clouds.

Research paper thumbnail of In situ detection of biological particles in cloud ice-crystals

Nature Geoscience, 2009

Each month, Nature Geoscience will bring you top-quality research papers, reviews and opinion pie... more Each month, Nature Geoscience will bring you top-quality research papers, reviews and opinion pieces - in print and online.

Research paper thumbnail of Cirrus Cloud Microphysical Property Retrieval Using Lidar and Radar Measurements. Part II: Midlatitude Cirrus Microphysical and Radiative Properties

Journal of The Atmospheric Sciences, 2002

Research paper thumbnail of Improved Radar Ice Water Content Retrieval Algorithms Using Coincident Microphysical and Radar Measurements

Journal of Applied Meteorology, 2005

Airborne radar reflectivity measurements at frequencies of 9.6 and 94 GHz, with collocated, in si... more Airborne radar reflectivity measurements at frequencies of 9.6 and 94 GHz, with collocated, in situ particle size distribution and ice water content measurements from the Cirrus Regional Study of Tropical Anvils and Cirrus Layers (CRYSTAL) Florida Area Cirrus Experiment (FACE) in Florida in July 2002, offer one of the first opportunities to evaluate and improve algorithms for retrieving ice water content from single-wavelength spaceborne radar measurements. Both ice water content and radar reflectivity depend on the distribution of particle mass with size. It is demonstrated that single, power-law, mass dimensional relationships are unable to adequately account for the dominating contribution of small particles at lower reflectivities and large particles at higher reflectivities. To circumvent the need for multiple, or complex, mass dimensional relationships, analytic expressions that use particle ensemble mean ice particle densities that are derived from the coincident microphysical and radar observations are developed. These expressions, together with more than 5000 CRYSTAL FACE size distributions, are used to develop radar reflectivity ice water content relationships for the two radar wavelengths that appear to provide improvements over earlier relationships, at least for convectively generated stratiform ice clouds.

Research paper thumbnail of Midlatitude Cirrus Clouds Derived from Hurricane Nora: A Case Study with Implications for Ice Crystal Nucleation and Shape

Journal of The Atmospheric Sciences, 2003

Hurricane Nora traveled up the Baja Peninsula coast in the unusually warm El Niño waters of Septe... more Hurricane Nora traveled up the Baja Peninsula coast in the unusually warm El Niño waters of September 1997 until rapidly decaying as it approached southern California on 24 September. The anvil cirrus blowoff from the final surge of tropical convection became ...

Research paper thumbnail of A Refined Two-Channel Microwave Radiometer Liquid Water Path Retrieval for Cold Regions by Using Multiple-Sensor Measurements

IEEE Geoscience and Remote Sensing Letters, 2007

Abstract—Traditional two-channel microwave radiometers (MWRs) are widely used to measure cloud li... more Abstract—Traditional two-channel microwave radiometers (MWRs) are widely used to measure cloud liquid water path (LWP); however, the retrieved LWPs are subject to relatively large uncertainties, particularly for low LWP clouds. By reformulating the statistical retrieval ...

Research paper thumbnail of Airborne dust distributions over the Tibetan Plateau and surrounding areas derived from the first year of CALIPSO lidar observations

Atmospheric Chemistry and Physics, 2008

Research paper thumbnail of A height resolved global view of dust aerosols from the first year CALIPSO lidar measurements

Journal of Geophysical Research, 2008

Based on the first year of CALIPSO lidar measurements under cloud-free conditions, a height-resol... more Based on the first year of CALIPSO lidar measurements under cloud-free conditions, a height-resolved global distribution of dust aerosols is presented for the first time. Results indicate that spring is the most active dust season, during which ˜20% and ˜12% of areas between 0 and 60°N are influenced by dust at least 10% and 50% of the time, respectively. In summer within 3-6 km, ˜8.3% of area between 0 and 60°N is impacted by dust at least 50% of the time. Strong seasonal cycles of dust layer vertical extent are observed in major source regions, which are similar to the seasonal variation of the thermally driven boundary layer depth. The arid and semiarid areas in North Africa and the Arabian Peninsula are the most persistent and prolific dust sources. African dust is transported across the Atlantic all yearlong with strong seasonal variation in the transport pathways mainly in the free troposphere in summer and at the low altitudes in winter. However, the trans-Atlantic dust is transported at the low altitudes is important for all seasons, especially transported further cross the ocean. The crossing Atlantic dusty zones are shifted southward from summer to winter, which is accompanied by a similar southward shift of dust-generating areas over North Africa. The Taklimakan and Gobi deserts are two major dust sources in East Asia with long-range transport mainly occurring in spring. The large horizontal and vertical coverage of dust aerosols indicate their importance in the climate system through both direct and indirect aerosol effects.

Research paper thumbnail of Classifying clouds around the globe with the CloudSat radar: 1-year of results

Geophysical Research Letters, 2008

CloudSat supports a 94 GHz cloud profiling radar as part of the innovative A-train formation of s... more CloudSat supports a 94 GHz cloud profiling radar as part of the innovative A-train formation of satellites studying the Earths clouds and atmosphere. Using the vertical profiles of clouds and precipitation, an algorithm has been developed to determine the type of clouds present. ...

Research paper thumbnail of Testing IWC Retrieval Methods Using Radar and Ancillary Measurements with In Situ Data

Journal of Applied Meteorology and Climatology, 2008

Vertical profiles of ice water content (IWC) can now be derived globally from spaceborne cloud sa... more Vertical profiles of ice water content (IWC) can now be derived globally from spaceborne cloud satellite radar (CloudSat) data. Integrating these data with Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) data may further increase accuracy. Evaluations of the ...

Research paper thumbnail of CALIPSO/CALIOP Cloud Phase Discrimination Algorithm

Journal of Atmospheric and Oceanic Technology, 2009

Research paper thumbnail of Association of Antarctic polar stratospheric cloud formation on tropospheric cloud systems

Geophysical Research Letters, 2008

Research paper thumbnail of The Cloudsat Mission and the A-Train

Bulletin of The American Meteorological Society, 2002

CloudSat is a satellite experiment designed to measure the vertical structure of clouds from spac... more CloudSat is a satellite experiment designed to measure the vertical structure of clouds from space. The expected launch of CloudSat is planned for 2004, and once launched, CloudSat will orbit in formation as part of a constellation of satellites (the A-Train) that includes NASA's Aqua and Aura satellites, a NASA-CNES lidar satellite (CALIPSO), and a CNES satellite carrying a polarimeter (PARASOL). A unique feature that CloudSat brings to this constellation is the ability to fly a precise orbit enabling the fields of view of the CloudSat radar to be overlapped with the CALIPSO lidar footprint and the other measurements of the constellation. The precision and near simultaneity of this overlap creates a unique multisatellite observing system for studying the atmospheric processes essential to the hydrological cycle.The vertical profiles of cloud properties provided by CloudSat on the global scale fill a critical gap in the investigation of feedback mechanisms linking clouds to climate. Measuring these profiles requires a combination of active and passive instruments, and this will be achieved by combining the radar data of CloudSat with data from other active and passive sensors of the constellation. This paper describes the underpinning science and general overview of the mission, provides some idea of the expected products and anticipated application of these products, and the potential capability of the A-Train for cloud observations. Notably, the CloudSat mission is expected to stimulate new areas of research on clouds. The mission also provides an important opportunity to demonstrate active sensor technology for future scientific and tactical applications. The CloudSat mission is a partnership between NASA's JPL, the Canadian Space Agency, Colorado State University, the U.S. Air Force, and the U.S. Department of Energy.

Research paper thumbnail of Ozone Destruction in Continental Stratus Clouds: An Aircraft Case Study

Journal of Applied Meteorology, 2000

Research paper thumbnail of Cloud Type and Macrophysical Property Retrieval Using Multiple Remote Sensors

Journal of Applied Meteorology, 2001

A cloud detection algorithm based on ground-based remote sensors has been developed that can diff... more A cloud detection algorithm based on ground-based remote sensors has been developed that can differentiate among various atmospheric targets such as ice and water clouds, virga, precipitation, and aerosol layers. Standard cloud type and macrophysical properties are identified by combining polarization lidar, millimeter-wave radar, infrared radiometer, and dual-channel microwave radiometer measurements. These algorithms are applied to measurements collected during 1998

Research paper thumbnail of Cirrus Cloud Microphysical Property Retrieval Using Lidar and Radar Measurements. Part I: Algorithm Description and Comparison with In Situ Data

Journal of Applied Meteorology, 2002

Research paper thumbnail of Cirrus Cloud Ice Water Content Radar Algorithm Evaluation Using an Explicit Cloud Microphysical Model

Journal of Applied Meteorology, 2002

Research paper thumbnail of THE CLOUDSAT MISSION AND THE A-TRAIN A New Dimension of Space-Based Observations of Clouds and Precipitation

Research paper thumbnail of Studying Altocumulus with Ice Virga Using Ground-Based Active and Passive Remote Sensors

Journal of Applied Meteorology, 2004

Research paper thumbnail of Cloud and Aerosol Research Capabilities at FARS: The Facility for Atmospheric Remote Sensing

Bulletin of The American Meteorological Society, 2001

Since October 1987, the University of Utah Facility for Atmospheric Remote Sensing (FARS) has bee... more Since October 1987, the University of Utah Facility for Atmospheric Remote Sensing (FARS) has been applied to the probing of the atmosphere, concentrating on the study of high-level clouds. Regular FARS measurements, which currently total ~3000 h of ruby lidar ...

Research paper thumbnail of Continental Stratus Clouds: A Case Study Using Coordinated Remote Sensing and Aircraft Measurements

Journal of The Atmospheric Sciences, 1999

A continental stratus cloud layer was studied by advanced ground-based remote sensing instruments... more A continental stratus cloud layer was studied by advanced ground-based remote sensing instruments and aircraft probes on 30 April 1994 from the Cloud and Radiation Testbed site in north-central Oklahoma. The boundary layer structure clearly resembled that of a cloud-topped mixed layer, and the cloud content is shown to be near adiabatic up to the cloud-top entrainment zone. A cloud retrieval algorithm using the radar reflectivity and cloud droplet concentration (either measured in situ or deduced using dual-channel microwave radiometer data) is applied to construct uniquely high-resolution cross sections of liquid water content and mean droplet radius. The combined evidence indicates that the 350-600 m deep, slightly supercooled (2.0° to 2.0°C) cloud, which failed to produce any detectable ice or drizzle particles, contained an average droplet concentration of 347 cm3, and a maximum liquid water content of 0.8 g m3 and mean droplet radius of 9 m near cloud top. Lidar data indicate that the Ka-band radar usually detected the cloud-base height to within 50 m, such that the radar insensitivity to small cloud droplets had a small impact on the findings. Radar-derived liquid water paths ranged from 71 to 259 g m2 as the stratus deck varied, which is in excellent agreement with dual-channel microwave radiometer data, but 20% higher than that measured in situ. This difference appears to be due to the undersampling of the few largest cloud droplets by the aircraft probes. This combination of approaches yields a unique image of the content of a continental stratus cloud, as well as illustrating the utility of modern remote sensing systems for probing nonprecipitating water clouds.

Research paper thumbnail of In situ detection of biological particles in cloud ice-crystals

Nature Geoscience, 2009

Each month, Nature Geoscience will bring you top-quality research papers, reviews and opinion pie... more Each month, Nature Geoscience will bring you top-quality research papers, reviews and opinion pieces - in print and online.

Research paper thumbnail of Cirrus Cloud Microphysical Property Retrieval Using Lidar and Radar Measurements. Part II: Midlatitude Cirrus Microphysical and Radiative Properties

Journal of The Atmospheric Sciences, 2002

Research paper thumbnail of Improved Radar Ice Water Content Retrieval Algorithms Using Coincident Microphysical and Radar Measurements

Journal of Applied Meteorology, 2005

Airborne radar reflectivity measurements at frequencies of 9.6 and 94 GHz, with collocated, in si... more Airborne radar reflectivity measurements at frequencies of 9.6 and 94 GHz, with collocated, in situ particle size distribution and ice water content measurements from the Cirrus Regional Study of Tropical Anvils and Cirrus Layers (CRYSTAL) Florida Area Cirrus Experiment (FACE) in Florida in July 2002, offer one of the first opportunities to evaluate and improve algorithms for retrieving ice water content from single-wavelength spaceborne radar measurements. Both ice water content and radar reflectivity depend on the distribution of particle mass with size. It is demonstrated that single, power-law, mass dimensional relationships are unable to adequately account for the dominating contribution of small particles at lower reflectivities and large particles at higher reflectivities. To circumvent the need for multiple, or complex, mass dimensional relationships, analytic expressions that use particle ensemble mean ice particle densities that are derived from the coincident microphysical and radar observations are developed. These expressions, together with more than 5000 CRYSTAL FACE size distributions, are used to develop radar reflectivity ice water content relationships for the two radar wavelengths that appear to provide improvements over earlier relationships, at least for convectively generated stratiform ice clouds.

Research paper thumbnail of Midlatitude Cirrus Clouds Derived from Hurricane Nora: A Case Study with Implications for Ice Crystal Nucleation and Shape

Journal of The Atmospheric Sciences, 2003

Hurricane Nora traveled up the Baja Peninsula coast in the unusually warm El Niño waters of Septe... more Hurricane Nora traveled up the Baja Peninsula coast in the unusually warm El Niño waters of September 1997 until rapidly decaying as it approached southern California on 24 September. The anvil cirrus blowoff from the final surge of tropical convection became ...