An intercomparison of radar-based liquid cloud microphysics retrievals and implications for model evaluation studies

Abstract. This paper presents a statistical comparison of three cloud retrieval products of the Atmospheric Radiation Measurement (ARM) program at the Southern Great Plains (SGP) site from 1998 to 2006: MICROBASE, University of Utah (UU), and University of North Dakota (UND) products. The probability density functions of the various cloud liquid water content (LWC) retrievals appear to be consistent with each other. While the mean MICROBASE and UU cloud LWC retrievals agree well in the middle of cloud, the discrepancy increases to about 0.03 gm−3 at cloud top and cloud base. Alarmingly large differences are found in the droplet effective radius (re) retrievals. The mean MICROBASE re is more than 6 μm lower than the UU re, whereas the discrepancy is reduced to within 1 μm if columns containing raining and/or mixed-phase layers are excluded from the comparison. A suite of stratified comparisons and retrieval experiments reveal that the LWC difference stems primarily from rain contamination, partitioning of total liquid later path (LWP) into warm and supercooled liquid, and the input cloud mask and LWP. The large discrepancy among the re retrievals is mainly due to rain contamination and the presence of mixed-phase layers. Since rain or ice particles are likely to dominate radar backscattering over cloud droplets, the large discrepancy found in this paper can be thought of as a physical limitation of single-frequency radar approaches. It is therefore suggested that data users should use the retrievals with caution when rain and/or mixed-phase layers are present in the column.

[1]  G. Isaac,et al.  Aircraft Icing Measurements in East Coast Winter Storms , 1995 .

[2]  James J. Hack,et al.  Response of Climate Simulation to a New Convective Parameterization in the National Center for Atmospheric Research Community Climate Model (CCM3) , 1998 .

[3]  A. Slingo,et al.  Sensitivity of the Earth's radiation budget to changes in low clouds , 1990, Nature.

[4]  Pavlos Kollias,et al.  Cloud radar Doppler spectra in drizzling stratiform clouds: 1. Forward modeling and remote sensing applications , 2011 .

[5]  S. Schwartz,et al.  The Atmospheric Radiation Measurement (ARM) Program: Programmatic Background and Design of the Cloud and Radiation Test Bed , 1994 .

[6]  Robin J. Hogan,et al.  Comparison of ECMWF Winter-Season Cloud Fraction with Radar-Derived Values , 2001 .

[7]  D. Mechem,et al.  Assessment of variability in continental low stratiform clouds based on observations of radar reflectivity , 2005 .

[8]  Robert E. McIntosh,et al.  Continental Stratus Clouds: A Case Study Using Coordinated Remote Sensing and Aircraft Measurements , 1999 .

[9]  D. Zrnic,et al.  Doppler Radar and Weather Observations , 1984 .

[10]  Taneil Uttal,et al.  On cloud radar and microwave radiometer measurements of stratus cloud liquid water profiles , 1998 .

[11]  Krista Gaustad,et al.  CLOUDS AND MORE: ARM Climate Modeling Best Estimate Data , 2010 .

[12]  M. Miller,et al.  Threshold radar reflectivity for drizzling clouds , 2008 .

[13]  C. Fairall,et al.  Measurement of Stratus Cloud and Drizzle Parameters in ASTEX with a K , 1995 .

[14]  G. Stephens.  Cloud Feedbacks in the Climate System: A Critical Review , 2005 .

[15]  E. Clothiaux,et al.  Objective Determination of Cloud Heights and Radar Reflectivities Using a Combination of Active Remote Sensors at the ARM CART Sites , 2000 .

[16]  S. Bony,et al.  Comparing clouds and their seasonal variations in 10 atmospheric general circulation models with satellite measurements , 2005 .

[17]  Brooks E. Martner,et al.  An Unattended Cloud-Profiling Radar for Use in Climate Research , 1998 .

[18]  S. McFarlane,et al.  Clouds and Shortwave Fluxes at Nauru. Part II: Shortwave Flux Closure , 2004 .

[19]  Shepard A. Clough,et al.  Retrieving Liquid Wat0er Path and Precipitable Water Vapor From the Atmospheric Radiation Measurement (ARM) Microwave Radiometers , 2007, IEEE Transactions on Geoscience and Remote Sensing.

[20]  The Potential of a Spaceborne Cloud Radar for the Detection of Stratocumulus Clouds , 1997 .

[21]  Sergey Y. Matrosov,et al.  Attenuation-Based Estimates of Rainfall Rates Aloft with Vertically Pointing Ka-Band Radars , 2005 .

[22]  Dong Huang,et al.  High resolution retrieval of liquid water vertical distributions using collocated Ka‐band and W‐band cloud radars , 2009 .

[23]  J. Curry,et al.  Confronting Models with Data: The Gewex Cloud Systems Study , 2003 .

[24]  E. O'connor,et al.  The CloudSat mission and the A-train: a new dimension of space-based observations of clouds and precipitation , 2002 .

[25]  J. C. Liljegren,et al.  A new retrieval for cloud liquid water path using a ground‐based microwave radiometer and measurements of cloud temperature , 2001 .

[26]  Minghua Zhang,et al.  Simulations of midlatitude frontal clouds by single-column and cloud--resolving models during the Atmospheric Radiation Measurement March 2000 cloud intensive operational period , 2005 .

[27]  Roger Lhermitte,et al.  A 94-GHz Doppler Radar for Cloud Observations , 1987 .

[28]  G. Stephens,et al.  Comparison of regime‐sorted tropical cloud profiles observed by CloudSat with GEOS5 analyses and two general circulation model simulations , 2011 .

[29]  R. Houze,et al.  Three-Dimensional Kinematic and Microphysical Evolution of Florida Cumulonimbus. Part II: Frequency Distributions of Vertical Velocity, Reflectivity, and Differential Reflectivity , 1995 .

[30]  Michael Jensen,et al.  The Microbase Value-Added Product: A Baseline Retrieval of Cloud Microphysical Properties , 2011 .

[31]  G. Mace,et al.  The Vertical Structure of Cloud Occurrence and Radiative Forcing at the SGP ARM Site as Revealed by 8 Years of Continuous Data , 2008 .

[32]  Pavlos Kollias,et al.  Cloud radar Doppler spectra in drizzling stratiform clouds: 2. Observations and microphysical modeling of drizzle evolution , 2011 .

[33]  Ben S Cooper,et al.  Confronting models with data. , 2007, The Journal of hospital infection.

[34]  S. Crewell,et al.  On characterizing the error in a remotely sensed liquid water content profile , 2010 .

[35]  Patrick Minnis,et al.  Evaluating cloud retrieval algorithms with the ARM BBHRP framework , 2008 .

[36]  Gerald G. Mace,et al.  Global hydrometeor occurrence as observed by CloudSat: Initial observations from summer 2006 , 2007 .

[37]  E. Luke,et al.  Detection of supercooled liquid in mixed‐phase clouds using radar Doppler spectra , 2010 .

[38]  Clemens Simmer,et al.  Profiling Cloud Liquid Water by Combining Active and Passive Microwave Measurements with Cloud Model Statistics , 2001 .

[39]  Gerald M. Stokes,et al.  The Atmospheric Radiation Measurement Program , 2003 .

[40]  Gerald G. Mace,et al.  A constrained algorithm for retrieval of stratocumulus cloud properties using solar radiation, microwave radiometer, and millimeter cloud radar data , 2000 .

[41]  Ulrich Löhnert,et al.  Accuracy assessment of an integrated profiling technique for operationally deriving profiles of temperature, humidity, and cloud liquid water , 2007 .

[42]  David D. Turner,et al.  Toward understanding of differences in current cloud retrievals of ARM ground‐based measurements , 2012 .

[43]  E. Clothiaux,et al.  Doppler Cloud Radar Derived Drop Size Distributions in Liquid Water Stratus Clouds , 2001 .

[44]  Mark A. Miller,et al.  An Evaluation of a 94-GHz Radar for Remote Sensing of Cloud Properties , 1995 .

[45]  E. Clothiaux,et al.  The Atmospheric Radiation Measurement Program Cloud Profiling Radars: An Evaluation of Signal Processing and Sampling Strategies , 2005 .

[46]  Eugene E. Clothiaux,et al.  Parameterizations of the microphysical and shortwave radiative properties of boundary layer stratus from ground-based measurements , 1998 .

[47]  Peter Pilewskie,et al.  Microphysical and radiative properties of boundary layer stratiform clouds deduced from ground‐based measurements , 1997 .

[48]  P. Hobbs,et al.  Evaluation of a 35 GHz Radar for Cloud Physics Research , 1985 .

[49]  G. Mace,et al.  Profiles of Low-Level Stratus Cloud Microphysics Deduced from Ground-Based Measurements , 2003 .

[50]  Patrick Minnis,et al.  Cloud radiative forcing at the Atmospheric Radiation Measurement Program Climate Research Facility: 1. Technique, validation, and comparison to satellite‐derived diagnostic quantities , 2006 .

[51]  D. Troyan.  Merged Sounding Value-Added Product , 2010 .

[52]  Patrick Minnis,et al.  An Intercomparison of Microphysical Retrieval Algorithms for Upper-Tropospheric Ice Clouds , 2007 .

[53]  K. Sassen,et al.  Investigation of relationships between Ka-band radar reflectivity and ice and liquid water contents , 1994 .

[54]  Sungsu Park,et al.  Intercomparison of model simulations of mixed‐phase clouds observed during the ARM Mixed‐Phase Arctic Cloud Experiment. I: single‐layer cloud , 2009 .

[55]  Nicolas Gaussiat,et al.  Stratocumulus Liquid Water Content from Dual-Wavelength Radar , 1999 .