SACRCOR

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sacrcor > Scanning ARM Cloud Radar CorrectionsVAP Type(s) > Evaluation

This dataset contains moments from the Scanning ARM Cloud Radars (SACRs) which have been filtered and corrected in order to provide a product for non-radar meteorologists which contains fewer measurement artifacts and effects from signal propagation.

Corrections have been applied to selected moments. The 'reflectivity_corrected' variable has been corrected for gaseous attenuation effects. Dealiasing of Doppler velocities is performed using two algorithms, with the results stored in the variables 'mean_doppler_velocity_corrected' and 'mean_doppler_velocity_corrected2.'

This product removes returns from non-atmospheric source, such as insects, ground clutter, and second trip echoes, leaving only meaningful returns from clouds and precipitation.  Users should note that the filter mask in this product is not perfect.  A small amount of clutter, insects and second trip echo artifacts may still be present in the filtered data, especially near the radar where classification is particularly challenging.  Additionally, due to the instrument configuration, no filtering of insects was performed on data from the X-band SACR.  Improvements to these algorithms are planned as further testing is performed and additional data becomes available. The filter applied to the reflectivity is also applied to both corrected mean Doppler velocity variables.  This filter is appropriate for filtering other radar moments contained in this product but the task of extracting this filter and applying it to these additional moments is left to the user.  By not filtering all radar moments it is possible to examine both the filtered and unfiltered radar moments using a single data product.

Finally, the locations of each sweep in the radar volume are detected by examining the elevation and azimuth angles. These locations are stored in the same variables as in the a1 level files, simply prefixed by the string 'a1_.'

As mentioned earlier, two independent algorithms were used to dealias the Doppler velocities.  This duplication is intended to solicit feedback from users on the performance and reliability of these two algorithms to direct future development.  Users should note that the algorithm used to perform the dealiasing corresponding to the 'mean_doppler_velocity_corrected' variable performs unfolding ray-by-ray and provides a flag indicating whether the algorithm succeeded in dealiasing each individual ray.   These flags are stored in the 'velocity_unfolding_flag' variable.   Rays for which this variable indicates that dealiasing was unsuccessful, should not relied upon.  The second dealiasing algorithm unfolds velocities by finding regions of similar velocities in two dimensions and unfolds these regions  in order to minimize the difference between regions. Results are stored in the field 'mean_doppler_velocity_corrected2.'  Users should note that this algorithm does not use data from external sources such as soundings for comparison and therefore may report velocities which globally differ from the true velocities in the atmosphere by multiples of the Nyquist interval.  Additionally, in some cases the algorithm does not handle the periodic nature of PPI scans properly which may lead to subpar unfolding across  0 degrees azimuth.

Input datastreams for the SACRCOR product are the corresponding sacr.a1 datastream, the ceil.b1 datastream for insect detection and the mergesonde1mace.c1 datastream for dealiasing. Many of the algorithms used in processing are described in the 2014 article by Kollias et al. Feedback on this product from users is greatly appreciated and will help drive future development.

Purpose

The purpose of the SACRCOR data product is to provide radar observables from the Scanning ARM Cloud Radars (SACRs) for use by non-radar meteorologists who do not wish to be concerned with identifying and filtering measurement artifacts or correcting signal propagation effects. For details of the collection of the SACR data, refer to the Scanning ARM Cloud Radar (X/Ka/W-SACR) Handbook (DOE/SC-ARM/TR-113).

Measurements

Locations

  • Fixed
  • AMF1
  • AMF2
  • AMF3

Components

kasacr: Ka-Band Scanning ARM Cloud Radar

wsacr: W-band Scanning ARM Cloud Radar

xsacr: X-Band Scanning ARM Cloud Radar

Data Details

Developed By Jonathan Helmus | Karen Johnson | Michael Jensen | Scott Collis | Aleksandra Tatarevic | Pavlos Kollias | Katia Lamer
Contact Jonathan Helmus
Resource(s) Data Directory
ReadMe
Data format NetCDF, png
Site PVC
SGP
TMP
Content time range 1 August 2012 - 31 August 2014
Attribute accuracy No formal attribute accuracy tests were conducted
Positional accuracy No formal positional accuracy tests were conducted
Data Consistency and Completeness The corrected reflectivity and mean Doppler velocity variables (reflectivity_corrected, mean_doppler_velocity_corrected, and mean_doppler_velocity_corrected2) use the value specified by the '_FillValue' attribute to specify a feature mask. Data within these variables marked with '_FillValue' indicate locations of non-atmospheric returns: insects, ground clutter or second-trip echoes. Data with other values indicate atmospheric returns, most likely from hydrometeors. The success of the Doppler velocity dealiasing algorithm used to generate the data in the 'mean_doppler_velocity_corrected variable' is indicated by data in the 'velocity_unfolding_flag' variable. This flag indicates for each ray whether the algorithm succeeded in dealiasing the data (indicated by a value of 1) or failed to dealias the data (indicated by a value of 0). Users are advised to read the entire metadata record carefully for additional details on the feature mask and the Doppler velocity correction.
Access Restriction No access constraints are associated with this data.
Use Restriction No use constraints are associated with this data.
File naming convention ARM Standard naming convention with datastream name of sacrcor
Directory Organization Files are seperated first by site (sgp, pvc, tmp) and then by datastream (sgpkasacrcorawrhiC1.c1, sgpkasacrcorppiC1.c1)
Citations Kollias, Pavlos, Nitin Bharadwaj, Kevin Widener, Ieng Jo, and Karen Johnson. "Scanning ARM Cloud Radars. Part I: Operational Sampling Strategies." Journal of Atmospheric and Oceanic Technology, 31, March 2014, 569. doi:10.1175/JTECH-D-13-00044.1.

Kollias, Pavlos, Ieng Jo, Paloma Borque, Aleksandra Tatarevic, Katia Lamer, Nitin Bharadwaj, Kevin Widener, Karen Johnson, and Eugene E. Clothiaux. "Scanning ARM Cloud Radars. Part II: Data Quality Control and Processing." Journal of Atmospheric and Oceanic Technology, 31, March 2014, 583. doi:10.1175/JTECH-D-13-00045.1.