Note: the steps with a * indicate steps that are currently performed by EOL.
Software programming languages are indicated in parentheses, and EOL
developed software is highlighted with a +.
The software tools listed here are meant to provide an overview of the known tools available for ELDORA processing. Software listed here is not necessarily supported by either EOL or the developer of the software. All questions regarding the use of a particular software package should be directed to the appropriate entity.
ELDORA field format data. This is a variation of the DORADE format
where
fore and aft beams may be interleaved and unsorted.
DOppler RAdar Data Exchange Format. Developed by Wen-Chau Lee, Craig Walther, and Richard Oye of EOL for efficiently storing and exchanging airborne and ground-based radar data. Please refer to the Dorade Format Overview for further information.
The internal format for the SOLO program. The
sweep file format is a
variation of the DORADE format, where each individual sweep of the
radar beam is stored in its own file. Please refer to the Dorade
Format Overview for further information.
The Common Doppler Radar Exchange Format, more commonly referred to
as Universal Format (UF). Designed primarily to accomodate data for a
single ground-based radar, it lacks some of the descriptor information
needed to fully describe ELDORA data.
The 'pure' binary format for CEDRIC data. This is the output format for both REORDER and CEDRIC. It is a simple gridded data format, developed by Carl Mohr and Jay Miller at the Mesoscale & Microscale Meteorology Division of NCAR. Please refer to Appendix D of the CEDRIC documentation for further information.
The metafile that is produced by CEDRIC
when the
GRAPHICS command is invoked. These files can be viewed using idt,
which is a product that is part of NCAR
graphics.
ASCII files contains the navigation corrections and radar pointing angle corrections. Fore and Aft radars each have a CFAC file (they are usually different). For historical reasons, the ground-speed correction is read in via the E-W velocity entry. The roll correction is not used because the error in rotation angle and roll cannot be separated.
The Translator generates one ground-echo file (with gde prefix) for fore and aft radars that contain information (INS, pointing angles, reflectivity, and Doppler velocity) for the ground gates selected in each beam that intersects the ground. The ground-echo files will be the input files for the plotscatter program to compute the INS and pointing angle errors.
NetCDF (network Common Data Form) is an interface for array-oriented data access and a library that provides an implementation of the interface. The netCDF library also defines a machine-independent format for representing scientific data. Together, the interface, library, and format support the creation, access, and sharing of scientific data. The netCDF software was developed at the Unidata Program Center in Boulder, Colorado. Please refer to the netCDF home page for further information on the format or the RAF Data Catalog for further information on RAF data.
Radar data format used by the NOAA P-3 tail and lower Fuselage radars. Takes its name from the Hurricane Research Division. Can be translated into DORADE sweep files for use with SOLO.
An NCAR/EOL supported software that converts several popular radar data formats (e.g., UF, HRD, ELDORA field) into sweep files (the internal format for the editing software, SOLO) and converts edited sweep files into UF and DORADE format for further processing. The translator has other functions such as generating the ground-echo files for navigation corrections and merging updated information (e.g., RAF flight-level data and correction factors). Please refer to the translator documentation for further information.
An NCAR/EOL supported radar/lidar data display and editing software. SOLO is a X-window based interactive software that replaced the RDSS software in 1993. Please refer to the SOLO documentation for further information.
An NCAR/EOL supported program that computes the INS and radar pointing angle errors. The framework of the plotscatter program is documented in Testud et al. (1995). The plotscatter program output suggestions on possible errors/biases on 8 parameters. Users need to manually update these corrections in the CFAC files. New ground-echo files using the updated navigation corrections (CFAC files). The final corrections are obtained via an iterative process until the ground is flat and not moving. A batch version of the plotscatter program (driven by Perl script) is available to automate the entire process. Please refer to the plotscatter documentation for further information.
REORDER is a program that transforms radar data from radar space to
cartesian space or cylindrical (coplane) space. The data can then be
ingested
into CEDRIC for synthesis. Please refer to the REORDER
documentation for further information.
Sprint is an NCAR/MMM program to interpolate radar measurements taken at spherical coordinates (range, azimuth, and elevation) to regularly-spaced Cartesian or longitude-latitude grids, in either constant height or constant elevation angle surfaces. It accepts radar data in any of the EOL field, univeral, DORADE, or NEXRAD Level II formats. SPRINT outputs interpolated data in pure binary format readable by CEDRIC. A description of the CEDRIC binary format can be found in Appendix D of the documentation for SPRINT or CEDRIC. Data from PPI scans can be interpolated to Cartesian or longitude-latitude grids, either at constant height or constant elevation angle surfaces. Both airborne helical scans and constant-azimuth (RHI) scans from ground-based radars are only interpolated to Cartesian grids (X, Y, and Z)
An NCAR/MMM supported mesoscale data analysis program that processes datasets on regular Cartesian and longitude-latitude grids. The analysis options include many numerical operations such as algebraic, filtering, and Doppler radar wind synthesis, both ground-based and airborne, as well as graphical operations. Several REMAPpings (interpolations) are possible: XYE --> XYZ, LLE--> LLZ, XYE <--> LLE, and XYZ <--> LLZ, where XY (LL) is a regular Cartesian (longitude-latitude) grid. Z (E) refers to a constant height (elevation angle) surface. CEDRIC uses its own self-describing, binary format as well as the network Common Data Format (netCDF) that was developed by NASA and UCAR's UNIDATA. CEDRIC can ingest Mudras data (pure format) from Reorder or Sprint interpolation software. The synthesized data can be saved in Mudras or Netcdf format for further processing. Graphical output is saved as gmeta file and can be viewed using NCAR IDT software. Please refer to the CEDRIC documentation for further information.
An NCAR/EOL developed software that produced publication quality 2-D vector and contour plots in PostScript form. Grid2PS can ingest Mudras data and produce horizontal and/or vertical cross-sections. Multiple panels of plots can be arranged on a single page. Please refer to the grid2ps documentation for further information.
idt provides a graphical user interface to the NCAR View interactive metafile translator ictrans. idt supports a subset of the ictrans command interface. Please refer to the idt man page for further information
NCAR/EOL developed software for calculating navigation corrections. It implements both the THL method and the GRH method for complex terrain, and allows for direct visualization of the correction factor application. It is currently still under development.
IDL tool for fine-tuning navigation corrections on a leg-by-leg basis using the ETHL method.
Fortran program developed by Brian Bosart at UCLA to fine-tuning navigation corrections on a leg-by-leg basis using the BLW method.
These complementary programs developed by John Gamache at NOAA's Hurricane Research Division (HRD) provide interpolation and synthesis for multiple Doppler datasets. Wind3_fill is a fully three-dimensional wind solver that includes the continuity equation and a small amount of filtering of the solution when determining the cost function.
Airborne weather Doppler radar data (Doppler velocity) contains both meteorological signals and aircraft motion. In order to accurately obtain multiple Doppler wind synthesis, the aircraft motion must be properly removed from the Doppler velocities. Errors in the aircraft intertial navigation system (INS) and the radar pointing angles can be corrected using various methodologies, outlined briefly here.
The corrections currently calculated and distributed by EOL use the "THL" (Testud-Hildebrand-Lee)
methodology, described in A
Procedure To Correct Airborne Doppler Radar Data For Navigation Errors,
Using
The Echo Returned From the Earth Surface (Testud, et al. 1995).
These corrections are obtained primarily
from calibration legs performed on each research flight, but in some
cases are from other legs. The algorithm uses the fact that the ground
echo return should be flat, and have zero residual velocity. Solving a
system of equations iteratively computes the correction to the INS
parameters and radar pointing angle needed for accurate radial
velocities.
For datasets involving complex terrain, such as that over
mountainous areas, an improved corrections algorithm was developed
which incorporates digital elevation maps into the corrections
calculation. The "GRH" (Georgis-Roux-Hildebrand)
method is described in Observation
of precipitating systems over complex orography with meteorological
Doppler radars: A feasibility study (Georgis, et al. 2000).
While several of the INS corrections remain stable throughout a
research flight, the ground speed and drift corrections may vary from
leg to leg during
a flight. These corrections are tightly coupled with the tilt angle,
and can be further refined on a leg-by-leg basis using the techniques
defined in Procedures
to Improve the Accuracy of Airborne Doppler Radar Data
(Bosart, et al 2002). The "ETHL" (Extended THL)
method works similarly to the original algorithm by iteratively
reducing ground velocity residuals to zero. In cases where the ground
velocity is not expected to be zero (ie. moving ocean surface), or over
complex terrain, the "BLW" (Bosart-Lee-Wakimoto)
method can be applied, which compares the in situ wind recorded on the
aircraft with the near-aircraft Doppler winds, reducing the discrepancy
between them to produce corrections.
It is strongly recommended that the user ensure that the ground residual velocities are near zero for the legs of interest before performing multiple Doppler analysis. If you have problems or questions regarding these procedures, please contact Wen-Chau Lee or Michael Bell.
Data editing is one of the more difficult aspects of airborne Doppler processing for newcomers. Users who are unfamiliar with solo are often at a loss as to where to begin. A Frequently Asked Questions (FAQ) page for ELDORA editing has been compiled with some sample editing commands for new users. It should be emphasized however, that careful editing is a key aspect of producing a quality Doppler analysis, and the techniques listed in the FAQ are no substitute for study with an experienced radar meteorologist.