Data Types
For ingest data (stored in the raw product) and other products, the data formats for reflectivity, velocity, width, and ZDR differ slightly. When these data types are converted to a Cartesian product, the data values of 255 are replaced with 254, and 255 takes on the meaning of area not scanned.
For polar data, the name in parenthesis after each section title is the data type name used by IRIS to identify the data. Parameters for these numbers are defined in the sigtypes.h file.
| Data type | Description |
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Integral attenuation for horizontal (H) and vertical (V) channels |
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Integral attenuation of ZDR (dB) format |
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Doppler channel clutter-to-signal (CSR) ratio of dBT to -dBZ |
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Total power |
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Clutter corrected reflectivity |
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Uncorrected reflectivity |
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Hydrometeor classification Estimated hydrometeor type in the precipitation area |
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Specific differential phase An indicator of the rate of change of the phase difference between horizontally and vertically polarized pulses of the radar. A greater horizontal shift results in a positive KDP value, and a greater vertical shift results in a negative KDP value. Typical cause for a high KDP area is heavy rain. |
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Linear depolarization ratio H to V (or V to H) The ratio of cross-polar to co-polar reflectivity measured in dB |
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Log receiver signal-to-noise ratio |
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Horizontal (V) or vertical (V) differential phase Phase difference for the total round
trip between radar and the volume where the signal is reflected.
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Differential phase The phase difference due to propagation between the HH and VV channels of the radar. |
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Polarimetric meteo index |
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Rate of accumulation of precipitation in units of mm/hour For snow, this is usually refers to the liquid equivalent. |
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Correlation coefficient between HH and VV (or HH & HV / VV & VH) channels Higher (>0.95) values indicate uniform precipitation areas, and lower values indicate more mixed hydrometeor types, such as melting snow, wet snowflakes, or airborne debris. |
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Signal-to-noise ratio Generic measurement of signal-noise ratio in dB |
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Signal quality index A value between 0-1 that measures
the signal's Doppler coherency, that is, the correlation between the signal and its
Doppler lag:
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Total reflectivity Total power returned to the radar in reflectivity units. It typically represents the horizontal reflectivity without ground clutter correction. |
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Total vertical (HV enhanced) reflectivity Total reflectivity from the vertical polarization channel (TV) and combination of the horizontal and vertical channel (TE) |
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Velocity Average radial velocity (towards or away from the radar) of detected hydrometeor areas |
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Corrected velocity Same as velocity |
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Velocity and corrected velocity of wind shear |
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Spectral width Variability of Doppler velocity values within the measurement area |
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Polar cross-correlation, uncorrected
Because this value is not noise corrected, this is a direct indicator of the PHIDP uncertainty. |
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Reflectivity Usually referred to as dBZ, this is the common data type that measures radar signal reflectivity, and is used to estimate precipitation intensity from that. All |
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Vertical (HV enhanced) reflectivity Total reflectivity from the vertical polarization channel ( |
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Corrected reflectivity Same as reflectivity
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Differential reflectivity The ratio of SNR in the horizontal channel to the SNR in the vertical channel. Positive values indicate more prominent horizontal echoes and negative values more prominent vertical echoes. Larger hydrometeor sizes are usually identified by high positive ZDR values. |
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Corrected differential reflectivity Same as differential reflectivity
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