![]() Digital Base Reflectivity (TR0, TR1, TR2/181 or after TZ0, TZ1, TZ2/180)Ī display of echo intensity measured in dBZ. General products include Base Reflectivity and Base Velocity as well as graphical products derived from algorithms including Spectrum Width, Vertically Integrated Liquid, and the Velocity Azimuth Display (VAD) Wind Profile. See Data Certification for more information on hard copy radar products, pricing, and certification information. Each copy includes state, county, and city background maps. Most Level-III products are available as digital images, color or grayscale hard copy, and acetate overlay copies. NCEI provides access to 26 TDWR Level-III products. A data file consists of a 24-byte volume scan header record followed by numerous 2,432-byte base data and message records. Data are stored in files that typically contain four, five, six, or ten minutes of base data. Level-II data are grouped into three meteorological base quantities: reflectivity, mean radial velocity, and spectrum width. NCEI provides access to all TDWR Level-II data. The data access pages include lists or visualizations of file availability that document these absences. Note: There are occasional gaps and missing data for each site in the archive that are caused by scheduled maintenance at radar sites, unplanned downtime due to severe weather, communications problems, archival problems, and other issues related to maintenance and infrastructure. Since hail can cause the rainfall estimates to be higher than what is actually occurring, steps are taken to prevent these high dBZ values from being converted to rainfall.The online store provides access to documentation, paper copies of data, and other related products. Hail is a good reflector of energy and will return very high dBZ values. These values are estimates of the rainfall per hour, updated each volume scan, with rainfall accumulated over time. Depending on the type of weather occurring and the area of the U.S., forecasters use a set of rainrates which are associated to the dBZ values. The higher the dBZ, the stronger the rainrate. Typically, light rain is occurring when the dBZ value reaches 20. The scale of dBZ values is also related to the intensity of rainfall. The value of the dBZ depends upon the mode the radar is in at the time the image was created. Notice the color on each scale remains the same in both operational modes, only the values change. The other scale (near left) represents dBZ values when the radar is in precipitation mode (dBZ values from 5 to 75). One scale (far left) represents dBZ values when the radar is in clear air mode (dBZ values from -28 to +28). Each reflectivity image you see includes one of two color scales. The dBZ values increase as the strength of the signal returned to the radar increases. So, a more convenient number for calculations and comparison, a decibel (or logarithmic) scale (dBZ), is used. Reflectivity (designated by the letter Z) covers a wide range of signals (from very weak to very strong). "Reflectivity" is the amount of transmitted power returned to the radar receiver. The colors are the different echo intensities (reflectivity) measured in dBZ (decibels of Z) during each elevation scan.
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