North of Little Rock are a number of squall lines imbedded in a The thunderstorm cells become organized into a line, called a squall Multicell thunderstorm between El Dorado and Pine Bluff, where the individual cells are circled. In Fig H 4 actually contains 3 smaller cells.įig H4. Range of sizes, and one can see that the circle just north of El Dorado That contains about 5 cells of different intensities (shown in Fig H 4 by the 5Ĭircled regions of relatively high reflectivity). That the cell south of El Dorado is part of a multicell thunderstorm Than one thunderstorm rain cell (as viewed by radar). One massive thunderstorm cloud (as viewed by eye) will contain more (a) Ground clutter near the Little Rock radar, and (b) a thunderstorm cell south of El Dorado. Thunderstorm cell has a peak reflectivity of roughly 52 dBZ, which corresponds to "intense" rain from the info in Fig H 1.įig H 3. To stronger rain at the center of the cell. Rings of colour, going from the colours for weakest rain at the outside Near the center of the display, ground clutter is shown as the tiny dots of blue (see Fig H 3a.) South of El Dorado is one thunderstorm cell (Fig H 3b).Ī cell is a small region of intense rain, which shows up as concentric Radar reflectivity image from the radar at Little Rock, Arkansas. Highways) are shown as thin red lines, and some lakes are outlined inįig H2. White lines show state boundaries, with Arkansas in the center, and the Particular image, the radar is in the center of the image. In the reflectivity image below (Fig H 2) for US National Weather Service radar at Little Rock, Arkansas (station KLZK), the dBZ colour scale is along the left side. Of the radar echo, so be sure to look at the scale before you try to Weather web sites give the colour scale vs. 502 pp.)Ĭolours that are used to represent different echo strengths areĪrbitrary - different weather web sites use different colours. (from Stull, 2000: "Meteorology for Scientists and Engineers, 2nd Ed., Brooks/Cole Thomson Learning. Rainfall intensity chart, for radar reflectivity returns in units of dBZ. Radar reflectivity of 40 dBZ corresponds to an approximate rainfall rate of RR = 10 mm/h, which is a moderate rainfall rate.įig H 1. Straight to the left to read the RR along the left axis. That value at the bottom of the figure, then go straight up in theįigure to you hit the diagonal line, and finally move horizontally To use this figure, start with the value of dBZ measured by radar, find An approximate relationship between dBZ, RR, and descriptive The rate of increase of depth of water in a rainguage, measured in Thunderstorms, while small values correspond to light rain from shallowĬlouds, or returns from bugs. Values of dBZ correspond to heavier rain from more intense Hence, the numbers that are usually displayed on reflectivity radar images are in units of dBZ. Z, which is expressed in units of decibels ( dB). Viewable on computer screens, the software first takes the logarithm of To make this wide range of Z accessible and But Z can vary from extremely large values for heavy rain, to Radar software automatically computes a range-corrected andĮquipment-calibrated measure of reflectivity, which is given the symbol Rain that is furtherĪway returns a weaker signal than rain close by. Sensitivity of the radar antenna and electronics. Of the rain from the radar, the shape of the hydrometers, and the Intensity of the return signal (radar echo) received by the radarĭepends not only on the intensity of the rain, but also on the distance UBC ATSC 201 - Meteorology of Storms - Radar Storm Image Interpretation INTERPRETING RADAR REFLECTIVITY IMAGES
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