National Weather Service United States Department of Commerce

Z/R Relationship Table

{ "timestamp":"Sat Feb 04 18:29:01 EDT 2023", "zrData":[ { "bgstyle":"row-even", "id":"BUF", "cellbg":"", "update":"6pm EDT 04-Feb-2023", "zrCoef":"130", "zrExp":"2", "icon":"Winter ZR.png", "iconAlt":"Cool Season (East) Stratiform Z/R icon", "rate":"0.11", "formulaName":"Cool Season (East) Stratiform Z/R", "bcfTitle":"252 positive gage-radar pairings found over the past 168 hours", "bcfTitle2":" suggest that the radar estimates need to be multiplied by 1.17", "bcfTitle3":" to bring them in line with what the gages are reporting.", "bcfDur":"168-hr", "bcfColor":"#00CC00", "bcf":"1.17", "bcfNumPairs":"252", "bcfDesc":"under-estimation" }, { "bgstyle":"row-odd", "id":"CCX", "cellbg":"", "update":"6pm EDT 04-Feb-2023", "zrCoef":"130", "zrExp":"2", "icon":"Winter ZR.png", "iconAlt":"Cool Season (East) Stratiform Z/R icon", "rate":"0.11", "formulaName":"Cool Season (East) Stratiform Z/R", "bcfTitle":"462 positive gage-radar pairings found over the past 168 hours", "bcfTitle2":" suggest that the radar estimates need to be multiplied by 1.12", "bcfTitle3":" to bring them in line with what the gages are reporting.", "bcfDur":"168-hr", "bcfColor":"#00CC00", "bcf":"1.12", "bcfNumPairs":"462", "bcfDesc":"under-estimation" }, { "bgstyle":"row-even", "id":"CLE", "cellbg":"", "update":"6pm EDT 04-Feb-2023", "zrCoef":"130", "zrExp":"2", "icon":"Winter ZR.png", "iconAlt":"Cool Season (East) Stratiform Z/R icon", "rate":"0.11", "formulaName":"Cool Season (East) Stratiform Z/R", "bcfTitle":"642 positive gage-radar pairings found over the past 168 hours", "bcfTitle2":" suggest that the radar estimates need to be multiplied by 1.40", "bcfTitle3":" to bring them in line with what the gages are reporting.", "bcfDur":"168-hr", "bcfColor":"#CC0000", "bcf":"1.40", "bcfNumPairs":"642", "bcfDesc":"under-estimation" }, { "bgstyle":"row-odd", "id":"DTX", "cellbg":"", "update":"6pm EDT 04-Feb-2023", "zrCoef":"200", "zrExp":"1.6", "icon":"Gen Stratiform ZR.png", "iconAlt":"Marshall/Palmer Stratiform Z/R icon", "rate":"0.11", "formulaName":"Marshall/Palmer Stratiform Z/R", "bcfTitle":"75 positive gage-radar pairings found over the past 168 hours", "bcfTitle2":" suggest that the radar estimates need to be multiplied by 1.70", "bcfTitle3":" to bring them in line with what the gages are reporting.", "bcfDur":"168-hr", "bcfColor":"#CC0000", "bcf":"1.70", "bcfNumPairs":"75", "bcfDesc":"under-estimation" }, { "bgstyle":"row-even", "id":"FCX", "cellbg":"", "update":"6pm EDT 04-Feb-2023", "zrCoef":"130", "zrExp":"2", "icon":"Winter ZR.png", "iconAlt":"Cool Season (East) Stratiform Z/R icon", "rate":"0.11", "formulaName":"Cool Season (East) Stratiform Z/R", "bcfTitle":"1577 positive gage-radar pairings found over the past 168 hours", "bcfTitle2":" suggest that the radar estimates need to be multiplied by 1.24", "bcfTitle3":" to bring them in line with what the gages are reporting.", "bcfDur":"168-hr", "bcfColor":"#CC0000", "bcf":"1.24", "bcfNumPairs":"1577", "bcfDesc":"under-estimation" }, { "bgstyle":"row-odd", "id":"GRR", "cellbg":"", "update":"6pm EDT 04-Feb-2023", "zrCoef":"200", "zrExp":"1.6", "icon":"Gen Stratiform ZR.png", "iconAlt":"Marshall/Palmer Stratiform Z/R icon", "rate":"0.11", "formulaName":"Marshall/Palmer Stratiform Z/R", "bcfTitle":"81 positive gage-radar pairings found over the past 168 hours", "bcfTitle2":" suggest that the radar estimates need to be multiplied by 1.52", "bcfTitle3":" to bring them in line with what the gages are reporting.", "bcfDur":"168-hr", "bcfColor":"#CC0000", "bcf":"1.52", "bcfNumPairs":"81", "bcfDesc":"under-estimation" }, { "bgstyle":"row-even", "id":"HPX", "cellbg":"", "update":"6pm EDT 04-Feb-2023", "zrCoef":"200", "zrExp":"1.6", "icon":"Gen Stratiform ZR.png", "iconAlt":"Marshall/Palmer Stratiform Z/R icon", "rate":"0.11", "formulaName":"Marshall/Palmer Stratiform Z/R", "bcfTitle":"1535 positive gage-radar pairings found over the past 168 hours", "bcfTitle2":" suggest that the radar estimates need to be multiplied by 1.19", "bcfTitle3":" to bring them in line with what the gages are reporting.", "bcfDur":"168-hr", "bcfColor":"#CC0000", "bcf":"1.19", "bcfNumPairs":"1535", "bcfDesc":"under-estimation" }, { "bgstyle":"row-odd", "id":"HTX", "cellbg":"", "update":"6pm EDT 04-Feb-2023", "zrCoef":"300", "zrExp":"1.4", "icon":"Deep Convective ZR.png", "iconAlt":"Summer Deep Convection Z/R icon", "rate":"0.09", "formulaName":"Summer Deep Convection Z/R", "bcfTitle":"2435 positive gage-radar pairings found over the past 168 hours", "bcfTitle2":" suggest that the radar estimates need to be multiplied by 0.93", "bcfTitle3":" to bring them in line with what the gages are reporting.", "bcfDur":"168-hr", "bcfColor":"#00CC00", "bcf":"0.93", "bcfNumPairs":"2435", "bcfDesc":"over-estimation" }, { "bgstyle":"row-even", "id":"ILN", "cellbg":"", "update":"6pm EDT 04-Feb-2023", "zrCoef":"130", "zrExp":"2", "icon":"Winter ZR.png", "iconAlt":"Cool Season (East) Stratiform Z/R icon", "rate":"0.11", "formulaName":"Cool Season (East) Stratiform Z/R", "bcfTitle":"1142 positive gage-radar pairings found over the past 168 hours", "bcfTitle2":" suggest that the radar estimates need to be multiplied by 1.26", "bcfTitle3":" to bring them in line with what the gages are reporting.", "bcfDur":"168-hr", "bcfColor":"#CC0000", "bcf":"1.26", "bcfNumPairs":"1142", "bcfDesc":"under-estimation" }, { "bgstyle":"row-odd", "id":"ILX", "cellbg":"", "update":"6pm EDT 04-Feb-2023", "zrCoef":"200", "zrExp":"1.6", "icon":"Gen Stratiform ZR.png", "iconAlt":"Marshall/Palmer Stratiform Z/R icon", "rate":"0.11", "formulaName":"Marshall/Palmer Stratiform Z/R", "bcfTitle":"175 positive gage-radar pairings found over the past 168 hours", "bcfTitle2":" suggest that the radar estimates need to be multiplied by 1.47", "bcfTitle3":" to bring them in line with what the gages are reporting.", "bcfDur":"168-hr", "bcfColor":"#CC0000", "bcf":"1.47", "bcfNumPairs":"175", "bcfDesc":"under-estimation" }, { "bgstyle":"row-even", "id":"IND", "cellbg":"", "update":"6pm EDT 04-Feb-2023", "zrCoef":"200", "zrExp":"1.6", "icon":"Gen Stratiform ZR.png", "iconAlt":"Marshall/Palmer Stratiform Z/R icon", "rate":"0.11", "formulaName":"Marshall/Palmer Stratiform Z/R", "bcfTitle":"389 positive gage-radar pairings found over the past 168 hours", "bcfTitle2":" suggest that the radar estimates need to be multiplied by 1.35", "bcfTitle3":" to bring them in line with what the gages are reporting.", "bcfDur":"168-hr", "bcfColor":"#CC0000", "bcf":"1.35", "bcfNumPairs":"389", "bcfDesc":"under-estimation" }, { "bgstyle":"row-odd", "id":"IWX", "cellbg":"", "update":"6pm EDT 04-Feb-2023", "zrCoef":"200", "zrExp":"1.6", "icon":"Gen Stratiform ZR.png", "iconAlt":"Marshall/Palmer Stratiform Z/R icon", "rate":"0.11", "formulaName":"Marshall/Palmer Stratiform Z/R", "bcfTitle":"223 positive gage-radar pairings found over the past 168 hours", "bcfTitle2":" suggest that the radar estimates need to be multiplied by 1.35", "bcfTitle3":" to bring them in line with what the gages are reporting.", "bcfDur":"168-hr", "bcfColor":"#CC0000", "bcf":"1.35", "bcfNumPairs":"223", "bcfDesc":"under-estimation" }, { "bgstyle":"row-even", "id":"JKL", "cellbg":"", "update":"6pm EDT 04-Feb-2023", "zrCoef":"130", "zrExp":"2", "icon":"Winter ZR.png", "iconAlt":"Cool Season (East) Stratiform Z/R icon", "rate":"0.11", "formulaName":"Cool Season (East) Stratiform Z/R", "bcfTitle":"3088 positive gage-radar pairings found over the past 168 hours", "bcfTitle2":" suggest that the radar estimates need to be multiplied by 1.04", "bcfTitle3":" to bring them in line with what the gages are reporting.", "bcfDur":"168-hr", "bcfColor":"#00CC00", "bcf":"1.04", "bcfNumPairs":"3088", "bcfDesc":"unbiased estimation" }, { "bgstyle":"row-odd", "id":"LOT", "cellbg":"", "update":"6pm EDT 04-Feb-2023", "zrCoef":"130", "zrExp":"2", "icon":"Winter ZR.png", "iconAlt":"Cool Season (East) Stratiform Z/R icon", "rate":"0.11", "formulaName":"Cool Season (East) Stratiform Z/R", "bcfTitle":"238 positive gage-radar pairings found over the past 168 hours", "bcfTitle2":" suggest that the radar estimates need to be multiplied by 1.03", "bcfTitle3":" to bring them in line with what the gages are reporting.", "bcfDur":"168-hr", "bcfColor":"#00CC00", "bcf":"1.03", "bcfNumPairs":"238", "bcfDesc":"unbiased estimation" }, { "bgstyle":"row-even", "id":"LSX", "cellbg":"", "update":"6pm EDT 04-Feb-2023", "zrCoef":"200", "zrExp":"1.6", "icon":"Gen Stratiform ZR.png", "iconAlt":"Marshall/Palmer Stratiform Z/R icon", "rate":"0.11", "formulaName":"Marshall/Palmer Stratiform Z/R", "bcfTitle":"212 positive gage-radar pairings found over the past 168 hours", "bcfTitle2":" suggest that the radar estimates need to be multiplied by 1.22", "bcfTitle3":" to bring them in line with what the gages are reporting.", "bcfDur":"168-hr", "bcfColor":"#CC0000", "bcf":"1.22", "bcfNumPairs":"212", "bcfDesc":"under-estimation" }, { "bgstyle":"row-odd", "id":"LVX", "cellbg":"", "update":"6pm EDT 04-Feb-2023", "zrCoef":"130", "zrExp":"2", "icon":"Winter ZR.png", "iconAlt":"Cool Season (East) Stratiform Z/R icon", "rate":"0.11", "formulaName":"Cool Season (East) Stratiform Z/R", "bcfTitle":"1339 positive gage-radar pairings found over the past 168 hours", "bcfTitle2":" suggest that the radar estimates need to be multiplied by 1.56", "bcfTitle3":" to bring them in line with what the gages are reporting.", "bcfDur":"168-hr", "bcfColor":"#CC0000", "bcf":"1.56", "bcfNumPairs":"1339", "bcfDesc":"under-estimation" }, { "bgstyle":"row-even", "id":"LWX", "cellbg":"", "update":"6pm EDT 04-Feb-2023", "zrCoef":"200", "zrExp":"1.6", "icon":"Gen Stratiform ZR.png", "iconAlt":"Marshall/Palmer Stratiform Z/R icon", "rate":"0.11", "formulaName":"Marshall/Palmer Stratiform Z/R", "bcfTitle":"98 positive gage-radar pairings found over the past 168 hours", "bcfTitle2":" suggest that the radar estimates need to be multiplied by 1.78", "bcfTitle3":" to bring them in line with what the gages are reporting.", "bcfDur":"168-hr", "bcfColor":"#CC0000", "bcf":"1.78", "bcfNumPairs":"98", "bcfDesc":"under-estimation" }, { "bgstyle":"row-odd", "id":"MRX", "cellbg":"", "update":"6pm EDT 04-Feb-2023", "zrCoef":"200", "zrExp":"1.6", "icon":"Gen Stratiform ZR.png", "iconAlt":"Marshall/Palmer Stratiform Z/R icon", "rate":"0.11", "formulaName":"Marshall/Palmer Stratiform Z/R", "bcfTitle":"3884 positive gage-radar pairings found over the past 168 hours", "bcfTitle2":" suggest that the radar estimates need to be multiplied by 1.00", "bcfTitle3":" to bring them in line with what the gages are reporting.", "bcfDur":"168-hr", "bcfColor":"#00CC00", "bcf":"1.00", "bcfNumPairs":"3884", "bcfDesc":"unbiased estimation" }, { "bgstyle":"row-even", "id":"OHX", "cellbg":"", "update":"6pm EDT 04-Feb-2023", "zrCoef":"300", "zrExp":"1.4", "icon":"Deep Convective ZR.png", "iconAlt":"Summer Deep Convection Z/R icon", "rate":"0.09", "formulaName":"Summer Deep Convection Z/R", "bcfTitle":"2591 positive gage-radar pairings found over the past 168 hours", "bcfTitle2":" suggest that the radar estimates need to be multiplied by 0.91", "bcfTitle3":" to bring them in line with what the gages are reporting.", "bcfDur":"168-hr", "bcfColor":"#00CC00", "bcf":"0.91", "bcfNumPairs":"2591", "bcfDesc":"over-estimation" }, { "bgstyle":"row-odd", "id":"PAH", "cellbg":"", "update":"6pm EDT 04-Feb-2023", "zrCoef":"200", "zrExp":"1.6", "icon":"Gen Stratiform ZR.png", "iconAlt":"Marshall/Palmer Stratiform Z/R icon", "rate":"0.11", "formulaName":"Marshall/Palmer Stratiform Z/R", "bcfTitle":"939 positive gage-radar pairings found over the past 168 hours", "bcfTitle2":" suggest that the radar estimates need to be multiplied by 0.97", "bcfTitle3":" to bring them in line with what the gages are reporting.", "bcfDur":"168-hr", "bcfColor":"#00CC00", "bcf":"0.97", "bcfNumPairs":"939", "bcfDesc":"unbiased estimation" }, { "bgstyle":"row-even", "id":"PBZ", "cellbg":"", "update":"6pm EDT 04-Feb-2023", "zrCoef":"200", "zrExp":"1.6", "icon":"Gen Stratiform ZR.png", "iconAlt":"Marshall/Palmer Stratiform Z/R icon", "rate":"0.11", "formulaName":"Marshall/Palmer Stratiform Z/R", "bcfTitle":"899 positive gage-radar pairings found over the past 168 hours", "bcfTitle2":" suggest that the radar estimates need to be multiplied by 1.19", "bcfTitle3":" to bring them in line with what the gages are reporting.", "bcfDur":"168-hr", "bcfColor":"#CC0000", "bcf":"1.19", "bcfNumPairs":"899", "bcfDesc":"under-estimation" }, { "bgstyle":"row-odd", "id":"RLX", "cellbg":"", "update":"6pm EDT 04-Feb-2023", "zrCoef":"200", "zrExp":"1.6", "icon":"Gen Stratiform ZR.png", "iconAlt":"Marshall/Palmer Stratiform Z/R icon", "rate":"0.11", "formulaName":"Marshall/Palmer Stratiform Z/R", "bcfTitle":"1599 positive gage-radar pairings found over the past 168 hours", "bcfTitle2":" suggest that the radar estimates need to be multiplied by 1.15", "bcfTitle3":" to bring them in line with what the gages are reporting.", "bcfDur":"168-hr", "bcfColor":"#00CC00", "bcf":"1.15", "bcfNumPairs":"1599", "bcfDesc":"under-estimation" }, { "bgstyle":"row-even", "id":"VWX", "cellbg":"", "update":"6pm EDT 04-Feb-2023", "zrCoef":"200", "zrExp":"1.6", "icon":"Gen Stratiform ZR.png", "iconAlt":"Marshall/Palmer Stratiform Z/R icon", "rate":"0.11", "formulaName":"Marshall/Palmer Stratiform Z/R", "bcfTitle":"772 positive gage-radar pairings found over the past 168 hours", "bcfTitle2":" suggest that the radar estimates need to be multiplied by 1.03", "bcfTitle3":" to bring them in line with what the gages are reporting.", "bcfDur":"168-hr", "bcfColor":"#00CC00", "bcf":"1.03", "bcfNumPairs":"772", "bcfDesc":"unbiased estimation" }] }
 

 

The table above shows WSR-88D Z/R relationships for sites used in the OHRFC radar mosaic. A Z/R relationship is a empirical formula that is used to estimate rainfall rates from reflectivity signal strength. Parameters that can be varied at each radar site are those shown in red.

Most stratiform rain events in the Ohio River Valley have a reflectivity signal strength of 20-40dBZ with occasional peaks to 45dBZ, but rarely anything higher (that isn't "brightbanding"). For more information and recommendations regarding Z/R relationships, see the Radar Operations Center's Handbook. Refer to Section 7.7.2 Z-R Coefficients. (This handbook is for agency use only, and requires a NOAA LDAP login.)

The bias correction factor can only be computed if there are at least 10 gage-radar pairs with both values 0.03 inches or more. Sometimes, data has to be searched back several hours to find at least 10 such pairs. (The actual number of pairs used in computing this bias factor is shown following the # sign.) The number of hours searched is shown preceding the bias factor. Bias factors are color-coded green if the radar estimates are within 15% tolerance of what the gages verify, or red otherwise. Values over 1.0 mean the radar is under-estimating. Values under 1.0 means the radar is over-estimating. This may seem counter-intuitive. To get the radar estimates to verify well with the gage values, the radar estimates would have to be multiplied by this bias factor shown for each radar.

Any cells with a yellow background under the "Last Reported" column indicate that the latest report is not up-to-date (perhaps the radar is down for maintenance).