Z/R Relationships Table

Z/R Relationship Table

{ "timestamp":"02/21/25 at 10:26:06 PM", "zrData":[ { "bgstyle":"row-odd", "id":"AKQ (Wakefield)", "cellbg":"", "update":"Feb 21, 2025 10:00 PM", "zrCoef":"200", "zrExp":"1.6", "icon":"GenStratiformZR.gif", "iconAlt":"Marshall/Palmer General Stratiform Z/R", "rate":"0.11", "formulaName":"Marshall/Palmer General Stratiform Z/R", "bcfTitle":"1266 positive gage-radar pairings found over the past 6 hours", "bcfTitle2":" suggest that the radar estimates need to be multiplied by 1.45", "bcfTitle3":" to bring them in line with what the gages are reporting.", "bcfDur":"168", "bcfColor":"red", "bcf":"1.45", "bcfNumPairs":"1266", "bcfDesc":"under-" }, { "bgstyle":"row-even", "id":"BGM (Binghamton)", "cellbg":"", "update":"Feb 21, 2025 09:00 PM", "zrCoef":"130", "zrExp":"2", "icon":"WinterZR.gif", "iconAlt":"Cool Season (East) Stratiform Z/R", "rate":"0.11", "formulaName":"Cool Season (East) Stratiform Z/R", "bcfTitle":"12 positive gage-radar pairings found over the past 5 hours", "bcfTitle2":" suggest that the radar estimates need to be multiplied by 0.69", "bcfTitle3":" to bring them in line with what the gages are reporting.", "bcfDur":"10", "bcfColor":"red", "bcf":"0.69", "bcfNumPairs":"12", "bcfDesc":"over-" }, { "bgstyle":"row-odd", "id":"BUF (Buffalo)", "cellbg":"", "update":"Feb 21, 2025 10:00 PM", "zrCoef":"130", "zrExp":"2", "icon":"WinterZR.gif", "iconAlt":"Cool Season (East) Stratiform Z/R", "rate":"0.11", "formulaName":"Cool Season (East) Stratiform Z/R", "bcfTitle":"739 positive gage-radar pairings found over the past 6 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", "bcfColor":"red", "bcf":"1.22", "bcfNumPairs":"739", "bcfDesc":"under-" }, { "bgstyle":"row-even", "id":"CCX (State College)", "cellbg":"", "update":"Feb 21, 2025 10:00 PM", "zrCoef":"130", "zrExp":"2", "icon":"WinterZR.gif", "iconAlt":"Cool Season (East) Stratiform Z/R", "rate":"0.11", "formulaName":"Cool Season (East) Stratiform Z/R", "bcfTitle":"1188 positive gage-radar pairings found over the past 6 hours", "bcfTitle2":" suggest that the radar estimates need to be multiplied by 1.23", "bcfTitle3":" to bring them in line with what the gages are reporting.", "bcfDur":"168", "bcfColor":"red", "bcf":"1.23", "bcfNumPairs":"1188", "bcfDesc":"under-" }, { "bgstyle":"row-odd", "id":"DIX (Mt. Holly)", "cellbg":"", "update":"Feb 21, 2025 09:00 PM", "zrCoef":"300", "zrExp":"1.4", "icon":"DeepConvectiveZR.gif", "iconAlt":"Summertime Deep Convection Z/R", "rate":"0.09", "formulaName":"Summertime Deep Convection Z/R", "bcfTitle":"1573 positive gage-radar pairings found over the past 6 hours", "bcfTitle2":" suggest that the radar estimates need to be multiplied by 1.91", "bcfTitle3":" to bring them in line with what the gages are reporting.", "bcfDur":"168", "bcfColor":"red", "bcf":"1.91", "bcfNumPairs":"1573", "bcfDesc":"under-" }, { "bgstyle":"row-even", "id":"DOX (Dover)", "cellbg":"", "update":"Feb 21, 2025 10:00 PM", "zrCoef":"300", "zrExp":"1.4", "icon":"DeepConvectiveZR.gif", "iconAlt":"Summertime Deep Convection Z/R", "rate":"0.09", "formulaName":"Summertime Deep Convection Z/R", "bcfTitle":"2309 positive gage-radar pairings found over the past 6 hours", "bcfTitle2":" suggest that the radar estimates need to be multiplied by 1.46", "bcfTitle3":" to bring them in line with what the gages are reporting.", "bcfDur":"168", "bcfColor":"red", "bcf":"1.46", "bcfNumPairs":"2309", "bcfDesc":"under-" }, { "bgstyle":"row-odd", "id":"ENX (Albany)", "cellbg":"", "update":"Feb 21, 2025 10:00 PM", "zrCoef":"130", "zrExp":"2", "icon":"WinterZR.gif", "iconAlt":"Cool Season (East) Stratiform Z/R", "rate":"0.11", "formulaName":"Cool Season (East) Stratiform Z/R", "bcfTitle":"774 positive gage-radar pairings found over the past 6 hours", "bcfTitle2":" suggest that the radar estimates need to be multiplied by 1.11", "bcfTitle3":" to bring them in line with what the gages are reporting.", "bcfDur":"168", "bcfColor":"green", "bcf":"1.11", "bcfNumPairs":"774", "bcfDesc":"under-" }, { "bgstyle":"row-even", "id":"FCX (Blacksburg)", "cellbg":"", "update":"Feb 21, 2025 10:00 PM", "zrCoef":"130", "zrExp":"2", "icon":"WinterZR.gif", "iconAlt":"Cool Season (East) Stratiform Z/R", "rate":"0.11", "formulaName":"Cool Season (East) Stratiform Z/R", "bcfTitle":"633 positive gage-radar pairings found over the past 6 hours", "bcfTitle2":" suggest that the radar estimates need to be multiplied by 1.38", "bcfTitle3":" to bring them in line with what the gages are reporting.", "bcfDur":"168", "bcfColor":"red", "bcf":"1.38", "bcfNumPairs":"633", "bcfDesc":"under-" }, { "bgstyle":"row-odd", "id":"LWX (Sterling)", "cellbg":"", "update":"Feb 21, 2025 10:00 PM", "zrCoef":"130", "zrExp":"2", "icon":"WinterZR.gif", "iconAlt":"Cool Season (East) Stratiform Z/R", "rate":"0.11", "formulaName":"Cool Season (East) Stratiform Z/R", "bcfTitle":"2392 positive gage-radar pairings found over the past 6 hours", "bcfTitle2":" suggest that the radar estimates need to be multiplied by 1.27", "bcfTitle3":" to bring them in line with what the gages are reporting.", "bcfDur":"168", "bcfColor":"red", "bcf":"1.27", "bcfNumPairs":"2392", "bcfDesc":"under-" }, { "bgstyle":"row-even", "id":"OKX (Brookhaven)", "cellbg":"", "update":"Feb 21, 2025 10:00 PM", "zrCoef":"200", "zrExp":"1.6", "icon":"GenStratiformZR.gif", "iconAlt":"Marshall/Palmer General Stratiform Z/R", "rate":"0.11", "formulaName":"Marshall/Palmer General Stratiform Z/R", "bcfTitle":"970 positive gage-radar pairings found over the past 6 hours", "bcfTitle2":" suggest that the radar estimates need to be multiplied by 1.74", "bcfTitle3":" to bring them in line with what the gages are reporting.", "bcfDur":"168", "bcfColor":"red", "bcf":"1.74", "bcfNumPairs":"970", "bcfDesc":"under-" }, { "bgstyle":"row-odd", "id":"PBZ (Pittsburgh)", "cellbg":"", "update":"Feb 21, 2025 10:00 PM", "zrCoef":"300", "zrExp":"1.4", "icon":"DeepConvectiveZR.gif", "iconAlt":"Summertime Deep Convection Z/R", "rate":"0.09", "formulaName":"Summertime Deep Convection Z/R", "bcfTitle":"379 positive gage-radar pairings found over the past 6 hours", "bcfTitle2":" suggest that the radar estimates need to be multiplied by 1.53", "bcfTitle3":" to bring them in line with what the gages are reporting.", "bcfDur":"168", "bcfColor":"red", "bcf":"1.53", "bcfNumPairs":"379", "bcfDesc":"under-" }, { "bgstyle":"row-even", "id":"RAX (Raleigh)", "cellbg":"", "update":"Feb 21, 2025 10:00 PM", "zrCoef":"200", "zrExp":"1.6", "icon":"GenStratiformZR.gif", "iconAlt":"Marshall/Palmer General Stratiform Z/R", "rate":"0.11", "formulaName":"Marshall/Palmer General Stratiform Z/R", "bcfTitle":"213 positive gage-radar pairings found over the past 6 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", "bcfColor":"red", "bcf":"1.22", "bcfNumPairs":"213", "bcfDesc":"under-" }, { "bgstyle":"row-odd", "id":"RLX (Charleston)", "cellbg":"", "update":"Feb 21, 2025 09:00 PM", "zrCoef":"300", "zrExp":"1.4", "icon":"DeepConvectiveZR.gif", "iconAlt":"Summertime Deep Convection Z/R", "rate":"0.09", "formulaName":"Summertime Deep Convection Z/R", "bcfTitle":"43 positive gage-radar pairings found over the past 6 hours", "bcfTitle2":" suggest that the radar estimates need to be multiplied by 1.61", "bcfTitle3":" to bring them in line with what the gages are reporting.", "bcfDur":"168", "bcfColor":"red", "bcf":"1.61", "bcfNumPairs":"43", "bcfDesc":"under-" } ]}

The table above shows WSR-88D Z/R relationships for sites used in the MARFC radar mosaic. A Z/R relationship is a empirical formula that is used to estimate rainfall rates from reflectivity signal strength.

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 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 more than two hours old. This most commonly occurs when the radar is down for maintenance.

Rainfall Rates for Each Relationship @ 30dBZ
Summertime Deep Convection	0.09 inches/hour
Rosenfeld Tropical	0.13 inches/hour
Marshal/Palmer General Stratiform	0.11 inches/hour
Cool Season (East) Stratiform	0.11 inches/hour