![Page 1: Radar Reflectivity (Z) and Rainfall (R) Relationships in Central Florida Part II](https://reader030.vdocuments.mx/reader030/viewer/2022032804/56812b07550346895d8ee883/html5/thumbnails/1.jpg)
By: Jeana Mascio
![Page 2: Radar Reflectivity (Z) and Rainfall (R) Relationships in Central Florida Part II](https://reader030.vdocuments.mx/reader030/viewer/2022032804/56812b07550346895d8ee883/html5/thumbnails/2.jpg)
The PointWant to be more accurate with estimating
rainfall amounts from Z/R relationships
![Page 3: Radar Reflectivity (Z) and Rainfall (R) Relationships in Central Florida Part II](https://reader030.vdocuments.mx/reader030/viewer/2022032804/56812b07550346895d8ee883/html5/thumbnails/3.jpg)
The PointWant to be more accurate with estimating
rainfall amounts from Z/R relationships
Drop Size Distribution (DSD) variations in storms causes most inaccuracies
![Page 4: Radar Reflectivity (Z) and Rainfall (R) Relationships in Central Florida Part II](https://reader030.vdocuments.mx/reader030/viewer/2022032804/56812b07550346895d8ee883/html5/thumbnails/4.jpg)
The PointWant to be more accurate with estimating
rainfall amounts from Z/R relationships
Drop Size Distribution (DSD) variations in storms causes most inaccuracies
Use meteorological parameters that may infer DSD
![Page 5: Radar Reflectivity (Z) and Rainfall (R) Relationships in Central Florida Part II](https://reader030.vdocuments.mx/reader030/viewer/2022032804/56812b07550346895d8ee883/html5/thumbnails/5.jpg)
The PointWant to be more accurate with estimating
rainfall amounts from Z/R relationships
Drop Size Distribution (DSD) variations in storms causes most inaccuracies
Use meteorological parameters that may infer DSD
Determine if these parameters can explain the discrepancies from Z/R relationship
![Page 6: Radar Reflectivity (Z) and Rainfall (R) Relationships in Central Florida Part II](https://reader030.vdocuments.mx/reader030/viewer/2022032804/56812b07550346895d8ee883/html5/thumbnails/6.jpg)
The PointWant to be more accurate with estimating
rainfall amounts from Z/R relationships
Drop Size Distribution (DSD) variations in storms causes most inaccuracies
Use meteorological parameters that may infer DSD
Determine if these parameters can explain the discrepancies from Z/R relationship
If results are found, could change the relationship
![Page 7: Radar Reflectivity (Z) and Rainfall (R) Relationships in Central Florida Part II](https://reader030.vdocuments.mx/reader030/viewer/2022032804/56812b07550346895d8ee883/html5/thumbnails/7.jpg)
Drop Size Distribution (DSD) Defines hydrometeor size, shape,
orientation and phase Each storm type, as well as phase of
storm, has a different DSD Affects Z/R relationship
Box 2 will give the greater rainfall
Both boxes have the same reflectivity measurement
![Page 8: Radar Reflectivity (Z) and Rainfall (R) Relationships in Central Florida Part II](https://reader030.vdocuments.mx/reader030/viewer/2022032804/56812b07550346895d8ee883/html5/thumbnails/8.jpg)
Using the Horizontal Rain Gage Horizontal gages
collect different rain angles
Different directions represent the u- and v-components
North = + v
South = - v
East = + u
West = - u
![Page 9: Radar Reflectivity (Z) and Rainfall (R) Relationships in Central Florida Part II](https://reader030.vdocuments.mx/reader030/viewer/2022032804/56812b07550346895d8ee883/html5/thumbnails/9.jpg)
How Horizontal Gage Works
Example: If rain came directly from the North, this direction gage would only collect rain…only v-component would have a value.
![Page 10: Radar Reflectivity (Z) and Rainfall (R) Relationships in Central Florida Part II](https://reader030.vdocuments.mx/reader030/viewer/2022032804/56812b07550346895d8ee883/html5/thumbnails/10.jpg)
Calculating Terminal Velocity
Wind velocity
Rai
n ra
te Unknown…
Infer a terminal velocity
Rain Angle
![Page 11: Radar Reflectivity (Z) and Rainfall (R) Relationships in Central Florida Part II](https://reader030.vdocuments.mx/reader030/viewer/2022032804/56812b07550346895d8ee883/html5/thumbnails/11.jpg)
Finding Mean Drop Size
Calculated terminal velocities can give a mean drop size
Mean drop size gives information on the DSD
![Page 12: Radar Reflectivity (Z) and Rainfall (R) Relationships in Central Florida Part II](https://reader030.vdocuments.mx/reader030/viewer/2022032804/56812b07550346895d8ee883/html5/thumbnails/12.jpg)
July 11 Rain Event
![Page 13: Radar Reflectivity (Z) and Rainfall (R) Relationships in Central Florida Part II](https://reader030.vdocuments.mx/reader030/viewer/2022032804/56812b07550346895d8ee883/html5/thumbnails/13.jpg)
July 11 Rain Event
![Page 14: Radar Reflectivity (Z) and Rainfall (R) Relationships in Central Florida Part II](https://reader030.vdocuments.mx/reader030/viewer/2022032804/56812b07550346895d8ee883/html5/thumbnails/14.jpg)
![Page 15: Radar Reflectivity (Z) and Rainfall (R) Relationships in Central Florida Part II](https://reader030.vdocuments.mx/reader030/viewer/2022032804/56812b07550346895d8ee883/html5/thumbnails/15.jpg)
•Terminal Velocity that best matches 7/11 observations is between 4 and 4.6 m/s
North (v-comp.) East (u-comp.)Observed 4.8 mm 1.1 mm
![Page 16: Radar Reflectivity (Z) and Rainfall (R) Relationships in Central Florida Part II](https://reader030.vdocuments.mx/reader030/viewer/2022032804/56812b07550346895d8ee883/html5/thumbnails/16.jpg)
•Terminal Velocity that best matches 7/11 observations is between 4 and 4.6 m/s
•From previous table: 4.03 m/s 1.0 mm mean drop
size
North (u-comp.) East (v-comp.)Observed 4.8 mm 1.1 mm
![Page 17: Radar Reflectivity (Z) and Rainfall (R) Relationships in Central Florida Part II](https://reader030.vdocuments.mx/reader030/viewer/2022032804/56812b07550346895d8ee883/html5/thumbnails/17.jpg)
Using Drop Size Data
Could classify measured drop sizes into storm types and storm phases if more data was collected
Use classification to compare to the Z/R relationship
Possible correlations to either an over- or under-estimation of rainfall from relationship
![Page 18: Radar Reflectivity (Z) and Rainfall (R) Relationships in Central Florida Part II](https://reader030.vdocuments.mx/reader030/viewer/2022032804/56812b07550346895d8ee883/html5/thumbnails/18.jpg)
Use Lightning Metrics as a Proxy Lightning Metrics :
Convective Available Potential Energy (CAPE)
Equilibrium Level temperature (EL)Lightning Flash Rate (LFR)
All help to determine if storms are convectively active
![Page 19: Radar Reflectivity (Z) and Rainfall (R) Relationships in Central Florida Part II](https://reader030.vdocuments.mx/reader030/viewer/2022032804/56812b07550346895d8ee883/html5/thumbnails/19.jpg)
CAPE
The potential an area of upper atmosphere has to produce convective storms
Higher CAPE convection more likely
Measured by upper-air balloon soundings
![Page 20: Radar Reflectivity (Z) and Rainfall (R) Relationships in Central Florida Part II](https://reader030.vdocuments.mx/reader030/viewer/2022032804/56812b07550346895d8ee883/html5/thumbnails/20.jpg)
Measured by upper-air balloon soundings
EL
The estimated temperature of possible storm cloud-top
![Page 21: Radar Reflectivity (Z) and Rainfall (R) Relationships in Central Florida Part II](https://reader030.vdocuments.mx/reader030/viewer/2022032804/56812b07550346895d8ee883/html5/thumbnails/21.jpg)
Lightning Flash Rate (LFR) Measured by the U.S. National Lightning
Detection Network Database (NLDN) Collects location, time, polarity and
amplitude of each cloud-to-ground strike
Methods: Tabulated flash count for each system Specified radius (5, 10 km) for varying
circular areas
![Page 22: Radar Reflectivity (Z) and Rainfall (R) Relationships in Central Florida Part II](https://reader030.vdocuments.mx/reader030/viewer/2022032804/56812b07550346895d8ee883/html5/thumbnails/22.jpg)
Comparing Metrics to Z/R Compared data to rainfall rate departure
(shown with red arrows on a cut-off portion of Z/R relationship graph)
= difference between the observed rainfall rate and rate that the reflectivities estimated by NWS relationship
![Page 23: Radar Reflectivity (Z) and Rainfall (R) Relationships in Central Florida Part II](https://reader030.vdocuments.mx/reader030/viewer/2022032804/56812b07550346895d8ee883/html5/thumbnails/23.jpg)
Comparing Metrics to Z/R Compared data to rainfall rate departure
Best results came from CAPE and
10 km LFR
Divided CAPE/10 km LFR into 2 groups:CAPE: high and low (dividing value = 2950 J/kg)
10 km LFR: zero and some lightning
![Page 24: Radar Reflectivity (Z) and Rainfall (R) Relationships in Central Florida Part II](https://reader030.vdocuments.mx/reader030/viewer/2022032804/56812b07550346895d8ee883/html5/thumbnails/24.jpg)
![Page 25: Radar Reflectivity (Z) and Rainfall (R) Relationships in Central Florida Part II](https://reader030.vdocuments.mx/reader030/viewer/2022032804/56812b07550346895d8ee883/html5/thumbnails/25.jpg)
![Page 26: Radar Reflectivity (Z) and Rainfall (R) Relationships in Central Florida Part II](https://reader030.vdocuments.mx/reader030/viewer/2022032804/56812b07550346895d8ee883/html5/thumbnails/26.jpg)
Statistical Analysis
Statistical T-tests completed for CAPE and 10 km LFR
Determined if there is any statistical difference between mean departures of groups for both metrics
P-value less than or equal to 0.05 allows rejection that groups are equal
![Page 27: Radar Reflectivity (Z) and Rainfall (R) Relationships in Central Florida Part II](https://reader030.vdocuments.mx/reader030/viewer/2022032804/56812b07550346895d8ee883/html5/thumbnails/27.jpg)
CAPE T-test Results
Low CAPE High CAPEMean 10.73 13.6Variance 318.27 427.53P-Value 0.643
No statistical support allows the statement that these two means are different
![Page 28: Radar Reflectivity (Z) and Rainfall (R) Relationships in Central Florida Part II](https://reader030.vdocuments.mx/reader030/viewer/2022032804/56812b07550346895d8ee883/html5/thumbnails/28.jpg)
10 km LFR T-test Results
There is about 90% confidence that these two means are different
Not enough for the 0.05 confidence value
Zero Lightning Some LightningMean 10.55 22.36Variance 208.19 1188.19P-Value 0.105
![Page 29: Radar Reflectivity (Z) and Rainfall (R) Relationships in Central Florida Part II](https://reader030.vdocuments.mx/reader030/viewer/2022032804/56812b07550346895d8ee883/html5/thumbnails/29.jpg)
Conclusions Rainfall rate mean departures for both
groups in both metrics cannot be claimed different
But results of 10 km LFR were close to confidence value
No new Z/R relationships can be inferred from the results
Could study other seasons throughout entire year; different storm types
Measure DSD with a disdrometer
![Page 30: Radar Reflectivity (Z) and Rainfall (R) Relationships in Central Florida Part II](https://reader030.vdocuments.mx/reader030/viewer/2022032804/56812b07550346895d8ee883/html5/thumbnails/30.jpg)
Questions?
Next: Sarah Collins