Jalon Gary

Date of Award

2024

Type

Thesis

Major

Master of Science

Degree Type

Environmental Science

Department

Natural Sciences

First Advisor

Dr. Stephen Jessup

Second Advisor

Dr. Troy Keller

Third Advisor

Dr. Shawn Milrad

Abstract

Z/R relationship is a power law relationship between radar reflectivity (Z) and rainfall rate (R). The relationship is expressed as Z = aRb where a and b are correlated with drop size distribution (DSD) and vary across locations. Using a Z/R relationship to translate radar reflectivity to rainfall rate can allow for real-time precipitation monitoring with a high temporal and spatial resolution. A dataset of 12 cases in Georgia from December 2021 to November 2022 was examined using the Georgia Weather Network rain gauge system and the KFFC radar to optimize the best Z/R relationship for each case. Radar-based precipitation estimates employed with a Dual Stratiform/Convective Z/R relationship outperformed the Single, Marshall-Palmer, and Summer Deep Convection relationships in all 12 cases. Both the weighted and unweighted Dual Z/R relationships obtained the lowest RMSE. The weighted Dual Z/R relationships had fewer stations over- or underestimating by more than 12.7 mm compared to the other relationships used in this study. ANOVA test revealed no significant impact of seasons or storm direction on error, but storm intensity correlated with higher errors. Locations farther from the radar tended to be underestimated, while higher elevations led to overestimations. A spatial analysis also revealed that storms that move north lead to more overestimations while storms headed south lead to more underestimations. The study recommends using unweighted Dual Z/R relationships for more precise precipitation estimates on a localized scale.

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