REU 2005

May 30 - Aug 6

Student Projects

National Weather Center REU

Aaron Botnick
senior atmospheric science major
University of Louisiana - Monroe

"Variability of Radar Reflectivity in Continental Boundary Layer Stratocumulus"

Boundary layer stratocumulus clouds play an important role in the Earth’s radiative budget and climate. This paper uses reflectivity data from the Millimeter-Wave Cloud Radar (MMCR) at the Southern Great Plains (SGP) Atmospheric Radiation Measurement Climate Research Facility (ACRF) to explore variability of continental boundary layer stratocumulus. Neglecting subgrid variability in numerical models can lead to biases in radiative heating and microphysical process rates. Analysis of over 70 hours of radar data demonstrates that cloud system variability increases with mean reflectivity, indicating that drizzling clouds are more variable than nondrizzling clouds. Variability is highly vertically dependent, suggesting that numerical model accuracy may improve if this vertical dependency is included in subgrid cloud parameterizations.

Ariel Cohen
sophomore atmospheric science major
The Ohio State University

"Discrimination Among Non-Severe, Severe, and Derecho Mesoscale Convective System Environments"

Previous studies have identified meteorological variables linked with intense mesoscale convective systems (MCSs) known as derecho-producing MCSs
(DCSs). The prediction of MCS intensity is of concern to operational meteorologists, and this study provides discussion on meteorological variables derived from proximity soundings that can be used to discriminate among non severe MCSs (NCSs), severe but non derecho-producing MCSs (SCSs), and DCSs. These variables have been grouped into three categories: kinematics, instability, and moisture. Each one of 269 warm season MCSs was rated based on intensity, and the stage within8 the typical MCS lifecycle of each was determined. Decaying and dissipating MCSs were removed from the data set to focus on the most intense stages of the MCS lifecycle. Variables were calculated from the proximity sounding associated with each MCS, and statistical analyses were performed on these calculations. System-relative inflow and mid-level environmental lapse rates were found to be variables that discriminate among all three MCS environments. Knowledge of the variables affecting MCS intensity can allow for improved forecasts and warnings of convective wind events.

Angela Fritz
junior meteorology major
Valparaiso University

"A Validation of Radar Reflectivity Quality Control Methods"

Quality control of radar reflectivity data is essential for accurate precipitation forecasts and products of algorithms that require clean data. Radar data is frequently contaminated with non-precipitation echoes. Quality control methods should be able to remove a majority of these non-precipitation echoes as well as retain all of the actual precipitation. In this validation study, three quality control methods are tested on sixteen independent radar cases. These cases included non-precipitation such as anomalous propagation, biological returns, and electronic interference as well as actual precipitation including weak and strong convection and stratiform rain events. The data was analyzed and then hand-truthed to remove the contamination and create what we refer to as the target. The data was then run through the quality control methods and the results from each were scored against the target. Skill scores were calculated to determine which methods excel in the situations that were chosen.

Michelle Harrold
junior meteorology major
Valparaiso University

"Hail Warning Decision Guidance"

Figures

National Weather Service (NWS) forecasters will have several new hail diagnostic attributes available to them in Advanced Weather Information Processing System (AWIPS), beginning with the Operation Build version 6 (OB6). In a warning decision environment, it is essential that forecasters have the best guidance available to them. Therefore, the purpose of this study is to determine compare these new hail diagnostic attributes with legacy attributes to determine which attributes are “best predictors” for hail warning guidance. This study is the first step in developing official NWS Hail Warning Guidance training information for warning forecasters.

A total of 11 hail producing storm events were analyzed. The events chosen had geographic diversity across the United States, and included events from both the warm and cool seasons. For each individual hail report, the values of 17 different hail diagnostic parameters were recorded. Each attribute was compared to ground truth reports, and the statistically analyzed, including the calculation of various correlation coefficients, as well as analyses of probability of detection (POD), false alarm rate (FAR), critical success index (CSI), and the Heike skill score (HSS) for varying forecast decision thresholds, as well as different severe hail criteria (i.e., not just 2 cm diameter). Results indicated that the new high-resolution hail diagnostic attributes outperformed the legacy hail diagnostic parameters. Suggestions for future work to complete the development of NWS Hail Warning Guidance are offered.

Kate Horgan
junior meteorology major
North Carolina State University

"A Five-Year Climatology of Elevated Severe Convective Storms in the United States East of the Rocky Mountains"

A five-year climatology of elevated severe convective storms was constructed for the calendar years 1983 – 1987 from east of the Rocky Mountains to the Atlantic coast. Of the 1689 surface boundaries examined, 129 (8%) were associated with elevated severe storm events. Of the 1066 severe reports associated with the 129 elevated severe storm events, 624 (58%) were hail reports; 396 (37%) were wind reports, and 46 (4%) were tornado reports. A maximum of elevated severe storm events occurred in May with a secondary maximum in September. Elevated severe storm events vary geographically throughout the year with a maximum on the Gulf coast in winter to a High Plains maximum in spring and summer. The diurnal maximum of elevated severe storm events occurred at 2100 UTC, which coincided with the diurnal maximum of hail reports. The wind reports had no pronounced diurnal maximum. Elevated severe storm wind-only events occur roughly five times a year and are difficult to forecast. To examine the conditions associated with events that produced severe winds only, five cases were examined in more detail. These cases consisted of three environments (Type A, B, and C). Type A events were characterized by strongly forced elevated squall lines. Type B events were elevated isolated cellular events, whereas Type C events were elevated northwest flow events. Several questions remain unanswered about elevated severe storm wind-only events such as: Does the strength or depth of the inversion matter? What factors affect the transfer of momentum down to the surface?

Sean Hribal
junior earth science major
California University of Pennsylvania

"More Accurate MOS Temperature Forecasts Using Bias Correction and Consensus"

Bias correction and consensus have been applied to MOS temperature forecasts in effort to increase accuracy. Temperature forecasts obtained for KOKC and KPIT from 1 May 2002 to 30 January 2005 were classified according to maximum and minimum, projection, initialization, and season to examine model behavior between these divisions. All forecasts were verified using RMSE.

Compared to the uncorrected individual model forecasts, a seasonal bias correction showed a slight increase in RMSE values. A lagged bias correction decreased RMSE by approximately 0.1°F to 0.5°F compared to the RMSE for the uncorrected forecasts. An equally weighted consensus decreased RMSE by about 0.5°F to 1.0°F and 0.1°F to 0.5°F for maximum and minimum temperatures, respectively, over the uncorrected individual model forecasts. This method improved upon the lagged bias correction of individual model forecasts by several tenths of a degree. A linear regression consensus performed slightly worse than the equally weighted consensus. An unequally weighted consensus method based on lagged variance was the most accurate of all forecast enhancement methods, decreasing RMSE values by approximately 0.5°F to 1.5°F compared to uncorrected individual model forecasts and by several tenths of a degree over the lagged bias corrected individual model forecasts. Thus, based on the methods examined in this study, it is shown that a model consensus using a lagged correction based on past performance will provide the most significant MOS temperature forecast improvement.

Elise Johnson
senior meteorology major
Iowa State University

"Three-dimensional lightning mapping of the central Oklahoma supercell on 26 May 2004."

Three-dimensional lightning mapping observations from the Oklahoma Lightning Mapping Array (OK-LMA) were used to analyze charge structure of a splitting supercell on 26 May 2004 during the Thunderstorm Electrification and Lightning Experiment (TELEX). The OK-LMA was used to evaluate cloud-to-ground (CG) flashes reported by the National Lightning Detection Network’s (NLDN). Each NLDN flash between 2300 UTC and 2310 UTC was classified as either a CG or an intra-cloud (IC) flash using LMA-inferred charge structure. The LMA analysis of the charge structure supports charge structure for 23% of the positive CGs. Most of the negative NLDN flashes that were analyzed were not confirmed by the LMA.

Rebekah LaBar
senior geography major
Central Washington University

"The Llanos Low-Level Jet and its association with Venezuelan Convective Precipitation"

Low-level jets play an important role in transporting moisture and heat from one location to another. The NCEP North American Regional Reanalysis indicates the existence of a nocturnal low-level jet over the central Venezuelan plains, known as the Llanos, during the austral summer. Pilot balloon observations taken at San Fernando de Apure, Venezuela are used to validate the reanalysis data and verify the time of year and altitude at which upper-air Llanos wind speeds are greatest. Vertical profiles of pilot balloon-observed and regional reanalysis-estimated wind speeds during the dry and wet seasons of 2001 to 2004 show good agreement. Deep convection was expected to occur near the exit region of the Llanos low-level jet, close to the average position of the intertropical convergence zone during the austral winter. Cloud-top temperature frequency composites of northern South America during strong and weak low-level jet events in the dry and wet seasons are constructed to show that a strong Llanos jet is associated with deep convection in the southern Llanos.

Brandon Miller
junior earth and atmospheric science major
Georgia Tech University

"Evaluating the Distance Learning Operations Course by Measuring Prolonged Learning and Application"

Aisha Muhammad
sophomore meteorology major
University of Oklahoma

"Weather Awareness among Hispanics in Oklahoma City, OK"
Survey in English
Survey in Spanish

This study investigates public weather awareness within the Hispanic population of Oklahoma City by gathering information on how, when and where hazardous weather information is received, understood and acted upon by the Spanish-speaking community. In evaluating and assessing the credibility and availability of Spanish weather information, this study will attempt to uphold a null hypothesis which states that there is a significant difference in the availability and perception of hazardous weather information based upon the Spanish-speaking demographics of age, gender, education, time of residency and primary language spoken at home. A survey was publicized by radio, online and distributed in person at a local community center. Statistical models were intended to show the distribution of Spanish-speaking demographics in relation to knowledge of weather awareness. At the end of a two-week period, 35 surveys were completed and an assessment was performed. Results suggest that a larger sample size and an unbiased, random systematic test would be required to perform a statistical analysis; however, the descriptive results given provide insight to weather awareness and Hispanic communications.

Julie Phillipson
junior meteorology major
University of Northern Colorado

"Establishment and Instrumentation of the Kessler Farm Field Laboratory Piconet"

Rain gauge networks are used world-wide to provide information regarding local rainfall and variances thereof over large areas. Most of these networks, however, are on regular grids in which the distance between each gauge is several kilometers or more. Since most convection is on a much smaller scale than the gauge spacing found in the networks, a higher resolution network is required to examine small-scale variabilities within any given storm.

Currently, a PicoNet is being developed to install at the Kessler Farm Field Laboratory (KFFL) near Purcell, Oklahoma. This PicoNet will consist of 6 different rain gauge sites variably spaced over a 350 acre property. Unlike other networks, the KFFL PicoNet will have gauge-to-gauge spacing of only several hundred meters, with a maximum spacing between any two locations of 1.5km. This high resolution network will allow researchers to observe the small scale variabilities in convective precipitation, and then in turn, compare these findings to the estimated precipitation intensities reported by the KTLX and KOUN radars to test rainfall retrieval algorithm accuracies.

Bryan Smith
senior geography major
Ball State University

"Climatology of the Supercell Composite Parameter (1979-2004)"

The Storm Prediction Center uses “ingredients-based” indices as one part of severe storm prediction and one of the indices is named the Supercell Composite Parameter. The Supercell Composite Parameter (SCP) is a multi-component index that includes CAPE, storm relative helicity, and deep layer vertical wind shear. Each SCP component is normalized to "threshold" values determined to be favorable for supercell storms, and the product of these three normalized components forms the SCP. With the availability of 32km resolution North American Regional Reanalysis data, a 26-year climatology of the SCP at 00 UTC was developed in order to view daily, monthly, and seasonal variations in the SCP across the continental U.S. The SCP was investigated quantitatively by the number of days that the values were greater than or equal to one at a gridpoint during each month of the year. The central plains were found to have the highest number of days with environments supportive of supercells.

**CASA-Norman Site REU**
Renee Curry sophomore meteorology major University of Oklahoma "Kinematic Analysis of Hurricane Isabel at Landfall" A unique dual-Doppler data set of the landfall of Hurricane Isabel was analyzed. These data were collected with the Shared Mobile Atmospheric Research and Teaching (SMART) radars that were deployed in North Carolina along a 54 km north-south baseline. The radars collected more than 14 hours of coordinated dual-Doppler scans during the landfall of this category two hurricane, including the passage of the eye-wall that went through the dual-Doppler lobe. High spatial resolution volumes were collected every 2-4 minutes providing exceptional temporal resolution. This study focused on the mesoscale evolution of several of the rainbands during landfall. In particular, variability in precipitation was related to kinematics of the airflow through the forward right flank of the hurricane as the rainbands made landfall. The variability of precipitation at different temporal and spatial scales during hurricane landfalls is a particularly relevant issue for the student-led test-bed being deployed in Puerto Rico. This study also has implications to the Houston, TX test-bed that will focus on hydrological applications.
Carlos Rodriguez-Rivera junior electrical engineering major University of Puerto Rico, Mayaguez "Is Spectral Processing Important for Future WSR-88D Radar?" Processing speed and memory capacity are reaching a point where future weather radar systems will be able to exploit the power of full spectral processing. The work focuses on data from the polarimetric KOUN radar at NSSL. Want to study the validity of the Gaussian Doppler spectrum for different region of storms. It is our hypothesis that the Gaussian Doppler spectrum will be valid for only relatively homogenous parts of the complex structure of storms. Many processing algorithms, such those used to estimate reflectivity, velocity and dual-polarization parameters, assume a Gaussian-shaped spectrum. The data are in time-series (time domain) form (Level I) and want to convert them to the frequency domain using a Fourier transform. We have to process the data to find the Doppler spectrum of each gate of the radar. Need to know how close the actual Doppler spectra are to the Gaussian form and relate a goodness-of-fit measure to different regions of various types of storms.

**ORISE**
Kar'retta Venable sophomore Jackson State University "Determining Environmental Parameters Most Important for Significant Cool Season Tornadoes across the Gulf Coastal States" The purpose of this study is to derive a set of parameters for improved forecasting of significant cool season tornado occurrences in the Gulf coastal states during the period from mid November through mid February. It is important to examine these tornado events because they are characterized by strong shear and weaker instability than the more typical warm season tornado events. These cool season tornado occurrences are rare, which makes them more difficult to forecast. When cold season tornadoes do occur, they tend to be of the stronger variety due to the strong vertical shear. This makes it important to analyze these tornado events since the chance for loss of life is greater with strong tornadoes. The study is based on six cool seasons from 1998 and 2004 and examined F2 and stronger tornado events. Temperatures, dew points and wind data was examined at various levels to see which, if any, parameters were better discriminators for these types of events.