Ten years (1997 - 2006) of summer (June, July, August) daytime (14 - 00 Z) Weather Surveillance Radar - 1988 Doppler data for Houston, TX were examined to determine the best radar-derived lightning forecasting predictors. Convective cells were tracked using a modified version of the Storm Cell Identification and Tracking (SCIT) algorithm and then correlated to cloud-to-ground lightning data from the National Lightning Detection Network (NLDN). Combinations of three radar reflectivity values (30, 35, and 40 dBZ) at four isothermal levels (-10, -15, -20, and updraft -10 degrees C) and a new radar-derived product, vertically integrated ice (VII), were used to optimize a radar-based lightning forecast algorithm. Forecasts were also delineated by range and the number of times a cell was identified and tracked by the modified SCIT algorithm. This study objectively analyzed 65,399 unique cells, and 1,028,510 to find the best lightning forecast criteria. Results show that using 30 dBZ at the -20 degrees C isotherm on cells within 75 km of the radar that have been tracked for at least 2 consecutive scan produces the best forecasts with a critical success index (CSI) of 0.71. The best VII predictor was 0.734 kg m-2 on cells within 75 km of the radar that have been tracked for at least 2 consecutive scans producing a CSI of 0.68. Results of this study further suggest that combining the radar reflectivity and VII methods can result in a more accurate lightning forecast than either method alone.

Indiana University-Purdue University Indianapolis (IUPUI) / Driving safety is a very important topic in vehicle development. One of the biggest threat of driving safety is road departure. Many vehicle active safety technologies have been developed to warn and mitigate road departure in recent years. In order to evaluate the performance of road departure warning and mitigation technologies, the standard testing environment need to be developed. The testing environment shall be standardized to provide consistent and repeatable features in various locations worldwide and in various seasons. The testing environment should also be safe to the vehicle under test in case the safety features do not function well. Therefore, soft, durable and reusable surrogates of roadside objects need to be used. Meanwhile, all surrogates should have the same representative characteristics of real roadside objects to di erent automotive sensors (e.g. radar, LIDAR and camera). This thesis describes the study on identifying the radar characteristics of common roadside objects, metal guardrail, grass, and concrete divider, and the development of the required radar characteristics of surrogate objects. The whole process is divided into two steps. The rst step is to nd the proper methods to measure the radar properties of those three roadside objects. The measurement result of each roadside object will be used as the requirement for making its surrogate. The second step is to create the material for developing the surrogate of each roadside object. In the experimental results demonstrate that all three surrogates satisfy their radar characteristics requirements.

ModClark and Clark’s Unit Hydrograph (Clark’s UH) within HEC-HMS software are distributed and lumped models, respectively. Clark’s UH simulates the transformation and attenuation of excess precipitation, and requires time of concentration (Tc) and Storage Coefficient (R) parameters. ModClark transformation accounts for variations in travel time to catchment outlet from all regions of a catchment, and it additionally requires gridded representation of a catchment and Gridded cell-based input files. Four cases (three from observed rain, and one from radar reflectivity) of three chosen events were specifically chosen and examined for the comparison of simulation results with the same estimated initial parameters apart from different rainfall inputs. The Upper Waimakariri River Catchment was divided into ten subcatchments, and the HEC-HMS basin model parameters were estimated by using the physical/hydrological characteristics. However, ModClark transformation was unavailable because of an output error from converting ASCII to gridded Soil Conservation Service Curve Number (SCS CN) format by the conversion tool – ai2dssgrid.exe. Therefore, Mean Aerial Precipitation (MAP) for each subcatchment was calculated by Thiessen polygon method combined with an overlay analysis for grid-cell-based rainfall estimation from radar with geographic information system (GIS) tools. The automated calibration/optimisation procedure included in HEC-HMS package was applied to the cases which showed a deviation between simulation and observed flows. The purpose is to ‘optimise’ the initial estimates of parameters only in a mathematical-fit manner based on the observed flows from the only discharge gauge at Old Highway Bridge (OHB). The TC values calculated from the five equations vary in a relatively narrow range apart from the one from Bransby-Williams equation. Therefore, the values from all the other four equations were averaged and used as the initial TC input. The simulation results showed that there was a notable difference between observed and simulated hydrographs for some case studies even though TC, R, CN, and lag time were calibrated/optimised separately. Also, radar estimated rainfall and grid-based data storage system (DSS) need more investigations.

L’estimation quantitative des précipitations à l’échelle locale est une nécessité sociétale, à cause de l’augmentation des dégâts provoqués par des inondations exacerbées par l’urbanisation croissante. Or, des estimations locales sont particulièrement difficiles à réaliser à cause de la forte variabilité des précipitations. De plus, ce genre d’estimation est sollicité par de petits organismes tels qu’une commune, pour lesquels il n’est pas envisageable d’utiliser des instruments à la pointe de la recherche technologique à cause de leur coût prohibitif. Ainsi, il est nécessaire de développer des méthodes d’estimation quantitative des précipitations applicables à un dispositif expérimental de prix abordable. Dans ce but, un dispositif expérimental innovant est utilisé dans cette thèse. Il est constitué d’instruments de mesure directe, au sol, tels que des pluviomètres et des disdromètres, et d’un prototype de radar à balayage horizontal basé sur un radar nautique commercial, associé à un MRR (Micro Rain Radar) à visée verticale qui fournissent une estimation en altitude de la pluie, respectivement sur une surface donnée et le long d’un profil vertical. Le radar à balayage horizontal est un radar en bande X, c’est-à-dire qu’il fonctionne à une longueur d’onde lui procurant une très haute résolution radiale, mais qui est très atténuée par les précipitations. Le MRR permet d’obtenir une description précise de la microphysique des précipitations et sert de relais entre les mesures au sol et les mesures en altitude du radar en bande X. Ces deux radars étant novateurs, une grande partie de cette thèse consiste à valider leurs mesures : étalonnage, filtrage d’échos aberrants, correction de l’atténuation, etc. Une fois les mesures rendues exploitables, cette thèse se focalise sur l’étude de la variabilité des précipitations afin de proposer et développer différentes méthodes de classification, selon leur type ou leur variations locales, et de vérifier leur potentiel pour l’amélioration de l’estimation des précipitations. Les résultats montrent que cet objectif ne peut être atteint que si la qualité des mesures des radars est encore améliorée : moins d’échos parasites pour le radar en bande X et prise en compte du vent vertical pour le MRR. / Due to the increase of damage associated with floods enhanced by expanding urbanisation, the quantitative estimation of precipitation on a local scale is a societal need. However, such estimations are difficult because of the high variability of precipitation. Moreover, these estimations are requested by small organisations such as local authorities which cannot afford top level research instruments. Hence, new methods of estimation applicable to a cheap experimental set are needed. Toward this goal, an innovative experimental set is used in this work. It consists of ground instruments such as raingauges and disdrometers, and two radars, a prototype of a scanning radar based on a modified marine radar and a vertically pointing MRR (Micro Rain Radar), which give estimation of rain aloft, over an area and along a profile, respectively. The scanning radar works at X-band, meaning that it uses a longwave very attenuated by precipitation, but which provides a high range resolution. The MRR yields a detailed description of microphysics of precipitation and fills the gap between ground measurements and X-band radar measurements aloft. As both these radars are innovative, a large part of this PhD thesis was spent on the measurements validation : radar calibration, abnormal echoes filtering, attenuation consideration, etc. Using these corrected measurements, this PhD focus then on the study of the variability of precipitation, and aims to propose and develop several classification methods based on precipitation type or local variability, and to check their potential for the improvement of precipitation estimation. Results show that this goal can be reached only if the radar measurements quality is further improved : less interference echoes for the X-band radar, and consideration of vertical wind for the MRR.

<div>Driving safety is a very important topic in vehicle development. One of the biggest threat of driving safety is road departure. Many vehicle active safety technologies have been developed to warn and mitigate road departure in recent years. In order to evaluate the performance of road departure warning and mitigation technologies, the standard testing environment need to be developed. The testing environment shall be standardized to provide consistent and repeatable features in various locations worldwide and in various seasons. The testing environment should also be safe to the vehicle under test in case the safety features do not function well. Therefore, soft, durable and reusable surrogates of roadside objects need to be used. Meanwhile, all surrogates should have the same representative characteristics of real roadside objects to different automotive sensors (e.g. radar, LIDAR and camera). This thesis describes the study on identifying the radar characteristics of common roadside objects, metal guardrail, grass, and concrete divider, and the development of the required radar characteristics of surrogate objects. The whole process is divided into two steps. The first step is to find the proper methods to measure the radar properties of those three roadside objects. The measurement result of each roadside object will be used as the requirement for making its surrogate. The second step is to create the material for developing the surrogate of each roadside object. In the experimental results demonstrate that all three surrogates satisfy their radar characteristics requirements.</div>

Modification of land use/land cover in South Florida has posed a major challenge in the region’s eco-hydrology by shifting the surface-atmosphere water and energy balance. Although drainage and development in South Florida took place extensively between the mid- and late- 20th century, converting half of the original Everglades into agricultural and urban areas, urban expansion still accounts for a dominant mode of surface cover change in South Florida. Changes in surface cover directly affect the radiative, thermophysical and aerodynamic parameters which determine the absorption and partitioning of radiation into different components at the Earth surface. The alteration is responsible for changing the thermal structure of the surface and surface layer atmosphere, eventually modifying surface-induced convection. This dissertation is aimed at analyzing the extent and pattern of land cover change in South Florida and delineating the associated development of urban heat island (UHI), energy flux alteration, and convective rainfall modification using observed data, remotely sensed estimates, and modeled results. Urban land covers in South Florida are found to have increased by 10% from 1974 to 2011. Higher Landsat-derived land surface temperatures (LST) are observed in urban areas (LSTu-r =2.8°C) with satisfactory validation statistics for eastern stations (Nash-Sutcliffe coefficient =0.70 and R2 =0.79). Time series trends, significantly negative for diurnal temperature range (DTR= -1°C, p=0.005) and positive for lifting condensation level (LCL > 20m) reveal temporal and conspicuous urban-rural differences in nocturnal temperature (ΔTu-r = 4°C) shows spatial signatures of UHI. Spatially higher (urban: 3, forest: 0.14) and temporally increasing (urban: 1.67 to 3) Bowen’s ratios, and sensible heat fluxes exceeding net radiation in medium and high-intensity developed areas in 2010 reflect the effect of urbanization on surface energy balance. Radar reflectivity-derived surface-induced convective rainfall reveals significantly positive mean differences (thunderstorm cell density: 6/1000 km2and rain rate: 0.24 mm/hr/summer, p < 0.005) between urban and entire South Florida indicating convective enhancement by urban covers. The research fulfils its two-fold purposes: advancing the understanding of post-development hydrometeorology in South Florida and investigating the spatial and temporal impacts of land cover change on the microclimate of a subtropical city.