Mora Navarro, Keyla M.

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    Development and implemetation of an attenuation correction algorithm for casa off the grid x-band radar network
    (2012) Mora Navarro, Keyla M.; León Colón, Leyda V.; College of Engineering; Cruz Pol, Sandra L.; Colom-Ustáriz, José G.; Department of Electrical and Computer Engineering; Huérfano, Victor
    Weather radars as, part of forecasting systems, are useful tools for meteorology and hydrology purposes. Meteorological trends and patterns can be analyzed with the highest precision possible provided by these types of radars. In particular, X-band weather radars have various advantages such as high temporal and spatial resolution and low cost as compared to S-band systems. Yet, the main X-band radar limitation is the attenuation caused by rain and others hydrometeors. Several attenuation correction algorithms have been proposed for both single and dual polarized X-band radars. Here we present the development and implementation of a modified algorithm to correct for atmospheric attenuation for low-cost single-pol X-band weather radars, which will greatly improve the data provided by these systems. Previous studies have focused on the limitation (attenuation) of X-band weather radars and possible solutions. These studies were the motivation to develop and implement an 12 attenuation correction algorithm for the NSF CASA-ERC at UPRM Off-The-Grid (OTG) X-band radar network installed in the western region of Puerto Rico. This thesis describes the process of the development of this attenuation correction algorithm as well as the validation of such. This algorithm is then implemented to the data provided by the CASA OTG X-band radar. The method applied to estimate and correct the attenuation caused mainly by rain was based on a hybrid between Hitschfeld – Bordan (HB) method and Surface Reference Technique (SRT). A similar method was first adapted and tested by Colorado State University (CSU) with CASA radar but for estimating and correcting wet ice attenuation. The method was refered to as the SRT-modified correction method. This mentioned method uses the measured reflectivity (Zv) to estimate true reflectivity and specific attenuation (Av) at each range gate based on a power law Av-Zv relationship. The coefficient β is fixed, and α is adjusted along the path such that the path – integrated attenuation (PIA) estimated with Hitschfeld – Bordan method matches with the path – integrated attenuation estimated with surface reference technique method as specified in the SRT modified method. SRT modified method requires computing the difference between the un-attenuated S-band reference reflectivity (from the WSR-88D S-band NEXRAD located at Puerto Rico) and the X-band measured reflectivity (from the OTG X-band radar). The corrected radar reflectivity data was finally compared and the method was validated using X-band TropiNet radar data, an NSF funded network of dual-polarization, Doppler weather radars also located at UPRM. Before applying the attenuation correction algorithm, some aspects were taken into consideration such as: radar calibration, theoretical analysis of atmospheric attenuation and the effect of radar polarization.