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Calibration scans are important for the maintenance of data and the quality of the information that radars output. In this study we looked for a temperature dependency in a full year’s worth of differential reflectivity (ZDR) calibration scan data collected by the X-band Teaching and Research Radar (XTRRA) located near the Purdue University campus. In a vertically pointing calibration scan, the radar scans the drops from below while rotating. From this angle, the overall shape will be circular, which corresponds to a ZDR value of approximately 0 dB. To process the data for the year 2021, a Python script was written to be used by the students in Radar Meteorology (EAPS 523) as part of their Course-based Undergraduate Research Experience (CURE). The ZDR mean values were then compared to the temperature data from the FAA Automated Surface Observing System (ASOS) station located at the Purdue Airport in West Lafayette (KLAF). In cases where temperatures changed quickly diurnally, the ZDR mean changed inversely to temperature, a quick rise in environmental temperature corresponded to a decrease in ZDR mean relative 0 dB, and vice versa. A positive correlation of 0.79 indicated a relationship between ZDR and temperature. The XTRRA is housed in a radome and has temperature regulation via the internal air conditioning systems in Wang Hall. We speculate that there isn’t a stronger relationship due to the KLAF ASOS station experiencing more solar radiation and therefore being warmer than the cooled radar, as well as the fact that XTRRA and the station are situated 3.6 km apart.

Calibration scans are important for the maintenance of data and the quality of the information that radars output. In this study we looked for a temperature dependency in a full year’s worth of differential reflectivity (ZDR) calibration scan data collected by the X-band Teaching and Research Radar (XTRRA) located near the Purdue University campus. In a vertically pointing calibration scan, the radar scans the drops from below while rotating. From this angle, the overall shape will be circular, which corresponds to a ZDR value of approximately 0 dB. To process the data for the year 2021, a Python script was written to be used by the students in Radar Meteorology (EAPS 523) as part of their Course-based Undergraduate Research Experience (CURE). The ZDR mean values were then compared to the temperature data from the FAA Automated Surface Observing System (ASOS) station located at the Purdue Airport in West Lafayette (KLAF). In cases where temperatures changed quickly diurnally, the ZDR mean changed inversely to temperature, a quick rise in environmental temperature corresponded to a decrease in ZDR mean relative 0 dB, and vice versa. A positive correlation of 0.79 indicated a relationship between ZDR and temperature. The XTRRA is housed in a radome and has temperature regulation via the internal air conditioning systems in Wang Hall. We speculate that there isn’t a stronger relationship due to the KLAF ASOS station experiencing more solar radiation and therefore being warmer than the cooled radar, as well as the fact that XTRRA and the station are situated 3.6 km apart.

TFG MOBILITY, Weather forecast estimation has been a matter of analysis for many years. The arrival of dual polarization radars meant an improvement due to the incorporation of new variables. This project illustrates how to obtain the standard and new meteorological variables (Reflectivity, Doppler Velocity, Spectrum Width, Differential Reflectivity, Co-Polar Correlation Coefficient and Differential Propagation Phase). Reflectivity and Doppler velocity appear to be more advantageous because they are more consistent since the Spectrum Width is easily corrupted. Variables retrieved from the dual polarization radars happen to be even more reliable than the standard ones because most of them are independent from miscalibrations and attenuations. It also analyzes two different noise identification methods in order to estimate the noise floor. One of them based on the Co-Polar Correlation Coefficient characteristics that, for most of the cases, show a better performance than the other method based on three different features that threshold the noise., El estudio de eventos meteorológicos es un campo de interés des de hace años. La llegada de radares de doble polarización ha causado una mejora importante en la estimación del tiempo gracias a la incorporación de las nuevas variables meteorológicas. Este proyecto ilustra la forma de obtener las variables estándar y las de doble polarización para el análisis del tiempo. La reflectividad y la velocidad doppler tienen unos resultados más consistentes que el ancho de espectro, ya que son más difíciles de corromper. Las variables calculadas a partir de la doble polarización son incluso más fiables ya que la mayoría de ellas no dependen de errores de calibración ni atenuaciones. En el proyecto, también se estudian dos métodos diferentes de identificación de ruido. Uno de los métodos está basado en las características propias del coeficiente de correlación co-polar que, en la mayoría de casos, resulta tener mejores resultado que el otro método, basado en el cálculo de tres variables que analizan el ruido., L'estudi d'esdeveniments meteorològics és un camp d'interès des de fa anys. L'arribada de radars de doble polarització ha causat una millora significativa en l'estimació del temps gràcies a la incorporació de les noves variables meteorològiques. Aquest projecte il·lustra com obtenir les variables estàndards i de doble polarització de l'anàlisi meteorològic. La reflectivitat i la velocitat doppler tenen uns resultats més consistents que l'ample d'espectre, ja que és més difícil corrompre-les. Les variables calculades a partir de la doble polarització són molt més fiables ja que la majoria d'elles, són independents dels errors de calibrat i d'atenuacions. En el projecte, també s'estudien dos mètodes d'identificació del soroll per a poder fer l'estimació d'aquest. Un dels mètodes està basat en les característiques pròpies del coeficient de correlació co-polar que, per la majoria de situacions, té un comportament millor que l'altre mètode, basat en el càlcul de tres variables que analitzen el soroll.

The error structure of multiparameter radar and surface disdrometer measurements of rainfall has been studied in detail. The radar observables studied were reflectivity, differential reflectivity and X-band specific attenuation. These radar observables were simulated from fundamental considerations which incorporated statistical fluctuations due to the Doppler spectrum and the cross-correlation between H and V-polarized signals at zero time lag. Surface disdrometer measurements were also simulated accounting for the Poisson and Gamma distributed nature of the drop samples. Sampling fluctuation as well as physical variabilities of the drop size distribution were incorporated into the radar and disdrometer simulations. An intercomparison of these simulated variables revealed the nature and reason for certain inconsistencies. The use of differential reflectivity does indeed improve the characterization of the median drop size, and that its use in rainfall rate estimation will increase the accuracy by approximately a factor of 2 over conventional reflectivity based methods. The axis ratio of raindrops is analyzed as functions of their size using 2D-PMS probe images of drops in convective rainshafts. Axis ratios were estimated for about 3500 drops using the Fourier descriptor technique.

A real time data processor has been designed for use with the AFGL 10-cm Doppler weather radar which is to be operated with alternating transmission of horizontally and vertically polarized signals. In this mode of operation the reception of backscattered signals of polarizations identical to those of the transmitted signals allows the computation of the differential reflectivity between the two polarizations in addition to the absolute reflectivity and the Doppler mean velocity and variance. The switching of transmitted polarization introduces difficulties in the estimation of the autocovariance of the received signals, from which the Doppler velocity parameters are derived. The processor design and the allowed modes of radar operation circumvent these difficulties. This report describes the processing algorithms theoretically and presents details of the implementation of these algorithms in hardware. (Author)