Evaluation of a Regional Climate Model for the Upper Blue Nile Region

The fourth version of the International Center for Theoretical Physics (ICTP) Regional Climate Model (RegCM4) model is evaluated for its performance over Upper Blue Nile River Basin Region (UBNRBR). The model rainfall captured the observed spatial and temporal variability of rainfall over the basin during the spring (MAM) and summer (JJA) seasons. The simulation dataset is generated using the RegCM4 for the period 1982–2009. The UBNRBR is first divided into 14 homogeneous regions using criteria including Rotated Empirical Orthogonal Function (REOF), spatial correlation and topographical features. Spatially averaged observed and simulated rainfall time series are then generated and analyzed for each region. Standardized rainfall anomalies of the observations and the simulated data are highly correlated over most of central regions, while a weak correlation is found over the east border regions of the basin. The dominant modes of rainfall variability are identified using REOF. The first leading patterns of rainfall and upper wind (averaged between 100 and 300 hpa) are highly correlated and exhibit similar features between simulated and observed dataset over the basin. Similarly, the first loading pattern of low level wind (averaged between 850 and 1000 hpa) exhibits a dipole structure across the southwestern and southeastern regions of the UBNRBR. The correlations with significant rotated principal components (RPCs) across gridded gauge, and model rainfall fields with that of low- and upper level winds show the presence of significant relationship (correlation exceeding ~0.6). Overall, that the RegCM4 shows a good performance in simulating the spatial and temporal variability of precipitation over UBNRBR

New incoherent scatter radar measurement techniques and data analysis methods

Abstract This dissertation presents new incoherent scatter radar measurement techniques and data analysis methods. The measurements used in the study were collected by connecting a computer-based receiver to the EISCAT (European Incoherent SCATter) radar on Svalbard. This hardware consists of a spectrum analyzer, a PCI-bus-based programmable digital I/O card and a desktop computer with a large-capacity hard disk. It takes in the 70-MHz signal from the ESR (Eiscat Svalbard Radar) signal path and carries out down-conversion, AD conversion, quadrature detection, and finally stores the output samples effective sampling rate is 1 MHz, large enough to span all the frequency channels used in the experiment. Hence the total multichannel signal was stored instead of separate lagged products for each frequency channel, which is the procedure in the standard hardware. This solution has some benefits including elimination of ground clutter with only a small loss in statistical accuracy. The capability of our hardware in storing the incoherent scatter radar signals directly allows us to use very flexible and versatile signal processing methods, which include clutter suppression, filtering, decoding, lag prole calculation, inversion and optimal height integration. The performance of these incoherent scatter radar measurement techniques and data analysis methods are demonstrated by employing an incoherent scatter experiment that applies a new binary phase code. Each bit of this code has been further coded by a 5-bit Barker code. In the analysis, stochastic inversion has been used for the first time in decoding Barker-coded incoherent scatter measurements, and this method takes care of the ambiguity problems associated with the measurements. Finally, we present new binary phase codes with corresponding sidelobe-free decoding filters that maximize the signal-to-noise ratio (SNR) and at the same time eliminate unwanted sidelobes completely.Original papers The original papers are not included in the electronic version of the dissertation. Lehtinen, M., Markkanen, J., Väänänen, A., Huuskonen, A., Damtie, B., Nygrén, T., & Rahkola, J. (2002). A new incoherent scatter technique in the EISCAT Svalbard Radar. Radio Science, 37(4), 3-1-3–14. https://doi.org/10.1029/2001rs002518 Damtie, B., Nygrén, T., Lehtinen, M. S., & Huuskonen, A. (2002). High resolution observations of sporadic-E layers within the polar cap ionosphere using a new incoherent scatter radar experiment. Annales Geophysicae, 20(9), 1429–1438. https://doi.org/10.5194/angeo-20-1429-2002 Damtie, B., Lehtinen, M. S., & Nygrén, T. (2004). Decoding of Barker-coded incoherent scatter measurements by means of mathematical inversion. Annales Geophysicae, 22(1), 3–13. https://doi.org/10.5194/angeo-22-3-2004 Lehtinen, M. S., Damtie, B., & Nygrén, T. (2004). Optimal binary phase codes and sidelobe-free decoding filters with application to incoherent scatter radar. Annales Geophysicae, 22(5), 1623–1632. https://doi.org/10.5194/angeo-22-1623-200

Mismatch between the progression of the mathematics course and the level of mathematics required to do advanced physics

Whenever students appear to have trouble with mathematics in their physics courses, they either hate physics or fear it. The blame for this plight could be due to the structure of the mathematics and physics curricula or the incompetence of the teachers. This paper focuses on investigating the progression of the mathematics courses and the level of mathematics required of students in the Department of Physics at the Bahir Dar University, Ethiopia. The key objective of the research is to find out how the mathematics courses are integrated into the physics curriculum especially in terms of providing students with fundamental mathematical skills needed in the corresponding physics courses. A content analysis of the physics curriculum was carried out to determine whether an apparent mismatch or relevant integration exist between the progression of the mathematics courses and the level of mathematics required to learn the physics courses. As a preliminary work, we examined the correlation between student performance (final grade) in the mathematics courses and performance in the physics courses. Despite the significant efforts that gone to improve the undergraduate physics curriculum in Ethiopia, the present study showed that the curriculum made students to attend some senior physics courses without the essential mathematical skills. For example, essential topics in mathematics like vector calculus and partial differential equations are not taught until the end of the second year first term. On the other hand classical mechanics course, which extensively make use of these mathematical topics, begins in the second year first term. Recommendations and implications for physics curriculum and instruction are made.Siempre que los estudiantes tienen problemas con las Matemáticas en sus cursos de Física, acaban por odiarla o por temerle. La culpa de esta situación podría deberse a la estructura curricular de los programas Física y Matemáticas o a la incompetencia de los profesores. Este trabajo se centra en el progreso que alcanzan los cursos de Matemáticas y el nivel de conocimientos en Matemáticas requerido por los estudiantes del Departamento de Física en la Universidad de "Bahir Dar" en Etiopía. El objetivo clave de la investigación se centra en encontrar cómo son integrados los cursos de Matemáticas en el curriculum de Física, especialmente en términos de proveer al estudiante con las habilidades matemáticas fundamentales, necesarias en los cursos de Física correspondientes. Se llevó a cabo un análisis de contenido del currículo de Física para determinar si una aparente desintegración o integración existe entre el progreso en los cursos de Matemáticas y el nivel de Matemáticas requerido para aprender los cursos de Física. Como trabajo preliminar, examinamos la correlación entre el rendimiento de los alumnos (calificación final) en los cursos de matemáticas y el rendimiento en los cursos de Física. A pesar de los esfuerzos significativos que se han hecho para mejorar el curriculum de los estudiantes de Física de pregrado en Etiopía, el presente estudio mostró que había estudiantes que cursaban la materia de Física en sus últimos temas sin tener todavía las habilidades Matemáticas necesarias. Por ejemplo, los tópicos esenciales en la materia de Matemáticas como el Cálculo Vectorial y Ecuaciones Diferenciales Parciales no son enseñados sino hasta el final del segundo año del primer período. Por otro lado, el curso de Mecánica Clásica, el cual hace uso extensivo de estos tópicos matemáticos, empieza en el segundo año del primer período. Recomendaciones e implicaciones al currículum e instrucción de la Física son hechas

Wave-particle duality and uncertainty principle: Phenomenographic categories of description of tertiary physics students’ depictions

Quantum mechanics is often thought to be a difficult subject to understand, not only in the complexity of its mathematics but also in its conceptual foundation. In this paper we emphasize students’ depictions of the uncertainty principle and wave-particle duality of quantum events, phenomena that could serve as a foundation in building an understanding of quantum mechanics. A phenomenographic study was carried out to categorize a picture of students’ descriptions of these key quantum concepts. Data for this study were obtained from a semistructured in-depth interview conducted with undergraduate physics students (N=25) from Bahir Dar, Ethiopia. The phenomenographic data analysis revealed that it is possible to construct three qualitatively different categories to map students’ depictions of the concept wave-particle duality, namely, (1) classical description, (2) mixed classical-quantum description, and (3) quasiquantum description. Similarly, it is proposed that students’ depictions of the concept uncertainty can be described with four different categories of description, which are (1) uncertainty as an extrinsic property of measurement, (2) uncertainty principle as measurement error or uncertainty, (3) uncertainty as measurement disturbance, and (4) uncertainty as a quantum mechanics uncertainty principle. Overall, we found students are more likely to prefer a classical picture of interpretations of quantum mechanics. However, few students in the quasiquantum category applied typical wave phenomena such as interference and diffraction that cannot be explained within the framework classical physics for depicting the wavelike properties of quantum entities. Despite inhospitable conceptions of the uncertainty principle and wave- and particlelike properties of quantum entities in our investigation, the findings presented in this paper are highly consistent with those reported in previous studies. New findings and some implications for instruction and the curricula are discussed

Ionospheric Perturbations and Their Impact on GNSS - Investigated by DLRs High-Rate Receiver Chain

Global Navigation Satellite Systems (GNSS) such as GPS, Galileo or Glonass provide good positioning results for a lot of applications. However, they can be heavily disturbed by space weather hazards. Severe temporal and spatial changes of the electron density in the ionosphere can lead to strong GNSS signal fluctuations in phase and amplitude – so-called scintillations. Processes leading to such ionospheric perturbations are ionization fronts, Travelling Ionospheric Disturbances (TIDs), plasma bubbles and plasma turbulences. Since a guaranteed performance is crucial for precise positioning and safety of life applications, it is necessary to monitor this thread. This can be done by multi-frequency measurements of GNSS signals. From these measurements signal amplitude and signal phase scintillation indices can be derived. These indices are a characteristic measure of occurring scintillations, should they surpass a certain threshold. Additionally, these multi-frequency measurements offer the unique opportunity to probe the electron density structure of the global ionosphere-plasmasphere system. As the ionosphere is a dispersive medium, multi-frequency measurements allow for a tomography of the ionosphere. Thus maps of the total electron content (TEC) of the ionosphere can be derived, which are strongly related to the ionospheric impact on GNSS applications. Our contribution will be twofold. First, we will explain the setup of the DLR high-rate receiver chain, the so called Experimentation and Verification Network (EVnet). The EVnet - developed by DLR's Institute of Communications and Navigation - is an infrastructure component for the near-real-time reception, processing and distribution of any kind of GNSS data to the EVnet user community. The network as shown in the figure includes, among others, stations in Kiruna, Neustrelitz, Munich, Toulouse, Tenerife and Bahir Dar. The data can be distributed over the Internet or any local area networks by specific EVnet services. It is designed as a one-stop shop system and products can be directly derived at the stations. These products can then be distributed or disseminated via a web service such as the Space Weather Application Center – Ionosphere (SWACI). Second, we will show, how ionospheric perturbation can be observed in real-time with the EVnet along its associated stations. In particular, we will show the propagation of scintillations at high-latitudes as well as those at equatorial latitudes in stations such as Kiruna and Bahir Dar

A Method for Automatic Detection of Plasma Depletions by Using GNSS Measurements

Enhanced scintillation activities observed at transionospheric radio signals are often correlated with slant total electron content (STEC) depletions in the equatorial ionosphere. In this study, the data derived from high-rate Global Navigation Satellite System (GNSS) receivers were used to analyze the observed STEC depletions, commonly associated with plasma bubbles causing radio scintillations in the equatorial ionosphere. We found that the observed STEC depletion can be described by a wedge-shaped structure. To quantitatively describe the structure of STEC depletions, we developed an effective method to routinely characterize the depth and the width of equatorial plasma depletion in automatized data screening. The developed method has been validated by analyzing data obtained from mostly African GNSS stations in 2014 and 2015. The results confirm current knowledge regarding the seasonal occurrence of radio scintillations and related bubbles. The detection results are compared with those from other published plasma bubble detection techniques

Optimal true time delay filter with application to FPGA firmware-based phased array radar signal processing

Abstract The European Incoherent Scatter‐3D phased array radar system will be largely based on field‐programmable gate array (FPGA) firmware electronics that carry out the signal processing by using different digital filters. In this paper we have presented a method of designing an optimal true time delay finite impulse response filter with applications to an FPGA firmware‐based multichannel signal processing system. The method provides an optimal true time delay finite impulse response filter with the desired responses at both band pass and stopband. This is possible by finding a mathematical minimization solution for the total power of all filter coefficients longer than a prespecified half‐length. The analysis is based on freely choosing the responses in the transition band until user‐specified desired responses are achieved. We have investigated the performance of these optimal digital filters in terms of the required digital signal processing (DSP) resources in GMACs (giga multiply accumulates per second) by considering both all‐in‐one stage filtering and cascaded solutions for ion and plasma line incoherent scatter radar measurements. We have shown that the cascaded solution provides more efficient utilization of DSP resources and hence represents the optimal choice for processing the proposed European Incoherent Scatter‐3D phased array radar signals. An example is demonstrated in which 906.88 GMACs are required to process 208 ion line beams with 2×4‐bit resolution in all‐in‐one stage processing, as compared to the 79.16 GMACs needed for a similar task in a cascaded solution

The spatiotemporal variations of total column ozone concentration over Ethiopia

We have studied spatiotemporal characteristics of ozone concentration over Ethiopia using data from the Ozone Mapper and Profiling Suite-Nadir Mapper (OMPS-NM). Daily total column ozone data of 108 observation points with spatial resolution 1° × 1° over the study area for the period of 2012–2019 have been analyzed. The spatial variations over the region have been studied by considering longitudinal and latitudinal bands separately through the sample mean difference among different bands using multi-comparison analysis of variance technique in order to identify the clusters in the region. For the temporal variability, we model the total column ozone timeseries observation as a sum of seasonal, trend, and temporally correlated noise components. We have found that the total column ozone concentration has a maximum value of 301DU during summer on August 18, 2013 and a minimum value of 216DU during winter on January 03, 2013 over the study period. The 95% confidence level of the overall mean of the total column ozone concentration during the study period was found to be (261.35 ± 2.38)DU. Our spatial data analysis revealed that the spatial distribution of ozone over Ethiopia can be classified into three clusters: southern cluster (4.5°N–8.5°N and 33.5°E–47.5°E), north-eastern cluster (9.5°N to 14.5°N and 41.5°E–47.5°E), and north-western cluster (9.5°N–14.5°N and 33.5°E–40.5°E). We have checked the coefficient of determination among bands in the same cluster to see if the concentration of ozone in one band can be explained by the concentration in another band for each cluster and confirmed the reliability of the classification. In order to capture temporal characteristics, we have computed the spectral periodogram for each cluster and obtained a power peak at frequency f = 0.002 768 Hz, which indicates that the ozone concentration over the region exhibits an annual cyclic behavior. A truncated Fourier series fit is used to determine the annual seasonal component. The non-parametric Mann–Kendall’s trend test with a 95% confidence level of significant has indicated a decreasing linear trend with a depletion rate of 0.77, 0.73, and 0.43 DU/yr over north-western, north-eastern, and southern clusters, respectively. The analysis of residuals for each cluster indicated that the residuals are normally distributed with no significant outliers, and the model explains 85%, 86%, and 79% of the variance in the north-western, north-eastern, and southern clusters, respectively, demonstrating the reliability of the model considered in this study