scholarly journals Correction of artificial jumps in the historical geomagnetic measurements of Coimbra Observatory, Portugal

2014 ◽  
Vol 32 (1) ◽  
pp. 19-40 ◽  
Author(s):  
A. L. Morozova ◽  
P. Ribeiro ◽  
M. A. Pais
Keyword(s):  
Geomagnetic Field ◽  
Visual Analysis ◽  
Statistical Tests ◽  
Time Derivative ◽  
Liquid Core ◽  
Homogeneity Test ◽  
Magnetic Observatory ◽  
K Index ◽  
Standard Normal Homogeneity Test ◽  
Geomagnetic Measurements

Abstract. The Coimbra Magnetic Observatory (International Association of Geomagnetism and Aeronomy code COI) in Portugal has a long history of observation of the geomagnetic field, spanning almost 150 yr since the first geomagnetic measurements in 1866. These long instrumental geomagnetic records provide very important information about variability of geomagnetic elements and indices, their trends and cycles, and can be used to improve our knowledge on the sources that drive variations of the geomagnetic field: liquid core dynamics (internal) and solar forcing (external). However, during the long life of the Coimbra Observatory, some inevitable changes in station location, instrument's park and electromagnetic environment have taken place. These changes affected the quality of the data collected at COI causing breaks and jumps in the series of geomagnetic field components and local K index. Clearly, these inhomogeneities, typically shift-like (step-like) or trend-like, have to be corrected or, at least, minimized in order for the data to be used in scientific studies or to be submitted to international databases. In this study, the series of local K index and declination of the geomagnetic field are analysed: the former because it allows direct application of standard homogenization methods and the latter because it is the longest continuous series produced at COI. For the homogenization, visual and statistical tests (e.g. standard normal homogeneity test) have been applied directly to the local geomagnetic K index series (from 1951 to 2012). The homogenization of the monthly averages of declination (from 1867 to 2012) has been done using visual analysis and statistical tests applied to the time series of the first differences of declination values, as an approximation to the first time derivative. This allowed not only estimating the level of inhomogeneity of the studied series but also detecting the highly probable homogeneity break points. These points have been cross-checked with the metadata, and the COI series have been compared with reference series from the nearest geomagnetic stations and, in the case of declination series, from the recent geomagnetic field model COV-OBS to set up the required correction factors. As a result, the homogenized series measured in COI are considered to be essentially free of artificial shifts starting from the second half of the 20th century, and ready to be used by the scientific community.

scholarly journals Mudança no Regime Temporal da Temperatura do Ar e Precipitação Pluviométrica na Região de Rio Largo, Alagoas (Change in the Temporal Regime of Air Temperature and Rainfall in the Region of Rio Largo, Alagoas, Brazil)

2014 ◽  
Vol 7 (4) ◽  
pp. 662
Author(s):  
Henderson Silva Wanderley ◽  
André Luiz de Carvalho ◽  
Ronabson Cardoso Fernandes ◽  
José Leonaldo de Souza
Keyword(s):  
Time Series ◽  
Air Temperature ◽  
Change Point ◽  
Statistical Tests ◽  
Linear Regression Analysis ◽  
Homogeneity Test ◽  
Significance Level ◽  
Standard Normal Homogeneity Test ◽  
Standard Normal ◽  
History Of

Compreender como as alterações no clima têm modificado a temperatura do ar e a precipitação pluvial de uma região é essencial, sobretudo para regiões como o Nordeste brasileiro, que apresentam vasto histórico de secas e altas temperaturas. No entanto, estudos com esse fim são escassos ou até mesmo inexistentes para essa região. Deste modo, objetivou-se identificar mudanças ocorridas no regime temporal da temperatura diurna e noturna e na precipitação na região de Rio Largo, Alagoas. Para isto, utilizaram-se dados de temperatura diurna (máxima) e noturna (mínima) compreendidos entre 1973 e 2002, e de precipitação dispostos entre 1973 e 2008. As séries temporais foram submetidas ao teste estatístico SNHT (Standard Normal Homogeneity Test) para identificar possíveis pontos de mudança na média. A análise de regressão linear simples foi utilizada para identificar alterações nas séries temporais, testada por meio do teste t de Student, adotando-se nível de significância estatística de 0,05%, para ambos os testes estatísticos. A análise mostrou que as temperaturas demostraram pontos de mudanças significativos, no entanto, foi observada uma defasagem de quase dez anos entre os pontos. A tendência identificada entre as temperaturas foram opostas entre si, sendo de aumento para a temperatura diurna e de redução para a noturna. A precipitação demostrou tendência de redução, no entanto, não apresentou mudança estatística significativa.  ABSTRACTUnderstanding how changes in climate have changed air temperature and rainfall in a region is essential, especially for regions such as the Brazilian Northeast, which have long history of drought and high temperatures. However, studies for this purpose are scarce or even nonexistent for this region. Thus, this study aimed to identify changes in the temporal regime of daytime and nighttime temperature and rainfall in the region of Rio Largo, Alagoas, Brazil. For this, it was used data of daytime temperature (maximum) and night (minimum) ranging from 1973 to 2002, and rainfall arranged between 1973 and 2008. Time series were submitted to SNHT (Standard Normal Homogeneity Test) statistical test to identify possible change point in average. A simple linear regression analysis was used to identify changes in time series, tested using the Student t test, adopting a significance level of 0.05%, for both statistical tests. The analysis showed that temperatures demonstrated significant change points, however, there was a gap of almost ten years between the points. The trend identified among the temperatures was opposed to each other, with increasing daytime temperature and reduction of nighttime temperature. Rainfall demonstrated trend of reducing, however, showed no statistically significant change.Keywords: daytime and nighttime temperature, SNHT, trend, change point. 

scholarly journals Statistical analysis of temperature regime change on the example of Sokobanja basin in eastern Serbia

2015 ◽  
Vol 19 (suppl. 2) ◽  
pp. 323-330
Author(s):  
Aleksandar Radivojevic ◽  
Natasa Martic-Bursac ◽  
Milena Gocic ◽  
Ivan Filipovic ◽  
Mila Pavlovic ◽  
...  
Keyword(s):  
Air Temperature ◽  
Statistical Tests ◽  
Local Level ◽  
Homogeneity Test ◽  
Von Neumann ◽  
Early 21St Century ◽  
Scientific Disciplines ◽  
Standard Normal Homogeneity Test ◽  
Standard Normal ◽  
Almost All

The changes and oscillations in air temperature during the second half of the 20th and in the early 21st century, have become one of the major concerns of almost all scientific disciplines. Such changes are noticeable both at the local and global level. The objective of this paper is to point out that the changes of this climate element can also be detected at the local level. The research underlying this paper is, in terms of territory, limited to the Sokobanja basin in Eastern Serbia. The analysis relies on the data on air temperature for the period 1946-2012 taken from the Meteorological weather station located in Sokobanja. The obtained data were processed in line with the recommendations of the World Meteorological Organization (WMO). The evidenced statistically significant changes in air temperature were examined using the following statistical tests: Pettit test, Standard Normal Homogeneity test, Buishand range test, and von Neumann test.

scholarly journals Inhomogeneity detection in the rainfall series for the Mae Klong River Basin, Thailand

2021 ◽  
Vol 11 (9) ◽  
Author(s):  
Alamgir Khalil
Keyword(s):  
River Basin ◽  
Curve Analysis ◽  
Rainfall Series ◽  
Rainfall Data ◽  
Homogeneity Test ◽  
Significance Level ◽  
Von Neumann ◽  
Standard Normal Homogeneity Test ◽  
Double Mass ◽  
Climate Studies

AbstractAn accurate and complete rainfall record is prerequisite for climate studies. The purpose of this research study was to evaluate the homogeneity of the rainfall series for the Mae Klong River Basin in Thailand. Monthly rainfall data of eight stations in the Mae Klong River Basin for the period 1971–2015 were used. The double mass curve analysis was used to check the consistency of rainfall data, whereas the absolute homogeneity was assessed using the Pettitt test, standard normal homogeneity test, Buishand test, and von Neumann test at a 5% significance level. The results of these tests were qualitatively classified as ‘useful’, ‘doubtful’, and ‘suspect’ according to the null hypothesis. Results of the monthly time series indicated the rainfall data as ‘useful’ for 75% of the stations, while two stations’ data were classified as ‘doubtful’ (Stn130221) and ‘suspect’ (Stn376401). On an annual scale, seven out of eight stations data were classified as ‘useful,’ while one station (Stn376401) data were classified as ‘suspect’. Double mass curve analysis technique was used for the adjustment of inhomogeneous data. The results of this study can help provide reliable rainfall data for climate studies in the basin.

The Application of the Smirnov Test in the Homogeneity Test for Non-Normal Distribution Temperature Series

2012 ◽  
Vol 516-517 ◽  
pp. 530-535
Author(s):  
Xin Jie Deng ◽  
Yang Sheng You ◽  
Yan Ying Chen ◽  
Xue Mei Yang
Keyword(s):  
Normal Distribution ◽  
Classical Method ◽  
Temperature Series ◽  
Homogeneity Test ◽  
Test Results ◽  
Standard Normal Homogeneity Test ◽  
Standard Normal ◽  
Better Than ◽  
Smirnov Test

The homogeneity test is the first stage to revise the climate records. Its accuracy will directly affect the follow-up work. The classic method SNHT (Standard Normal Homogeneity Test) can only be applied in climatic sequences obey normal distribution, but lots of non-normality climate sequences need to be examined. In this paper, the Smirnov Test was introduced to test the homogeneity of the temperature series, which is a classical method for distribution test, and it can apply for the temperature sequences obey any distribution. The homogeneity test results by testing Chongqing Municipality's temperature sequences show that: the Smirnov Test is better than SNHT

scholarly journals THE EFFECT OF LEADERSHIP STYLE, ORGANIZATIONAL CULTURE, MOTIVATION ON THE PERFORMANCE OF JUNIOR HIGH SCHOOL PRINCIPAL

2018 ◽  
Vol 2 (2) ◽  
pp. 262-273
Author(s):  
Virgana Natawidjaja
Keyword(s):  
High School ◽  
Organizational Culture ◽  
Path Analysis ◽  
Leadership Style ◽  
Junior High School ◽  
Junior High ◽  
Work Motivation ◽  
Statistical Tests ◽  
School Principal ◽  
Homogeneity Test

This study was aimed at determining the direct and indirect effects of leadership style, organizational culture and motivation on the performance of the junior high school principals. This study used survey methods with quantitative approaches and path analysis (path analysis) as a research design. The research respondents were 100 heads of Junior high schools located in Jakarta. The data collection was done through research instruments in the form of questionnaires using Likert scale models. Before analyzing the data with path analysis, a number of statistical tests were carried out first which became a requirement in the path analysis, namely: Error Normality Test; Homogeneity Test; and Test the significance and linearity of the regression coefficient. The results show a direct influence of some factors namely leadership style on the work motivation of the principal; organizational culture on the work motivation of the principal; leadership style on the performance of principals; organizational culture on the performance of principals; work motivation on the performance of the principal. Indirect influences were also found in two factors namely leadership on the performance of principals through motivation and organizational culture factor on the performance of principals through motivation.PENGARUH GAYA KEPEMIMPINAN, BUDAYA ORGANISASI, MOTIVASI TERHADAP KINERJA KEPALA SEKOLAH MENENGAH PERTAMAAbstrakPenelitian ini bertujuan untuk mengetahui pengaruh gaya kepemimpinan, budaya organisasi dan motivasi terhadap kinerja kepala SMP Negeri, baik secara langsung maupun tidak langsung. Penelitian ini menggunakan metode survei dengan pendekatan kuantitatif  dan analisis jalur (path analysis) sebagai desain penelitian. Responden penelitian adalah 100 kepala SMP Negeri di DKI Jakarta. Pengumpulan data dilakukan melalui instrumen penelitian berupa kuesioner melalui model skala likert. Sebelum melakukan analisis data dengan analisis jalur terlebih dulu dilakukan beberapa uji statistik yang menjadi syarat dalam analisis jalur yaitu: Uji Normalitas Galat; Uji Homogenitas; serta Uji signifikansi dan linearitas koefisien regresi. Hasil analisis menemukan bahwa terdapat: pengaruh langsung gaya kepemimpinan terhadap motivasi kerja kepala sekolah; pengaruh langsung budaya organisasi terhadap motivasi kerja kepala sekolah; pengaruh langsung gaya kepemimpinan  terhadap kinerja kepala sekolah; pengaruh langsung budaya organisasi  terhadap kinerja kepala sekolah; pengaruh langsung motivasi kerja terhadap kinerja kepala sekolah; pengaruh tidak langsung kepemimpinan terhadap kinerja kepala sekolah melalui motivasi; dan pengaruh tidak langsung budaya organisasi terhadap kinerja kepala sekolah melalui motivasi.

scholarly journals Statistical relationships between variations of the geomagnetic field, auroral electrojet, and geomagnetically induced currents

2019 ◽  
Vol 5 (1) ◽  
pp. 48-58
Author(s):  
Андрей Воробьев ◽  
Andrey Vorobev ◽  
Вячеслав Пилипенко ◽  
Vyacheslav Pilipenko ◽  
Ярослав Сахаров ◽  
...  
Keyword(s):  
Geomagnetic Field ◽  
Extreme Values ◽  
Time Derivative ◽  
Geomagnetically Induced Currents ◽  
Ae Index ◽  
Induced Currents ◽  
Statistical Relationships ◽  
Highly Correlated ◽  
Log Normal ◽  
Field Variability

Using observations from the IMAGE magnetic observatories and the station for recording geomagnetically induced currents (GIC) in the electric transmission line in 2015, we examine relationships between geomagnetic field and GIC variations. The GIC intensity is highly correlated (R>0.7) with the field variability |dB/dt| and closely correlated with variations in the time derivatives of X and Y components. Daily variations in the mean geomagnetic field variability |dB/dt| and GIC intensity have a wide night maximum, associated with the electrojet, and a wide morning maximum, presumably caused by intense Pc5–Pi3 geomagnetic pulsations. We have constructed a regression linear model to estimate GIC from the time derivative of the geomagnetic field and AE index. Statistical distributions of the probability density of the AE index, geomagnetic field derivative, and GIC correspond to the log-normal law. The constructed distributions are used to evaluate the probabilities of extreme values of GIC and |dB/dt|.

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