Slope Of Linear Trend Research Articles

A Comparison of the Rank-based and Slope-based Nonparametric Tests for Trend Detection in Climate Time Series

Trend detection in climate time series data is crucial for understanding climate change, predicting future climate patterns, assessing impacts, managing resources, and formulating policies. Several trend detection methods have been introduced in the literature, including parametric and non-parametric approaches. Nonparametric trend detection methods are often considered more preferable than parametric methods in certain situations due to their flexibility and robustness. Comparing various nonparametric methods of trend detection is vital in data analysis because different techniques can yield divergent results based on the same dataset. In this study, three nonparametric trend tests which were the MannKendall (MK), Sen’s Innovative Trend Analysis (ITA) and Modified Mann-Kendall by Sen’s Innovative Trend Analysis (MMK_ITA) were compared based on their power. The MK test is a rank-based test and the ITA is a slope-based test. Meanwhile, the combination of rank-based and slope-based methods is known as the MMK_ITA test. The power analysis was conducted through Monte Carlo simulation on normal, non-normal and autocorrelated time series. The simulation results indicated that test power relied on magnitude of linear trend slope, sample sizes, distribution type and variation in time series. These tests were then applied to monthly maximum temperature from 2002 until 2021 for Selangor, Malaysia. This study found that the slope-based test performed better compared to the rank-based test and their combined methods from the simulation studies and real data application based on the calculated power.

Multitemporal dual-pol Sentinel-1 data to support monitoring of forest post-fire dynamics

Approaches based on multitemporal analysis of optical-retrieved vegetation index time series were successfully applied to describe forest disturbances like forest fires; conversely, only few works make use of multitemporal Synthetic Aperture Radar (SAR) data. In this work, a multi-temporal approach based on Sentinel-1 data (S1) is proposed based on CR polarimetric index to monitor forest canopy along the considered period (2016–2019) preceding and following an important fire event occurred in the Piemonte Region (NW Italy) in November 2017. The Pettitt test, applied to the polarimetric index time series, was used for testing fire occurrence date and map burned areas (795 ha) resulting in user’s accuracy of burned area equal to 88%. A trend analysis was also conducted, on ‘burned’ pixels only, to describe tree canopy damage and strength of the consequent recovery process at pixel level using linear trend slope values of cross ratio polarimetric index time series. Finally, a k-means cluster analysis was applied to define classes having the same ecological behaviour with respect to two different criteria: one aimed at mapping type and intensity of damage and a second one aimed at describing the ecological behaviour in terms of resistance and resilience of burned patches. In the study area, the cluster layer called forest damage map classifies about the 22% of burned area as characterized by an early high severity whiled the residual by moderate-low severity levels. The second cluster layer called ecological response map defined the 61% of the burned area as resistant forests, the 20% as resilient forests and the 19% as increasing forest zones. All maps were generated with the aim of supporting post-fire assessment and management with free satellite SAR data.

Inflammatory signals hidden in the CBC are detectable prior to durvalumab-induced pneumonitis.

e21116 Background: For patients with unresectable stage III non-small cell lung cancer (NSCLC), chemoradiation followed by 1 year of durvalumab is standard of care. Treatment-induced pneumonitis can be life-threatening. Neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR) and systemic immune inflammation index (SII, defined as platelet x neutrophil / lymphocyte counts) are calculated from the CBC and have been studied as inflammatory biomarkers in a variety of settings. This study assessed trends in these indices among patients treated for stage III NSCLC. Methods: We reviewed medical records of adults with stage III NSCLC who completed chemoradiation and durvalumab from 1/2017 to 9/2021 as part of routine care. Patients who developed non-pneumonitis immune toxicity were excluded. NLR, PLR and SII were calculated at dates of first and last radiation dose and first durvalumab dose. For patients who developed pneumonitis, indices were also calculated at each of 8 weeks leading up to pneumonitis onset, defined as the first diagnostic CT scan and graded as 1-5 based on CTCAE criteria. Indices were compared between the pneumonitis and no pneumonitis group using rank-sum test. P values < 0.05 were considered statistically significant without adjustment for multiple testing. The slope of linear trend for each index was examined via log-gamma generalized linear regression model using a random intercept for each patient and robust standard error. Results: Of 65 patients who received chemoradiation followed by durvalumab, 2 were excluded because they were on clinical trial and 28 were excluded for non-pneumonitis immune toxicity. Among the 35 patients eligible for analysis, median age was 67 years; 20 (57%) were female; 6 (17%) were current smokers; 15 (43%) had COPD; and 17 (49%) developed pneumonitis (2 G1; 11 G2; 3 G3; 0 G4; 1 G5). In the pneumonitis group, NLR (p = 0.022), PLR (p = 0.007) and SII (p = 0.001) showed a statistically significant linear increase in the 5 weeks preceding pneumonitis onset. There were no differences in clinical characteristics, SII, NLR or PLR between the pneumonitis and no pneumonitis groups at the 3 time points examined. Conclusions: In this exploratory analysis, patients who developed pneumonitis showed a linear increase in inflammatory indices for 5 weeks before pneumonitis onset, suggesting information hidden in routine blood tests can anticipate development of a life-threatening complication. Our hypothesis-generating study will need validation in a larger prospective analysis with a control group. Future directions may also include examination of selected acute phase reactants or cytokines.

50 Years of Pollen Monitoring in Basel (Switzerland) Demonstrate the Influence of Climate Change on Airborne Pollen.

Climate change and human impact on vegetation modify the timing and the intensity of the pollen season. The 50 years of pollen monitoring in Basel, Switzerland provide a unique opportunity to study long-term changes in pollen data. Since 1969, pollen monitoring has been carried out in Basel with a Hirst-type pollen trap. Pollen season parameters for start dates, end dates and duration were calculated with different pollen season definitions, which are commonly used in aerobiology. Intensity was analyzed by the annual pollen integral (APIn), peak value and the number of days above specific thresholds. Linear trends were calculated with the non-parametric Mann Kendall method with a Theil-Sen linear trend slope. During the last 50 years, linear increase of the monthly mean temperatures in Basel was 0.95–1.95°C in the 3 winter months, 2–3.7°C in spring months and 2.75–3.85°C in summer months. Due to this temperature increase, the start dates of the pollen season for most of the spring pollen species have advanced, from 7 days for Poaceae to 29 days for Taxus/Cupressaceae. End dates of the pollen season depend on the chosen pollen season definition. Negative trends predominate, i.e., the pollen season mostly ends earlier. Trends in the length of the pollen season depend even more on the season definitions and results are contradictory and often not significant. The intensity of the pollen season of almost all tree pollen taxa increased significantly, while the Poaceae pollen season did not change and the pollen season of herbs decreased, except for Urticaceae pollen. Climate change has a particular impact on the pollen season, but the definitions used for the pollen season parameters are crucial for the calculation of the trends. The most stable results were achieved with threshold definitions that indicate regular occurrence above certain concentrations. Percentage definitions are not recommended for trend studies when the annual pollen integral changed significantly.

Detection and quantification of trends in time series of significant wave heights: An application in the Mediterranean Sea

The analysis of long-term trends in time series of wave parameters has an high engineering relevance. These trends may affect the estimates of parameters with high return period that are used for the design of several engineering projects. This work analyses the use of linear regressions for detecting and quantifying long-term trends in time series of data. In particular, the reliability of a linear trend slope, modified in order to minimize the weight of possible outliers, is evaluated. To this end, this slope is compared against the outcomes of two methods that do not imply the hypothesis of linear trend: the Mann–Kendall test and the Innovative Trend Analysis. An application to significant wave height time series over the Mediterranean Sea is presented. Time series of 40 years of numerical hindcast of sea states over the whole basin were analysed, and the methods taken into account were applied to the annual maxima, the annual 98th percentile and the annual mean significant wave height. The results show that the use of the investigated linear slope is meaningful, therefore this was used to assess the spatial distribution of trends in the Mediterranean Sea. Results are presented and discussed for all the statistics investigated.

Spatial Distribution of NDVI Trends for Forest Vegetation in the Natural Reserve “Stolby” Based on MODIS Satellite Data

The purpose of this work is to assess the long-term changes in the state of forest vegetation on the territory of the Nature Reserve “Stolby” for the period 2000-2018. An algorithm has been developed for this and a map of the spatial distribution of the average annual NDVI trends of forest vegetation according to MODIS satellite data has been created (May – September as averaging period). In the work, a map of vegetation cover was used according to the electronic ecological atlas of the Nature Reserve “Stolby”. The analysis of the distribution of the number of pixels on the values of the average annual NDVI trend revealed that for the class of coniferous vegetation negative values of the linear trend prevail (by 30%). For the deciduous vegetation class, the number of pixels with negative values of linear trend slope is 3.1% higher than with positive ones. In general, for most types of forest vegetation negative trends NDVI prevail. The negative NDVI trend slope of vegetation indicates degradation processes. The reasons for this are the changes of climatic factors, anthropogenic impact, fires, aging and forest vegetation diseases

Current Climatic Changes in the Troposphere, Stratosphere, and Mesosphere, and Inter-Layer Interactions

Using new data about near-surface air temperature in the Northern Hemisphere (from 1850 to 2018) and ERA5 reanalysis of temperature distributions up to s height of 80 km (from 1979 to 2018), the authors calculate and analyse mean and root-mean square deviations, linear trend slope coefficients, and low-frequency components of temperature at various levels and latitude zones. A 60-year quasi-cyclicity of the temperature near the Earth’s surface has been discovered. The authors evaluate the rates of tropospheric warming and stratospheric cooling observed over the last decades. Much attention is given to the search for correlations between the atmospheric layers, thermal regime characteristics, and the Arctic Oscillation. A predictive valuation of temperature oscillations is obtained for Kazan until 2051, taking into account distant relationships revealed between the temperature status of the ocean surface and the region considered.

PECULIARITIES OF VERTICAL DISTRIBUTION OF AIR TEMPERATURE IN THE TROPOSPHERE AND LOWER STRATOSPHERE

The article presents the analysis of annual values of the temperature indicators of the troposphere and lower stratosphere obtained using radio sounding at upper-air stations of Kazan, Orenburg, Ufa in the period 1979-2016. Comparison of air temperature data from radiosonde observations and reanalysis series Era-interim, Ncep/Ncar, Ncep/Doe was performed. The average long-term indicators of air temperature and its standard deviation are calculated. The difference was found when comparing within 0.5-1 °C for the troposphere and 1-2 °C for the lower stratosphere. The calculated correlation coefficients also testify to a better agreement of heterogeneous data in the troposphere than in the stratosphere. The linear trend slope coefficient (LTSC) of air temperature is positive in the troposphere and negative in the stratosphere.

Empirical Statistical Model of Climatic Changes in the Volga Region

Climatic changes in the Volga Federal Region from 1928 to 2017 are examined. CRU data, meteorological stations, and reanalysis ERA-Interim data are used. An estimation of global factors in the variability of air temperature in the region is made. For the first time, for the VFR, an empirical-statistical model is constructed for vertical distributions (up to 64 km) of air temperature, average standard deviation of temperature, linear trend slope coefficient, and low frequency temperature component. The effect of Arctic Oscillation on temperature changes near the Earth’s surface and in the layer of 7-3 hPa in the stratosphere are evaluated.

Quantitative Dual-Energy Computed Tomography Predicts Regional Perfusion Heterogeneity in a Model of Acute Lung Injury.

ObjectiveThe aims of this study were to investigate the ability of contrast-enhanced dual-energy computed tomography (DECT) for assessing regional perfusion in a model of acute lung injury, using dynamic first-pass perfusion CT (DynCT) as the criterion standard and to evaluate if changes in lung perfusion caused by prone ventilation are similarly demonstrated by DECT and DynCT.MethodsThis was an institutional review board–approved study, compliant with guidelines for humane care of laboratory animals. A ventilator-induced lung injury protocol was applied to 6 landrace pigs. Perfused blood volume (PBV) and pulmonary blood flow (PBF) were respectively quantified by DECT and DynCT, in supine and prone positions. The lungs were segmented in equally sized regions of interest, namely, dorsal, middle, and ventral. Perfused blood volume and PBF values were normalized by lung density. Regional air fraction (AF) was assessed by triple-material decomposition DECT. Per-animal correlation between PBV and PBF was assessed with Pearson R. Regional differences in PBV, PBF, and AF were evaluated with 1-way analysis of variance and post hoc linear trend analysis (α = 5%).ResultsMean correlation coefficient between PBV and PBF was 0.70 (range, 0.55–0.98). Higher PBV and PBF values were observed in dorsal versus ventral regions. Dorsal-to-ventral linear trend slopes were −10.24 mL/100 g per zone for PBV (P < 0.001) and −223.0 mL/100 g per minute per zone for PBF (P < 0.001). Prone ventilation also revealed higher PBV and PBF in dorsal versus ventral regions. Dorsal-to-ventral linear trend slopes were −16.16 mL/100 g per zone for PBV (P < 0.001) and −108.2 mL/100 g per minute per zone for PBF (P < 0.001). By contrast, AF was lower in dorsal versus ventral regions in supine position, with dorsal-to-ventral linear trend slope of +5.77%/zone (P < 0.05). Prone ventilation was associated with homogenization of AF distribution among different regions (P = 0.74).ConclusionsDual-energy computed tomography PBV is correlated with DynCT-PBF in a model of acute lung injury, and able to demonstrate regional differences in pulmonary perfusion. Perfusion was higher in the dorsal regions, irrespectively to decubitus, with more homogeneous lung aeration in prone position.

Estimation and Inference of Linear Trend Slope Ratios With an Application to Global Temperature Data

We examine estimation and inference of the ratio of linear trend slopes between two time series. Our methodological results are motivated by recent empirical climate papers that estimate and test hypotheses about the relative warming rate in the lower‐troposphere relative to surface warming, i.e. the amplification ratio. We analyze statistical properties of several estimators and test statistics that allow serial correlation. Relative merits of the estimators and test statistics depend on the magnitude of the trend slopes relative to the noise in the data. We make specific recommendations for practitioners. We revisit the empirical findings of Klotzbach et al. (2009, 2010) and obtain similar results using our recommended approach.

Change point detection of the Persian Gulf sea surface temperature

In this study, the Student’s t parametric and Mann-Whitney nonparametric change point models (CPMs) were applied to detect change point in the annual Persian Gulf sea surface temperature anomalies (PGSSTA) time series for the period 1951–2013. The PGSSTA time series, which were serially correlated, were transformed to produce an uncorrelated pre-whitened time series. The pre-whitened PGSSTA time series were utilized as the input file of change point models. Both the applied parametric and nonparametric CPMs estimated the change point in the PGSSTA in 1992. The PGSSTA follow the normal distribution up to 1992 and thereafter, but with a different mean value after year 1992. The estimated slope of linear trend in PGSSTA time series for the period 1951–1992 was negative; however, that was positive after the detected change point. Unlike the PGSSTA, the applied CPMs suggested no change point in the Nino3.4SSTA time series.

Spatial analysis of the temperature trends in Serbia during the period 1961–2010

The spatial analysis of annual and seasonal temperature trends in Serbia during the period 1961–2010 was carried out using mean monthly data from 64 meteorological stations. Change year detection was achieved using cumulative sum charts. The magnitude of trends was derived from the slopes of linear trends using the least square method. The same formalism of least square method was used to assess the statistical significance of the determined trends. Maps of temperature trends were generated by applying a spatial regression method to visualize the detected tendencies. The obtained results indicate a negative temperature trend for the period before the change year except for winter and a more pronounced positive trend after the change year. Besides being more pronounced, the vast majority of trends after the change year were also clearly statistically significant. Our estimate of the average temperature trend over Serbia is in agreement with those obtained at the global and European scale. Calculated global autocorrelation statistics (Moran’s I) indicate an apparent random spatial pattern of temperature trends across the Serbia for both periods before and after the change year.

Efficiency of nutrient management in controlling eutrophication of running waters in the Middle Danube Basin

Nutrient emission dropped significantly during the last two decades in the Danube Basin. To assess the effect of reduced nutrient loads on the trophic status of running waters, this regional study analyzed the relationships between nutrients (P and N) and suspended chlorophyll (Chl) using long-term monitoring data in Hungary. Including the upstream catchments of trans-boundary rivers, the study covered an approximate area of 400,000 km2, equivalent to the half of the entire Danube catchment. Decadal median Chl was unrelated to P and N concentrations in the whole data set and weakly related to total P (TP) at natural-moderately polluted (N-MP) sites, which were distinguished from highly polluted (HP) sites by using cutoff values for chloride, chemical oxygen demand and TP. At both the N-MP sites and most of the HP sites, Chl increased with channel length. This indicated that water residence time was a more important determinant of Chl than nutrients. Nutrient concentrations showed a significant downward trend in time at half of our sites. With a nearly equal frequency, a parallel trend might or might not occur in Chl. The apparent efficiency of nutrient management was expressed as the quotient of the slopes of linear trends in Chl and nutrients. At sites within 150 km from source, this efficiency was marginal. In larger rivers, efficiency improved steeply. The highest efficiency was observed in the downstream reach of the Danube (upstream length >1,300 km) where P availability might frequently limit algal growth. The results suggest that eutrophication management in rivers should be based on Chl response functions, rather than universal nutrient criteria. Four Chl response classes were identified based on the observed longitudinal P and Chl gradients.

Re–Os isotope systematics of mantle xenoliths from South Korea: Evidence for complex growth and loss of lithospheric mantle beneath East Asia

We report Re–Os isotopic data for seventeen mantle xenoliths from the Jeju and Baekryeong Islands, Pyeongtaek, and Boeun, South Korea. All are spinel peridotites, hosted by late Tertiary to Quaternary (∼5.0 Ma to historic) alkali basalt flows and range in composition from depleted harzburgites to variably depleted lherzolites. All of the measured 187Os/188Os and 187Re/188Os ratios are subchondritic to chondritic (0.1155 to 0.1285 and 0.022 to 0.391, respectively), with the exception of two samples with 187Re/188Os (>0.6). Model Os TRD ages of ∼1.9 to 1.8 Ga for three strongly depleted harzburgites (Mg#=90.6 to 91.2) indicate that Paleoproterozoic subcontinental lithospheric mantle (SCLM) is currently preserved beneath the Korean peninsula. The slopes of linear trends of 187Os/188Os vs. Al2O3 are also consistent with this interpretation, although a lack of correlation between 187Re/188Os and 187Os/188Os indicates likely recent perturbations in Re concentrations, especially in the lherzolites. Collectively, the new data indicate that the age of the current SCLM beneath South Korea is considerably younger than the overlying Archean crust, suggesting possible removal and replacement of the Archean SCLM during the Proterozoic. This replacement event may be temporally coincident with widespread intracrustal reworking events that occurred in South Korea during the Paleoproterozoic (∼2.1 to 1.8 Ga). The results of this study and previous studies of other East Asian tectonic blocks provide strong evidence for the periodic construction and destruction of SCLM beneath East Asia during the Archean, Proterozoic, and Phanerozoic, and extend to the east the range of known complicated age structure of the current SCLM beneath East Asia.

Clostridium difficileInfection in Patients Discharged from US Short-stay Hospitals, 1996–20031

US hospital discharges for which Clostridium difficile-associated disease (CDAD) was listed as any diagnosis doubled from 82,000 (95% confidence interval [CI] 71,000-94,000) or 31/100,000 population in 1996 to 178,000 (95% CI 151,000-205,000) or 61/100,000 in 2003; this increase was significant between 2000 and 2003 (slope of linear trend 9.48; 95% CI 6.16-12.80, p = 0.01). The overall rate during this period was severalfold higher in persons >65 years of age (228/100,000) than in the age group with the next highest rate, 45-64 years (40/100,000; p < or = 0.001). CDAD appears to be increasing rapidly in the United States and is disproportionately affecting older persons. Clinicians should be aware of the increasing risk for CDAD and make efforts to control transmission of C. difficile and prevent disease.

Clostridium difficileInfection in Patients Discharged from US Short-stay Hospitals, 1996–20031

US hospital discharges for which Clostridium difficile-associated disease (CDAD) was listed as any diagnosis doubled from 82,000 (95% confidence interval [CI] 71,000-94,000) or 31/100,000 population in 1996 to 178,000 (95% CI 151,000-205,000) or 61/100,000 in 2003; this increase was significant between 2000 and 2003 (slope of linear trend 9.48; 95% CI 6.16-12.80, p = 0.01). The overall rate during this period was severalfold higher in persons >65 years of age (228/100,000) than in the age group with the next highest rate, 45-64 years (40/100,000; p < or = 0.001). CDAD appears to be increasing rapidly in the United States and is disproportionately affecting older persons. Clinicians should be aware of the increasing risk for CDAD and make efforts to control transmission of C. difficile and prevent disease.

Effect of Gestational Age and Position on Peak Expiratory Flow Rate: A Longitudinal Study

We sought to study the effects of gestational age and maternal position on peak expiratory flow rates. Peak expiratory flow rates were measured in the standing, sitting, and supine positions in 38 healthy pregnant women at 4-week intervals starting at less than 10 weeks until delivery and again at 6 weeks postpartum. The highest reading of 3 consecutive peak expiratory flow rate measurements for each encounter and position was used in the analysis. Repeated measures analysis of covariance was performed with subjects, gestational age, position, and gestational age times position as the model effects. Least squares mean peak expiratory flow rates were compared among positions at different gestation ages using Bonferroni-adjusted least significant difference t tests. Peak expiratory flow rate declined significantly throughout gestation in all positions (P < .001) with mean rate of decline of 0.65 L/min per week). The slopes of linear trends were not statistically different between positions (P = .222). However, the rate of decline for the supine position was higher than for standing and sitting positions (0.86 compared with 0.46 and 0.57 L/min per week), respectively. On average, the postpartum peak expiratory flow rate returned to 71.9% of its measurement in early gestation. Nomograms depicting mean and the 5th and 95th percentiles of peak expiratory flow rates were constructed for each position. Peak expiratory flow rate measurements are affected by maternal position and advancing gestational age, especially in the supine position. Adjustment of patient's flow rate in relation to gestational age and maternal position is recommended, especially in pregnant women with asthma. III.

Statistical modeling of intensive TBT monitoring data in two tidal creeks of the Chesapeake Bay

Abstract Results are presented from a three year program of weekly tributyltin (TBT) monitoring at nine stations in two tidal creeks of the Chesapeake Bay. Most stations are near dense moorings of recreational boats. The logarithm of TBT + concentration is shown to have appropriate statistical and mathematical properties for modeling. All stations with a relatively high concentration of TBT + (> 10 ng/liter) show a significant annual variation superimposed upon a decreasing linear trend. The trend slope corresponds to a half-life of about 2–3 years. There is strong evidence that the model residuals are uncorrelated in time. All the high concentration stations in a creek system can be adequately modeled by the same annual component amplitude and phase values and the same linear trend slope, while individual stations differ only in overall concentration.

Circadian variation of the plasma 17-hydroxycorticosteroids in central nervous system disease.

The pattern of the circadian variation of the plasma 17-OHCS was studied in 48 patients with focal disease of the central nervous system unassociated with disturbance of consciousness. Disease of the temporal lobe, pretectum or hypothalamus was present in 27 patients (Group A). Pituitary disease characterized by sellar enlargement, but with minimal evidence of endocrinopathy, was present in 13 patients (Group B). The control group consisted of 21 patients with focal central nervous system disease outside these areas (Group C), and 47 normal subjects (Group D). The circadian patterns of the patient groups were compared to those of the normal subjects with respect to 3 criteria: (a) slope of linear trend (calculated by the method of least squares); (b) extent of variation of plasma steroid levels from this fitted straight line; and (c) average plasma steroid levels. Patients in Group A differed significantly (at an over-all 5% level) from normal subjects with respect to the first 2 criteria. In patients in ...