scholarly journals Trends and fluctuations of the cyclonic systems over North Indian Ocean

MAUSAM ◽  
2021 ◽  
Vol 52 (1) ◽  
pp. 37-46
Author(s):  
D. V. BHASKAR RAO ◽  
C. V. NAIDU ◽  
B. R. SRINIVASA RAO
Keyword(s):  
Time Series ◽  
Indian Ocean ◽  
Maximum Entropy Method ◽  
Entropy Method ◽  
North Indian Ocean ◽  
Pass Filter ◽  
Long Term Trends ◽  
High Pass ◽  
Cyclone Frequency

The data of the monthly cyclone frequencies over North Indian Ocean for the period 1877-1998 has been analysed to study the long-term trends and fluctuations. Analysis has been made separately for depressions and cyclones for the pre-monsoon, monsoon and post-monsoon seasons along with the annual frequencies. The data was subjected to 11-year moving averages and the epochs of increasing and decreasing trends have been identified. A consistent decreasing trend after 1950s is a notable feature.   The time series of the monthly cyclone frequency were passed through a high-pass filter to eliminate periods greater than 21 years and then subjected to spectrum analysis using Maximum Entropy Method to obtain dominant periodicities. Three significant periodicities at 2.2-2.8; 3.5-6.5 and 10-15 years have been identified which could be attributed to QBO, ENSO and decadal frequencies.

scholarly journals Seasonal Nature and Trends of Tropical Cyclone Frequency and Intensity over the North Indian Ocean

2020 ◽  
Vol 15 (3) ◽  
pp. 526-534
Author(s):  
Abhisek Pal ◽  
Soumendu Chatterjee
Keyword(s):  
Time Series ◽  
Tropical Cyclone ◽  
Indian Ocean ◽  
Monsoon Season ◽  
North Indian Ocean ◽  
Post Monsoon ◽  
The North ◽  
Increasing Trend ◽  
Post Monsoon Season ◽  
Cyclone Frequency

Tropical cyclone (TC) genesis over the North Indian Ocean (NIO) region showed significant amount of both spatial and temporal variability.It was observed that the TC genesis was significantly suppressed during the monsoon (June-September) compared to pre-monsoon (March-May) and post-monsoon (October-December) season specifically in terms of severe cyclonic storms (SCS) frequency. The Bay of Bengal (BoB) was characterized by higher TC frequency but lower intensity compared to the Arabian Sea (AS). It was also observed that the TC genesis locations were shifted significantly seasonally.The movement of the TCs also portrayed some significant seasonal differences. The pre-monsoon and post-monsoon season was responsible for generating TCs with higher values of accumulated cyclone energy (ACE) compared to the monsoon. The time series of TC frequency showed a statistically significant decreasing trend whereas the time series of ACE showed astatistically significant increasing trend over the NIO.

scholarly journals Maps, trends, and temperature sensitivities—phenological information from and for decreasing numbers of volunteer observers

2021 ◽  
Author(s):  
Ye Yuan ◽  
Stefan Härer ◽  
Tobias Ottenheym ◽  
Gourav Misra ◽  
Alissa Lüpke ◽  
...  
Keyword(s):  
Climate Change ◽  
Time Series ◽  
Strong Decrease ◽  
Temperature Changes ◽  
Interpolation Accuracy ◽  
Observation Network ◽  
Shiny App ◽  
Long Term Trends ◽  
Autumn And Winter

AbstractPhenology serves as a major indicator of ongoing climate change. Long-term phenological observations are critically important for tracking and communicating these changes. The phenological observation network across Germany is operated by the National Meteorological Service with a major contribution from volunteering activities. However, the number of observers has strongly decreased for the last decades, possibly resulting in increasing uncertainties when extracting reliable phenological information from map interpolation. We studied uncertainties in interpolated maps from decreasing phenological records, by comparing long-term trends based on grid-based interpolated and station-wise observed time series, as well as their correlations with temperature. Interpolated maps in spring were characterized by the largest spatial variabilities across Bavaria, Germany, with respective lowest interpolated uncertainties. Long-term phenological trends for both interpolations and observations exhibited mean advances of −0.2 to −0.3 days year−1 for spring and summer, while late autumn and winter showed a delay of around 0.1 days year−1. Throughout the year, temperature sensitivities were consistently stronger for interpolated time series than observations. Such a better representation of regional phenology by interpolation was equally supported by satellite-derived phenological indices. Nevertheless, simulation of observer numbers indicated that a decline to less than 40% leads to a strong decrease in interpolation accuracy. To better understand the risk of declining phenological observations and to motivate volunteer observers, a Shiny app is proposed to visualize spatial and temporal phenological patterns across Bavaria and their links to climate change–induced temperature changes.

Mercury trends and cycling in northern Wisconsin related to atmospheric and hydrologic processes

2019 ◽  
Vol 76 (5) ◽  
pp. 831-846 ◽  
Author(s):  
C.J. Watras ◽  
D. Grande ◽  
A.W. Latzka ◽  
L.S. Tate
Keyword(s):  
Time Series ◽  
Water Cycle ◽  
Water Levels ◽  
Hydrologic Processes ◽  
Littoral Sediments ◽  
Long Term Trends ◽  
Acid Base Status ◽  
Explanatory Mechanism ◽  
Regional Water

Atmospheric deposition is the principal source of mercury (Hg) to remote northern landscapes, but its fate depends on multiple factors and internal feedbacks. Here we document long-term trends and cycles of Hg in the air, precipitation, surface water, and fish of northern Wisconsin that span the past three decades, and we investigate relationships to atmospheric processes and other variables, especially the regional water cycle. Consistent with declining emission inventories, there was evidence of declining trends in these time series, but the time series for Hg in some lakes and most fish were dominated by a near-decadal oscillation that tracked the regional oscillation of water levels. Concentrations of important solutes (SO4, dissolved organic carbon) and the acid–base status of lake water also tracked water levels in ways that cannot be attributed to simple dilution or concentration. The explanatory mechanism is analogous to the “reservoir effect” wherein littoral sediments are periodically exposed and reflooded, altering the internal cycles of sulfur, carbon, and mercury. These climatically driven, near-decadal oscillations confound short or sparse time series and complicate relationships among Hg emissions, deposition, and bioaccumulation.

Warming is Driving Decreases in Snow Fractions While Runoff Efficiency Remains Mostly Unchanged in Snow-Covered Areas of the Western United States

2018 ◽  
Vol 19 (5) ◽  
pp. 803-814 ◽  
Author(s):  
Gregory J. McCabe ◽  
David M. Wolock ◽  
Melissa Valentin
Keyword(s):  
United States ◽  
Time Series ◽  
Winter Precipitation ◽  
Western United States ◽  
Balance Model ◽  
Winter Temperatures ◽  
Long Term Trends ◽  
Monthly Water Balance ◽  
Surface Water Supply

Abstract Winter snowfall and accumulation is an important component of the surface water supply in the western United States. In these areas, increasing winter temperatures T associated with global warming can influence the amount of winter precipitation P that falls as snow S. In this study we examine long-term trends in the fraction of winter P that falls as S (Sfrac) for 175 hydrologic units (HUs) in snow-covered areas of the western United States for the period 1951–2014. Because S is a substantial contributor to runoff R across most of the western United States, we also examine long-term trends in water-year runoff efficiency [computed as water-year R/water-year P (Reff)] for the same 175 HUs. In that most S records are short in length, we use model-simulated S and R from a monthly water balance model. Results for Sfrac indicate long-term negative trends for most of the 175 HUs, with negative trends for 139 (~79%) of the HUs being statistically significant at a 95% confidence level (p = 0.05). Additionally, results indicate that the long-term negative trends in Sfrac have been largely driven by increases in T. In contrast, time series of Reff for the 175 HUs indicate a mix of positive and negative long-term trends, with few trends being statistically significant (at p = 0.05). Although there has been a notable shift in the timing of R to earlier in the year for most HUs, there have not been substantial decreases in water-year R for the 175 HUs.

scholarly journals Spectral characteristics of Atlantic seasonal storm frequency

MAUSAM ◽  
2021 ◽  
Vol 57 (4) ◽  
pp. 597-608
Author(s):  
R. P. KANE
Keyword(s):  
Time Series ◽  
Maximum Entropy Method ◽  
Southern Oscillation ◽  
Spectral Characteristics ◽  
Entropy Method ◽  
Sea Surface ◽  
Low Latitude ◽  
Storm Activity ◽  
Oscillation Phenomenon ◽  
Storm Frequency

lkj & o"kZ 1900&2000 dh vof/k esa vVykafVd egklkxj dh rwQkuh xfrfof/k ¼ftUgas rwQku] izpaM rwQku] vkfn uke fn, x, gaS½ ds fofHkUu lwpdkadksa ds dky Jsf.k;ksa dk vuqØe fo’ys"k.k ,e-b-,e-¼vf/kdre ,uVªkWih fof/k½ }kjk rFkk mldh vkofrZrk ds vk;ke ,e- vkj- ,- ¼cgqq lekJ;.k fo’ys"k.k½ }kjk izkIr fd, x, gaSA fiNys dqN o"kksZa ds vkadM+ksa ¼o"kZ 1950 ls vkxss½ ds vuqlkj budh egRoiw.kZ vkofrZrk,¡ n’kd lfgr( f}okf"kZd dYi] f=okf"kZd dYi {ks=ksa rFkk buls mPp {ks=ksa esa Hkh jghA 2-40 o"kkasZ esa 50 feyhckj ds fuEu v{kka’k {ks=h; iou vkSj 2-40 ,oa 2-85 o"kkasZ ds b- ,u- ,l- vks- ¼,y uhuks/nf{k.kh nksyu½ ?kVuk ds ln`’k f}o"khZ dYi nksyu {ks= esa ¼3&4 o"kkasZ½ rwQku lwpdkad 2-40 rFkk 2-85 o"kksZa ds djhc pje ij jgsA mPp vkofrZrk okys {ks=ksa esa rwQku lwpdkad 4-5&5-5-] 8&9] 11&12 rFkk 14&15 o"kkasZ esa pje ij jgs tcfd b- ,u- ,l- vks- 7-4 ,oa 12&14 o"kksZa esa pje ij jgsA cgq n’kdh; Js.kh esa 28&34]40]50&53]61&63]~70 ,oa ~80 o"kksZa esa ¼ijUrq fHkUu lwpdkadksa ds fy, fHkUu&fHkUu½ rwQku pje ij jgs tks LFky ,oa leqnzh lrg ds rkiekuksa ds leku pje ekuksa ds vuq:Ik jgsA dqy lwpdkadksa esa 90 o"kkZsa esa yxHkx 50 izfr’kr dh m/oZ izo`fr jghA     The time series of the various indices of Atlantic storm activity (number of named storms, hurricanes, etc.) for 1900-2000 were subjected to spectral analysis by MEM (Maximum Entropy Method) and amplitudes of the periodicities were obtained by MRA (Multiple Regression Analysis).  For recent data (1950 onwards), significant periodicities were in the quasi-biennial, quasi-triennial regions and also in higher regions, including decadal. In the QBO region (2-3 years), storm indices had peaks near 2.40 and 2.85 years, similar to 2.40 years of 50 hPa low latitude zonal wind and 2.40 and 2.85 years of ENSO (El Niño/Southern Oscillation) phenomenon. In the QTO region (3-4 years), storm indices and ENSO had common peaks near 3.5 years. In higher periodicity regions, storm indices had peaks at 4.5-5.5, 8-9, 11-12 and 14-15 years, while ENSO had peaks at 7.4 and 12-14 years. In the multi-decadal range, storm peaks were at 28-34, 40, 50-53, 61-63, ~70 and ~80 years (but different for different indices), which matched with similar peaks in land and sea surface temperatures. Some indices had large uptrends, ~50% in 90 years.

Availability and Sales of Alcohol in Four Canadian Provinces: A Time-Series Analysis

2005 ◽  
Vol 32 (3) ◽  
pp. 343-372 ◽  
Author(s):  
Björn Trolldal
Keyword(s):  
Time Series ◽  
Research Question ◽  
Pure Alcohol ◽  
Dependent Variables ◽  
Long Term Trends ◽  
Time Series Analyses ◽  
Canadian Provinces ◽  
Physical Availability ◽  
Total Sales

The research question addressed in the present study, with ARIMA time-series analyses, was the extent to which changes in economic and physical availability had an effect on sales of alcohol in four Canadian provinces during the second half of the 20th century. The annual sales, by type of beverage (spirits, wine and beer) as well as total sales, measured in pure alcohol per inhabitant age 15 and above in each province, were used as dependent variables in the analyses. The inhabitants' real disposable income, the real price of alcohol, and the number of on- and off-premise outlets per 100,000 inhabitants were used as independent variables. All the time-series were differenced to remove long-term trends. The main study period was 1951–2000. In some of the analyses the study periods were shorter, primarily due to lack of data. Changes in economic availability in general, and in price in particular, had larger effects on sales than physical availability. Among the beverages analyzed in the study, the demand for spirits was most sensitive to changes in availability. Economic availability had a greater effect on sales than the number of outlets. However, one might question to what extent the number of outlets really is a feasible measure of transaction costs associated with purchases of alcohol.

scholarly journals Climatic modeling of the distribution of Oxytropis triphylla (Fabaceae) by maximum entropy method

2018 ◽  
Vol 11 ◽  
pp. 00002
Author(s):  
Konstantin Baikov ◽  
Denis Krivenko
Keyword(s):  
Maximum Entropy ◽  
Maximum Entropy Method ◽  
Spatial Models ◽  
Entropy Method ◽  
Air Temperatures ◽  
Variable Contribution ◽  
Key Variables ◽  
The Republic ◽  
Maximum Temperatures

Predictive spatial models of the distribution of Oxytropis triphylla (Pall.) Pers. (Fabaceae), an endemic species of Baikal Siberia, were generated in MAXENT computer program using maximum entropy method. Long-term data of air temperatures for every month of the year were downloaded from the world database of open access WorldClim. Modeling was performed separately for minimum, average and maximum temperatures. Each variable contribution to the modeling was the basis to select the key variables having higher influence on the obtained models. The selected 10 key variables are the following: minimum temperatures of December and January; average temperatures of October, December, January and February; maximum temperatures of November, December, January and February. Then a model of the second level was calculated using only the ten key variables. There are three northern localities in the zone of adverse temperature effects: cape Malyi Cheremshanyi, Chencha and Sakhuli villages (all of them are in the Republic of Buryatia). It has been experimentally confirmed that the values of the key variables along the coasts of the Maloe More of Lake Baikal (Irkutskaya Oblast) are the most favorable for habitation of O. triphylla in this part of its range.

MULTIVARIATE SPECTRAL ANALYSIS USING HILBERT WAVELET PAIRS

2004 ◽  
Vol 02 (04) ◽  
pp. 567-587 ◽  
Author(s):  
BRANDON WHITCHER ◽  
PETER F. CRAIGMILE
Keyword(s):  
Time Series ◽  
Spectral Analysis ◽  
Wavelet Transform ◽  
Discrete Wavelet Transform ◽  
Multivariate Time Series ◽  
Discrete Wavelet ◽  
Pass Filter ◽  
Wavelet Filters ◽  
The Hilbert Transform ◽  
High Pass

We investigate the use of Hilbert wavelet pairs (HWPs) in the non-decimated discrete wavelet transform for the time-varying spectral analysis of multivariate time series. HWPs consist of two high-pass and two low-pass compactly supported filters, such that one high-pass filter is the Hilbert transform (approximately) of the other. Thus, common quantities in the spectral analysis of time series (e.g., power spectrum, coherence, phase) may be estimated in both time and frequency. Compact support of the wavelet filters ensures that the frequency axis will be partitioned dyadically as with the usual discrete wavelet transform. The proposed methodology is used to analyze a bivariate time series of zonal (u) and meridional (v) winds over Truk Island.

scholarly journals Evaluation of Dynamic Uncertainty of Rolling Bearing Vibration Performance

2019 ◽  
Vol 2019 ◽  
pp. 1-17 ◽  
Author(s):  
Liang Ye ◽  
Xintao Xia ◽  
Zhen Chang
Keyword(s):  
Time Series ◽  
Chaos Theory ◽  
Maximum Entropy Method ◽  
Bootstrap Method ◽  
Rolling Bearing ◽  
Entropy Method ◽  
Performance Time ◽  
Dynamic Uncertainty ◽  
Bearing Vibration ◽  
Vibration Performance

The variation trend, failure trajectory, probability distribution, and other information vary with time and working conditions for rolling bearing vibration performance, which makes the evaluation and prediction of the evolution process difficult for the performance reliability. In view of this, the chaos theory, grey bootstrap method, and maximum entropy method were effectively fused to propose a mathematical model for the dynamic uncertainty evaluation of rolling bearing vibration performance. After reconstructing the phase space of the vibration performance time series, four local prediction methods were applied to predict the vibration values of bearings to verify the effectiveness and validity of chaos theory. The estimated true value and estimated interval were calculated using the grey bootstrap method (GBM) and maximum entropy method. Finally, the validity of the proposed model was verified by comparing the probability that the original data fall into the estimated interval with the given confidence level. The experimental results show that the proposed method can effectively predict the variation trend and failure trajectory of the vibration performance time series so as to realize the dynamic monitoring of the evolution process for rolling bearing vibration performance online.

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