Long-memory processes in global ozone and temperature variations

Abstract. Global column ozone and tropospheric temperature observations made by ground-based (1964–2004) and satellite-borne (1978–2004) instrumentation are analyzed. Ozone and temperature fluctuations in small time-intervals are found to be positively correlated to those in larger time-intervals in a power-law fashion. For temperature, the exponent of this dependence is larger in the mid-latitudes than in the tropics at long time scales, while for ozone, the exponent is larger in tropics than in the mid-latitudes. In general, greater persistence could be a result of either stronger positive feedbacks or larger inertia. Therefore, the increased slope of the power distribution of temperature in mid-latitudes at long time scales compared to the slope in the tropics could be connected to the poleward increase in climate sensitivity predicted by the global climate models. The detrended fluctuation analysis of model and observed time series provides a helpful tool for visualizing errors in the treatment of long-range correlations, whose correct modeling would greatly enhance confidence in long-term climate and atmospheric chemistry modeling.

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Scaling behaviour of the global tropopause

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-8-17891-2008 ◽

2008 ◽

Vol 8 (5) ◽

pp. 17891-17905

Author(s):

C. Varotsos ◽

M. Efstathiou ◽

C. Tzanis

Keyword(s):

Detrended Fluctuation Analysis ◽

Small Time ◽

Radiosonde Data ◽

Fluctuation Analysis ◽

Tropopause Height ◽

Time Intervals ◽

Long Range Correlations ◽

The Tropics ◽

Detrended Fluctuation ◽

Climatic Characteristics

Abstract. Detrended fluctuation analysis is applied to the time series of the global tropopause height derived from the 1980–2004 daily radiosonde data, in order to detect long-range correlations in its time evolution. Global tropopause height fluctuations in small time-intervals are found to be positively correlated to those in larger time intervals in a power-law fashion. The exponent of this dependence is larger in the tropics than in the middle and high latitudes in both hemispheres. Greater persistence is observed in the tropopause of the Northern than in the Southern Hemisphere. This finding for the tropopause height variability should reduce the existing uncertainties in assessing the climatic characteristics.

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Optimal Perturbations of an Oceanic Vortex Lens

Fluids ◽

10.3390/fluids3030063 ◽

2018 ◽

Vol 3 (3) ◽

pp. 63 ◽

Cited By ~ 3

Author(s):

Thomas Meunier ◽

Claire Ménesguen ◽

Xavier Carton ◽

Sylvie Le Gentil ◽

Richard Schopp

Keyword(s):

Normal Mode ◽

Growth Rates ◽

Time Interval ◽

Time Intervals ◽

Horizontal Structure ◽

Azimuthal Wave ◽

Wave Numbers ◽

Non Linear ◽

Long Time ◽

Short Time

The stability properties of a vortex lens are studied in the quasi geostrophic (QG) framework using the generalized stability theory. Optimal perturbations are obtained using a tangent linear QG model and its adjoint. Their fine-scale spatial structures are studied in details. Growth rates of optimal perturbations are shown to be extremely sensitive to the time interval of optimization: The most unstable perturbations are found for time intervals of about 3 days, while the growth rates continuously decrease towards the most unstable normal mode, which is reached after about 170 days. The horizontal structure of the optimal perturbations consists of an intense counter-shear spiralling. It is also extremely sensitive to time interval: for short time intervals, the optimal perturbations are made of a broad spectrum of high azimuthal wave numbers. As the time interval increases, only low azimuthal wave numbers are found. The vertical structures of optimal perturbations exhibit strong layering associated with high vertical wave numbers whatever the time interval. However, the latter parameter plays an important role in the width of the vertical spectrum of the perturbation: short time interval perturbations have a narrow vertical spectrum while long time interval perturbations show a broad range of vertical scales. Optimal perturbations were set as initial perturbations of the vortex lens in a fully non linear QG model. It appears that for short time intervals, the perturbations decay after an initial transient growth, while for longer time intervals, the optimal perturbation keeps on growing, quickly leading to a non-linear regime or exciting lower azimuthal modes, consistent with normal mode instability. Very long time intervals simply behave like the most unstable normal mode. The possible impact of optimal perturbations on layering is also discussed.

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A harmonically weighted filter for cyclical long memory processes

AStA Advances in Statistical Analysis ◽

10.1007/s10182-021-00394-9 ◽

2021 ◽

Author(s):

Federico Maddanu

Keyword(s):

Spectral Density ◽

Long Memory ◽

Convergence In Probability ◽

Simulation Methods ◽

Integrated Process ◽

Paleoclimatic Data ◽

Memory Time ◽

Long Memory Processes ◽

Short Memory ◽

Memory Parameter

AbstractThe estimation of the long memory parameter d is a widely discussed issue in the literature. The harmonically weighted (HW) process was recently introduced for long memory time series with an unbounded spectral density at the origin. In contrast to the most famous fractionally integrated process, the HW approach does not require the estimation of the d parameter, but it may be just as able to capture long memory as the fractionally integrated model, if the sample size is not too large. Our contribution is a generalization of the HW model, denominated the Generalized harmonically weighted (GHW) process, which allows for an unbounded spectral density at $$k \ge 1$$ k ≥ 1 frequencies away from the origin. The convergence in probability of the Whittle estimator is provided for the GHW process, along with a discussion on simulation methods. Fit and forecast performances are evaluated via an empirical application on paleoclimatic data. Our main conclusion is that the above generalization is able to model long memory, as well as its classical competitor, the fractionally differenced Gegenbauer process, does. In addition, the GHW process does not require the estimation of the memory parameter, simplifying the issue of how to disentangle long memory from a (moderately persistent) short memory component. This leads to a clear advantage of our formulation over the fractional long memory approach.

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Minimization of the Instability of Hydrogen Frequency Standards in Long Time Intervals

Measurement Techniques ◽

10.1007/s11018-018-1454-x ◽

2018 ◽

Vol 61 (5) ◽

pp. 474-480

Author(s):

V. I. Vasil’ev

Keyword(s):

Time Intervals ◽

Frequency Standards ◽

Long Time ◽

Hydrogen Frequency

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A Simple Method for Measuring Small Time Intervals

Science ◽

10.1126/science.79.2039.82-b ◽

1934 ◽

Vol 79 (2039) ◽

pp. 82-83

Author(s):

K. D. Roeder

Keyword(s):

Small Time ◽

Time Intervals ◽

Simple Method

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Semiparametric Inference in Seasonal and Cyclical Long Memory Processes

Journal of Time Series Analysis ◽

10.1111/1467-9892.00170 ◽

2000 ◽

Vol 21 (1) ◽

pp. 1-25 ◽

Cited By ~ 80

Author(s):

Josu Arteche ◽

Peter M. Robinson

Keyword(s):

Long Memory ◽

Memory Processes ◽

Semiparametric Inference ◽

Long Memory Processes

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Super-Fine Structure in the Critical Flow-Rate of Critical Flow Venturi Nozzles

Volume 1: Fora, Parts A and B ◽

10.1115/fedsm2002-31079 ◽

2002 ◽

Cited By ~ 3

Author(s):

Masahiro Ishibashi

Keyword(s):

Fine Structure ◽

Steady State ◽

Discharge Coefficient ◽

Constant Pressure ◽

Pressure Ratio ◽

Critical Flow ◽

Time Intervals ◽

Critical Flow Rate ◽

A Value ◽

Long Time

It is shown that critical flow Venturi nozzles need time intervals, i.e., more than five hours, to achieve steady state conditions. During these intervals, the discharge coefficient varies gradually to reach a value inherent to the pressure ratio applied. When a nozzle is suddenly put in the critical condition, its discharge coefficient is trapped at a certain value then afterwards approaches gradually to the inherent value. Primary calibrations are considered to have measured the trapped discharge coefficient, whereas nozzles in applications, where a constant pressure ratio is applied for a long time, have a discharge coefficient inherent to the pressure ratio; inherent and trapped coefficients can differ by 0.03–0.04%.

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Markov chains in small time intervals

Journal of Applied Probability ◽

10.2307/3213331 ◽

1981 ◽

Vol 18 (3) ◽

pp. 747-751

Author(s):

Stig I. Rosenlund

Keyword(s):

Markov Chain ◽

Markov Chains ◽

Transition Probability ◽

Small Time ◽

Exact Order ◽

Time Intervals ◽

Continuous Parameter ◽

Minimum Number

For a time-homogeneous continuous-parameter Markov chain we show that as t → 0 the transition probability pn,j (t) is at least of order where r(n, j) is the minimum number of jumps needed for the chain to pass from n to j. If the intensities of passage are bounded over the set of states which can be reached from n via fewer than r(n, j) jumps, this is the exact order.

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Construction of merged satellite total O<sub>3</sub> and NO<sub>2</sub> time series in the tropics for trend studies and evaluation by comparison to NDACC SAOZ measurements

Atmospheric Measurement Techniques ◽

10.5194/amt-7-3337-2014 ◽

2014 ◽

Vol 7 (10) ◽

pp. 3337-3354 ◽

Cited By ~ 7

Author(s):

M. Pastel ◽

J.-P. Pommereau ◽

F. Goutail ◽

A. Richter ◽

A. Pazmiño ◽

...

Keyword(s):

Time Series ◽

Lower Stratosphere ◽

Atmospheric Composition ◽

Data Sets ◽

Composition Change ◽

Long Time ◽

Uv Visible ◽

The Tropics ◽

Lower Noise ◽

Total Column

Abstract. Long time series of ozone and NO2 total column measurements in the southern tropics are available from two ground-based SAOZ (Système d'Analyse par Observation Zénithale) UV-visible spectrometers operated within the Network for the Detection of Atmospheric Composition Change (NDACC) in Bauru (22° S, 49° W) in S-E Brazil since 1995 and Reunion Island (21° S, 55° E) in the S-W Indian Ocean since 1993. Although the stations are located at the same latitude, significant differences are observed in the columns of both species, attributed to differences in tropospheric content and equivalent latitude in the lower stratosphere. These data are used to identify which satellites operating during the same period, are capturing the same features and are thus best suited for building reliable merged time series for trend studies. For ozone, the satellites series best matching SAOZ observations are EP-TOMS (1995–2004) and OMI-TOMS (2005–2011), whereas for NO2, best results are obtained by combining GOME version GDP5 (1996–2003) and SCIAMACHY – IUP (2003–2011), displaying lower noise and seasonality in reference to SAOZ. Both merged data sets are fully consistent with the larger columns of the two species above South America and the seasonality of the differences between the two stations, reported by SAOZ, providing reliable time series for further trend analyses and identification of sources of interannual variability in the future analysis.

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