QBO, ENSO and Solar Cycle Effects in Short-term Nonmigrating Tidal Variability on Planetary Wave Timescales from SABER - An Information-Theoretic Approach

2020 ◽  
Author(s):  
Komal Kumari ◽  
Jens Oberheide
Keyword(s):  
Solar Cycle ◽  
Planetary Wave ◽  
Wave Number ◽  
Atmospheric Tides ◽  
Theoretic Approach ◽  
Short Term ◽  
Quasi Biennial Oscillation ◽  
Information Theoretic ◽  
Leibler Divergence ◽  
Tidal Variability

<p>Earth’s atmosphere supports a variety of internal wave motion which are responsible for spatio-temporal changes in temperature, winds, density, and chemical constituents. One of the most striking dynamical features of the upper atmosphere (i.e. mesosphere and lower thermosphere [MLT], 50-120 km) are atmospheric tides. In particular, the eastward-propagating nonmigrating diurnal tide with zonal wave number 3 (DE3), originating from tropical deep convection, introduces a large longitudinal and local time variability in temperature, wind and density in the MLT region. The DE3 is thus key to understanding how tropospheric weather influences space weather. However, DE3 short-term tidal variability is not well understood and part of the motivation for constellation missions. Single satellites such as TIMED nevertheless provide a pathway to identify multi-timescale tidal variability from days to years. We utilize 16 years of SABER (an instrument onboard the TIMED satellite) DE3 “tidal deconvolution” diagnostic that provides a unique opportunity to investigate interannual changes in short-term (days to weeks) tidal variability on various planetary wave time scales. The approach is based on information-theoretic techniques using Bayesian statistics, time dependent probability density functions and Kullback-Leibler divergence followed by multiple linear regression analysis. In this presentation, we focus on interannual changes in short-term DE3 variability on a 10-day planetary wave timescale and how it changes as a function of the quasi-biennial oscillation (QBO), El Niño-Southern Oscillation (ENSO) and the solar cycle.</p>

Image Retrieval Using Mutual Information

2013 ◽  
Vol 427-429 ◽  
pp. 1537-1543 ◽  
Author(s):  
Ya Fen Wang ◽  
Feng Zhen Zhang ◽  
Shan Jian Liu ◽  
Meng Huang
Keyword(s):  
Mutual Information ◽  
Image Retrieval ◽  
Image Similarity ◽  
Theoretic Approach ◽  
Information Theoretic ◽  
Content Base Image Retrieval ◽  
Leibler Divergence ◽  
Similar Images ◽  
Information Theoretic Approach ◽  
The Given

In this paper, we study an information theoretic approach to image similarity measurement for content-base image retrieval. In this novel scheme, similarities are measured by the amount of information the images contained about one another mutual information (MI). The given approach is based on the premise that two similar images should have high mutual information, or equivalently, the querying image should convey high information about those similar to it. The method first generates a set of statistically representative visual patterns and uses the distributions of these patterns as images content descriptors. To measure the similarity of two images, we develop a method to compute the mutual information between their content descriptors. Two images with larger descriptor mutual information are regarded as more similar. We present experimental results, which demonstrate that mutual information is a more effective image similarity measure than those have been used in the literature such as Kullback-Leibler divergence and L2 norms.

scholarly journals The Information Theoretic Approach to Signal Anomaly Detection for Cognitive Radio

2010 ◽  
Vol 2010 ◽  
pp. 1-18 ◽  
Author(s):  
Mostafa Afgani ◽  
Sinan Sinanović ◽  
Harald Haas
Keyword(s):  
Cognitive Radio ◽  
Anomaly Detection ◽  
Information Content ◽  
Spectrum Sharing ◽  
High Speed ◽  
Periodic Structures ◽  
Theoretic Approach ◽  
Information Theoretic ◽  
Leibler Divergence ◽  
Information Theoretic Approach

Efficient utilisation and sharing of limited spectrum resources in an autonomous fashion is one of the primary goals of cognitive radio. However, decentralised spectrum sharing can lead to interference scenarios that must be detected and characterised to help achieve the other goal of cognitive radio—reliable service for the end user. Interference events can be treated as unusual and therefore anomaly detection algorithms can be applied for their detection. Two complementary algorithms based on information theoretic measures of statistical distribution divergence and information content are proposed. The first method is applicable to signals with periodic structures and is based on the analysis of Kullback-Leibler divergence. The second utilises information content analysis to detect unusual events. Results from software and hardware implementations show that the proposed algorithms are effective, simple, and capable of processing high-speed signals in real time. Additionally, neither of the algorithms require demodulation of the signal.

scholarly journals Migrating and Non-Migrating Tides Observed in the Stratosphere from FORMOSAT-3/COSMIC Temperature Retrievals

2019 ◽  
Author(s):  
Uma Das ◽  
William Ward ◽  
Chen Jeih Pan ◽  
Sanat Kumar Das
Keyword(s):  
Planetary Wave ◽  
Middle Atmosphere ◽  
High Latitudes ◽  
Short Term ◽  
The Mean ◽  
Tidal Variability ◽  
Using Data ◽  
Stationary Planetary Wave ◽  
Linear Interactions ◽  
Winter Hemisphere

Abstract. FORMOSAT-3/COSMIC temperature data during 2009 to 2010 are analysed for tides in the middle atmosphere from ~ 10 to 50 km. COSMIC is a set of six micro satellites in near sun synchronous orbits with 30° orbital separations and provides good phase space sampling of tides. Short term tidal variability is deduced by considering ± 10 days' data together. The DW1 tide is found to peak over the equator at 30 km. It maximises and slightly shifts poleward during winters and thus is attributed to ozone absorption. Over mid and high latitudes, DW1 and the non-migrating tides DS0 and DW2 are intermittent in nature. Numerical experiments in the current study show that these could be a result of aliasing as they are found to occur at times of steep rise or fall in the mean temperature, particularly during the SSW of 2010. Further, stationary planetary wave components are found to be of very large amplitudes in the northern hemispheres reaching 18 K at 30 km over 65° N. By using data from COSMIC over shorter durations, aliasing between SPW and non-migrating tides is reduced and thus results in the large amplitudes of the former. This study clearly indicates that non-linear interactions are not a very important source of generation of the non migrating tides in the high latitude winter hemisphere. There is also a modulation of SPW1 by ~ 60 days in the high latitudes, which was not seen earlier.

scholarly journals Solar cycle effect on oscillations in the period range of 2-20 days in the F region of the ionosphere

1996 ◽  
Vol 39 (4) ◽  
Author(s):  
J. Lastovicka ◽  
P. Mlch
Keyword(s):  
Solar Cycle ◽  
Planetary Wave ◽  
The Other ◽  
Short Term ◽  
Wave Type ◽  
Period Range ◽  
F Region ◽  
Other Hand

The results of Lastovicka and Mlch (1994) and Altadill and Lastovicka (1996) are extended by the use of f0F2 and h'F data from Juliusruh, Lannion and Rome. There is a strong solar cycle effect in amplitudes of oscillations in f0F2 but none or a weak solar cycle effect in relative amplitudes of oscillations in f0F2 and in amplitudes of oscillations in h'F. The conditions when the planetary wave type oscillations should be taken into account in short-term predictions and when, on the other hand, they need not be taken into account, are partly specified.

scholarly journals Migrating and non-migrating tides observed in the stratosphere from FORMOSAT-3/COSMIC temperature retrievals

2020 ◽  
Vol 38 (2) ◽  
pp. 421-435 ◽  
Author(s):  
Uma Das ◽  
William E. Ward ◽  
Chen Jeih Pan ◽  
Sanat Kumar Das
Keyword(s):  
Planetary Wave ◽  
Middle Atmosphere ◽  
High Latitudes ◽  
Sudden Stratospheric Warming ◽  
Short Term ◽  
The Mean ◽  
Tidal Variability ◽  
Using Data ◽  
Stationary Planetary Wave ◽  
Linear Interactions

Abstract. Formosa Satellite-3 and Constellation Observing System for Meteorology, Ionosphere and Climate (FORMOSAT-3/COSMIC) temperature data during October 2009–December 2010 are analysed for tides in the middle atmosphere from ∼10 to 50 km. COSMIC is a set of six micro-satellites in near-Sun-synchronous orbits with 30∘ orbital separations that provides good phase space sampling of tides. Short-term tidal variability is deduced by considering ±10 d data together. The migrating diurnal (DW1) tide is found to peak over the Equator at 30 km. It maximises and slightly shifts poleward during winters. Over middle and high latitudes, DW1 and the non-migrating diurnal tides with wavenumber 0 (DS0) and wavenumber 2 (DW2) are intermittent in nature. Numerical experiments in the current study show that these could be a result of aliasing as they are found to occur at times of a steep rise or fall in the mean temperature, particularly during the sudden stratospheric warming (SSW) of 2010. Further, the stationary planetary wave component of wavenumber 1 (SPW1) is found to be of very large amplitudes in the Northern Hemisphere, reaching 18 K at 30 km over 65∘ N. By using data from COSMIC over shorter durations, it is shown that aliasing between stationary planetary wave and non-migrating tides is reduced and thus results in the large amplitudes of the former. This study clearly indicates that non-linear interactions are not a very important source for the generation of non-migrating tides in the middle- and high-latitude winter stratosphere. There is also a modulation of SPW1 by a ∼60 d oscillation in the high latitudes, which was not seen earlier.

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