scholarly journals The spatio-temporal structure of the Lateglacial to early Holocene transition reconstructed from the pollen record of Lake Suigetsu and its precise correlation with other key global archives: Implications for palaeoclimatology and archaeology

2021 ◽  
pp. 103493
Author(s):  
Takeshi Nakagawa ◽  
Pavel Tarasov ◽  
Richard Staff ◽  
Christopher Bronk Ramsey ◽  
Michael Marshall ◽  
...  
Keyword(s):  
Temporal Structure ◽  
Early Holocene ◽  
Pollen Record ◽  
Spatio Temporal

scholarly journals Rainfall spatio-temporal correlation and intermittency structure from micro-γ to meso-β scale in the Netherlands

2021 ◽  
Author(s):  
Thomas C. van Leth ◽  
Hidde Leijnse ◽  
Aart Overeem ◽  
Remko Uijlenhoet
Keyword(s):  
The Netherlands ◽  
Spatial Scales ◽  
Rainfall Variability ◽  
Temporal Structure ◽  
Temporal Correlation ◽  
Exponential Model ◽  
Rain Gauges ◽  
Wide Range ◽  
Spatio Temporal ◽  
Two Parameter

AbstractWe investigate the spatio-temporal structure of rainfall at spatial scales from 7m to over 200 km in the Netherlands. We used data from two networks of laser disdrometers with complementary interstation distances in two Dutch cities (comprising five and six disdrometers, respectively) and a Dutch nationwide network of 31 automatic rain gauges. The smallest aggregation interval for which raindrop size distributions were collected by the disdrometers was 30 s, while the automatic rain gauges provided 10-min rainfall sums. This study aims to supplement other micro-γ investigations (usually performed in the context of spatial rainfall variability within a weather radar pixel) with new data, while characterizing the correlation structure across an extended range of scales. To quantify the spatio-temporal variability, we employ a two-parameter exponential model fitted to the spatial correlograms and characterize the parameters of the model as a function of the temporal aggregation interval. This widely used method allows for a meaningful comparison with seven other studies across contrasting climatic settings all around the world. We also separately analyzed the intermittency of the rainfall observations. We show that a single parameterization, consisting of a two-parameter exponential spatial model as a function of interstation distance combined with a power-law model for decorrelation distance as a function of aggregation interval, can coherently describe rainfall variability (both spatial correlation and intermittency) across a wide range of scales. Limiting the range of scales to those typically found in micro-γ variability studies (including four of the seven studies to which we compare our results) skews the parameterization and reduces its applicability to larger scales.

scholarly journals New methods for retrieval of chlorophyll red fluorescence from hyper-spectral satellite instruments: simulations and application to GOME-2 and SCIAMACHY

2016 ◽  
Author(s):  
J. Joiner ◽  
Y. Yoshida ◽  
L. Guanter ◽  
E. M. Middleton
Keyword(s):  
Spatial Scales ◽  
Temporal Structure ◽  
Emission Feature ◽  
Ozone Monitoring Instrument ◽  
Additional Information ◽  
Time Space ◽  
Hyper Spectral ◽  
Spatio Temporal ◽  
Gas Measurements ◽  
Satellite Instruments

Abstract. Global satellite measurements of solar-induced fluorescence (SIF) from chlorophyll over land and ocean have proven useful for a number of different applications related to physiology, phenology, and productivity of plants and phytoplankton. Terrestrial chlorophyll fluorescence is emitted throughout the red and far-red spectrum, producing two broad peaks near 683 and 736 nm. From ocean surfaces, phytoplankton fluorescence emissions are entirely from the red region. Studies using satellite-derived SIF over land have focused almost exclusively on measurements in the far- red, since those are the most easily obtained with existing instrumentation. Here, we examine new ways to use existing hyper-spectral satellite data sets to retrieve red SIF over both land and ocean. Our approach offers noise reductions as compared with previously published solar line filling retrievals by making use of the oxygen (O2) γ-band that is not affected by SIF. The O2 γ-band in conjunction with solar Fraunhofer lines help to anchor the O2 B-band that provides additional information on red SIF. Biases due to instrumental artifacts that vary in time, space, and with instrument, must be addressed in order to obtain reasonable results. The satellite instruments that we use were designed to make atmospheric trace- gas measurements and are therefore not optimal for observing SIF; they have coarse spatial resolution and only moderate spectral resolution (∼0.5 nm). Nevertheless, these instruments offer a unique opportunity to compare red and far-red terrestrial SIF at regional spatial scales. Our eight year record of red SIF observations over land with the Global Ozone Monitoring Instrument 2 (GOME-2) allows for the first time reliable global mapping of monthly anomalies. These anomalies are shown to have similar spatio-temporal structure as those in the far-red, particularly for drought-prone regions. There is a somewhat larger percentage response in the red as compared with the far-red for these areas that are sensitive to soil moisture, although the differences are within the specified uncertainties that are dominated by systematic errors. We also demonstrate that high quality ocean fluorescence line height retrievals can be achieved with GOME-2 and similar instruments by utilizing the full complement of radiance measurements that span the red SIF emission feature.

GICS IN THE MAIN TRANSMISSION LINE “NORTHERN TRANSIT” IN RUSSIA AND IN THE MÄNTSÄLÄ FINLAND PIPELINE: A CASE STUDY

2021 ◽  
Vol 44 ◽  
pp. 20-23
Author(s):  
I.V. Despirak ◽  
◽  
P.V. Setsko ◽  
Ya.A. Sakharov ◽  
V.N. Selivanov ◽  
...  
Keyword(s):  
Negative Impact ◽  
Temporal Structure ◽  
Auroral Zone ◽  
Magnetic Data ◽  
Geomagnetically Induced Currents ◽  
Camera System ◽  
Natural Gas Pipeline ◽  
Spatio Temporal ◽  
Using Data

Geomagnetically induced currents (GICs), arising both on power lines and on pipelines, may have strong negative impact on the technological networks up to accidents ("blackouts"). Magnetospheric disturbances are one of the factors in the appearance of GICs, however there is no unambiguous relationship between substorm and presence of currents. In this paper, we consider two intense cases of GIC (15March 2012 and 17 March 2013), registered on two different technological networks: 1) on the "Nothern Transit" power line (Vykhodnoy, Revda and Kondopoga stations) located in the auroral zone, 2) on the Finnish natural gas pipeline near Mäntsälä located in the subauroral zone. Both GIC cases are compared with substorm development in the auroral zone, using data from IMAGE magnetometers network and MAIN camera system in Apatity. We found a good correlation between the GIC appearance and variations of geomagnetic indexes: IL – index, which characterized of westward electrojet intensity on the IMAGE meridian and Wp - index, which describes the wave activity of the substorm. Besides, it was shown also a good correlation between GICs and the thin spatio-temporal structure of the substorm development (the appearance and the propagation to the pole of substorm activations), which is appeared both in the magnetic data and in the all sky camera images.

scholarly journals On impulse excitation of the global poloidal modes in the magnetosphere

2006 ◽  
Vol 24 (10) ◽  
pp. 2429-2433 ◽  
Author(s):  
P. N. Mager ◽  
D. Yu. Klimushkin
Keyword(s):  
Second Harmonic ◽  
Temporal Structure ◽  
Background Field ◽  
Plasma Pressure ◽  
Radial Structure ◽  
Combined Action ◽  
Spatio Temporal ◽  
Field Lines ◽  
Hermitian Polynomials ◽  
Impulsive Source

Abstract. Through the combined action of the field line curvature and finite plasma pressure in some regions of the magnetosphere (plasmapause, ring current) there can exist global poloidal Alfvén modes standing both along field lines and across magnetic shells and propagating along azimuth. In this paper we investigate the spatio-temporal structure of such waves generated by an impulsive source. In general, the mode is the sum of radial harmonics whose structure is described by Hermitian polynomials. For the usually observed second harmonic structure along the background field, frequencies of these radial harmonics are very close to each other; therefore, the generated wave is almost a monochromatic oscillation. But mixing of the harmonics with different radial structure causes the evolution of the initially poloidal wave into the toroidal one. This casts some doubts upon the interpretation of observed high-m poloidal waves as global poloidal modes.

FREEMAN'S K MODELS AS RESERVOIR COMPUTING ARCHITECTURES

2009 ◽  
Vol 05 (01) ◽  
pp. 265-286
Author(s):  
MUSTAFA C. OZTURK ◽  
JOSE C. PRINCIPE
Keyword(s):  
Computational Models ◽  
Temporal Dynamics ◽  
Temporal Structure ◽  
Reservoir Computing ◽  
Short Term ◽  
System Parameters ◽  
History Of ◽  
Spatio Temporal ◽  
Universal Approximators ◽  
Theoretical Results

Walter Freeman in his classic 1975 book "Mass Activation of the Nervous System" presented a hierarchy of dynamical computational models based on studies and measurements done in real brains, which has been known as the Freeman's K model (FKM). Much more recently, liquid state machine (LSM) and echo state network (ESN) have been proposed as universal approximators in the class of functionals with exponential decaying memory. In this paper, we briefly review these models and show that the restricted K set architecture of KI and KII networks share the same properties of LSM/ESNs and is therefore one more member of the reservoir computing family. In the reservoir computing perspective, the states of the FKM are a representation space that stores in its spatio-temporal dynamics a short-term history of the input patterns. Then at any time, with a simple instantaneous read-out made up of a KI, information related to the input history can be accessed and read out. This work provides two important contributions. First, it emphasizes the need for optimal readouts, and shows how to adaptively design them. Second, it shows that the Freeman model is able to process continuous signals with temporal structure. We will provide theoretical results for the conditions on the system parameters of FKM satisfying the echo state property. Experimental results are presented to illustrate the validity of the proposed approach.

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