scholarly journals Climatological characteristics of sea breeze parameters at Chennai

MAUSAM ◽  
2022 ◽  
Vol 53 (1) ◽  
pp. 31-44
Author(s):  
Y. E. A. RAJ ◽  
P. V. SANKARAN ◽  
B. RAMAKRISHNAN ◽  
P. L. PADMAKUMAR
Keyword(s):  
Relative Humidity ◽  
Surface Temperature ◽  
Diurnal Variation ◽  
Large Data ◽  
Sea Breeze ◽  
Large Data Base ◽  
Superposed Epoch Analysis ◽  
Normal Speed ◽  
Epoch Analysis ◽  
Chennai City

Several sea breeze parameters such as time of onset, withdrawal, duration, depth, variation with height, direction etc.  have been derived and studied for Chennai city and Chennai AP observatories in this study, which has been based on a large  data base for the period March-October,1969-83. The monthly and sub monthly values of several sea breeze parameters have been derived. By invoking the concept of superposed epoch analysis the important role played by sea breeze in modulating diurnal variation of surface temperature and relative humidity has been established. The sea breeze at Chennai has been shown to be shallow with a depth of under 1 km. Modal directions of sea breeze and its normal speed have been  derived.

Statistical Global Investigation of Pre-Earthquake Anomalous Geomagnetic Diurnal Variation Using Superposed Epoch Analysis

2021 ◽  
pp. 1-13
Author(s):  
Khairul Adib Yusof ◽  
Mardina Abdullah ◽  
Nurul Shazana Abdul Hamid ◽  
Suaidi Ahadi ◽  
Essam Ghamry
Keyword(s):  
Diurnal Variation ◽  
Superposed Epoch Analysis ◽  
Epoch Analysis

scholarly journals Solar Irradiance Variability Due to Solar Flares Observed in Lyman-Alpha Emission

Solar Physics ◽  
2021 ◽  
Vol 296 (3) ◽  
Author(s):  
Ryan O. Milligan
Keyword(s):  
Solar Flares ◽  
Solar Spectrum ◽  
Neutral Hydrogen ◽  
Solar Limb ◽  
High Background ◽  
Superposed Epoch Analysis ◽  
Lyman Alpha ◽  
Alpha Emission ◽  
Epoch Analysis ◽  
Very High

AbstractAs the Lyman-alpha (Ly$\upalpha $ α ) line of neutral hydrogen is the brightest emission line in the solar spectrum, detecting increases in irradiance due to solar flares at this wavelength can be challenging due to the very high background. Previous studies that have focused on the largest flares have shown that even these extreme cases generate enhancements in Ly$\upalpha $ α of only a few percent above the background. In this study, a superposed-epoch analysis was performed on ≈8500 flares greater than B1 class to determine the contribution that they make to changes in the solar EUV irradiance. Using the peak of the 1 – 8 Å X-ray emission as a fiducial time, the corresponding time series of 3123 B- and 4972 C-class flares observed in Ly$\upalpha $ α emission by the EUV Sensor on the Geostationary Operational Environmental Satellite 15 (GOES-15) were averaged to reduce background fluctuations and improve the flare signal. The summation of these weaker events showed that they produced a 0.1 – 0.3% enhancement to the solar Ly$\upalpha $ α irradiance on average. For comparison, the same technique was applied to 453 M- and 31 X-class flares, which resulted in a 1 – 4% increase in Ly$\upalpha $ α emission. Flares were also averaged with respect to their heliographic angle to investigate any potential center-to-limb variation. For each GOES class, the relative enhancement in Ly$\upalpha $ α at the flare peak was found to diminish for flares that occurred closer to the solar limb due to the opacity of the line and/or foreshortening of the footpoints. One modest event included in the study, a C6.6 flare, exhibited an unusually high increase in Ly$\upalpha $ α of 7% that may have been attributed to a failed filament eruption. Increases of this magnitude have hitherto only been associated with a small number of X-class flares.

A two-level architecture for a large data base

1976 ◽  
Vol 10 (4) ◽  
pp. 23-23 ◽  
Author(s):  
Tomas Lang
Keyword(s):  
Data Base ◽  
Large Data ◽  
Large Data Base

scholarly journals Optimization of the Local Split-Window Algorithm for FY-4A Land Surface Temperature Retrieval

2019 ◽  
Vol 11 (17) ◽  
pp. 2016
Author(s):  
Lijuan Wang ◽  
Ni Guo ◽  
Wei Wang ◽  
Hongchao Zuo
Keyword(s):  
Surface Temperature ◽  
Diurnal Variation ◽  
Land Surface Temperature ◽  
Satellite Data ◽  
Land Surface ◽  
Regional Scale ◽  
Pso Algorithm ◽  
Variation Characteristics ◽  
Split Window Algorithm ◽  
Mean Square Errors

FY-4A is a second generation of geostationary orbiting meteorological satellite, and the successful launch of FY-4A satellite provides a new opportunity to obtain diurnal variation of land surface temperature (LST). In this paper, different underlying surfaces-observed data were applied to evaluate the applicability of the local split-window algorithm for FY-4A, and the local split-window algorithm parameters were optimized by the artificial intelligent particle swarm optimization (PSO) algorithm to improve the accuracy of retrieved LST. Results show that the retrieved LST can efficiently reproduce the diurnal variation characteristics of LST. However, the estimated values deviate hugely from the observed values when the local split-window algorithms are directly used to process the FY-4A satellite data, and the root mean square errors (RMSEs) are approximately 6K. The accuracy of the retrieved LST cannot be effectively improved by merely modifying the emissivity-estimated model or optimizing the algorithm. Based on the measured emissivity, the RMSE of LST retrieved by the optimized local split-window algorithm is reduced to 3.45 K. The local split-window algorithm is a simple and easy retrieval approach that can quickly retrieve LST on a regional scale and promote the application of FY-4A satellite data in related fields.

Superposed Epoch Analysis of Nighttime Magnetic Perturbation Events Observed in Arctic Canada

2021 ◽  
Author(s):  
Mark J. Engebretson ◽  
Lidiya Y. Ahmed ◽  
Vyacheslav A. Pilipenko ◽  
Erik S. Steinmetz ◽  
Mark B. Moldwin ◽  
...  
Keyword(s):  
Arctic Canada ◽  
Magnetic Perturbation ◽  
Superposed Epoch Analysis ◽  
Epoch Analysis

scholarly journals Specific interplanetary conditions for CIR-, Sheath-, and ICME-induced geomagnetic storms obtained by double superposed epoch analysis

2010 ◽  
Vol 28 (12) ◽  
pp. 2177-2186 ◽  
Author(s):  
Yu. I. Yermolaev ◽  
N. S. Nikolaeva ◽  
I. G. Lodkina ◽  
M. Yu. Yermolaev
Keyword(s):  
Large Scale ◽  
Geomagnetic Storms ◽  
Magnetic Cloud ◽  
Magnetic Storms ◽  
Main Phase ◽  
Corotating Interaction Region ◽  
Superposed Epoch Analysis ◽  
Epoch Analysis ◽  
Archive Data ◽  
Scale Types

Abstract. A comparison of specific interplanetary conditions for 798 magnetic storms with Dst <−50 nT during 1976–2000 was made on the basis of the OMNI archive data. We categorized various large-scale types of solar wind as interplanetary drivers of storms: corotating interaction region (CIR), Sheath, interplanetary CME (ICME) including both magnetic cloud (MC) and Ejecta, separately MC and Ejecta, and "Indeterminate" type. The data processing was carried out by the method of double superposed epoch analysis which uses two reference times (onset of storm and minimum of Dst index) and makes a re-scaling of the main phase of the storm in a such way that all storms have equal durations of the main phase in the new time reference frame. This method reproduced some well-known results and allowed us to obtain some new results. Specifically, obtained results demonstrate that (1) in accordance with "output/input" criteria the highest efficiency in generation of magnetic storms is observed for Sheath and the lowest one for MC, and (2) there are significant differences in the properties of MC and Ejecta and in their efficiencies.

Trends in volcanic degassing through eruption cycles: insights from satellite measurements

2021 ◽  
Author(s):  
Simon Carn ◽  
Vitali Fioletov ◽  
Chris McLinden ◽  
Nickolay Krotkov ◽  
Can Li
Keyword(s):  
Volcanic Emissions ◽  
Ozone Monitoring Instrument ◽  
Satellite Measurements ◽  
Volcanic Gas ◽  
Volcanic Degassing ◽  
Superposed Epoch Analysis ◽  
Decadal Scale ◽  
Gas Measurements ◽  
Epoch Analysis ◽  
Lower Magnitude

&lt;p&gt;Effective use of volcanic gas measurements for eruption forecasting and hazard mitigation at active volcanoes requires an understanding of long-term degassing behavior as context. Much recent progress has been made in quantifying global volcanic emissions of sulfur dioxide (SO&lt;sub&gt;2&lt;/sub&gt;) and other gas species by expanding the coverage of ground-based sensor networks and through analysis of decadal-scale satellite datasets. Combined, these advances have provided valuable constraints on the magnitude and variability of SO&lt;sub&gt;2&lt;/sub&gt; emissions at over 120 actively degassing volcanoes worldwide. Being less constrained by the style or location of volcanic activity, satellite measurements can provide greater insight into trends in volcanic degassing during eruption cycles. Here, we present an analysis of ~15 years of volcanic SO&lt;sub&gt;2&lt;/sub&gt; measurements by the ultraviolet (UV) Ozone Monitoring Instrument (OMI) aboard NASA&amp;#8217;s Aura satellite, focused on observed trends in SO&lt;sub&gt;2&lt;/sub&gt; emissions spanning eruptions of varying magnitude. The Aura/OMI measurements have been used to estimate annual mean SO&lt;sub&gt;2&lt;/sub&gt; emissions at ~100 volcanoes active between 2005 and 2020, around 80 of which erupted during the 15-year period. Superposed epoch analysis (SEA) of SO&lt;sub&gt;2&lt;/sub&gt; emission trends for the erupting volcanoes (with eruption magnitudes ranging from Volcanic Explosivity Index [VEI] 2 to 4) provides evidence that volcanoes exhibiting higher levels of SO&lt;sub&gt;2&lt;/sub&gt; emission in the years prior to eruption typically produce eruptions of lower magnitude, and vice versa. Post-eruptive SO&lt;sub&gt;2&lt;/sub&gt; degassing exceeds pre-eruptive emissions for several years after eruptions with VEI 3-4 and may scale with eruption size; perhaps consistent with larger eruptions being supplied by larger magma intrusions which continue to degas in subsequent years. The SEA is most robust for eruptions of intermediate magnitude (VEI 3) which are the most common events in the recent global eruption record covered by the OMI measurements. Limited observations of larger eruptions (VEI 5+) suggest significant differences in degassing trends during these larger events. Future work will extend the satellite-based estimates of volcanic SO&lt;sub&gt;2&lt;/sub&gt; emissions both forward and backward in time using other UV satellite instruments, generating longer records of SO&lt;sub&gt;2&lt;/sub&gt; degassing (extending back to 1978 for the strongest volcanic sources of SO&lt;sub&gt;2&lt;/sub&gt;) that will be used to further explore and constrain these relationships. &amp;#160;&lt;/p&gt;

The Variation of Ionospheric O+ and H+ Outflow during Sawtooth Oscillations

2021 ◽  
Author(s):  
Niloufar Nowrouzi ◽  
Lynn Kistler ◽  
Eric Lund ◽  
Kai Zhao
Keyword(s):  
Plasma Sheet ◽  
Statistical Study ◽  
Onset Time ◽  
Direct Access ◽  
Data Set ◽  
Superposed Epoch Analysis ◽  
3D Data ◽  
Before And After ◽  
Epoch Analysis ◽  
Sawtooth Oscillations

&lt;p&gt;Sawtooth events are repeated injections of energetic particles at geosynchronous orbit. Although studies have shown that 94% of sawtooth events occur during &amp;#160;magnetic storm times, the main factor that causes a sawtooth event is unknown. Simulations have suggested that heavy ions like O&lt;sup&gt;+&lt;/sup&gt;&amp;#160;may play a role in driving the sawtooth mode by increasing the magnetotail pressure and causing the magnetic tail to stretch. O&lt;sup&gt;+&lt;/sup&gt;&amp;#160;ions located in the nightside auroral region have a direct access to the near-earth plasma-sheet. O&lt;sup&gt;+&lt;/sup&gt; in the dayside cusp can reach to the midtail plasma-sheet when the convection velocity is sufficiently strong. Whether the dayside or nightside source is more important is not known.&lt;/p&gt;&lt;p&gt;We show results of a statistical study of the variation of the O+ and H+ outflow flux during sawtooth events for SIR and ICME sawtooth events. We perform a superposed epoch analysis of the ion outflow using the TEAMS (Time-of-Flight Energy Angle Mass Spectrograph) instrument on the FAST spacecraft. TEAMS measures the ion composition over the energy range of 1 eV e&lt;sup&gt;-1&lt;/sup&gt;&amp;#160;to 12 keV e&lt;sup&gt;-1&lt;/sup&gt;.&amp;#160;&amp;#160;We have done major corrections and calibrations (producing 3D data set, anode calibration, mass classification, removing ram effect and incorporating dead time corrections) on&amp;#160;TEAMS data and produced a data set for four data species (H&lt;sup&gt;+&lt;/sup&gt;, O&lt;sup&gt;+&lt;/sup&gt;, and He&lt;sup&gt;+&lt;/sup&gt;).&amp;#160;From 1996 to 2007, we have data for 133 orbits of CME-driven and for 103 orbits of SIR-driven sawtooth events with an altitude above 1500 km. We found that:&lt;/p&gt;&lt;ul&gt;&lt;li&gt;the averaged O&lt;sup&gt;+&lt;/sup&gt; outflow flux is more intense in the cusp dayside than in the nightside, before and after onset time.&lt;/li&gt; &lt;li&gt;&lt;span&gt;Before onset, an intense averaged outflow flux in the dawnside of CME events is seen. This outflow decreases after onset time.&lt;/span&gt;&lt;/li&gt; &lt;li&gt;&lt;span&gt;In both CME-driven and SIR-driven, the averaged O&lt;/span&gt;&lt;sup&gt;+&lt;/sup&gt;&lt;span&gt; outflow increases after onset time, in the nightside, cusp dayside. This increase is greater on the nightside than in the cusp.&lt;/span&gt;&lt;/li&gt; &lt;/ul&gt;&lt;p&gt;We will develop this study by performing a similar statistical study for H&lt;sup&gt;+&lt;/sup&gt; outflow and finally will compare the H&lt;sup&gt;+&lt;/sup&gt; result with the O&lt;sup&gt;+ &lt;/sup&gt;result.&lt;/p&gt;

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