Spectral Characteristics of RV Tauri Stars

Spectroscopic properties of RV Tau variables are summarized. We report on our detailed spectroscopic investigation of a sample of RV Tau stars covering all three RV Tau subgroups. Though the observed abundance pattern is similar to those of a few post-AGB stars, we find considerable variation in the observed chemical compositions indicating that there is some non-homogeneity among subgroups of RV Tau variables. Possible scenarios of dust-gas separation in the material ejected by the dusty wind are discussed to explain the observed abundances. This mechanism would work better if the star happens to possess a binary companion. Interestingly, one of our sample stars, EP Lyr, shows long-term variations in radial velocity possibly caused by the presence of a companion.

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Evaluations of Surface PM10 Concentration and Chemical Compositions in MERRA-2 Aerosol Reanalysis over Central and Eastern China

Remote Sensing ◽

10.3390/rs13071317 ◽

2021 ◽

Vol 13 (7) ◽

pp. 1317

Author(s):

Xiaodan Ma ◽

Peng Yan ◽

Tianliang Zhao ◽

Xiaofang Jia ◽

Jian Jiao ◽

...

Keyword(s):

Eastern China ◽

Mainland China ◽

Chemical Components ◽

Chemical Compositions ◽

Observation Data ◽

Causative Factors ◽

Routine Sampling ◽

Aerosol Compositions ◽

Modern Era

The chemical composition dataset of Aerosol Reanalysis of NASA’s Modern-Era Retrospective Analysis for Research and Application, version 2 (MERRAero) has not been thoroughly evaluated with observation data in mainland China due to the lack of long-term chemical components data. Using the 5-year data of PM10 mass concentrations and chemical compositions obtained from the routine sampling measurements at the World Meteorological Organization the Global Atmosphere Watch Programme regional background stations, Jing Sha (JS) and Lin’An (LA), in central and eastern China, we comprehensively evaluate the surface PM10 concentrations and chemical compositions such as sulfate (SO42−), organic carbon (OC) and black carbon (BC) derived from MERRAero. Overall, the concentrations of PM10, SO42−, OC and BC from the MERRAero agreed well with the measurements, despite a slight and consistent overestimation of BC concentrations and a moderate and persistent underestimation of PM10 concentrations throughout the study period. The MERRAero reanalysis of aerosol compositions performs better during the summertime than wintertime. By considering the nitrate particles in PM10 reconstruction, MERRAero performance can be significantly improved. The unreasonable seasonal variations of PM10 chemical compositions at station LA by MERRAero could be causative factors for the larger MERRAero discrepancies during 2016–2017 than the period of 2011–2013.

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Fluvial magnetic susceptibility as a proxy for long‐term variations of mountain permafrost development in the Alp‐Carpathian region

Boreas ◽

10.1111/bor.12520 ◽

2021 ◽

Author(s):

Zoltán Püspöki ◽

Philip Leonard Gibbard ◽

Annamária Nádor ◽

Edit Thamó‐Bozsó ◽

Pál Sümegi ◽

...

Keyword(s):

Magnetic Susceptibility ◽

Carpathian Region ◽

Mountain Permafrost ◽

Long Term Variations

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Long-term variations of surface solar radiation in China from routine meteorological observations

Atmospheric Research ◽

10.1016/j.atmosres.2021.105715 ◽

2021 ◽

pp. 105715

Author(s):

Xuefang Yang ◽

Wenmin Qin ◽

Lunche Wang ◽

Ming Zhang ◽

Zigeng Niu

Keyword(s):

Solar Radiation ◽

Surface Solar Radiation ◽

Meteorological Observations ◽

Long Term Variations

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Long-term variations of C1–C5 alkyl nitrates and their sources in Hong Kong

Environmental Pollution ◽

10.1016/j.envpol.2020.116285 ◽

2021 ◽

Vol 270 ◽

pp. 116285

Author(s):

Lewei Zeng ◽

Hai Guo ◽

Xiaopu Lyu ◽

Beining Zhou ◽

Zhenhao Ling ◽

...

Keyword(s):

Hong Kong ◽

Alkyl Nitrates ◽

Long Term Variations

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Application of singular spectrum analysis in reconstruction of the annual signal from GRACE

Journal of Applied Geodesy ◽

10.1515/jag-2020-0005 ◽

2020 ◽

Vol 14 (3) ◽

pp. 295-302

Author(s):

Chuandong Zhu ◽

Wei Zhan ◽

Jinzhao Liu ◽

Ming Chen

Keyword(s):

Time Series ◽

Spectrum Analysis ◽

Singular Spectrum Analysis ◽

Mixture Effect ◽

Singular Spectrum ◽

Grace Data ◽

Terrestrial Water ◽

Annual Signal ◽

Long Term Variations

AbstractThe mixture effect of the long-term variations is a main challenge in single channel singular spectrum analysis (SSA) for the reconstruction of the annual signal from GRACE data. In this paper, a nonlinear long-term variations deduction method is used to improve the accuracy of annual signal reconstructed from GRACE data using SSA. Our method can identify and eliminate the nonlinear long-term variations of the equivalent water height time series recovered from GRACE. Therefore the mixture effect of the long-term variations can be avoided in the annual modes of SSA. For the global terrestrial water recovered from GRACE, the peak to peak value of the annual signal is between 1.4 cm and 126.9 cm, with an average of 11.7 cm. After the long-term and the annual term have been deducted, the standard deviation of residual time series is between 0.9 cm and 9.9 cm, with an average of 2.1 cm. Compared with the traditional least squares fitting method, our method can reflect the dynamic change of the annual signal in global terrestrial water, more accurately with an uncertainty of between 0.3 cm and 2.9 cm.

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