scholarly journals Permafrost Biases Climate Signals in δ18Otree-ring Series from a Sub-alpine Tree Stand in Val Bever/Switzerland

Atmosphere ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 836
Author(s):  
Jussi Grießinger ◽  
Wolfgang Jens-Henrik Meier ◽  
Alexander Bast ◽  
Annette Debel ◽  
Isabelle Gärtner-Roer ◽  
...  
Keyword(s):  
Time Series ◽  
Large Scale ◽  
High Sensitivity ◽  
High Elevation ◽  
Significant Loss ◽  
Summer Temperature ◽  
Tree Stand ◽  
Climate Proxy ◽  
Temperature And Precipitation ◽  
Discontinuous Permafrost

During recent decades, stable oxygen isotopes derived from tree-ring cellulose (δ18OTRC) have been frequently utilised as the baseline for palaeoclimatic reconstructions. In this context, numerous studies take advantage of the high sensitivity of trees close to their ecological distribution limit (high elevation or high latitudes). However, this increases the chance that indirect climatic forces such as cold ground induced by permafrost can distort the climate-proxy relationship. In this study, a tree stand of sub-alpine larch trees (Larix decidua Mill.) located in an inner alpine dry valley (Val Bever), Switzerland, was analysed for its δ18OTRC variations during the last 180 years. A total of eight L. decidua trees were analysed on an individual base, half of which are located on verified sporadic permafrost lenses approximately 500 m below the expected lower limit of discontinuous permafrost. The derived isotope time series are strongly dependent on variations in summer temperature, precipitation and large-scale circulation patterns (geopotential height fields). The results demonstrate that trees growing outside of the permafrost distribution provide a significantly stronger and more consistent climate-proxy relationship over time than permafrost-affected tree stands. The climate sensitivity of permafrost-affected trees is analogical to the permafrost-free tree stands (positive and negative correlations with temperature and precipitation, respectively) but attenuated partly leading to a complete loss of significance. In particular, decadal summer temperature variations are well reflected in δ18OTRC from permafrost-free sites (r = 0.62, p < 0.01), while permafrost-affected sites demonstrate a full lack of this dependency (r = 0.30, p > 0.05). Since both tree stands are located just a few meters away from one another and are subject to the same climatic influences, discrepancies in the isotope time series can only be attributed to variations in the trees’ source water that constraints the climatic fingerprints on δ18OTRC. If the two individual time series are merged to one local mean chronology, the climatic sensitivity reflects an intermediate between the permafrost-free and –affected δ18OTRC time series. It can be deduced, that a significant loss of information on past climate variations arises by simply averaging both tree stands without prior knowledge of differing subsurface conditions.

scholarly journals Weak precipitation, warm winters and springs impact glaciers of south slopes of Mt. Everest (central Himalaya) in the last 2 decades (1994–2013)

2015 ◽  
Vol 9 (3) ◽  
pp. 1229-1247 ◽  
Author(s):  
F. Salerno ◽  
N. Guyennon ◽  
S. Thakuri ◽  
G. Viviano ◽  
E. Romano ◽  
...  
Keyword(s):  
Time Series ◽  
Monsoon Season ◽  
High Elevation ◽  
Maximum Temperature ◽  
Mountain Range ◽  
Climate Trends ◽  
Monsoon Period ◽  
Temperature And Precipitation ◽  
Recent Climate ◽  
Koshi Basin

Abstract. Studies on recent climate trends from the Himalayan range are limited, and even completely absent at high elevation (> 5000 m a.s.l.). This study specifically explores the southern slopes of Mt. Everest, analyzing the time series of temperature and precipitation reconstructed from seven stations located between 2660 and 5600 m a.s.l. during 1994–2013, complemented with the data from all existing ground weather stations located on both sides of the mountain range (Koshi Basin) over the same period. Overall we find that the main and most significant increase in temperature is concentrated outside of the monsoon period. Above 5000 m a.s.l. the increasing trend in the time series of minimum temperature (+0.072 °C yr−1) is much stronger than of maximum temperature (+0.009 °C yr−1), while the mean temperature increased by +0.044 °C yr−1. Moreover, we note a substantial liquid precipitation weakening (−9.3 mm yr−1) during the monsoon season. The annual rate of decrease in precipitation at higher elevations is similar to the one at lower elevations on the southern side of the Koshi Basin, but the drier conditions of this remote environment make the fractional loss much more consistent (−47% during the monsoon period). Our results challenge the assumptions on whether temperature or precipitation is the main driver of recent glacier mass changes in the region. The main implications are the following: (1) the negative mass balances of glaciers observed in this region can be more ascribed to a decrease in accumulation (snowfall) than to an increase in surface melting; (2) the melting has only been favoured during winter and spring months and close to the glaciers terminus; (3) a decrease in the probability of snowfall (−10%) has made a significant impact only at glacier ablation zone, but the magnitude of this decrease is distinctly lower than the observed decrease in precipitation; (4) the decrease in accumulation could have caused the observed decrease in glacier flow velocity and the current stagnation of glacier termini, which in turn could have produced more melting under the debris glacier cover, leading to the formation of numerous supraglacial and proglacial lakes that have characterized the region in the last decades.

scholarly journals Robust regional clustering and modeling of nonstationary summer temperature extremes across Germany

2020 ◽  
Vol 6 (1) ◽  
pp. 61-77
Author(s):  
Meagan Carney ◽  
Holger Kantz
Keyword(s):  
Time Series ◽  
Climate Modeling ◽  
Summer Temperature ◽  
Machine Learning Techniques ◽  
Temperature Extremes ◽  
Clustering Methods ◽  
Temperature And Precipitation ◽  
Weighted Kernel ◽  
Regional Clustering ◽  
Time Invariant

Abstract. We use sophisticated machine-learning techniques on a network of summer temperature and precipitation time series taken from stations throughout Germany for the years from 1960 to 2018. In particular, we consider (normalized) maximized mutual information as the measure of similarity and expand on recent clustering methods for climate modeling by applying a weighted kernel-based k-means algorithm. We find robust regional clusters that are both time invariant and shared by networks defined separately by precipitation and temperature time series. Finally, we use the resulting clusters to create a nonstationary model of regional summer temperature extremes throughout Germany and are thereby able to quantify the increase in the probability of observing high extreme summer temperature values (>35 ∘C) compared with the last 30 years.

scholarly journals Coherent Region-, Species-, and Frequency-Dependent Local Climate Signals in Northern Hemisphere Tree-Ring Widths*

2011 ◽  
Vol 24 (23) ◽  
pp. 5998-6012 ◽  
Author(s):  
Justin J. Wettstein ◽  
Jeremy S. Littell ◽  
John M. Wallace ◽  
Ze’ev Gedalof
Keyword(s):  
Time Series ◽  
Northern Hemisphere ◽  
Tree Ring ◽  
Ring Width ◽  
Frequency Component ◽  
Summer Temperature ◽  
Frequency Dependent ◽  
Local Climate ◽  
Temperature And Precipitation ◽  
Species Specific

Abstract Patterns of correlation between tree rings and local temperature or precipitation are investigated using 762 International Tree-Ring Data Bank standardized ring width site chronology time series, and a gridded dataset of temperature and precipitation. Coherent regional- and, in some cases, hemispheric-scale patterns of correlation are found in the extratropical Northern Hemisphere for both the summer prior to and the summer concurrent with ring width formation across different species and over large distances. Among those chronologies that are primarily linked to temperature, thicker ring widths are generally associated with anomalously cool prior summer temperature and anomalously warm concurrent summer temperature. Reconstructions of local summer temperature using prior, concurrent, and/or subsequent year ring widths as predictors demonstrate that useful climate–growth information generally exists in ring widths that are both concurrent with and subsequent to the summer temperature anomaly. Consistent prior summer temperature–ring width relationships have received relatively little previous attention. Among those chronologies that are primarily linked to precipitation, thicker ring widths are generally associated with high summer precipitation in both the year prior to and the year concurrent with ring formation. The magnitude and spatial consistency of temperature correlations are greater than those for precipitation, at least on the hemispheric scale. These results support and serve to generalize the conclusions of prior regionally restricted and/or species-specific studies relating ring width to energy and/or water limitations. Regional- and hemispheric-scale patterns of ring width–temperature or ring width–precipitation correlations show up more clearly in species-specific and frequency-dependent analyses. Different species respond differently to temperature and precipitation anomalies. Consistent with the hemispheric patterns described above, most standardized ring width time series more faithfully record the high frequency component of the temperature signal than the low frequency component. The potential for enhanced coherence in regionally restricted, species-specific, and frequency-dependent analyses is independently verified by examining the correlation between ring width time series over geographical distance. This broader characterization of relationships between tree-ring widths and local climate provides an objective basis for selecting tree ring or other similarly high-resolution proxy data for regional-, hemispheric-, or global-scale paleoclimate reconstructions.

scholarly journals Building long-term and high spatio-temporal resolution precipitation and air temperature reanalyses by mixing local observations and global atmospheric reanalyses: the ANATEM method

2015 ◽  
Vol 12 (1) ◽  
pp. 311-361 ◽  
Author(s):  
A. Kuentz ◽  
T. Mathevet ◽  
J. Gailhard ◽  
B. Hingray
Keyword(s):  
Time Series ◽  
Temporal Resolution ◽  
Air Temperature ◽  
Large Scale ◽  
Precipitation Time Series ◽  
Time Step ◽  
Spatial Homogeneity ◽  
Temperature And Precipitation ◽  
Spatio Temporal

Abstract. Improving the understanding of past climatic or hydrologic variability has received a large attention in different fields of geosciences, such as glaciology, dendrochronology, sedimentology or hydrology. Based on different proxies, each research community produces different kind of climatic or hydrologic reanalyses, at different spatio-temporal scales and resolution. When considering climate or hydrology, numerous studies aim at characterising variability, trends or breaks using observed time-series of different regions or climate of world. However, in hydrology, these studies are usually limited to reduced temporal scale (mainly few decades, seldomly a century) because they are limited to observed time-series, that suffers from a limited spatio-temporal density. This paper introduces a new model, ANATEM, based on a combination of local observations and large scale climatic informations (such as 20CR Reanalysis). This model allow to build long-term air temperature and precipitation time-series, with a high spatio-temporal resolution (daily time-step, few km2). ANATEM was tested on the air temperature and precipitation time-series of 22 watersheds situated on the Durance watershed, in the french Alps. Based on a multi-criteria and multi-scale diagnostic, the results show that ANATEM improves the performances of classical statistical models. ANATEM model have been validated on a regional level, improving spatial homogeneity of performances and on independent long-term time-series, being able to capture the regional low-frequency variabilities over more than a century (1883–2010).

Analysis and design of suitable model structures for activated sludge tanks with circulating flow

1999 ◽  
Vol 39 (4) ◽  
pp. 55-60 ◽  
Author(s):  
J. Alex ◽  
R. Tschepetzki ◽  
U. Jumar ◽  
F. Obenaus ◽  
K.-H. Rosenwinkel
Keyword(s):  
Activated Sludge ◽  
Large Scale ◽  
Wastewater Treatment Plants ◽  
Treatment Plant ◽  
High Sensitivity ◽  
Suitable Model ◽  
Model Structure ◽  
Analysis And Design ◽  
Hydraulic Behaviour ◽  
Model Structures

Activated sludge models are widely used for planning and optimisation of wastewater treatment plants and on line applications are under development to support the operation of complex treatment plants. A proper model is crucial for all of these applications. The task of parameter calibration is focused in several papers and applications. An essential precondition for this task is an appropriately defined model structure, which is often given much less attention. Different model structures for a large scale treatment plant with circulation flow are discussed in this paper. A more systematic method to derive a suitable model structure is applied to this case. Results of a numerical hydraulic model are used for this purpose. The importance of these efforts are proven by a high sensitivity of the simulation results with respect to the selection of the model structure and the hydraulic conditions. Finally it is shown, that model calibration was possible only by adjusting to the hydraulic behaviour and without any changes of biological parameters.

scholarly journals Analytical Validation and Clinical Application of Rapid Serological Tests for SARS-CoV-2 Suitable for Large-Scale Screening

Diagnostics ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 869
Author(s):  
Amedeo De Nicolò ◽  
Valeria Avataneo ◽  
Jessica Cusato ◽  
Alice Palermiti ◽  
Jacopo Mula ◽  
...  
Keyword(s):  
Early Diagnosis ◽  
Real Time Pcr ◽  
Large Scale ◽  
High Sensitivity ◽  
Analytical Validation ◽  
Pcr Assay ◽  
Serological Tests ◽  
Flow Test ◽  
Lateral Flow Test ◽  
Large Scale Screening

Recently, large-scale screening for COVID-19 has presented a major challenge, limiting timely countermeasures. Therefore, the application of suitable rapid serological tests could provide useful information, however, little evidence regarding their robustness is currently available. In this work, we evaluated and compared the analytical performance of a rapid lateral-flow test (LFA) and a fast semiquantitative fluorescent immunoassay (FIA) for anti-nucleocapsid (anti-NC) antibodies, with the reverse transcriptase real-time PCR assay as the reference. In 222 patients, LFA showed poor sensitivity (55.9%) within two weeks from PCR, while later testing was more reliable (sensitivity of 85.7% and specificity of 93.1%). Moreover, in a subset of 100 patients, FIA showed high sensitivity (89.1%) and specificity (94.1%) after two weeks from PCR. The coupled application for the screening of 183 patients showed satisfactory concordance (K = 0.858). In conclusion, rapid serological tests were largely not useful for early diagnosis, but they showed good performance in later stages of infection. These could be useful for back-tracing and/or to identify potentially immune subjects.

scholarly journals GASTON: Galactic Star Formation with NIKA2. Evidence for the mass growth of star-forming clumps

2021 ◽  
Author(s):  
A J Rigby ◽  
N Peretto ◽  
R Adam ◽  
P Ade ◽  
M Anderson ◽  
...  
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Galactic Plane ◽  
High Sensitivity ◽  
High Mass ◽  
Evolutionary Stage ◽  
Mass Star ◽  
Mass Growth ◽  
Star Forming ◽  
Compact Source

Abstract Determining the mechanism by which high-mass stars are formed is essential for our understanding of the energy budget and chemical evolution of galaxies. By using the New IRAM KIDs Array 2 (NIKA2) camera on the Institut de Radio Astronomie Millimétrique (IRAM) 30-m telescope, we have conducted high-sensitivity and large-scale mapping of a fraction of the Galactic plane in order to search for signatures of the transition between the high- and low-mass star-forming modes. Here, we present the first results from the Galactic Star Formation with NIKA2 (GASTON) project, a Large Programme at the IRAM 30-m telescope which is mapping ≈2 deg2 of the inner Galactic plane (GP), centred on ℓ = 23${_{.}^{\circ}}$9, b = 0${_{.}^{\circ}}$05, as well as targets in Taurus and Ophiuchus in 1.15 and 2.00 mm continuum wavebands. In this paper we present the first of the GASTON GP data taken, and present initial science results. We conduct an extraction of structures from the 1.15 mm maps using a dendrogram analysis and, by comparison to the compact source catalogues from Herschel survey data, we identify a population of 321 previously-undetected clumps. Approximately 80 per cent of these new clumps are 70 μm-quiet, and may be considered as starless candidates. We find that this new population of clumps are less massive and cooler, on average, than clumps that have already been identified. Further, by classifying the full sample of clumps based upon their infrared-bright fraction – an indicator of evolutionary stage – we find evidence for clump mass growth, supporting models of clump-fed high-mass star formation.

scholarly journals Subsidence Monitoring of Fill Area in Yan’an New District Based on Sentinel-1A Time Series Imagery

2021 ◽  
Vol 13 (15) ◽  
pp. 3044
Author(s):  
Mingjie Liao ◽  
Rui Zhang ◽  
Jichao Lv ◽  
Bin Yu ◽  
Jiatai Pang ◽  
...  
Keyword(s):  
Time Series ◽  
Large Scale ◽  
Ground Deformation ◽  
Dynamic Change ◽  
Deformation Monitoring ◽  
Chinese Loess Plateau ◽  
Ground Subsidence ◽  
Shanxi Province ◽  
Environment Change ◽  
Loess Area

In recent years, many cities in the Chinese loess plateau (especially in Shanxi province) have encountered ground subsidence problems due to the construction of underground projects and the exploitation of underground resources. With the completion of the world’s largest geotechnical project, called “mountain excavation and city construction,” in a collapsible loess area, the Yan’an city also appeared to have uneven ground subsidence. To obtain the spatial distribution characteristics and the time-series evolution trend of the subsidence, we selected Yan’an New District (YAND) as the specific study area and presented an improved time-series InSAR (TS-InSAR) method for experimental research. Based on 89 Sentinel-1A images collected between December 2017 to December 2020, we conducted comprehensive research and analysis on the spatial and temporal evolution of surface subsidence in YAND. The monitoring results showed that the YAND is relatively stable in general, with deformation rates mainly in the range of −10 to 10 mm/yr. However, three significant subsidence funnels existed in the fill area, with a maximum subsidence rate of 100 mm/yr. From 2017 to 2020, the subsidence funnels enlarged, and their subsidence rates accelerated. Further analysis proved that the main factors induced the severe ground subsidence in the study area, including the compressibility and collapsibility of loess, rapid urban construction, geological environment change, traffic circulation load, and dynamic change of groundwater. The experimental results indicated that the improved TS-InSAR method is adaptive to monitoring uneven subsidence of deep loess area. Moreover, related data and information would provide reference to the large-scale ground deformation monitoring and in similar loess areas.

scholarly journals Meso- and microscale sea-ice motion in the East Siberian Sea as determined from ERS-1 SAR Data

1999 ◽  
Vol 45 (150) ◽  
pp. 370-383 ◽  
Author(s):  
Kim Morris ◽  
Shusun Li ◽  
Martin Jeffries
Keyword(s):  
Time Series ◽  
Sea Ice ◽  
Large Scale ◽  
Vector Fields ◽  
Lateral Displacement ◽  
Motion Vector ◽  
Sar Interferometry ◽  
East Siberian Sea ◽  
Pack Ice ◽  
Sar Data

Abstract Synthetic aperture radar- (SAR-)derived ice-motion vectors and SAR interferometry were used to study the sea-ice conditions in the region between the coast and 75° N (~ 560 km) in the East Siberian Sea in the vicinity of the Kolyma River. ERS-1 SAR data were acquired between 24 December 1993 and 30 March 1994 during the 3 day repeat Ice Phase of the satellite. The time series of the ice-motion vector fields revealed rapid (3 day) changes in the direction and displacement of the pack ice. Longer-term (≥ 1 month) trends also emerged which were related to changes in large-scale atmospheric circulation. On the basis of this time series, three sea-ice zones were identified: the near-shore, stationary-ice zone; a transitional-ice zone;and the pack-ice zone. Three 3 day interval and one 9 day interval interferometric sets (amplitude, correlation and phase diagrams) were generated for the end of December, the begining of February and mid-March. They revealed that the stationary-ice zone adjacent to the coast is in constant motion, primarily by lateral displacement, bending, tilting and rotation induced by atmospheric/oceanic forcing. The interferogram patterns change through time as the sea ice becomes thicker and a network of cracks becomes established in the ice cover. It was found that the major features in the interferograms were spatially correlated with sea-ice deformation features (cracks and ridges) and major discontinuities in ice thickness.

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