scholarly journals Storm Driven Seasonal Variation in the Thermal Response of the Streambed Water of a Low-Gradient Stream

Water ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2498
Author(s):  
Erasmus K. Oware ◽  
Eric W. Peterson
Keyword(s):  
Hyporheic Zone ◽  
Thermal Response ◽  
Temperature Data ◽  
Warm Period ◽  
Cold Period ◽  
Temperature Profiles ◽  
Storm Events ◽  
Stream Channels ◽  
Multi Level ◽  
Substrate Temperatures

Storm events strongly influence water temperatures in the saturated substrate underlying stream channels, or the hyporheic zone (HZ). The goal of this study was to evaluate the impacts of storm events on thermal transport in the HZ. A year of temperature data were collected from six (6) multi-level samplers at multiple depths (30 cm, 60 cm, 90 cm and 150 cm) and were categorized into seasonal storm events. Analysis of the HZ temperature profiles revealed a seasonal reversal in the post-storm temperature change (ΔT) in the substrate. Increases in the ΔT were observed in the warm period (summer), whereas decreases occurred during the cold period (winter); both were associated with the direction of the pre-storm thermal gradient between the stream and substrate temperatures. The amplitude of ΔT became muted with increasing depth. Two-sample t-test analyses showed statistically significant differences between the pre- and post-storm temperatures at all depths during the warm period and at all depths except 150 cm in the cold period. Upwelling groundwater moderates the thermal response. There were no statistically significant differences in the pre- and post-storm stream temperatures during both the cold and warm periods.

scholarly journals Climate Variability in Central Europe during the Last 2500 Years Reconstructed from Four High-Resolution Multi-Proxy Speleothem Records

Geosciences ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 166
Author(s):  
Sarah Waltgenbach ◽  
Dana F. C. Riechelmann ◽  
Christoph Spötl ◽  
Klaus P. Jochum ◽  
Jens Fohlmeister ◽  
...  
Keyword(s):  
Trace Elements ◽  
High Resolution ◽  
Climate Variability ◽  
Little Ice Age ◽  
Medieval Warm Period ◽  
Warm Period ◽  
Ice Age ◽  
Cold Period ◽  
Cave System ◽  
Dark Ages

The Late Holocene was characterized by several centennial-scale climate oscillations including the Roman Warm Period, the Dark Ages Cold Period, the Medieval Warm Period and the Little Ice Age. The detection and investigation of such climate anomalies requires paleoclimate archives with an accurate chronology as well as a high temporal resolution. Here, we present 230Th/U-dated high-resolution multi-proxy records (δ13C, δ18O and trace elements) for the last 2500 years of four speleothems from Bunker Cave and the Herbstlabyrinth cave system in Germany. The multi-proxy data of all four speleothems show evidence of two warm and two cold phases during the last 2500 years, which coincide with the Roman Warm Period and the Medieval Warm Period, as well as the Dark Ages Cold Period and the Little Ice Age, respectively. During these four cold and warm periods, the δ18O and δ13C records of all four speleothems and the Mg concentration of the speleothems Bu4 (Bunker Cave) and TV1 (Herbstlabyrinth cave system) show common features and are thus interpreted to be related to past climate variability. Comparison with other paleoclimate records suggests a strong influence of the North Atlantic Oscillation at the two caves sites, which is reflected by warm and humid conditions during the Roman Warm Period and the Medieval Warm Period, and cold and dry climate during the Dark Ages Cold period and the Little Ice Age. The Mg records of speleothems Bu1 (Bunker Cave) and NG01 (Herbstlabyrinth) as well as the inconsistent patterns of Sr, Ba and P suggests that the processes controlling the abundance of these trace elements are dominated by site-specific effects rather than being related to supra-regional climate variability.

scholarly journals COMPARISON OF WAVE ACTIVITY IN THE MESOPAUSE REGION AT MAIMAGA STATION WITH EOS MLS (AURA) TEMPERATURE DATA AND ACTIVITY OF PLANETARY WAVES AT TIKSI STATION

2019 ◽  
pp. 182-189
Author(s):  
В.И. Сивцева ◽  
П.П. Аммосов ◽  
Г.А. Гаврильева ◽  
И.И. Колтовской ◽  
А.М. Аммосова
Keyword(s):  
Gravity Waves ◽  
Internal Gravity Waves ◽  
Temperature Data ◽  
Planetary Waves ◽  
Winter Period ◽  
Temperature Profiles ◽  
Night Temperature ◽  
Mesopause Region ◽  
The Difference ◽  
The Waves

Исследованы данные температуры области мезопаузы, полученные за период 2013-2018 гг. на станции Маймага (63.04N, 129.51E) и за период 2015-2018 гг. на станции Тикси (71.58 N, 128.77 E). В зимний период сезона наблюдений 2014-2015 характеристика активности внутренних гравитационных волн (ВГВ) gwимеет более низкие значения, чем в другие сезоны, а средненочная температура, наоборот, превышает аналогичные значения в другие сезоны. Для сопоставления рассматривались спутниковые данные температурных профилей полученные EOS MLS (Aura). После выделения и вычитания вклада гравитационной составляющей из температурных профилей EOS MLS для области над станцией Маймага заметно отличие в зимней стратопаузе сезона 2014-2015. В этот сезон в зимний период, с учетом вычета вклада флуктуаций температуры обусловленных ВГВ, наблюдается отсутствие резких потеплений в районе стратопаузы в отличие от остальных сезонов. Измерение параметров планетарных волн в течение периода 2015-2018 гг. совместных наблюдений на станциях Маймага и Тикси показали, что фазы наблюдаемых на обеих станциях волн совпадают, а амплитуды на станции Тикси несколько (12 К) превышают амплитуды на станции Маймага. The temperature data of the mesopause region obtained for the period 2013-2018 at the station Maimaga (63.04 N, 129.51 E) and for the period 2015-2018 at the station Tiksi (71.58 N, 128.77 E) was investigated. During the winter period of the 20142015 observation season, the characteristic of the internal gravity waves (IGW) activity sgw has lower values than in other seasons, and the average night temperature of the mesopause region, on the contrary, exceeds corresponding values in other seasons. For comparison, satellite data of temperature profiles obtained by EOS MLS (Aura) are given. After isolating and subtracting the contribution of the gravitaty waves from the EOS MLS temperature profiles for the region above the st. Maimaga, the difference in the winter stratopause of the 2014-2015 season is noticeable. In this season in winter there is a lack of sharp warming in the stratopause region, in contrast to other seasons, taking into account the deduction of the contribution of temperature fluctuations due to IGW. Measurement of the parameters of planetary waves during the period 2015-2018 of joint observations at Maimaga and Tiksi stations showed that the phases of the waves observed at both stations coincide, and the amplitudes at Tiksi station are several (1-2 K) higher than the amplitudes at Maimaga station.

Defects and AlSb Precipitate Nucleation in Laser Irradiated Aluminum

1981 ◽  
Vol 4 ◽  
Author(s):  
P. S. Peercy ◽  
D. M. Follstaedt ◽  
S. T. Picraux ◽  
W. R. Wampler
Keyword(s):  
Room Temperature ◽  
Laser Energy ◽  
Ion Beam ◽  
Threshold Energy ◽  
Single Pulse ◽  
Temperature Profiles ◽  
Beam Analysis ◽  
Slip Deformation ◽  
Precipitate Nucleation ◽  
Substrate Temperatures

ABSTRACTLattice defects and precipitates induced in unimplanted and Sb-implanted <110> single crystal Al by single pulse irradiation with a Q-switched ruby laser were studied using ion beam analysis and electron microscopy. The absorbed laser energy during irradiation is directly measured in these studies to allow precise numerical modeling of the melt times and temperature profiles. For unimplanted Al, slip deformation gives rise to increased channeled yields throughout the analyzed depth and occurs for energies well below the melt threshold energy of 3.5 J/cm2. Slip deformation is also observed for irradiation energies above the melt threshold energy, and melting is accompanied by a discontinuous increase in the minimum channeling yield, X min- Implanted Sb (to ∼2 at.% peak concentrations) is found to impede epitaxial regrowth and result in polycrystalline Al formation for laser energies such that the melt front is believed not to penetrate through the Sb-containing region. For deeper melt depths, a metastable alloy is formed with up to 35% of the Sb located in substitutional sites. AlSb precipitate formation in the melt was not observed for room temperature irradiations; however, randomly oriented AlSb precipitates are observed for irradiation at substrate temperatures of 100 and 200 °C These measurements yield an estimated time for nucleation of AlSb precipitates in molten Al of 5 nsec < tnuc < 25 nsec.

Stream ecology and surface-hyporheic hydrologic exchange: Implications, techniques and limitations

1993 ◽  
Vol 44 (4) ◽  
pp. 553 ◽  
Author(s):  
AJ Boulton
Keyword(s):  
Surface Water ◽  
Hyporheic Zone ◽  
Stream Water ◽  
Stream Ecology ◽  
Benthic Algae ◽  
Benthic Invertebrate ◽  
Stream Channels ◽  
Hydrologic Exchange ◽  
Invertebrate Colonization ◽  
Oxygen Surface

In many streams with coarse substrata, there is continuous exchange between surface water and interstitial (hyporheic) water. Upwelling hyporheic water usually contains less dissolved oxygen and may provide nutrients that are limiting in the surface water. Downwelling stream water carries oxygen, surface detritus and other material to the hyporheic zone where microbes and invertebrates reside. The magnitude and direction of this hydrologic exchange can be measured using relatively simple techniques (such as dye injections and mini-piezometers) although there are some important limitations to consider. As hydrologic exchange has been shown to affect the distribution of benthic algae and invertebrates in some streams, this variable has implications for a variety of lotic studies including those of drift, leaf breakdown, benthic invertebrate colonization, sedimentation, and nutrient limitation. Experiments in flumes and artificial stream channels usually remove the influence of hydrologic exchange although it would be possible to incorporate this into their design. Stream ecologists should consider assessing the significance of the hyporheic zone to surface processes by quantifying the vectors of hydrologic exchange to ascertain how these may affect results of work conducted on the benthos at a variety of scales.

scholarly journals Determining the temporal variability in atmospheric temperature profiles measured using radiosondes and assessment of correction factors for different launch schedules

2014 ◽  
Vol 7 (8) ◽  
pp. 8339-8357
Author(s):  
D. Butterfield ◽  
T. Gardiner
Keyword(s):  
Weather Prediction ◽  
Atmospheric Temperature ◽  
Time Of Day ◽  
Temperature Data ◽  
Rate Of Change ◽  
Temperature Profiles ◽  
Correction Factors ◽  
Temporal Separation ◽  
General Observation ◽  
Diurnal Variability

Abstract. Radiosondes provide one of the primary sources of upper atmosphere temperature data for numerical weather prediction, the assessment of long-term trends in atmospheric temperature, the study atmospheric processes and provide a source of intercomparison data for other temperature sensors e.g. satellites. When intercomparing different temperature profiles it is important to include the effect of temporal mis-match between the measurements. To help quantify this uncertainty the atmospheric temperature variation through the day needs to be assessed, so that a correction and uncertainty for time difference can be calculated. Temperature data from an intensive radiosonde campaign were analysed to calculate the hourly rate of change in temperature at different altitudes and provide recommendations and correction factors for different launch schedules. Using these results, three additional longer term data sets were analysed to assess the diurnal variability temperature as a function of altitude, time of day and season of the year. This provides data on the appropriate correction factors to use for a given temporal separation and the uncertainty associated with them. A general observation was that 10 or more repeat measurements would be required to get a standard uncertainty of less than 0.1 K h−1 of temporal mis-match.

scholarly journals Using Stratasampler{sup {alpha}} Multi-Level Wells to Examine the Hyporheic Zone within a Riparian Wetland

1998 ◽  
Author(s):  
D.L. Dunn ◽  
K.L. Dixon ◽  
R.L. Nichols ◽  
A. Schwartzman ◽  
R. Roseberry
Keyword(s):  
Hyporheic Zone ◽  
Riparian Wetland ◽  
Multi Level

scholarly journals Particle sized-resolved source apportionment of primary and secondary organic tracer compounds at urban and rural locations in Spain

2015 ◽  
Vol 15 (7) ◽  
pp. 9897-9939 ◽  
Author(s):  
B. L. van Drooge ◽  
J. O. Grimalt
Keyword(s):  
Organic Compounds ◽  
Biomass Burning ◽  
Life Style ◽  
Warm Period ◽  
Urban Life ◽  
Atmospheric Particulate Matter ◽  
Cold Period ◽  
Multivariate Curve Resolution ◽  
Rural Site ◽  
Combustion Sources

Abstract. Atmospheric particulate matter (PM) was fractionated in six aerodynamic sizes, > 7.2, 7.2–3, 3–1.5, 1.5–1, 1–0.5, < 0.5 μm, using a cascade impactor. These fractions were collected at urban and rural sites during warm and cold seasons. Analysis of the organic tracer compounds by gas-chromatography coupled to mass-spectrometry showed that the composition in the smallest size fractions (< 0.5 μm) was more uniform than in the larger sizes (7.2 > PM > 0.5 μm). Thus, markers of photochemically synthesized organic compounds or combustion sources, either biomass burning or traffic emissions, were predominantly observed in the fraction < 0.5 μm whereas the larger particles were composed of mixed sources from combustion processes, vegetation emissions, soil re-suspension, road dust, urban life-style activities and photochemically synthesized organic compounds. Important seasonal differences were observed at the rural site. In the < 0.5 μm fraction these were related to strong predominance of biomass burning in the cold period and photochemically transformed biogenic organic compounds in the warm period. In the 7.2 > PM > 0.5 μm fractions the differences involved predominant soil-sourced compounds in the warm period and mixed combustion sources, photochemical products and vegetation emissions in the cold. Multivariate Curve Resolution Alternating Least Squares showed that these organic aerosols essentially originated from six source components. Four of them reflected primary emissions related with either natural products, e.g. vegetation emissions and up whirled soil dust, or anthropogenic contributions, e.g. combustion products and compounds related with urban life-style activities, mainly vehicular exhausts and tobacco smoking. Two secondary organic aerosol components were identified. They accumulated in the smallest (< 0.5 μm) or in the larger fractions (> 0.5 μm) and involved strong or mild photochemical transformations of vegetation precursor molecules, respectively. Toxicologically relevant information was also disclosed with the present approach. Thus, the strong predominance of biomass burning residues at the rural site during the cold period involved atmospheric concentrations of polycyclic aromatic hydrocarbons that were three times higher than at the urban sites and benzo[a]pyrene concentrations above legal recommendations.

scholarly journals Delimitation of the warm and cold period of the year based on the variation of the Aegean sea surface temperature

2004 ◽  
Vol 5 (1) ◽  
pp. 159
Author(s):  
A. MAVRAKIS ◽  
S. LYKOUDIS ◽  
G. THEOHARATOS
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Annual Variation ◽  
Aegean Sea ◽  
Cold Season ◽  
Living Conditions ◽  
Warm Period ◽  
Sea Surface ◽  
Cold Period ◽  
Occupational Activities

Knowledge of the warm and cold season onset is important for the living conditions and the occupational activities of the inhabitants of a given area, and especially for agriculture and tourism. This paper presents a way to estimate the onset/end of the cold and warm period of the year, based on the sinusoidal annual variation of the Sea Surface Temperature. The method was applied on data from 8 stations of the Hellenic Navy Hydrographic Service, covering the period from 1965-1995. The results showed that the warm period starts sometime between April 28th and May 21st while it ends between October 27th and November 19th in accordance with the findings of other studies. Characteristic of the nature of the parameter used is the very low variance per station – 15 days at maximum. The average date of warm period onset is statistically the same for the largest part of the Aegean, with only one differentiation, that between Kavala and the southern stations ( Thira and Heraklion).

scholarly journals Geological Oceanography of the Pliocene Warm Period: A Review with Predictions on the Future of Global Warming

2021 ◽  
Vol 9 (11) ◽  
pp. 1210
Author(s):  
Markes E. Johnson
Keyword(s):  
Global Warming ◽  
Warm Period ◽  
Sea Surface ◽  
Extreme Weather Events ◽  
Temperature Sensitive ◽  
Extensive Literature ◽  
Sea Surface Temperatures ◽  
Storm Events ◽  
Surface Temperatures ◽  
The Future

Atmospheric carbon dioxide reached a record concentration of 419 parts per million in May 2021, 50% higher than preindustrial levels at 280 parts per million. The rise of CO2 as a heat-trapping gas is the principal barometer tracking global warming attributed to a global average increase of 1.2 °C over the last 250 years. Ongoing global warming is expected to perturb extreme weather events such as tropical cyclones (hurricanes/typhoons), strengthened by elevated sea-surface temperatures. The melting of polar ice caps in Antarctica and Greenland also is expected to result in rising sea levels through the rest of this century. Various proxies for the estimate of long-term change in sea-surface temperatures (SSTs) are available through geological oceanography, which relies on the recovery of deep-sea cores for the study of sediments enriched in temperature-sensitive planktonic foraminifera and other algal residues. The Pliocene Warm Period occurred between ~4.5 and 3.0 million years ago, when sea level and average global temperatures were higher than today, and it is widely regarded as a predictive analog to the future impact of climate change. This work reviews some of the extensive literature on the geological oceanography of the Pliocene Warm Period together with a summary of land-based studies in paleotempestology focused on coastal boulder deposits (CBDs) and coastal outwash deposits (CODs) from the margin of the Pacific basin and parts of the North Atlantic basin. Ranging in age from the Pliocene through the Holocene, the values of such deposits serve as fixed geophysical markers, against which the micro-fossil record for the Pliocene Warm Period may be compared, as a registry of storm events from Pliocene and post-Pliocene times.

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