scholarly journals Ring-widths of Abies at tree-line ecotone reveal three centuries of early winter season temperature changes in Yunnan, China

2020 ◽  
Vol 55 (3-4) ◽  
pp. 945-959 ◽  
Author(s):  
Yingfeng Bi ◽  
Whitney Cory ◽  
Zenxin Fan ◽  
Jingchao Yang ◽  
Zhikun Wu ◽  
...  
Keyword(s):  
Winter Season ◽  
Early Winter ◽  
Tree Line ◽  
Temperature Changes

scholarly journals Temperature Projections over the Indus River Basin of Pakistan Using Statistical Downscaling

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 195
Author(s):  
Muhammad Saleem Pomee ◽  
Elke Hertig
Keyword(s):  
21St Century ◽  
Statistical Downscaling ◽  
General Circulation ◽  
Winter Season ◽  
Circulation Model ◽  
Indus Basin ◽  
Indus River ◽  
Temperature Changes ◽  
Basin Scale ◽  
Maximum Heating

We assessed maximum (Tmax) and minimum (Tmin) temperatures over Pakistan’s Indus basin during the 21st century using statistical downscaling. A particular focus was given to spatiotemporal heterogeneity, reference and General Circulation Model (GCM) uncertainties, and statistical skills of regression models using an observational profile that could significantly be improved by recent high-altitude observatories. First, we characterized the basin into homogeneous climate regions using K-means clustering. Predictors from ERA-Interim reanalysis were then used to model observed temperatures skillfully and quantify reference and GCM uncertainties. Thermodynamical (dynamical) variables mainly governed reference (GCM) uncertainties. The GCM predictors under RCP4.5 and RCP8.5 scenarios were used as “new” predictors in statistical models to project ensemble temperature changes. Our analysis projected non-uniform warming but could not validate elevation-dependent warming (EDW) at the basin scale. We obtained more significant warming during the westerly-dominated seasons, with maximum heating during the winter season through Tmin changes. The most striking feature is a low-warming monsoon (with the possibility of no change to slight cooling) over the Upper Indus Basin (UIB). Therefore, the likelihood of continuing the anomalous UIB behavior during the primary melt season may not entirely be ruled out at the end of the 21st century under RCP8.5.

Late-Quaternary summer temperature changes in the northern-European tree-line region

2008 ◽  
Vol 69 (03) ◽  
pp. 404-412 ◽  
Author(s):  
Heikki Seppä ◽  
Glen M. MacDonald ◽  
H. John B. Birks ◽  
Bruce R. Gervais ◽  
Jeffrey A. Snyder
Keyword(s):  
Kola Peninsula ◽  
Younger Dryas ◽  
Summer Temperature ◽  
The Arctic ◽  
Fossil Pollen ◽  
Tree Line ◽  
Temperature Changes ◽  
The Holocene ◽  
Northern European ◽  
Line Region

We present two new quantitative July mean temperature (Tjul) reconstructions from the Arctic tree-line region in the Kola Peninsula in north-western Russia. The reconstructions are based on fossil pollen records and cover the Younger Dryas stadial and the Holocene. The inferred temperatures are less reliable during the Younger Dryas because of the poorer fit between the fossil pollen samples and the modern samples in the calibration set than during the Holocene. The results suggest that the Younger Dryas Tjulin the region was 8.0–10.0°C, being 2.0–3.0°C lower than at present. The Holocene summer temperature maximum dates to 7500–6500 cal yr BP, with Tjulabout 1.5°C higher than at present. These new records contribute to our understanding of summer temperature changes along the northern-European tree-line region. The Holocene trends are consistent in most of the independent records from the Fennoscandian–Kola tree-line region, with the beginning of the Holocene thermal maximum no sooner than at about 8000 cal yr BP. In the few existing temperature-related records farther east in the Russian Arctic tree line, the period of highest summer temperature begins already at about 10,000 cal yr BP. This difference may reflect the strong influence of the Atlantic coastal current on the atmospheric circulation pattern and the thermal behaviour of the tree-line region on the Atlantic seaboard, and the more direct influence of the summer solar insolation on summer temperature in the region east of the Kola Peninsula.

Transition of the ENSO teleconnection to the Euro-Atlantic region from early to late winter: Role of the Indian Ocean

2020 ◽  
Author(s):  
Muhammad Adnan Abid ◽  
Fred Kucharski ◽  
Franco Molteni ◽  
In-Sik Kang ◽  
Adrian Tompkins ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Winter Season ◽  
Tropical Indian Ocean ◽  
Late Winter ◽  
Boreal Winter ◽  
Early Winter ◽  
Atlantic Region ◽  
Atlantic Sector ◽  
The Indian Ocean ◽  
Circulation Anomalies

<p>El Niño Southern Oscillation (ENSO) have a weak influence on the seasonal mean Euro-Atlantic circulation anomalies during the boreal winter (Dec-Feb) season. Therefore, monthly ENSO teleconnections to Euro-Atlantic region were studied during the boreal winter season for the period 1981-2015 using reanalysis and hindcast dataset. It is shown that the ENSO-forced signal to the Euro-Atlantic circulation anomalies does not persist throughout the boreal winter season. During earlier winter, a positive ENSO phase strongly enforces rainfall dipole anomalies in the tropical Indian Ocean, with increased rainfall over the western tropical Indian Ocean, and reduced in the eastern tropical Indian ocean.  This Indian Ocean rainfall dipole weakens in late winter. During early winter, the Indian Ocean rainfall dipole modifies the subtropical South Asian jet (SAJET) which forces a wavenumber-3 response projecting spatially onto the positive North Atlantic Oscillation (NAO) pattern. On contrary, during late winter, the response in the Euro-Atlantic sector is dominated by the well-known ENSO wavetrain from the tropical Pacific region, involving Pacific North American (PNA) pattern anomalies that project spatially on the negative phase of the NAO. Atmospheric General Circulation Model (AGCM) numerical experiments forced with an Indian Ocean heating dipole anomaly support the hypothesis that the Indian Ocean modulates the SAJET that enforces the Rossby wave propagation to the Euro-Atlantic region in early winter. Moreover, the ECMWF-SEAS5 hindcast dataset reproduces the observed ENSO-forced inter-basin tropical teleconnections transition from early to late winter and their response to the Euro-Atlantic circulation anomalies quite well. Therefore, it is important to understand the tropical inter-basin transition, which may lead to improve the sub-seasonal to seasonal variability and predictability of the Euro-Atlantic circulation anomalies. </p>

Impact of deforestation on surface radiative properties and temperature characteristics in Ukraine based on LUMIP CMIP6 datasets

2021 ◽  
Author(s):  
Larysa Pysarenko ◽  
Svitlana Krakovska
Keyword(s):  
Air Temperature ◽  
Forest Cover ◽  
Winter Season ◽  
Warm Season ◽  
Radiative Properties ◽  
Shortwave Radiation ◽  
Model Intercomparison ◽  
Temperature Changes ◽  
Intercomparison Project ◽  
The Impact

<p>The impact of temperate forests on climate still has open questions about their quantitative effect on radiative and thermal properties of the territory. The study addresses some of these questions and the analysis is based on the data from the Land-Use Model Intercomparison Project (LUMIP), which is the part of Coupled Model Intercomparison Project Phase 6 (CMIP6). The main aim of CMIP is to study climate on different periods of time from the past to the future with help of observations and Earth System Models (ESM).</p><p>LUMIP belongs to historical experiments and implies gradual deforestation with linear trend up to 1% all over the world during 50 years in pre-industrial period (1850-1899) and next 30 years with no change in forest cover. The goal of this experiment is to reveal the contribution of forest cover reduction on climate characteristics under quasi-constant anthropogenic forcing. This experiment was based on ESM simulations and the dataset of 8 ESM was retrieved for calculations of different climatic characteristics for the territory of Ukraine. These models have different spatial resolution, the initial and the final forest cover in grid cells respectively. Therefore, we analysed ESMs one-by-one and summarised the results over latitudinal zones. To analyse radiative regime we used monthly data of downwelling and upwelling shortwave radiation, which affect thermal regime estimated via surface and 2-m air temperature changes as well as mean daily and annual ranges. Anomalies of each characteristics were obtained over the base averages of the first 20 years of deforestation (1850-1869), which were further smoothed using the 5-year running mean.</p><p>It is known that the forest cover influences the ratio of surface downwelling and upwelling shortwave radiation, particularly, via albedo. We found the highest changes in albedo in winter season, most probably due to the presence of snow cover. Increase of albedo is well correlated with deforestation and the maximal rate of 18%/50 years was found in the Carpathians in winter. There were much less changes in warm season with rates up to 2%/50 years due to small difference between values of forest (~3-10%) with grass (~10-30%) than snow albedo (~40-90%).</p><p>These changes in radiative properties cause shifts in temperature regime with moderate and strong negative correlations between albedo and both surface and air temperatures. Higher albedo in winter season caused the decrease of mean monthly surface temperature up to -0.4℃/10 years in winter and -0.3℃/10 years in warm season. Values of changes of mean monthly air temperature corresponded to surface temperature changes and they were -0.4℃/10 years in winter and -0.2℃/10 years in warm season. Based on mean maximum and minimum monthly temperatures we found that deforestation also affected mean daily air temperature range only in winter with tendency up to 0.1–0.3℃/ 10 years. Meanwhile the models showed controversial results for annual air temperature range. One of the essential research outcomes we found that the impact of gradual deforestation on the thermal regime was shifted on approximately 20 years and diminished after stopping land cover change.</p>

Thermal controls on the development of fractures in dolostones of the Niagara Escarpment, Hamilton, Ontario, Canada

2021 ◽  
Author(s):  
Henry Gage ◽  
Carolyn Eyles ◽  
Rebecca Lee
Keyword(s):  
Thermal Stress ◽  
Temperature Fluctuations ◽  
Outdoor Environment ◽  
Slope Aspect ◽  
Rock Surface ◽  
Early Winter ◽  
Temperature Changes ◽  
Freeze Thaw ◽  
Niagara Escarpment ◽  
Thermal Changes

<p>Little research has been conducted to clarify the mechanism, extent, or factors involved in the fracturing of rocks exposed along the Niagara Escarpment in Ontario. Of particular interest are the effects of fluctuating temperatures during region’s cold winters which may be a contributor to the formation and expansion of fractures within these rocks. The results of a preliminary field-based study of temperature changes in fractured sedimentary rocks exposed at several sites along the Escarpment in Hamilton, Ontario are reported here. The objectives of the study were to examine the characteristics of operant thermal processes and to determine the effectiveness of mechanisms such as freeze-thaw and thermal stress in contributing to fracture formation and development. Fractured dolostone units were identified at three field sites along the escarpment that varied in their aspect, vegetation, and proximity to water. At each site, temperature probes were affixed to the exposed rock surface and inserted into a nearby fracture. Temperature measurements were taken at one-minute intervals throughout the winter of 2020-21.  In-situ field measurements of thermal changes within fractured dolostones on the escarpment were supplemented with recordings of rock surface and interior temperatures taken from unfractured dolostone blocks placed in a ‘controlled’ outdoor environment throughout the winter.  Initial results from the escarpment probes in the early winter show frequent, rapid shifts from warm to sub-zero temperatures and indicate that changes in temperature recorded at the rock surface closely follow diurnal atmospheric oscillations in both magnitude and timing.  However, temperature changes recorded within fractures are less extreme and show a temporal lag. Temperature fluctuations recorded at the field site with the highest degree of exposure, a southeasterly aspect, and little vegetation cover, are significantly higher and show larger thermal responses within fractures. Temperature fluctuations recorded from unfractured blocks in the ‘controlled’ outdoor environment show similar diurnal trends to those recorded on the escarpment but with reduced differential between temperatures at the block surface and interior. Together, these data indicate that temperature fluctuations sufficient to generate freeze-thaw cycles are abundant during the early winter months, temperature variability within fractures does occur, and slope aspect and exposure plays an important role in the determining the magnitude of diurnal temperature fluctuations experienced by surface rocks on the escarpment. The role of thermal stress in fracture development, created by rapid and substantial thermal changes, has yet to be determined.  </p>

scholarly journals Autumn–winter minimum temperature changes in the southern Sikhote-Alin mountain range of northeastern Asia since 1529 AD

2018 ◽  
Vol 14 (1) ◽  
pp. 57-71 ◽  
Author(s):  
Olga N. Ukhvatkina ◽  
Alexander M. Omelko ◽  
Alexander A. Zhmerenetsky ◽  
Tatyana Y. Petrenko
Keyword(s):  
Solar Activity ◽  
Minimum Temperature ◽  
Southern Oscillation ◽  
Russian Far East ◽  
Far East ◽  
Winter Season ◽  
Mountain Range ◽  
Sikhote Alin ◽  
Northeastern Asia ◽  
Temperature Changes

Abstract. The aim of our research was to reconstruct climatic parameters (for the first time for the Sikhote-Alin mountain range) and to compare them with global climate fluctuations. As a result, we have found that one of the most important limiting factors for the study area is the minimum temperatures of the previous autumn–winter season (August–December), and this finding perfectly conforms to that in other territories. We reconstructed the previous August–December minimum temperature for 485 years, from 1529 to 2014. We found 12 cold periods (1535–1540, 1550–1555, 1643–1649, 1659–1667, 1675–1689, 1722–1735, 1791–1803, 1807–1818, 1822–1827, 1836–1852, 1868–1887, 1911–1925) and seven warm periods (1560–1585, 1600–1610, 1614–1618, 1738–1743, 1756–1759, 1776–1781, 1944–2014). These periods correlate well with reconstructed data for the Northern Hemisphere and the neighboring territories of China and Japan. Our reconstruction has 3-, 9-, 20-, and 200-year periods, which may be in line with high-frequency fluctuations in El Niño–Southern Oscillation (ENSO), the short-term solar cycle, Pacific Decadal Oscillation (PDO) fluctuations, and the 200-year solar activity cycle, respectively. We suppose that the temperature of the North Pacific, expressed by the PDO may make a major contribution to regional climate variations. We also assume that the regional climatic response to solar activity becomes apparent in the temperature changes in the northern part of Pacific Ocean and corresponds to cold periods during the solar minimum. These comparisons show that our climatic reconstruction based on tree ring chronology for this area may potentially provide a proxy record for long-term, large-scale past temperature patterns for northeastern Asia. The reconstruction reflects the global traits and local variations in the climatic processes of the southern territory of the Russian Far East for more than the past 450 years.

scholarly journals Characteristics of Early-Winter Caribou, Rangifer tarandus caribou, Feeding Sites in the Southern Purcell Mountains, British Columbia

2003 ◽  
Vol 117 (3) ◽  
pp. 352 ◽  
Author(s):  
Trevor A. Kinley ◽  
John Bergenske ◽  
Julie-Anne Davies ◽  
David Quinn
Keyword(s):  
British Columbia ◽  
Rangifer Tarandus ◽  
Winter Season ◽  
Subalpine Forest ◽  
Winter Period ◽  
Late Winter ◽  
Abies Lasiocarpa ◽  
Rangifer Tarandus Caribou ◽  
Early Winter ◽  
Winter Habitat

Mountain Caribou are a rare ecotype of Woodland Caribou (Rangifer tarandus caribou) inhabiting the high-snowfall region of southeastern British Columbia, and are defined by their late-winter reliance on arboreal hair lichen of the genus Bryoria. During early winter, there is considerable variation in habitat use among populations. We snow-trailed Caribou in the southern Purcell Mountains during early winter to determine foraging patterns for the Purcell population. When snow was ≤51 cm deep, Caribou fed on Grouseberry (Vaccinium scoparium), the terrestrial lichen Cladonia, and arboreal lichens of the genus Bryoria. When snow was ≥62 cm deep, they ate exclusively arboreal lichens. In both periods, Caribou ate arboreal lichen from essentially every downed tree or branch encountered and fed with a higher intensity at downed trees than standing trees. During the low-snow period, Caribou fed at fewer trees but used those with greater lichen abundance, and fed more intensively at each, compared to the deep-snow period. In comparison to trees occurring on the foraging path but at which Caribou did not feed, those from which arboreal lichen was foraged intensively were of larger diameter, had greater lichen abundance, and were more likely to be Subalpine Fir (Abies lasiocarpa) or Engelmann Spruce (Picea engelmannii) and less likely to be Whitebark Pine (Pinus albicaulis), Lodgepole Pine (P. contorta) or Alpine Larch (Larix lyalli). The shift in diet between the low-snow and deep-snow periods reflected two modes of foraging within the early winter period, distinct from one another and apparently also distinct from the late-winter season. Management for early-winter habitat will require retention of some commercially significant forest across extensive areas, both near the subalpine forest – subalpine parkland ecotone and lower in the subalpine forest.

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