A multi-century spring precipitation history for northern Iran derived from tree-ring δ18O 

2021 ◽  
Author(s):  
Zeynab Foroozan ◽  
Jussi Grießinger ◽  
Kambiz Pourtahmasi ◽  
Achim Bräuning
Keyword(s):  
Tree Ring ◽  
Large Scale ◽  
Regional Climate ◽  
Spring Precipitation ◽  
Northern Iran ◽  
The Past ◽  
Precipitation Record ◽  
Hydroclimatic Variability ◽  
Semi Arid

<p>Knowledge about the long-term hydroclimatic variability is essential to analyze the historic course and recent impact of climate change, especially in semi-arid and arid regions of the world. In this study, we present the first tree-ring δ<sup>18</sup>O chronology for the semi-arid parts of northern Iran based on juniper trees. We were able to reconstruct past hydroclimatic variability for the past 500 years. The highly significant correlation between tree-ring δ<sup>18</sup>O and spring precipitation indicates the primary influence of spring moisture availability on δ<sup>18</sup>O variations. The thereof derived precipitation reconstruction reveals short and long-term variability of precipitation intensity, duration, and frequency of dry/wet events. During the past 500 years, the driest period occurred in the 16<sup>th</sup> century, whereas the 18th century was comparably wet. A gradual decline in the reconstructed spring precipitation is evident since the beginning of the 19th century, culminating in the continuing drought of the 20<sup>th</sup> century. An analysis of dry/wet years indicated that over the last three centuries, the occurrence of years with a relatively dry spring is increasing. In contrast, more humid spring conditions are decreasing. However, the overall frequency of the occurrence of extreme events increased over the past five centuries. In addition, past hydrological disasters recorded in Persian history were well represented in our reconstruction. Correlations between our reconstructed precipitation record and large-scale circulation systems revealed no significant influence of large-scale climatic drivers on spring precipitation variations in north Iran, which therefore seem to be mostly controlled by a regional climate forcing.</p>

scholarly journals 501 Years of Spring Precipitation History for the Semi-Arid Northern Iran Derived from Tree-Ring δ18O Data

Atmosphere ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 889
Author(s):  
Zeynab Foroozan ◽  
Jussi Grießinger ◽  
Kambiz Pourtahmasi ◽  
Achim Bräuning
Keyword(s):  
Tree Ring ◽  
Large Scale ◽  
Major Influence ◽  
World Knowledge ◽  
Spring Precipitation ◽  
Northern Iran ◽  
Climate Conditions ◽  
Atmospheric Circulation Indices ◽  
The Impact ◽  
Semi Arid

In semi-arid regions of the world, knowledge about the long-term hydroclimate variability is essential to analyze and evaluate the impact of current climate change on ecosystems. We present the first tree-ring δ18O based hydroclimatic reconstruction for northern semi-arid Iran spanning the period 1515–2015. A highly significant correlation between tree-ring δ18O variations of juniper trees and spring (April–June) precipitation reveals a major influence of spring water availability during the early growing season. The driest period of the past 501 years occurred in the 16th century while the 18th century was the wettest, during which the overall highest frequency of wet year events occurred. A gradual decline in spring precipitation is evident from the beginning of the 19th century, pointing to even drier climate conditions. The analysis of dry/wet events indicates that the frequency of years with relatively dry spring increased over the last three centuries, while the number of wet events decreased. Our findings are in accordance with historical Persian disaster records (e.g., the severe droughts of 1870–1872, 1917–1919; severe flooding of 1867, the 1930s, and 1950). Correlation analyses between the reconstruction and different atmospheric circulation indices revealed no significant influence of large-scale drivers on spring precipitation in northern Iran.

scholarly journals Global climatology and trends in convective environments from ERA5 and rawinsonde data

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Mateusz Taszarek ◽  
John T. Allen ◽  
Mattia Marchio ◽  
Harold E. Brooks
Keyword(s):  
Large Scale ◽  
Climate Models ◽  
Global Climate ◽  
Convective Available Potential Energy ◽  
Global Climate Models ◽  
Convective Precipitation ◽  
The Past ◽  
The Tropics ◽  
Rawinsonde Data

AbstractGlobally, thunderstorms are responsible for a significant fraction of rainfall, and in the mid-latitudes often produce extreme weather, including large hail, tornadoes and damaging winds. Despite this importance, how the global frequency of thunderstorms and their accompanying hazards has changed over the past 4 decades remains unclear. Large-scale diagnostics applied to global climate models have suggested that the frequency of thunderstorms and their intensity is likely to increase in the future. Here, we show that according to ERA5 convective available potential energy (CAPE) and convective precipitation (CP) have decreased over the tropics and subtropics with simultaneous increases in 0–6 km wind shear (BS06). Conversely, rawinsonde observations paint a different picture across the mid-latitudes with increasing CAPE and significant decreases to BS06. Differing trends and disagreement between ERA5 and rawinsondes observed over some regions suggest that results should be interpreted with caution, especially for CAPE and CP across tropics where uncertainty is the highest and reliable long-term rawinsonde observations are missing.

scholarly journals Tree Vitality and Forest Health: Can Tree-Ring Stable Isotopes Be Used as Indicators?

2021 ◽  
Author(s):  
Paolo Cherubini ◽  
Giovanna Battipaglia ◽  
John L. Innes
Keyword(s):  
Air Pollution ◽  
Stable Isotopes ◽  
Tree Ring ◽  
Forest Decline ◽  
Forest Health ◽  
Stress Factors ◽  
Tree Vitality ◽  
The Past ◽  
Physiological Processes

Abstract Purpose of Review Society is concerned about the long-term condition of the forests. Although a clear definition of forest health is still missing, to evaluate forest health, monitoring efforts in the past 40 years have concentrated on the assessment of tree vitality, trying to estimate tree photosynthesis rates and productivity. Used in monitoring forest decline in Central Europe since the 1980s, crown foliage transparency has been commonly believed to be the best indicator of tree condition in relation to air pollution, although annual variations appear more closely related to water stress. Although crown transparency is not a good indicator of tree photosynthesis rates, defoliation is still one of the most used indicators of tree vitality. Tree rings have been often used as indicators of past productivity. However, long-term tree growth trends are difficult to interpret because of sampling bias, and ring width patterns do not provide any information about tree physiological processes. Recent Findings In the past two decades, tree-ring stable isotopes have been used not only to reconstruct the impact of past climatic events, such as drought, but also in the study of forest decline induced by air pollution episodes, and other natural disturbances and environmental stress, such as pest outbreaks and wildfires. They have proven to be useful tools for understanding physiological processes and tree response to such stress factors. Summary Tree-ring stable isotopes integrate crown transpiration rates and photosynthesis rates and may enhance our understanding of tree vitality. They are promising indicators of tree vitality. We call for the use of tree-ring stable isotopes in future monitoring programmes.

Landscape-scale disturbances and regeneration in semi-arid woodlands of southwestern Australia

1994 ◽  
Vol 1 (3) ◽  
pp. 214 ◽  
Author(s):  
Colin J. Yates ◽  
Richard J. Hobbs ◽  
Richard W. Bell
Keyword(s):  
Tree Mortality ◽  
Landscape Scale ◽  
Eucalyptus Species ◽  
Natural Ecosystems ◽  
Fragmented Landscapes ◽  
The Past ◽  
Adult Tree ◽  
Western Australian ◽  
Semi Arid

Woodlands dominated by Eucalyptus salmonophloia occur both in the fragmented landscapes of the Western Australian wheatbelt and in the adjacent unfragmented goldfields area. We examined the responses of the unfragmented woodlands to landscape-scale disturbances caused by fire, floods, windstorms and drought. Sites known to have experienced disturbances of these types over the past 50 years all had cohorts of sapling-stage E. salmonophloia and other dominant Eucalyptus species. Sites disturbed either by fire, flood or storm during 1991-92 displayed adult tree mortality and extensive seedling establishment, although rates of establishment and survival varied between sites. No regeneration was observed at equivalent undisturbed sites. These results indicate that landscape-scale disturbances of several types are important drivers of the dynamics of these semi-arid woodlands. Lack of regeneration of fragmented woodlands in the wheatbelt is likely to be due to changed disturbance regimes coupled with altered physical and biotic conditions within remnants. We argue that it may be difficult to identify processes which are important for the long-term persistence of natural ecosystems in fragmented landscapes without reference to equivalent unfragmented areas.

scholarly journals Dendroclimatology in the Eastern Mediterranean

Radiocarbon ◽  
2014 ◽  
Vol 56 (04) ◽  
pp. S61-S68
Author(s):  
Ramzi Touchan ◽  
David M. Meko ◽  
Kevin J. Anchukaitis
Keyword(s):  
Resource Management ◽  
Climate Variability ◽  
20Th Century ◽  
Tree Ring ◽  
Large Scale ◽  
Eastern Mediterranean ◽  
Spatial Scales ◽  
Climatic Variation ◽  
Ring Network ◽  
The Past

Dendroclimatology in the Eastern Mediterranean (EM) region has made important contributions to the understanding of climate variability on timescales of decades to centuries. These contributions, beginning in the mid-20th century, have value for resource management, archaeology, and climatology. A gradually expanding tree-ring network developed by the first author over the past 15 years has been the framework for some of the most important recent advances in EM dendroclimatology. The network, now consisting of 79 sites, has been widely applied in large-scale climatic reconstruction and in helping to identify drivers of climatic variation on regional to global spatial scales. This article reviews EM dendroclimatology and highlights contributions on the national and international scale.

Trends in the frequency, extent, and severity of spruce budworm outbreaks in eastern Canada

1983 ◽  
Vol 13 (4) ◽  
pp. 539-547 ◽  
Author(s):  
J. R. Blais
Keyword(s):  
20Th Century ◽  
Large Scale ◽  
Spruce Budworm ◽  
Forest Composition ◽  
Eastern Canada ◽  
Clear Cutting ◽  
The Past ◽  
Spruce Stands ◽  
History Of

The history of spruce budworm (Choristoneurafumiferana (Clem.)) outbreaks for the past 200 to 300 years, for nine regions in eastern Canada, indicates that outbreaks have occurred more frequently in the 20th century than previously. Regionally, 21 outbreaks took place in the past 80 years compared with 9 in the preceding 100 years. Earlier infestations were restricted to specific regions, but in the 20th century they have coalesced and increased in size, the outbreaks of 1910, 1940, and 1970 having covered 10, 25, and 55 million ha respectively. Reasons for the increase in frequency, extent, and severity of outbreaks appear mostly attributable to changes caused by man, in the forest ecosystem. Clear-cutting of pulpwood stands, fire protection, and use of pesticides against budworm favor fir–spruce stands, rendering the forest more prone to budworm attack. The manner and degree to which each of these practices has altered forest composition is discussed. In the future, most of these practices are expected to continue and their effects could intensify, especially in regions of recent application. Other practices, including large-scale planting of white spruce, could further increase the susceptibility of forest stands. Forest management, aimed at reducing the occurrence of extensive fir–spruce stands, has been advocated as a long-term solution to the budworm problem. The implementation of this measure at a time when man's actions result in the proliferation of fir presents a most serious challenge to forest managers.

scholarly journals Geographic variation and temporal trends in ice phenology in Norwegian lakes during the period 1890–2020

2021 ◽  
Vol 15 (5) ◽  
pp. 2333-2356
Author(s):  
Jan Henning L'Abée-Lund ◽  
Leif Asbjørn Vøllestad ◽  
John Edward Brittain ◽  
Ånund Sigurd Kvambekk ◽  
Tord Solvang
Keyword(s):  
Large Scale ◽  
Regional Climate ◽  
Temporal Trends ◽  
Large Set ◽  
Time And Space ◽  
Nao Index ◽  
Break Up ◽  
Future Consequences ◽  
Ice Phenology

Abstract. Long-term observations of ice phenology in lakes are ideal for studying climatic variation in time and space. We used a large set of observations from 1890 to 2020 of the timing of freeze-up and break-up, and the length of ice-free season, for 101 Norwegian lakes to elucidate variation in ice phenology across time and space. The dataset of Norwegian lakes is unusual, covering considerable variation in elevation (4–1401 m a.s.l.) and climate (from oceanic to continental) within a substantial latitudinal and longitudinal gradient (58.2–69.9∘ N, 4.9–30.2∘ E). The average date of ice break-up occurred later in spring with increasing elevation, latitude and longitude. The average date of freeze-up and the length of the ice-free period decreased significantly with elevation and longitude. No correlation with distance from the ocean was detected, although the geographical gradients were related to regional climate due to adiabatic processes (elevation), radiation (latitude) and the degree of continentality (longitude). There was a significant lake surface area effect as small lakes froze up earlier due to less volume. There was also a significant trend that lakes were completely frozen over later in the autumn in recent years. After accounting for the effect of long-term trends in the large-scale North Atlantic Oscillation (NAO) index, a significant but weak trend over time for earlier ice break-up was detected. An analysis of different time periods revealed significant and accelerating trends for earlier break-up, later freeze-up and completely frozen lakes after 1991. Moreover, the trend for a longer ice-free period also accelerated during this period, although not significantly. An understanding of the relationship between ice phenology and geographical parameters is a prerequisite for predicting the potential future consequences of climate change on ice phenology. Changes in ice phenology will have consequences for the behaviour and life cycle dynamics of the aquatic biota.

Improvements in XCO2 accuracy from OCO-2 with the latest ACOS v10 product

2021 ◽  
Author(s):  
Christopher ODell ◽  
Annmarie Eldering ◽  
Michael Gunson ◽  
David Crisp ◽  
Brendan Fisher ◽  
...  
Keyword(s):  
Power Plants ◽  
Large Scale ◽  
Regional Scale ◽  
Surface Fluxes ◽  
Retrieval Algorithm ◽  
The Past ◽  
Tropical Oceans ◽  
Desert Areas ◽  
Global Carbon

<p>While initial plans for measuring carbon dioxide from space hoped for 1-2 ppm levels of accuracy (bias) and precision in the CO<sub>2</sub> column mean dry air mole fraction (XCO<sub>2</sub>), in the past few years it has become clear that accuracies better than 0.5 ppm are required for most current science applications.  These include measuring continental (1000+ km) and regional scale (100s of km) surface fluxes of CO<sub>2</sub> at monthly-average timescales.  Considering the 400+ ppm background, this translates to an accuracy of roughly 0.1%, an incredibly challenging target to hit. </p><p>Improvements in both instrument calibration and retrieval algorithms have led to significant improvements in satellite XCO<sub>2</sub> accuracies over the past decade.  The Atmospheric Carbon Observations from Space (ACOS) retrieval algorithm, including post-retrieval filtering and bias correction, has demonstrated unprecedented accuracy with our latest algorithm version as applied to the Orbiting Carbon Observatory-2 (OCO-2) satellite sensor.   This presentation will discuss the performance of the v10 XCO<sub>2</sub> product by comparisons to TCCON and models, and showcase its performance with some recent examples, from the potential to infer large-scale fluxes to its performance on individual power plants.  The v10 product yields better agreement with TCCON over land and ocean, plus reduced biases over tropical oceans and desert areas as compared to a median of multiple global carbon inversion models, allowing better accuracy and faith in inferred regional-scale fluxes.  More specifically, OCO-2 has single sounding precision of ~0.8 ppm over land and ~0.5 ppm over water, and RMS biases of 0.5-0.7 ppm over both land and water.  Given the six-year and growing length of the OCO-2 data record, this also enables new studies on carbon interannual variability, while at the same time allowing identification of more subtle and temporally-dependent errors.  Finally, we will discuss the prospects of future improvements in the next planned version (v11), and the long-term prospects of greenhouse gas retrievals in the coming years. </p><p> </p>

scholarly journals Influence of multidecadal variability on high and low flows: the case of the Seine basin

2020 ◽  
Vol 24 (4) ◽  
pp. 1611-1631
Author(s):  
Rémy Bonnet ◽  
Julien Boé ◽  
Florence Habets
Keyword(s):  
Large Scale ◽  
Hydrological Modeling ◽  
Spring Precipitation ◽  
Seine River ◽  
River Flows ◽  
Multidecadal Variability ◽  
Low Flows ◽  
The North ◽  
Hydrological Variability

Abstract. The multidecadal hydroclimate variations of the Seine basin since the 1850s are investigated. Given the scarcity of long-term hydrological observations, a hydrometeorological reconstruction is developed based on hydrological modeling and a method that combines the results of a downscaled long-term atmospheric reanalysis and local observations of precipitation and temperature. This method improves previous attempts and provides a realistic representation of daily and monthly river flows. This new hydrometeorological reconstruction, available over more than 150 years while maintaining fine spatial and temporal resolutions, provides a tool to improve our understanding of the multidecadal hydrological variability in the Seine basin, as well as its influence on high and low flows. This long-term reconstruction allows analysis of the strong multidecadal variations of the Seine river flows. The main hydrological mechanisms at the origin of these variations are highlighted. Spring precipitation plays a central role by directly influencing not only the multidecadal variability in spring flows but also soil moisture and groundwater recharge, which then regulate summer river flows. These multidecadal hydroclimate variations in the Seine basin are driven by anomalies in large-scale atmospheric circulation, which themselves appear to be influenced by sea surface temperature anomalies over the North Atlantic and the North Pacific. The multidecadal hydroclimate variations also influence high and low flows over the last 150 years. The analysis of two particularly severe historical droughts, the 1921 and the 1949 events, illustrates how long-term hydroclimate variations may impact short-term drought events, particularly through groundwater–river exchanges. The multidecadal hydroclimate variations described in this study, probably of internal origin, could play an important role in the evolution of water resources in the Seine basin in the coming decades. It is therefore essential to take the associated uncertainties into account in future projections.

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