In humid, broadleaf-dominated forests where gap dynamics and partial canopy mortality appears to dominate the disturbance regime at local scales, paleoecological evidence shows alteration at ...regional-scales associated with climatic change. Yet, little evidence of these broad-scale events exists in extant forests. To evaluate the potential for the occurrence of large-scale disturbance, we used 76 tree-ring collections spanning ∼840 000 km
2
and 5327 tree recruitment dates spanning ∼1.4 million km
2
across the humid eastern United States. Rotated principal component analysis indicated a common growth pattern of a simultaneous reduction in competition in 22 populations across 61 000 km
2
. Growth-release analysis of these populations reveals an intense and coherent canopy disturbance from 1775 to 1780, peaking in 1776. The resulting time series of canopy disturbance is so poorly described by a Gaussian distribution that it can be described as "heavy tailed," with most of the years from 1775 to 1780 comprising the heavy-tail portion of the distribution. Historical documents provide no evidence that hurricanes or ice storms triggered the 1775-1780 event. Instead, we identify a significant relationship between prior drought and years with elevated rates of disturbance with an intense drought occurring from 1772 to 1775. We further find that years with high rates of canopy disturbance have a propensity to create larger canopy gaps indicating repeated opportunities for rapid change in species composition beyond the landscape scale. Evidence of elevated, regional-scale disturbance reveals how rare events can potentially alter system trajectory: a substantial portion of old-growth forests examined here originated or were substantially altered more than two centuries ago following events lasting just a few years. Our recruitment data, comprised of at least 21 species and several shade-intolerant species, document a pulse of tree recruitment at the subcontinental scale during the late-1600s suggesting that this event was severe enough to open large canopy gaps. These disturbances and their climatic drivers support the hypothesis that punctuated, episodic, climatic events impart a legacy in broadleaf-dominated forests centuries after their occurrence. Given projections of future drought, these results also reveal the potential for abrupt, meso- to large-scale forest change in broadleaf-dominated forests over future decades.
Historical reanalyses that span more than a century are needed for a wide range of studies, from understanding large‐scale climate trends to diagnosing the impacts of individual historical extreme ...weather events. The Twentieth Century Reanalysis (20CR) Project is an effort to fill this need. It is supported by the National Oceanic and Atmospheric Administration (NOAA), the Cooperative Institute for Research in Environmental Sciences (CIRES), and the U.S. Department of Energy (DOE), and is facilitated by collaboration with the international Atmospheric Circulation Reconstructions over the Earth initiative. 20CR is the first ensemble of sub‐daily global atmospheric conditions spanning over 100 years. This provides a best estimate of the weather at any given place and time as well as an estimate of its confidence and uncertainty. While extremely useful, version 2c of this dataset (20CRv2c) has several significant issues, including inaccurate estimates of confidence and a global sea level pressure bias in the mid‐19th century. These and other issues can reduce its effectiveness for studies at many spatial and temporal scales. Therefore, the 20CR system underwent a series of developments to generate a significant new version of the reanalysis. The version 3 system (NOAA‐CIRES‐DOE 20CRv3) uses upgraded data assimilation methods including an adaptive inflation algorithm; has a newer, higher‐resolution forecast model that specifies dry air mass; and assimilates a larger set of pressure observations. These changes have improved the ensemble‐based estimates of confidence, removed spin‐up effects in the precipitation fields, and diminished the sea‐level pressure bias. Other improvements include more accurate representations of storm intensity, smaller errors, and large‐scale reductions in model bias. The 20CRv3 system is comprehensively reviewed, focusing on the aspects that have ameliorated issues in 20CRv2c. Despite the many improvements, some challenges remain, including a systematic bias in tropical precipitation and time‐varying biases in southern high‐latitude pressure fields.
A significant new version of the Twentieth Century Reanalysis data assimilation system, 20CRv3, has been developed. The 20CRv3 dataset will provide an ensemble of sub‐daily global atmospheric conditions spanning at least 180 years by assimilating only surface pressure observations into a coupled atmosphere–land forecast model. The new 20CRv3 system improves upon the previous system in several notable ways, including the use of upgraded data assimilation methods, a newer and higher‐resolution forecast model, and a larger set of available pressure observations.
This article reconstructed the track, intensity, and societal impacts of the Great Havana Hurricane of October 1846, using all available historical data, which include ship logs, newspapers, diaries, ...and early instrumental records. Most of the data were extracted from original manuscripts at historical libraries and repositories. Meteorological aspects of the hurricane were analyzed by mapping twice-daily surface synoptic weather maps from geographic information systems methods, estimating central pressures from known wind-pressure relationships derived from modern hurricane studies, and assessing intensity based on damage descriptions from the Saffir-Simpson Hurricane Wind Scale and an inland decay model. The storm was found to be much stronger than previously known. In this study, we clearly define the first known record of a landfalling Category 5 hurricane in the Atlantic Basin, which likely ranks among the top of all those known in the modern (1851-present) Atlantic Basin official hurricane database. Although this storm has been previously referred to as one of the most destructive hurricanes in the history of Cuba, the impacts of the Great Havana Hurricane actually spanned well beyond the Caribbean, tracking from Florida through many major populated cities along the East Coast and into Atlantic Canada. Clearly, such a storm today, with much larger metropolitan areas, would have caused enormous economic damage and should be anticipated in long-term hurricane mitigation, zoning, and worst-case scenarios. This study highlights the importance of examining historical documentary sources for extreme events, providing a framework on how to research case studies of premodern Atlantic hurricanes back in time.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Tree-Ring Isotope Records of Tropical Cyclone Activity Miller, Dana L.; Mora, Claudia I.; Grissino-Mayer, Henri D. ...
Proceedings of the National Academy of Sciences - PNAS,
09/2006, Letnik:
103, Številka:
39
Journal Article
Recenzirano
Odprti dostop
The destruction wrought by North Atlantic hurricanes in 2004 and 2005 dramatically emphasizes the need for better understanding of tropical cyclone activity apart from the records provided by ...meteorological data and historical documentation. We present a 220year record of oxygen isotope values of α-cellulose in longleaf pine tree rings that preserves anomalously low isotope values in the latewood portion of the ring in years corresponding with known 19th and 20th century landfalling/near-coastal tropical storms and hurricanes. Our results suggest the potential for a tree-ring oxygen isotope proxy record of tropical cyclone occurrence extending back many centuries based on remnant pine wood from protected areas in the southeastern U.S.
Deep persistent slab avalanches are capable of destroying infrastructure and are usually unsurvivable for those who are caught. Formation of a snowpack conducive to deep persistent slab avalanches is ...typically driven by meteorological conditions occurring in the beginning weeks to months of the winter season, and yet the avalanche event may not occur for several weeks to months later. While predicting the exact timing of the release of deep persistent slab avalanches is difficult, onset of avalanche activity is commonly preceded by rapid warming, heavy precipitation, or high winds. This work investigates the synoptic drivers of deep persistent slab avalanches at three sites in the western USA with long records: Bridger Bowl, Montana; Jackson, Wyoming; and Mammoth Mountain, California. We use self-organizing maps to generate 20 synoptic types that summarize 5899 daily 500 mbar geopotential height maps for the winters (November–March) of 1979/80–2017/18. For each of the three locations, we identify major and minor deep persistent slab avalanche seasons and analyze the number of days represented by each synoptic type during the beginning (November–January) of the major and minor seasons. We also examine the number of days assigned to each synoptic type during the 72 h preceding deep persistent slab avalanche activity for both dry and wet slab events. Each of the three sites exhibits a unique distribution of the number of days assigned to each synoptic type during November–January of major and minor seasons and for the 72 h period preceding deep persistent slab avalanche activity. This work identifies the synoptic-scale atmospheric circulation patterns contributing to deep persistent slab instabilities and the patterns that commonly precede deep persistent slab avalanche activity. By identifying these patterns, we provide an improved understanding of deep persistent slab avalanches and an additional tool to anticipate the timing of these difficult-to-predict events.
The flooding of 1861-1862 in California and Oregon is the most severe flood event documented in the far western USA and stands as a benchmark for a worst-case atmospheric-river flooding event. In ...western Washington, historical data are sparser, and 19th-century flood events have consequently not been well documented. We found that rainfall observations from five locations spanning western Washington had no detectable bias when compared to nearby 20th and 21st-century comparator stations. Time series of the four-day precipitation sum revealed an event in December 1867 that was greater than any of the last century at three locations, and in the top two events at the other two locations. Summing over all locations, the regional three-day or four-day peak precipitation in 1867 exceeded the 150-yr recurrence magnitude by nearly 150 mm, indicative of non-stationarity of precipitation extremes. Newspapers and historical accounts document flood damage to settlements, farms, and bridges from the Columbia River to central Puget Sound. Reported high water levels at two locations indicate floodplains under more than a meter of water. Reanalysis data (20CRv3) is poorly spatially constrained in 1867, and underestimates the magnitude of this event, but it clearly shows the atmospheric-river cause of the event and supports snowmelt as a significant contributor to flooding. Compared to the most recent extensive flooding in 1996, the 1867 floods were likely of a similar extent but centered further north, and with notably more precipitation and enhanced by snowmelt. The 1867 rainfall amounts were also greater than those produced by the 2006 atmospheric river, though flooding in 2006 was not enhanced by snowmelt and record stream discharges were limited to mountain catchments. The combined rainfall and flood evidence from 1867 shows the potential for events more extreme than have occurred in recent history in the major urban corridors of western Washington.
Some Perspectives on Avalanche Climatology Mock, Cary J.; Carter, Kristy C.; Birkeland, Karl W.
Annals of the American Association of Geographers,
03/2017, Letnik:
107, Številka:
2
Journal Article
Recenzirano
Avalanche climatology is defined as the study of the relationships between climate and snow avalanches, and it contributes in aiding avalanche hazard mitigation efforts. The field has evolved over ...the past six decades concerning methodology, data monitoring and field collection, and interdisciplinary linkages. Avalanche climate research directions are also expanding concerning treatment in both spatial scale and temporal timescales. This article provides an overview of the main themes of avalanche climate research in issues of scale from local to global, its expanding interdisciplinary nature, as well as its future challenges and directions. The growth of avalanche climatology includes themes such as its transformation from being mostly descriptive to innovative statistical methods and modeling techniques, new challenges in microscale efforts that include depth hoar aspects and increased field studies, expanding synoptic climatology applications on studying avalanche variations, efforts to reconstruct past avalanches and relate them to climatic change, and research on potential avalanche responses to recent twentieth-century and future global warming. Some suggestions on future avalanche climatology research directions include the expansion of data networks and studies that include lesser developed countries, stronger linkages of avalanche climate studies with GIScience and remote sensing applications, more innovative linkages of avalanches with climate and societal applications, and increased emphases on modeling and process-oriented approaches.
Many ecosystem processes that influence Earth system feedbacks - vegetation growth, water and nutrient cycling, disturbance regimes - are strongly influenced by multidecadal- to millennial-scale ...climate variations that cannot be directly observed. Paleoclimate records provide information about these variations, forming the basis of our understanding and modeling of them. Fossil pollen records are abundant in the NE US, but cannot simultaneously provide information about paleoclimate and past vegetation in a modeling context because this leads to circular logic. If pollen data are used to constrain past vegetation changes, then the remaining paleoclimate archives in the northeastern US (NE US) are quite limited. Nonetheless, a growing number of diverse reconstructions have been developed but have not yet been examined together. Here we conduct a systematic review, assessment, and comparison of paleotemperature and paleohydrological proxies from the NE US for the last 3000 years. Regional temperature reconstructions (primarily summer) show a long-term cooling trend (1000BCE - 1700CE) consistent with hemispheric-scale reconstructions, while hydroclimate data show gradually wetter conditions through the present day. Multiple proxies suggest that a prolonged, widespread drought occurred between 550 and 750CE. Dry conditions are also evident during the Medieval Climate Anomaly, which was warmer and drier than the Little Ice Age and drier than today. There is some evidence for an acceleration of the longer-term wetting trend in the NE US during the past century; coupled with an abrupt shift from decreasing to increasing temperatures in the past century, these changes could have wide-ranging implications for species distributions, ecosystem dynamics, and extreme weather events. More work is needed to gather paleoclimate data in the NE US to make inter-proxy comparisons and to improve estimates of uncertainty in reconstructions.
Plentiful documentary and pre‐twentieth century instrumental data from Louisiana, U.S.A., provide a record of continuous tropical cyclones, with daily resolution dating back to the late eighteenth ...century. The reconstruction provided new specific information for 83 storms prior to 1872. Parts of the early and mid‐nineteenth century exhibit greater tropical cyclone and hurricane activity than at any time within the last few hundred years. A major hurricane that impacted southeast Louisiana in August 1812 is very likely the closest landfalling hurricane known to impact New Orleans. The longer temporal perspective provides insight on historical hurricane impacts and information on assessing future hurricane mitigation strategies concerning potential worst‐case scenarios.
The International Surface Pressure Databank (ISPD) is the world's largest collection of global surface and sea‐level pressure observations. It was developed by extracting observations from ...established international archives, through international cooperation with data recovery facilitated by the Atmospheric Circulation Reconstructions over the Earth (ACRE) initiative, and directly by contributing universities, organizations, and countries. The dataset period is currently 1768–2012 and consists of three data components: observations from land stations, marine observing systems, and tropical cyclone best track pressure reports. Version 2 of the ISPD (ISPDv2) was created to be observational input for the Twentieth Century Reanalysis Project (20CR) and contains the quality control and assimilation feedback metadata from the 20CR. Since then, it has been used for various general climate and weather studies, and an updated version 3 (ISPDv3) has been used in the ERA‐20C reanalysis in connection with the European Reanalysis of Global Climate Observations project (ERA‐CLIM). The focus of this paper is on the ISPDv2 and the inclusion of the 20CR feedback metadata. The Research Data Archive at the National Center for Atmospheric Research provides data collection and access for the ISPDv2, and will provide access to future versions.
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