European temperature records of the past five centuries based on documentary/instrumental information compared to climate simulations     

Eduardo Zorita  Anders Moberg  Lotta Leijonhufvud  Rob Wilson  Rudolf Brázdil  Petr Dobrovolný  Jürg Luterbacher  Reinhard Böhm  Christian Pfister  Dirk Riemann  Rüdiger Glaser  Johan Söderberg  Fidel González-Rouco 《Climatic change》2010,101(1-2):143-168

Two European temperature reconstructions for the past half-millennium, January-to-April air temperature for Stockholm (Sweden) and seasonal temperature for a Central European region, both derived from the analysis of documentary sources and long instrumental records, are compared with the output of climate simulations with the model ECHO-G. The analysis is complemented by comparisons with the long (early)-instrumental record of Central England Temperature (CET). Both approaches to study past climates (simulations and reconstructions) are burdened with uncertainties. The main objective of this comparative analysis is to identify robust features and weaknesses in each method which may help to improve models and reconstruction methods. The results indicate a general agreement between simulations obtained with temporally changing external forcings and the reconstructed Stockholm and CET records for the multi-centennial temperature trend over the recent centuries, which is not reproduced in a control simulation. This trend is likely due to the long-term change in external forcing. Additionally, the Stockholm reconstruction and the CET record also show a clear multi-decadal warm episode peaking around AD 1730, which is absent in the simulations. Neither the reconstruction uncertainties nor the model internal climate variability can easily explain this difference. Regarding the interannual variability, the Stockholm series displays, in some periods, higher amplitudes than the simulations but these differences are within the statistical uncertainty and further decrease if output from a regional model driven by the global model is used. The long-term trend of the CET series agrees less well with the simulations. The reconstructed temperature displays, for all seasons, a smaller difference between the present climate and past centuries than is seen in the simulations. Possible reasons for these differences may be related to a limitation of the traditional ‘indexing’ technique for converting documentary evidence to temperature values to capture long-term climate changes, because the documents often reflect temperatures relative to the contemporary authors’ own perception of what constituted ‘normal’ conditions. By contrast, the amplitude of the simulated and reconstructed inter-annual variability agrees rather well.  相似文献   

An ice-core based history of Siberian forest fires since AD 1250     

Anja Eichler  Willy Tinner  Sabina Brütsch  Susanne Olivier  Tatyana Papina  Margit Schwikowski 《Quaternary Science Reviews》2011,30(9-10):1027-1034

Forest fires play a key role in the global carbon cycle and thus, can affect regional and global climate. Although fires in extended areas of Russian boreal forests have a considerable influence on atmospheric greenhouse gas and soot concentrations, estimates of their impact on climate are hampered by a lack of data on the history of forest fires. Especially regions with strong continental climate are of high importance due to an intensified development of wildfires. In this study we reconstruct the fire history of Southern Siberia during the past 750 years using ice-core based nitrate, potassium, and charcoal concentration records from Belukha glacier in the continental Siberian Altai. A period of exceptionally high forest-fire activity was observed between AD 1600 and 1680, following an extremely dry period AD 1540–1600. Ice-core pollen data suggest distinct forest diebacks and the expansion of steppe in response to dry climatic conditions. Coherence with a paleoenvironmental record from the 200 km distant Siberian lake Teletskoye shows that the vegetational shift AD 1540–1680, the increase in fire activity AD 1600–1680, and the subsequent recovery of forests AD 1700 were of regional significance. Dead biomass accumulation in response to drought and high temperatures around AD 1600 probably triggered maximum forest-fire activity AD 1600–1680. The extreme dry period in the 16th century was also observed at other sites in Central Asia and is possibly associated with a persistent positive mode of the Pacific Decadal Oscillation (PDO). No significant increase in biomass burning occurred in the Altai region during the last 300 years, despite strongly increasing temperatures and human activities. Our results imply that precipitation changes controlled fire-regime and vegetation shifts in the Altai region during the past 750 years. We conclude that high sensitivity of ecosystems to occasional decadal-scale drought events may trigger unprecedented environmental reorganizations under global-warming conditions.  相似文献   

The role of pollution versus natural geological sources for lead enrichment in recent lake sediments and surface forest soils   总被引：3，自引：0，他引：3  

M.-L. Brännvall  H. Kurkkio  R. Bindler  O. Emteryd  I. Renberg 《Environmental Geology》2001,40(9):1057-1065

This paper assesses the role of airborne pollution and natural geological sources for lead enrichment in lake sediments and in surface soils of boreal forests. This assessment is based on analyses of stable lead isotopes (²⁰⁶Pb and ²⁰⁷Pb) and lead concentrations in sediment cores (>30 lakes), ombrotrophic peat and soil samples in Sweden. The ²⁰⁶Pb/²⁰⁷Pb ratio and concentration profiles in the sediment cores change synchronously over the last 3,000 years in different lakes, temporal concentration changes in sediments and peat deposits are very consistent, and these temporal concentration changes coincide well with the history of lead production in Europe. The ²⁰⁶Pb/²⁰⁷Pb ratio is almost the same in all soil mor samples (1.152ǂ.009; n=94), and similar to values recorded in aerosols, despite very high and different ²⁰⁶Pb/²⁰⁷Pb ratio of the mineral soil in the C-horizon (1.3-1.7). This study provides evidence that lead enrichment in recent sediments and peat, and in the mor layer are caused by deposition of pollution lead and not natural processes.  相似文献   

The distribution of acetaldehyde in the lower troposphere during TROPOZ II     

D. W. Arlander  D. Brüning  U. Schmidt  D. H. Ehhalt 《Journal of Atmospheric Chemistry》1995,22(3):243-249

A series of 72 measurements of the acetaldehyde (CH₃CHO) mixing ratio were made in the lower troposphere during TROPOZ II. These measurements are the first ever made of the background level of this trace gas in the free troposphere. The data show a vertical decrease of the CH₃CHO mixing ratio with increasing altitude and indicate higher CH₃CHO concentrations in the Northern Hemisphere — in general agreement with a model-derived average CH₃CHO distribution. Deviations of the observed CH₃CHO mixing ratios from the modelled mean distribution are correlated with similar deviations in the corresponding HCHO mixing ratios.  相似文献   

The QBO signal in monthly precipitation fields over Europe     

R. Brázdil  A. N. Zolotokrylin 《Theoretical and Applied Climatology》1995,51(1-2):3-12

Summary Areal monthly precipitation totals of 24 West and Central European regions and of 74 regions of the European part of the former USSR are studied in respect to the westerly and easterly phases of the QBO for the longest available period from 1953 to the 1980s. A significant QBO signal has been detected in September and October in the region of the British Isles, in the Central European region and in Byelorussia (in the easterly phase more precipitation and its lower variability in September and higher variability in October), but also in small region of the south Ukraine in August and in October. Regions of the eastern Ukraine and adjoined regions of Russia had the significant QBO signal in May (more precipitation and its prevalent lower variability in the westerly phase). The observed effects are explained by circulation differences in the westerly and easterly phases of the QBO.With 2 Figures  相似文献   

Progress in the Study of Climatic Extremes in Northern and Central Europe   总被引：1，自引：0，他引：1  

R. Heino  R. Brázdil  E. Førland  H. Tuomenvirta  H. Alexandersson  M. Beniston  C. Pfister  M. Rebetez  G. Rosenhagen  S. Rösner  J. Wibig 《Climatic change》1999,42(1):151-181

A study of the long-term changes of various climatic extremes was made jointly by a number of European countries. It was found that the changes in maximum and minimum temperatures follow, in broad terms, the corresponding well-documented mean temperature changes. Minimum temperatures, however, have increased slightly more than maximum temperatures, although both have increased. As a result, the study confirms that the diurnal temperature range has mostly decreased during the present century in Northern and Central Europe. Frost has become less frequent. Two extreme-related precipitation characteristics, the annual maximum daily precipitation and the number of days with precipitation 10 mm, show no major trends or changes in their interannual variability. An analysis of return periods indicated that in the Nordic countries there were high frequencies of extraordinary 1-day rainfalls both in the 1930s and since the 1980s. There have been no long-term changes in the number of high wind speeds in the German Bight. Occurrences of thunderstorms and hails show a decreasing tendency in the Czech Republic during the last 50 years. Finally, using proxy data sources, a 500-year temperature and precipitation event graph for the Swiss Mittelland is presented. It shows large interdecadal variations as well as the exceptionality of the latest decade 1986-1995.  相似文献   

On the generation of synthetic wind roses in orographically structured terrain (research note)     

W. Brücher  M. J. Kerschgens  F. Steffany 《Theoretical and Applied Climatology》1994,48(4):203-207

Summary A strategy was developed to overcome the difficulty of unknown forcing for the modelling of fields of wind roses with meso- and microscale models. It was applied to a site with heavy orographically structured terrain. The supra-scale winds which act as forcing for the model were calculated from a measured distribution of surface winds by an optimized inversion technique. The method is applicable to all types of mesoscale models.With 3 Figures  相似文献   

Boundary-layer observations over water and arctic sea-ice during on-ice air flow     

Burghard Brümmer  Birgit Busack  Heinrich Hoeber  Gottfried Kruspe 《Boundary-Layer Meteorology》1994,68(1-2):75-108

Observations made on 8 and 9 May 1988 by aircraft and two ships in and around the marginal ice zone of the Fram Strait during on-ice air flow under cloudy and cloud-free conditions are presented.The thermodynamic modification of the air mass moving from the open water to the ice over horizontal distances of 100–300 km is only a few tenth of a degree for temperature and a few tenth of a gram per kilogram for specific humidity. This is due to the small temperature differences between sea and ice surfaces. During the day, the ice surface is even warmer than the sea surface. The stably stratified 200–400 m deep boundary layer is often topped by a moisture inversion leading to downward fluxes of sensible as well as latent heat.The radiation and energy balance at the surface are measured as functions of ice cover, cloud cover and sun elevation angle. The net radiationR _Nis the dominating term of the energy budget. During the day, the difference ofR _Nbetween clear and overcast sky is only a few W/m² over ice, but 100–200 W/m² over water. During the night,R _Nover ice is more sensitive to cloud cover.The kinematic structure is characterized by strong shears of the longitudinal and the transversal wind component. The profile of the latter one shows an inflection point near the top of the boundary layer. Dynamically-driven roll circulations are numerically separated from the mean flow. The secondary flow patterns have wavelengths of about 1 km and contribute substantially to the total variances and covariances.  相似文献   

Dendrochronology for the last 1400 years in eastern Tibet   总被引：11，自引：0，他引：11  

Achim Bräuning 《GeoJournal》1994,34(1):75-95

Twentyfour tree-ring chronologies of various tree-species(Picea, Abies, Larix, Juniperus) from sites near the upper timberline in eastern Tibet were established, the longest one dating back to 620 A.D. A new classification of pointer intervals is presented, distinguishing between different kinds of signatures in a tree-ring series and amount of growth change in relation to the previous year. The various types of signatures can be related to meteorological events like cold winters and summers, summer drought or to recreation reactions after years of reduced growth. The distribution pattern and type of pointer intervals combined with ring width variation enables the detection of periods of favourable or unfavourable growth conditions with regard to climate history. Based on far-distance correlations and signature analysis regions of similar tree-growth are mapped out.  相似文献   

A room-temperature phase transition in maximum microcline. Absorption in the far infrared (10–200 cm−1) in the temperature range 110–300 K     

B. Wyncke  P. F. McMillan  W. L. Brown  R. E. Openshaw  F. Bréhat 《Physics and Chemistry of Minerals》1981,7(1):31-34

The far infrared powder absorption spectra (10–200 cm^?1) for a maximum microcline sample (obtained by ion-exchange from Amelia albite) and for a natural maximum microcline were measured at steps of 10 K on lowering and raising the temperature between 300 and 110 K. Of the absorption bands at 97.5, 113.5, 137.5, 148, and 157 cm^?1 occurring at room temperature, those at 157 and eventually 148 cm^?1 showed evidence of a phase transition and only that at 157 cm^?1 showed hysteresis. The transition occurs at 245±5 K on lowering the temperature and the low-temperature form can be superheated to 300 K in the case of the ion-exchange sample. Oriented thin sections parallel to (001) and (010) were also measured to 110 K as a function of the direction of the electric vector E, but could not be unambiguously interpreted. Though the effect is very slight it is tentatively proposed that the phase transition (already characterized by calorimetry and lattice parameters) involves changes in K-O and T-O-T bonds.  相似文献