An inter-hemispheric comparison of the tropical storm response to global warming     

Stephanie Gleixner  Noel Keenlyside  Kevin I. Hodges  Wan-Ling Tseng  Lennart Bengtsson 《Climate Dynamics》2014,42(7-8):2147-2157

Model studies do not agree on future changes in tropical cyclone (TC) activity on regional scales. We aim to shed further light on the distribution, frequency, intensity, and seasonality of TCs that society can expect at the end of the twenty-first century in the Southern hemisphere (SH). Therefore, we investigate TC changes simulated by the atmospheric model ECHAM5 with T213 (~60 km) horizontal resolution. We identify TCs in present-day (20C; 1969–1990) and future (21C; 2069–2100) time slice simulations, using a tracking algorithm based on vorticity at 850 hPa. In contrast to the Northern hemisphere (NH), where tropical storm numbers reduce by 6 %, there is a more dramatic 22 % reduction in the SH, mainly in the South Indian Ocean. While an increase of static stability in 21C may partly explain the reduction in tropical storm numbers, stabilization cannot alone explain the larger SH drop. Large-scale circulation changes associated with a weakening of the Tropical Walker Circulation are hypothesized to cause the strong decrease of cyclones in the South Indian Ocean. In contrast the decrease found over the South Pacific appears to be partly related to increased vertical wind shear, which is possibly associated with an enhanced meridional sea surface temperature gradient. We find the main difference between the hemispheres in changes of the tropical cyclones of intermediate strength with an increase in the NH and a decrease in the SH. In both hemispheres the frequency of the strongest storms increases and the frequency of the weakest storms decreases, although the increase in SH intense storms is marginal.  相似文献   

Stratospheric climate and variability from a general circulation model and observations     

Elisa Manzini  Lennart Bengtsson 《Climate Dynamics》1996,12(9):615-639

The climate and natural variability of the large-scale stratospheric circulation simulated by a newly developed general circulation model are evaluated against available global observations. The simulation consisted of a 30-year annual cycle integration performed with a comprehensive model of the troposphere and stratosphere. The observations consisted of a 15-year dataset from global operational analyses of the troposphere and stratosphere. The model evaluation concentrates on the simulation of the evolution of the extratropical stratospheric circulation in both hemispheres. The December–February climatology of the observed zonal mean winter circulation is found to be reasonably well captured by the model, although in the Northern Hemisphere upper stratosphere the simulated westerly winds are systematically stronger and a cold bias is apparent in the polar stratosphere. This Northern Hemisphere stratospheric cold bias virtually disappears during spring (March–May), consistent with a realistic simulation of the spring weakening of the mean westerly winds in the model. A considerable amount of monthly interannual variability is also found in the simulation in the Northern Hemisphere in late winter and early spring. The simulated interannual variability is predominantly caused by polar warmings of the stratosphere, in agreement with observations. The breakdown of the Northern Hemisphere stratospheric polar vortex appears therefore to occur in a realistic way in the model. However, in early winter the model severely underestimates the interannual variability, especially in the upper troposphere. The Southern Hemisphere winter (June–August) zonal mean temperature is systematically colder in the model, and the simulated winds are somewhat too strong in the upper stratosphere. Contrary to the results for the Northern Hemisphere spring, this model cold bias worsens during the Southern Hemisphere spring (September–November). Significant discrepancies between the model results and the observations are therefore found during the breakdown of the Southern Hemisphere polar vortex. For instance, the simulated Southern Hemisphere stratosphere westerly jet continuously decreases in intensity more or less in situ from June to November, while the observed stratospheric jet moves downward and poleward.This paper was presented at the Third International Conference on Modelling of Global Climate Change and Variability, held in Hamburg 4–8 Sept. 1995 under the auspice of the Max Planck Institute for Meteorology, Hamburg. Editor for these papers is L. Dümenil.  相似文献   

Historical population assessment of Barents Sea harp seals (Pagophilus groenlandicus)     

Skaug  Hans J.; Frimannslund  Lennart; Oien  Nils I. 《ICES Journal of Marine Science》2007,64(7):1356-1365

  相似文献   

Comparison of DNA damage in the early life stages of cod, Gadus morhua, originating from the Barents Sea and Baltic Sea     

Gunilla Ericson  Gun kerman  Birgitta Liewenborg  Lennart Balk 《Marine environmental research》1996,42(1-4)

DNA adducts in cod embryos and larvae were analysed by ³²P-postlabeling to test the hypothesis that anthropogenic substances, which could form reactive intermediates, are involved in the reproductive failure of cod (Gadus morhua) from the Baltic Sea. A comparison with cod from the Barents Sea was performed. The mean value of DNA adducts in cod embryos/larvae from the Baltic Sea was 2.3 nmol of adducts/mol nucleotides, compared to 0.12 nmol of adducts/mol nucleotides in the embryos/larvae from the Barents Sea.  相似文献   

Estimation of chlorophyll-a concentration in the Zhujiang Estuary from SeaWiFS data   总被引：1，自引：0，他引：1  

Chen Chuqun  Shi Ping  Magnus Larson  Lennart J&#;nsson 《海洋学报(英文版)》2002,21(1):55-65

The chlorophyll-a concentration is generally overestimated for the southern China coastalwaters if the default algorithm of the SeaDAS is employed. An algorithm is developed for retrieval of chlorophyll-a concentration in the Zhujiang Estuary, Guangdong Province, China, by using simulated reflectance data. The simulated reflectance is calculated corresponding to the SeaWiFS wavelength bands, via a general model by inputting measured water components, i.e. , the suspended sediment, chlorophyll-a, and yellow substance (DOC) concentration data of 130 samples. Empirical relationships of the chlorophyll-a concentration to 240 different band combinations are investigated based on the simulated reflectance data, and the band combination, R_5R_6/R_3R_4, is found to be the optimum one for the development of an algorithm valid for the Zhujiang Estuary. This algorithm is then employed to determine the chlorophyll-a concentration from SeaWiFS data. The estimated concentrations have a better accuracy than those obtai  相似文献   

Geo-Engineering to Confine Climate Change: Is it at all Feasible?     

Lennart Bengtsson 《Climatic change》2006,77(3-4):229-234

  相似文献   

Erratum to: Foreword: International Space Science Institute (ISSI) Workshop on the Earth’s Hydrological Cycle     

Lennart Bengtsson 《Surveys in Geophysics》2014,35(3):489-489

  相似文献   

Trends in chronic marine oil pollution in Danish waters assessed using 22 years of beached bird surveys     

Larsen JL  Durinck J  Skov H 《Marine pollution bulletin》2007,54(9):1333-1340

Beached bird surveys provide an important tool for monitoring the level of oil pollution at sea, which is the most significant observable cause of death for a large number of waterbird species and pose a serious threat to wintering seabird populations. Linear regression analyses of oil rates from the Danish 22 year dataset show a decline in the oil pollution level in offshore areas of the eastern North Sea and Skagerrak and in near-shore parts of the Kattegat; but a worsening in the offshore areas of the Kattegat. These results raise concern for species such as common scoter, velvet scoter, eider and razorbill, for which the Kattegat serves as a globally important wintering area. It is recommended that surveillance for oil spills is intensified in inner Danish waters, and that action is taken to make responses towards offenders faster, and penalties for oil seepage higher.  相似文献   

Structuring problems in sustainability science: The multi-level DPSIR framework   总被引：2，自引：0，他引：2  

Barry Ness  Stefan Anderberg  Lennart Olsson 《Geoforum》2010,41(3):479-488

Sustainability science needs approaches that allow for the integration of knowledge across disciplines and scales. This paper suggests an approach to conceptualize problems of unsustainability by embedding the Drivers-Pressure-State-Impact-Response (DPSIR) scheme within a multi-level institutional framework represented by Hägerstrand’s system of nested domains. The proposed taxonomy helps to decipher and to better understand key casual chains and societal responses at the appropriate spatial levels for particular sustainability problem areas. To illustrate the scheme more concretely the example of recent problem-solving efforts for Baltic Sea eutrophication driven by Swedish agriculture is examined. The discussion focuses on how the scheme fulfills the four research strategy requirements within the field of sustainability science and how the scheme is distinct from alternative approaches.  相似文献   

Observations of propagating double layers in a high current discharge     

Lennart Lindberg 《Astrophysics and Space Science》1988,144(1-2):3-13

Observations of current disruptions and strong electric fields along the magnetic field in a high-density (2×10¹⁹ m^–3), highly-ionized, moving, and expanding plasma column are reported. The electric field is interpreted in terms of propagating, strong electric double layers (3–5 kV).An initial plasma column is formed in an axial magnetic field (0.1 T) by means of a conical theta-pinch plasma gun. When an axial current (max 5 kA, 3–5 kV) is drawn through the column spontaneous disruptions and double-layer formation occur within a few microseconds.Floating, secondary emitting Langmuir probes are used. They often indicate very high positive potential peaks (1–2 kV above the anode potential during a few s) in the plasma on the positive side of the double layer. Short, intense bursts of HF radiation are detected at the disruptions.Paper dedicated to Professor Hannes Alfvén on the occasion of his 80th birthday, 30 May 1988.  相似文献