Modulation transfer functions of some solar recording films     

P. N. Brandt 《Solar physics》1967,2(2):211-222

The modulation-transfer functions (MTF) of four solar recording films (Eastman-Kodak: 103a-G, IV E, RAR-SO-375; Gevaert: Duplopan-Rapid) are measured with the aid of an interference device. The MTF is used to estimate the smallest detectable element of a two-dimensional pattern; the so-called detectability threshold a ^* depends on: intensity modulation m, square of MTF, required signal-to-noise ratio q, gamma and granularity of the film. The calculated values of a ^* for the four emulsions are given in Table II. Finally the influence of exposure time on image quality is discussed.Mitteilungen aus dem Fraunhofer Institut Nr. 74.  相似文献   

A long-term Arctic snow depth record from Abisko, northern Sweden, 1913–2004     

Jack Kohler  Ola Brandt  Margareta Johansson  Terry Callaghan 《Polar research》2006,25(2):91-113

A newly digitized record of snow depth from the Abisko Scientific Research Station in northern Sweden covers the period 1913-present. Mean snow depths were taken from paper records of measurements made on a profile comprising 10 permanent stakes. This long-term record yields snow depths consistent with two other shorter term Abisko records: measurements made at another 10-stake profile (1974-present) and at a single stake (1956-present). The measurement interval is variable, ranging from daily to monthly, and there are no data for about half of the winter months in the period 1930-1956. To fill the gaps, we use a simple snowpack model driven by concurrent temperature and precipitation measurements at Abisko. Model snow depths are similar to observed; differences between the two records are comparable to those between profile and single stake measurements. For both model and observed snow depth records, the most statistically significant trend is in winter mean snow depths, amounting to an increase of about 2 cm or 5 % of the mean per decade over the whole measurement period, and 10% per decade since the 1930-40s, but all seasonal means of snow depth show positive trends on the longest timescales. However, the start, end, and length of the snow season do not show any statistically significant long-term trends. Finally, the relation between the Arctic Oscillation index and Abisko temperature, precipitation and snow depth is positive and highly significant, with the best correlations for winter.  相似文献   

Accelerated climate change and its potential impact on Yak herding livelihoods in the eastern Tibetan plateau   总被引：1，自引：0，他引：1  

Michelle A. Haynes  King-Jau Samuel Kung  Jodi S. Brandt  Yang Yongping  Donald M. Waller 《Climatic change》2014,123(2):147-160

The Tibetan Plateau has experienced rapid warming like most other alpine regions. Regional assessments show rates of warming comparable with the arctic region and decreasing Asian summer monsoons. We used meteorological station daily precipitation and daily maximum and minimum temperature data from 80 stations in the eastern Tibetan Plateau of southwest China to calculate local variation in the rates and seasonality of change over the last half century (1960–2008). Daily low temperatures during the growing season have increased greatly over the last 24 years (1984–2008). In sites of markedly increased warming (e.g., Deqin, Yunnan and Mangya, Qinghai), daily and growing season daily high temperatures have increased at a rate above 5 °C/100 years. In Deqin, precipitation prior to the 1980s fell as snow whereas in recent decades it has shifted to rain during March and April. These shifts to early spring rains are likely to affect plant communities. Animals like yaks adapted to cold climates are also expected to show impacts with these rising temperatures. This region deserves further investigation to determine how these shifts in climate are affecting local biodiversity and livelihoods.  相似文献   

Mechanism on how the spring Arctic sea ice impacts the East Asian summer monsoon   总被引：2，自引：0，他引：2  

Dong Guo  Yongqi Gao  Ingo Bethke  Daoyi Gong  Ola M. Johannessen  Huijun Wang 《Theoretical and Applied Climatology》2014,115(1-2):107-119

Observational analysis and purposely designed coupled atmosphere–ocean (AOGCM) and atmosphere-only (AGCM) model simulations are used together to investigate a new mechanism describing how spring Arctic sea ice impacts the East Asian summer monsoon (EASM). Consistent with previous studies, analysis of observational data from 1979 to 2009 show that spring Arctic sea ice is significantly linked to the EASM on inter-annual timescales. Results of a multivariate Empirical Orthogonal Function analysis reveal that sea surface temperature (SST) changes in the North Pacific play a mediating role for the inter-seasonal connection between spring Arctic sea ice and the EASM. Large-scale atmospheric circulation and precipitation changes are consistent with the SST changes. The mechanism found in the observational data is confirmed by the numerical experiments and can be described as follows: spring Arctic sea ice anomalies cause atmospheric circulation anomalies, which, in turn, cause SST anomalies in the North Pacific. The SST anomalies can persist into summer and then impact the summer monsoon circulation and precipitation over East Asia. The mediating role of SST changes is highlighted by the result that only the AOGCM, but not the AGCM, reproduces the observed sea ice-EASM linkage.  相似文献   

Greenland Ice Sheet Contribution to Future Global Sea Level Rise based on CMIP5 Models简     

YAN Qing  WANG Huijun  Ola M.JOHANNESSEN  ZHANG Zhongshi 《大气科学进展》2014,31(1):8-16

Sea level rise （SLR） is one of the major socioeconomic risks associated with global warming. Mass losses from the Greenland ice sheet （GrIS） will be partially responsible for future SLR, although there are large uncertainties in modeled climate and ice sheet behavior. We used the ice sheet model SICOPOLIS （Simulation COde for POLythermal Ice Sheets） driven by climate projections from 20 models in the fifth phase of the Coupled Model Intercomparison Project （CMIP5） to estimate the GrlS contribution to global SLR. Based on the outputs of the 20 models, it is estimated that the GrIS will contribute 0-16 （0-27） cm to global SLR by 2100 under the Representative Concentration Pathways （RCP） 4.5 （RCP 8.5） scenarios. The projected SLR increases further to 7-22 （7-33） cm with 2~basal sliding included. In response to the results of the multimodel ensemble mean, the ice sheet model projects a global SLR of 3 cm and 7 cm （10 cm and 13 cm with 2~basal sliding） under the RCP 4.5 and RCP 8.5 scenarios, respectively. In addition, our results suggest that the uncertainty in future sea level projection caused by the large spread in climate projections could be reduced with model-evaluation and the selective use of model outputs.  相似文献   

New multifunctional hunting landscapes in Denmark     

Andreas Aagaard Christensen  Stig Roar Svenningsen  Maria Sofie Lommer  Jesper Brandt 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2014,114(1):25-40

Between 1992 and 2008 subsidization of mandatory set aside land under the EU Common Agricultural Policy (CAP) gave rise to the establishment of a characteristic type of multifunctional hunting landscapes in Denmark, primarily located on fallow land in tilled valley bottoms. A national survey of these landscapes in 2006 has been carried out and 1061 hunting areas have been identified nationwide. Subsidies relating to set aside land acted as a supplementary type of income, which supported the development of multifunctional land use on marginal soils where the income from hunting and subsidies in combination was a viable alternative to monofunctional rotational agriculture. Hunting landscapes developed as the consequence of landscape management strategies designed to comply with the requirements of the CAP while improving habitat conditions for wildlife and increasing income from hunting rental activities. Forty-seven percent of the hunting landscapes in 2006 were in rotational production in 2010 while 19% were used for other agricultural purposes and 34% were taken out of the subsidy regime and removed from the general agricultural register. In 2012, a total of 431 such areas ? 41% of the areas identified in 2006 ? were still used for hunting. The number and geographical distribution of the hunting landscapes seems closely related to the potential average hunting rent, the level of urbanisation and the occurrence of manorial estates with traditions for multifunctional land use as part of their economic strategy. Implications for the ongoing discussion on land use policy concerning land sharing vs. land sparing is discussed.  相似文献   

Obituary          下载免费PDF全文

WANG Hui-Jun  Ola M. JOHANNESSEN 《大气和海洋科学快报》2014,(4)

正In Memory of Dr.Peter James LAMB(21 June 1947-28 May 2014)Dr.Peter James LAMB,Editor of Atmospheric and Oceanic Science Letters(AOSL);George Lynn Cross Research Professor of Meteorology at the University of Oklahoma;Director,NOAA Cooperative Institute of Mesoscale Meteorological Studies,passed away in his home in Norman,Oklahoma on 28 May 2014.He was born on 21 June 1947  相似文献   

The Equatorial Undercurrent in the central Atlantic and its relation to tropical Atlantic variability   总被引：1，自引：0，他引：1  

Peter Brandt  Andreas Funk  Alexis Tantet  William E. Johns  Jürgen Fischer 《Climate Dynamics》2014,43(11):2985-2997

Seasonal to interannual variations of the Equatorial Undercurrent (EUC) in the central Atlantic at 23°W are studied using shipboard observation taken during the period 1999–2011 as well as moored velocity time series covering the period May 2005–June 2011. The seasonal variations are dominated by an annual harmonic of the EUC transport and the EUC core depth (both at maximum during September), and a semiannual harmonic of the EUC core velocity (maximum during April and September). Substantial interannual variability during the period of moored observation included anomalous cold/warm equatorial Atlantic cold tongue events during 2005/2008. The easterly winds in the western equatorial Atlantic during boreal spring that represent the preconditioning of cold/warm events were strong/weak during 2005/2008 and associated with strong/weak boreal summer EUC transport. The anomalous year 2009 was instead associated with weak preconditioning and smallest EUC transport on record from January to July, but during August coldest SST anomalies in the eastern equatorial Atlantic were observed. The interannual variations of the EUC are discussed with respect to recently described variability of the tropical Atlantic Ocean.  相似文献   

Sedimentary evolution and environmental history of Lake Van (Turkey) over the past 600 000 years   总被引：1，自引：0，他引：1  

Mona Stockhecke  Michael Sturm  Irene Brunner  Hans‐Ulrich Schmincke  Mari Sumita  Rolf Kipfer  Deniz Cukur  Ola Kwiecien  Flavio S. Anselmetti 《Sedimentology》2014,61(6):1830-1861

The lithostratigraphic framework of Lake Van, eastern Turkey, has been systematically analysed to document the sedimentary evolution and the environmental history of the lake during the past ca 600 000 years. The lithostratigraphy and chemostratigraphy of a 219 m long drill core from Lake Van serve to separate global climate oscillations from local factors caused by tectonic and volcanic activity. An age model was established based on the climatostratigraphic alignment of chemical and lithological signatures, validated by ⁴⁰Ar/³⁹Ar ages. The drilled sequence consists of ca 76% lacustrine carbonaceous clayey silt, ca 2% fluvial deposits, ca 17% volcaniclastic deposits and 5% gaps. Six lacustrine lithotypes were separated from the fluvial and event deposits, such as volcaniclastics (ca 300 layers) and graded beds (ca 375 layers), and their depositional environments are documented. These lithotypes are: (i) graded beds frequently intercalated with varved clayey silts reflecting rising lake levels during the terminations; (ii) varved clayey silts reflecting strong seasonality and an intralake oxic–anoxic boundary, for example, lake‐level highstands during interglacials/interstadials; (iii) CaCO₃‐rich banded sediments which are representative of a lowering of the oxic–anoxic boundary, for example, lake level decreases during glacial inceptions; (iv) CaCO₃‐poor banded and mottled clayey silts reflecting an oxic–anoxic boundary close to the sediment–water interface, for example, lake‐level lowstands during glacials/stadials; (v) diatomaceous muds were deposited during the early beginning of the lake as a fresh water system; and (vi) fluvial sands and gravels indicating the initial flooding of the lake basin. The recurrence of lithologies (i) to (iv) follows the past five glacial/interglacial cycles. A 20 m thick disturbed unit reflects an interval of major tectonic activity in Lake Van at ca 414 ka bp . Although local environmental processes such as tectonic and volcanic activity influenced sedimentation, the lithostratigraphic pattern and organic matter content clearly reflect past global climate changes, making Lake Van an outstanding terrestrial archive of unprecedented sensitivity for the reconstruction of the regional climate over the last 600 000 years.  相似文献