Effective algorithms for sourcewise approximation of geopotential fields     

P. I. Balk  A. S. Dolgal  A. V. Pugin  A. V. Michurin  A. A. Simanov  A. F. Sharkhimullin 《Izvestiya Physics of the Solid Earth》2016,52(6):896-911

A specialized class of fast algorithms for sourcewise approximation of potential fields, which is intended for mass use in the applications associated with handling large and extralarge measurement data, is developed. Pursuing the objective of the work, we included two informal requirements in the set of the criteria to be met by our algorithms: they should have a sufficiently simple mathematical structure which is transparent for the geophysicist and they should be quite easy to program. Both these requirements are dictated by the present-day practice existing in geology, when the absence of the centralized provision of program products by the geological organizations makes the interpreter create the necessary software themselves. Among the distinguishing features of the three suggested algorithms is the fact that the dimensionality of the approximating construction is not specified a priori but is determined a posteriori. Due to this, it turned out to be helpful to combine one of these algorithms with the fast wavelet transform, which enables the dimension of the future sourcewise approximation and the amount of computing resources required for the implementation of the main algorithm to be estimated a priori. The examples of the practical application of these technologies are presented. The promising paths for the future development of the algorithms for sourcewise approximation of the potential fields are outlined.  相似文献   

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

Lennart Bengtsson 《Surveys in Geophysics》2014,35(3):485-488

  相似文献   

Efficiency of mixing by a turbulent jet in a stably stratified fluid     

Magnus Larson  Lennart Jnsson 《Dynamics of Atmospheres and Oceans》1996,24(1-4)

Mixing in a two-layer stably stratified fluid by a turbulent jet was studied by a laboratory experiment. A non-swirling jet was discharged vertically downwards in a confined fluid system consisting initially of a top layer of fresh water and a bottom layer of salt water. In total, 16 experimental cases were considered, where the diameter and exit velocity of the jet were varied together with the density difference between the top and bottom layer. Vertical density profiles were determined from conductivity measurements. A three-layer density structure developed in all cases with an intermediate layer that grew in size with time elapsed as fresh and salt water were mixed. The mixing efficiency, defined as the percentage of the supplied kinetic jet energy that is used for increasing the potential energy of the fluid system, was related to a densimetric Froude number based on the intermediate layer depth. Overall, the calculated jet mixing efficiency displayed higher values than comparable efficiencies for destratification with air-bubble plumes.  相似文献   

Model　Study　on　the　Interannual　Variability　of　Asian　Winter　Monsoon　and　Its　Influence   总被引：40，自引：4，他引：40  

Ji Liren  Sun Shuqing  Klaus Arpe  Lennart Benglsson 《大气科学进展》1997,14(1):1-22

ＭｏｄｅｌＳｔｕｄｙｏｎｔｈｅＩｎｔｅｒａｎｎｕａｌＶａｒｉａｂｉｌｉｔｙｏｆＡｓｉａｎＷｉｎｔｅｒＭｏｎｓｏｏｎａｎｄＩｔｓＩｎｆｌｕｅｎｃｅＪｉＬｉｒｅｎ（纪立人），ＳｕｎＳｈｕｑｉｎｇ（孙淑清）ＩｎｓｔｉｔｕｔｅｏｆＡｔｍｏｓｐｈｅｒｉｃＰｈｙ...  相似文献   

Three-dimensional assembly technologies for the interpretation of gravimetric data     

P. I. Balk  A. S. Dolgal 《Doklady Earth Sciences》2009,427(2):971-974

The assembly method of solving a three-dimensional ore-type inverse problem is considered. The method is based on the unity of a grid (finite-element) approximation of a dense medium and a special type of structuring the iteration process of selection which makes it possible to effectively observe all a priori restrictions on the model of field sources. The examples of interpretations of gravity anomalies are presented.  相似文献   

Water column monitoring near oil installations in the North Sea 2001-2004     

Hylland K  Tollefsen KE  Ruus A  Jonsson G  Sundt RC  Sanni S  Røe Utvik TI  Johnsen S  Nilssen I  Pinturier L  Balk L  Barsiene J  Marigòmez I  Feist SW  Børseth JF 《Marine pollution bulletin》2008,56(3):414-429

Fisheries have been vital to coastal communities around the North Sea for centuries, but this semi-enclosed sea also receives large amounts of waste. It is therefore important to monitor and control inputs of contaminants into the North Sea. Inputs of effluents from offshore oil and gas production platforms (produced water) in the Norwegian sector have been monitored through an integrated chemical and biological effects programme since 2001. The programme has used caged Atlantic cod and blue mussels. PAH tissue residues in blue mussels and PAH bile metabolites in cod have confirmed exposure to effluents, but there was variation between years. Results for a range of biological effects methods reflected exposure gradients and indicated that exposure levels were low and caused minor environmental impact at the deployment locations. There is a need to develop methods that are sufficiently sensitive to components in produced water at levels found in marine ecosystems.  相似文献   

Implementing the Gaia Astrometric Global Iterative Solution (AGIS) in Java     

William O’Mullane  Uwe Lammers  Lennart Lindegren  Jose Hernandez  David Hobbs 《Experimental Astronomy》2011,31(2-3):215-241

  相似文献   

On the evaluation of temperature trends in the tropical troposphere     

Lennart Bengtsson  Kevin I. Hodges 《Climate Dynamics》2011,36(3-4):419-430

A series of model experiments with the coupled Max-Planck-Institute ECHAM5/OM climate model have been investigated and compared with microwave measurements from the Microwave Sounding Unit (MSU) and re-analysis data for the period 1979?C2008. The evaluation is carried out by computing the Temperature in the Lower Troposphere (TLT) and Temperature in the Middle Troposphere (TMT) using the MSU weights from both University of Alabama (UAH) and Remote Sensing Systems (RSS) and restricting the study to primarily the tropical oceans. When forced by analysed sea surface temperature the model reproduces accurately the time-evolution of the mean outgoing tropospheric microwave radiation especially over tropical oceans but with a minor bias towards higher temperatures in the upper troposphere. The latest reanalyses data from the 25?year Japanese re-analysis (JRA25) and European Center for Medium Range Weather Forecasts Interim Reanalysis are in very close agreement with the time-evolution of the MSU data with a correlation of 0.98 and 0.96, respectively. The re-analysis trends are similar to the trends obtained from UAH but smaller than the trends from RSS. Comparison of TLT, computed from observations from UAH and RSS, with Sea Surface Temperature indicates that RSS has a warm bias after 1993. In order to identify the significance of the tropospheric linear temperature trends we determined the natural variability of 30-year trends from a 500?year control integration of the coupled ECHAM5 model. The model exhibits natural unforced variations of the 30?year tropospheric trend that vary within ±0.2?K/decade for the tropical oceans. This general result is supported by similar results from the Geophysical Fluid Dynamics Laboratory (GFDL) coupled climate model. Present MSU observations from UAH for the period 1979?C2008 are well within this range but RSS is close to the upper positive limit of this variability. We have also compared the trend of the vertical lapse rate over the tropical oceans assuming that the difference between TLT and TMT is an approximate measure of the lapse rate. The TLT?CTMT trend is larger in both the measurements and in the JRA25 than in the model runs by 0.04?C0.06?K/decade. Furthermore, a calculation of all 30?year TLT?CTMT trends of the unforced 500-year integration vary between ±0.03?K/decade suggesting that the models have a minor systematic warm bias in the upper troposphere.  相似文献   

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   

High-resolution correlations between Gotland and Estonia near the base of the Wenlock     

Lennart Jeppsson  Peep Mnnik 《地学学报》1993,5(4):348-358

The strata of the Ireviken Event can be correlated between Gotland, Sweden and the Viki core on Saaremaa, Estonia, with a high degree of precision. Most of the ten datum planes are found with a precision of better than 0.1 m in the Lower and upper Visby Beds on Gotland and high in the Mustjala Member of the Jaani Formation on Saaremaa. Five of the latest Llandovery–early Wenlock units defined by these datum planes are between c. 0.12 and 1.77 m thick on Gotland and 0.12 and 0.67 m in Estonia. The duration of each was between a few thousand and c. 31 000 years. The stratigraphic resolution achieved in the interval of the Ireviken Event is 10,000 years. Ultimate range ends are lacking within a preceding, slightly longer interval, but the pattern of intermittent presence of some taxa agrees well with an unchanged relative rate of sedimentation. Their coeval presence in different places indicates ecological, regional or more widespread changes.  相似文献