| 1. |
- Elgered, Gunnar, 1955
(författare)
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TROPOSPHERIC WET PATH-DELAY MEASUREMENTS
- 1982
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Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 30:3, s. 502-505
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Tidskriftsartikel (refereegranskat)
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| 2. |
- Gollvik, Stefan, 1948-
(författare)
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Investigations of problems related to the choice of the initial state for numerical weather prediction models
- 1982
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In numerical prediction models, where the wind and mass fields are described as free variables (so called primitive equation models), the initial state has to be carefully chosen, to avoid spurious oscillations in the forecast. This thesis deals with this initialization problem. The general approach has been to use simplified models in the investigations.In one of the papers an investigation is performed, where the quasigeostrophic divergence is included in the initial state. This is done in a two-layer linearized model, and the results show a generally lower level of the gravity modes than that of the geostrophic initialization.The other papers deal with various aspects of the non-linear normal mode initialization. One of the papers is a description of a derivation of a shallow water model on the equatorial ß-plane. This model is used to examine the generation and non-linear interactions of gravity modes, as a function of physical parameters, such as the Rossby-number and the depth of the fluid.It is found that the level of the gravity amplitudes, created by the model (with zero initial gravity amplitudes), is a little higher than the corresponding value for non-linear normal mode initialization. The gravity amplitudes get larger when the fluid is shallower, or if the Rossby-number increases.In the last paper another model is used. This is a mid-latitude ß-plane model, with only longitudinal dependence in the variables. With this model experiments, connected to the convergence problem of non-linear normal mode initialization, are performed. The results show that, if no forcing is included, the lack of convergence, for small depths is due to the non-linear interactions between the gravity modes. Experiments are also made where a linear forcing is present. It is shown that linearizing around a basic state, where the forcing is included is preferable to letting the forcing act on the non-linear side of the equations of the system.
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| 3. |
- Hansson, Hans Christen, et al.
(författare)
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Long range aerosol transport in Southern Sweden : An example of multtvariate statistical evaluation methodology
- 1984
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Ingår i: Nuclear Inst. and Methods in Physics Research, B. - 0168-583X. ; 3:1-3, s. 483-488
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Tidskriftsartikel (refereegranskat)abstract
- The utilization of multivariate statistical techniques is discussed with emphasis on the rather new method SIMCA, when applied to multielemental data. The procedures of scaling and normalizing are described. The data base used is from a project studying long range aerosol transport to southern Sweden. SIMCA reveals low variability in fine mode elemental composition in southerly air masses being clearly different from the elemental compositions found in northerly air masses.
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| 4. |
- Martinsson, Bengt G., et al.
(författare)
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Southern scandinavian aerosol composition and elemental size distribution characteristics dependence on air-mass history
- 1984
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Ingår i: Atmospheric Environment. - 0004-6981. ; 18:10, s. 2167-2182
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Tidskriftsartikel (refereegranskat)abstract
- The influence of aerosol long range transport in southern Sweden was investigated from a data base consisting of simultaneous cascade impactor measurements at three sampling stations, two coastal and one inland rural location. The study focused on S and heavy metals determined by particle induced X-ray emission (PIXE) analysis. The influence of local emissions was minimized by eliminating samples which were strongly suspected to be contaminated. These were identified through size distribution alterations in combination with the concentration levels obtained. Based on air mass back trajectories the samples were classified into either a southern, a northern or an eastern sector or into one of the buffer sectors located in between the sectors mentioned above. Sector S elemental concentrations were generally one order of magnitude higher than those of sector N, while intermediate concentrations were found in the E sector. Intercomparisons of simultaneous fine mode elemental concentration measurements classified into sectors S and N, respectively, provides a method for calculating the sector S foreign contribution of the elemental concentrations in southern Sweden. These calculations, not based on emission data, result in a foreign contribution of the order of 50-90 % (lowest for components like V and Ni and highest for Ti, Mn and Zn) to the metal concentrations. The multivariate statistical method SIMCA revealed that the sector S aerosol elemental composition was dependent on particle size in the accumulation mode. Elements such as S and V (or Ni) normally assumed to originate mainly from the same sources (fossil fuel combustion) were clearly separated and instead S clustered with K, Mn and Zn. This indicates that the transformation processes are more important for the covariation of S with other elements than the source origin. Transformation of SO 2 in hygroscopic particles rich in K., Mn and Zn (compared with less hygroscopic particles rich in V and Ni) is a possible mechanism which would explain the results found.
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