摘要:

AbstractThe state of acidifying air pollution in Europe is reviewed, as is the ability and limitation of models to simulate concentrations and depositions. The lack of complete quality in emission data is often a significant problem in these modelling studies. Nevertheless, models, for all their uncertainties, can play an important, if not totally reliable, role in assessing the origins of acidic depositions on any area. Although emissions have changed over the years, generally having decreased over the last decade, the time trend in measured depositions appears to indicate no very simple response to these overall decreases: the unequal changes in different parts of the continent and year‐to‐year changes in weather preclude such simplicity. The total impact of acid deposition on the environment, which is reviewed, depends not only on the average magnitude but also on the range of magnitudes of the depositions, and in particular on the occurrence of severe episodes. Some discussion of the probability distribution function is gi

ISSN:0035-9009    

DOI:10.1002/qj.49711750002

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe recent analytic theory for the barotropic motion of an initially symmetric vortex on a beta plane at rest presented by Smith and Ulrich is extended to the case of a horizontal shear flow, enabling the precise effects of shear on vortex motion to be isolated. These effects are characterized by the contribution of the shear‐related terms in the vorticity equation to the evolution and structure of the wave‐number‐1 component of the vortex asymmetry. The analysis proceeds on the assumption that a general shear flow may be adequately approximated by the first three terms of a double Taylor‐series expansion about the initial vortex centre. The manner in which the linear and quadratic terms of this expansion affect the asymmetries is illustrated in detail for a zonal shear flow with a linear or quadratic variation in the meridional direction.For tropical‐cyclone‐scale vortices, the theory shows excellent agreement with equivalent numerical calculations for a period of one or two days. As well as providing insight into the effects of horizontal shear on tropical‐cyclone motion, the calculations have the potential to assist in the design of ‘bogus’ vortices for the initialization of dynamically based tropical‐cycl

ISSN:0035-9009    

DOI:10.1002/qj.49711750003

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractDiabatic heating and net condensation rates during winter are calculated over the Mediterranean and surrounding areas from the 1982‐88 ECMWF initialized analyses using the residual method for the heat and moisture budgets. The steady‐state contributions over the Mediterranean are found to be prominent as in the tropics, but contrary to the case of the tropics the transients contributions in the Mediterranean, attributed to cyclonic activity, are not at all negligible.A composite Cyprus low was constituted from 67 typical cyclones in the eastern Mediterranean. The diabatic heating and net condensation distribution indicate vigorous sea fluxes especially in the lee of the Turkish mountains over the Aegean Sea where the air‐sea contrast is maximized. In contrast with other regions, the maximum in the vertical profile of diabatic heating due to latent heat release is found at a lower altitude of about 850 hPa. It is suggested that this fact has important implications in modelling Mediterranean cyc

ISSN:0035-9009    

DOI:10.1002/qj.49711750004

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractMicrometeorological measurements of evaporation were made for the first six weeks of the dry season at a fallow savannah site in the Sahel. The evaporation fell from typically 4.5 mm per day at the start of the dry season to 1.5 mm per day six weeks later. The surface conductance was modelled in terms of empirical functions of time of day, and the number of days since the final rain of the season. It was found that there was little variation in surface conductance within each day, with no significant correlation with solar radiation and only a weak correlation with humidity deficit. Daily values of the surface conductance necessary to estimate the actual evaporation, from the data provided by a standard climate station, were also derived.

ISSN:0035-9009    

DOI:10.1002/qj.49711750005

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe morphology and density of ice depositions grown on fixed cylinders are studied in the ranges of Macklin's parameter,X, and of the Stokes number,K, of 0.5

ISSN:0035-9009    

DOI:10.1002/qj.49711750006

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe morphology and density of deposits grown on rotating cylinders of 0.5 cm radius, collecting droplets of median volume radius Δ = 10 μm, are studied. The wind speed and temperature are regulated so that Macklin's parameter and Stokes number are 0.5

ISSN:0035-9009    

DOI:10.1002/qj.49711750007

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractA model is presented of the turbulent deposition of cloud water and dissolved species to regions of complex topography where cloud forms in contact with the ground. A three‐dimensional airflow model (FLOWSTAR) which includes a treatment of atmospheric stability and boundary‐layer turbulence is used. Versions of the model are described which include either simple calculations of liquid‐water content or detailed calculations of the cloud microphysics. Both a simple equilibrium model of cloud‐water chemistry and a detailed model including the explicit calculation of the chemical processes in individual droplet size categories are used.The deposition velocities of the cloud droplets to the terrain are calculated from recent measurements of cloud‐water deposition to forest and moorland.It is found that good estimates of deposition may be obtained using the simplest cloud‐water and chemistry models with deposition velocities parametrized in terms of a mean droplet radius. The results indicate that the deposition is a very strong function of position within the terrain. The implications of this for the deposition of phytotoxic species to the flora and the deposition of radio‐nuclides following a nuclear accident a

ISSN:0035-9009    

DOI:10.1002/qj.49711750008

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractA survey of the distribution and scale of layers of enhanced and depleted ozone in the lower stratosphere was conducted over the altitude range 9.5–21.5 km using data recorded by balloon‐borne sondes released at various sites around the world.The results show clearly that lamination is primarily a winter‐spring phenomenon from subtropical to polar regions in both hemispheres, and seems to be linked to the presence of the polar vortex. A peak altitude of occurrence was found near 14 km. The interannual fluctuations in lamina abundance were found to be extremely large, varying at high latitudes by as much as a factor of three.Both the mean vertical thickness of the laminae and the associated rise or fall in ozone partial pressure within them vary progressively with latitude, season and alt

ISSN:0035-9009    

DOI:10.1002/qj.49711750009

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe model for global radiation at the sea surface proposed by Dobson and Smith was tested for the Inner German Bight, North Sea with an 18‐year time series of 3‐hourly measurements of cloudiness and daily global radiation. The model, with unchanged parameters that were originally derived for oceanic stations, is suitable for use in coastal seas and seems best suited for simulating global radiation for long time‐scales. Modelled monthly means of global radiation deviate from the measured monthly means by less than 5% except for June and July (11%), two months with large solar insolation. For short time‐scales, root‐mean‐square errors from 14% (for 10 days) to 24% (for 1 day) occur. The application of the bulk model will be particularly useful to researchers working in the marine coastal areas of nort

ISSN:0035-9009    

DOI:10.1002/qj.49711750010

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

ISSN:0035-9009    

DOI:10.1002/qj.49711750011

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY