摘要:

AbstractThis paper presents a case study to illustrate the value of water vapour and other satellite imagery, when used in conjunction with a conceptual model, to help the forecaster identify deficiencies in numerical model forecast guidance and to diagnose what is happening on the mesoscale. The specific application discussed is the triggering of frontal thunderstorms by the pattern of overrunning and ascent associated with an upper‐level vortex in the vicinity of a trailing cold fron

ISSN:1350-4827    

DOI:10.1002/met.5060010401

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractAircraft measurements of SO2were made on seven separate occasions to test whether trajectory methods could be used to predict realistic concentrations for the UK composite plume and identify individual sources. The profiles between computed and observed concentrations in south‐westerly meteorological situations were comparable but the agreement is less marked in different and more complex condition

ISSN:1350-4827    

DOI:10.1002/met.5060010402

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractA climatology of clear sky ultraviolet (UV) levels, weighted by the sensitivity of human skin, is presented. Away from the tropics the values are shown to be strongly dependent on the time of year, with peak values occurring in midsummer. Near the equator two annual maxima occur due to the twice‐yearly passage of the sun over the equator. The second factor influencing clear‐sky UV levels is the total ozone amount. In mid latitudes, because of lower ozone amounts, UV levels are generally higher around the autumn equinox than at the spring equinox. High UV levels also occur locally in spring due to the Antarctic ozone hole, although Arctic spring values have not yet been significantly affected. Next, total ozone amounts are shown to be related to meteorological parameters. Using a simple representation of the UV level in terms of the solar zenith angle and total ozone amount, an operational procedure for forecasting UV levels is outlined Finally, some comparisons with observed UV levels are presented and a sample UV forecast is sh

ISSN:1350-4827    

DOI:10.1002/met.5060010403

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractA heavy rainfall event which produced floods in Catalonia (Spain) during October 1987 is presented. Convection was located over the same area for several days, producing up to 431 mm of rain (67% of the mean annual rainfall). The synoptic‐scale pattern and forcing are studied using objective techniques, while mesoscale features are investigated with satellite imagery and subjective surface analysis. Strong quasi‐geostrophic forcing for vertical motion was diagnosed at low levels white only a weak forcing was evident at 500 hPa. Convective and latent instability characterized the region during the period of heavy rainfall. Also, there was strong low‐level moisture convergence combined with high ‐values of precipitable water over the north‐west Mediterranean Sea. Composite charts delineating the area covered by the indicated synoptic factors seem to be an effective tool for identifying the area where mesoscale focusing mechanisms became effective. Sub‐synoptic analyses show that the main focusing mechanism was a quasi‐stationary convergence line, located near the coast of Catalonia. This lay between the south‐eastern warm and humid flow, caused by a weak low centred north of the Algerian coast, and the cold outflow from a mesohigh located in Catalonia and mainly originated by the orographic blocking

ISSN:1350-4827    

DOI:10.1002/met.5060010404

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractWe describe a Bayesian approach to estimating the economic benefits from improved forecasts. The approach takes explicit account of how decision makers use forecast information, and can provide more reliable estimates of benefits than methods based on mitigated impacts. We discuss some practical considerations in applying the approach to weather and climate forecasts, and describe the results of an application to ENSO prediction.

ISSN:1350-4827    

DOI:10.1002/met.5060010405

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractOver the last decade global numerical weather prediction models have become sufficiently sophisticated to forecast the movement of tropical cyclones with a reasonable degree of accuracy. This paper describes the work being done at the Met. Office in Bracknell, UK, to improve and verify track forecasts, looking particularly at methods of ‘bogussing’ the initial conditions and of verifying the foreca

ISSN:1350-4827    

DOI:10.1002/met.5060010406

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThis paper examines the practical importance of convective gusts for operators of wind‐sensitive systems and for designers of Wind‐sensitive structures. The mechanics of gusts associated with turbulence (driven by momentum) and convective eddies (driven by buoyancy) are discussed‐Statistical analysis of gusts and gust factors is presented. This shows that extreme gust factors are always produced by the convective mechanism whereas extreme gusts can be produced by either mechanism. Severe convective gusts are shown to have important consequences for operators of Wind‐sensitive systems because they defy precise prediction, they can be isolated in their occurrence, they can occur in quite moderate mean winds and they can be associated with sudden changes of wind direction. Extreme convective gusts are of less importance to designers of wind‐sensitive structures. They are shown to have a relatively small influence on the magnitude of the predicted extreme gusts taken as design criteria for such structures. Nevertheless, there is a significant chance that when such extreme gusts occur, they are produced by the convective mechanism. When this occurs, the predicted aerodynamic effect may be underestimated, to some extent, because of inertial forces which change the nature of the flow and may increase th

ISSN:1350-4827    

DOI:10.1002/met.5060010407

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

ISSN:1350-4827    

DOI:10.1002/met.5060010408

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

ISSN:1350-4827    

DOI:10.1002/met.5060010409

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY