摘要:

AbstractIn a companion paper (Knox and Hay, 1983) the authors developed objective identification criteria, adaptable to machine processing methods, by relating the blocking anticyclone to its associated positive anomaly of 5‐day mean 500 mb height. Anomalies meeting the criteria were called ‘blocking signatures’. Moreover, by using an empirically derived pentad displacement threshold, it was possible to identify ‘blocking signature sequences’ corresponding to the life history of blocking episodes.In this paper we present and interpret the spatial and temporal distribution of blocking signatures during the 33 year period 1946 to 1978 inclusive. The frequency of occurrence is presented by area, and by longitude for each season and for the year. The results are, in general, in agreement with published studies for the oceans, but they also reveal a high frequency of blocking signatures over the North‐eastern Canadian Archipelago. This particular result, ‘the Baffin Island paradox’, is further investigated and rationalized.The interannual variation of blocking signature frequency over the Northern Hemisphere showed substantial fluctuations, particularly with regard to the more persistent episodes. However, because of the small size of the sample (33 years) relative to the time scale of the fluctuations (order of one decade) it was not possible to draw statisti

ISSN:0196-1748    

DOI:10.1002/joc.3370050102

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe annual rainfall distribution in west‐central Kenya (34°−38°E, 1°N–1°S) exhibits marked spatial variation because of the complicated nature of the local topography. The annual distributions are classified into a number of types on the basis of ‘rainfall seasons’. Over parts of the area of study, precipitation falling in July and August makes an important contribution to the yearly total (up to 33 per cent). The spatial variation of the rainfall in this period, during the so‐called ‘dry season’ over much of Kenya (between the two main ‘monsoon’ rains) is examined in some detail, especially its relationship with altitude. The distribution of the July and August rainfall indicates that it is associated with a westerly airstream overlying the lowest l

ISSN:0196-1748    

DOI:10.1002/joc.3370050103

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractA comparison of 5 to 20 years of qualitative and quantitative observations of hailfalls and hailstorms by three of the most active hail research groups in the world, shows very similar characteristics in a number of aspects of the hail phenomenon. The main similarities are that (a) the frequency of hailstorms decreases with increasing intensity, (b) the characteristics of hailstones (maximum size, number density) and hailswaths (length, surface area, energy) increase with increasing hailstorm intensity (i.e. lifetime, volume), (c) the single and multi‐cellular type storms are most frequent, whereas the supercell is rare, (d) the hail flux is not constant but pulsating, (e) the spatial structure of large hailswath is not uniform but contains ‘hailcores’ and (f) the post embryonic trajectories of common hailstones are often simple and similar.A number of differences are also observed between some of the regions, the main ones being (a) the upper limit of intensity of the more severe storms, (b) the succession and scale of cells in the storm development and (c) the percentage of various embryo types.A major conclusion of this comparative study is that the severe hailstorms, which cause most of the damage, are exceptional and show little similarity in the three regions. For the more requent light and moderate damaging ones, the study suggests that dynamics may be the result of pulsating phen

ISSN:0196-1748    

DOI:10.1002/joc.3370050104

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractMost weather elements are modified by urban areas. Humidity is among the least studied of the modified elements. Quantitative associations of urban and rural humidity variations with surface materials and land use in Lawrence, Kansas, a relatively small eastern Great Plains city are examined. Results are based on 45 dew point temperature distributions obtained in summer and autumn. Man‐made surface materials are consistently negatively correlated with humidity, whereas most natural surfaces are positively related. Residential and educational‐institutional land uses and undeveloped land are related positively to morning and afternoon humidity values; fewer significant relationships exist between evening humidity distributions and land

ISSN:0196-1748    

DOI:10.1002/joc.3370050105

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractMonthly and annual temperature and precipitation data were studied to determine the most efficient normal for predictive purposes using root mean square error. The number of years over which the normal was calculated was varied, and the value where the minimum error occurred was found to differ considerably from month to month, but there existed some conformity between stations within the same month.A Monte Carlo simulation was developed for the above procedure. The simulation of the station relocation for temperature data at Flemington, New Jersey suggested that the relocation could limit the most efficient length of the climatic normal to a shorter period. The results from a simulation of annual temperature trends at New Brunswick, New Jersey closely agreed with those found with actual data. Thus, the low value found for the most efficient normal is largely due to these trends. Relocations were found to have little effect on the most efficient normal for precipitation data.A modified procedure, varying the number of iterations, showed that RMSE was also dependent on the period of record selected. With this procedure the most efficient normal was found to be between 35 and 40 years for a station with minor relocations, and longer for a benchmark station. In most cases, however, there was little difference between a 10‐year normal and the most efficient norma

ISSN:0196-1748    

DOI:10.1002/joc.3370050106

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe goodness of fit of the Weibull and Rayleigh distributions to the observed wind speed distribution was investigated at seven coastal weather stations markedly influenced by local topography and possessing relatively long periods of record. Wind speeds will he Rayleigh or Weibull distributed if four conditions specifying the circular normal distribution for wind velocity are met. These conditions were not met at the seven stations because of the influences of local topography and storm systems. In all cases the null hypothesis that there is no difference between the Weibull or Rayleigh distributions and the observed distribution had to be rejected with the large sample sizes employed. The transformation of wind velocity involved in deriving the Weibull distribution helps make the distribution more circular normal and the Weibull distribution gave better fits than the Rayleigh distribution. The fits were generally best al those stations with the most circular normal wind velocity distributions and the lowest percentage of calms.

ISSN:0196-1748    

DOI:10.1002/joc.3370050107

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe many considerations which come into play in the determination of sites for wind energy conversion systems (WECS) are synthesized from a cross‐section of the literature. Prevailing strategies select candidate regions from interpolations of existing wind data and narrow the selection according to local terrain and sometimes vegetative and/or geomorphological indicators. The economic success of a WECS project requires that wind characteristics prove better than certain minima so that planners are obliged to apply scrupulous observational and statistical procedures both in making preliminary estimates of the wind climate and, afterwards, in validating the estimates at the chosen final site(s

ISSN:0196-1748    

DOI:10.1002/joc.3370050108

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

ISSN:0196-1748    

DOI:10.1002/joc.3370050109

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

ISSN:0196-1748    

DOI:10.1002/joc.3370050110

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

ISSN:0196-1748    

DOI:10.1002/joc.3370050111

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY