摘要:

AbstractTwo rainfall series for the Sahel region of West Africa have been updated to 1983. Annual and monthly series are presented and analysed. Relatively dry conditions have persisted in this region since 1968 due mainly to a decline in rainfall during August, the wettest month. Drought has probably been less severe in this region during the late rather than the early 1970s because of better rainfall early in the season. It is suggested that agricultural planning should be based on rainfall records for the last twenty years.

ISSN:0196-1748    

DOI:10.1002/joc.3370050402

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractExtensive measurements of solar radiation at Sede Boqer, Israel revealed considerable changes in the direct and diffuse solar irradiance on clear days beginning in September 1982. The direct beam irradiance showed a consistent decrease of about 10 per cent compared to clear‐day values of the previous year. The diffuse irradiance data showed an increase of about 50 per cent and the ratio between diffuse and global irradiance increased by 63 per cent. The prominent effects were observed from autumn 1982 to spring 1983. Weak effects were still noticeable in winter 1983/1984 although a tendency of back to ‘normal’, though not quite, is evident in spring and summer 1984. Another interesting result of the analysis is that only very small changes in global irradiance were evident.These observations may be attributed to the El Chichon dust cloud since they are in accord with various types of measurements made of the dust cloud in other areas of the

ISSN:0196-1748    

DOI:10.1002/joc.3370050403

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractAssociation between the all‐India summer monsoon (June to September) rainfall and an index of the Southern Oscillation (SO) is studied in relation to the vagaries of the monsoon rainfall and the seasonal characteristics of the SO. The Southern Oscillation index (SOI) used is the difference of normalized sea surface pressure between Tahiti and Darwin, two stations located in the core regions of the circulation systems associated with the SO. The data length of 46 years from 1935 to 1980 is used in the detailed examination of the nature of association between these parameters.The SOI values of different months and standard seasons show opposite tendencies during deficient and excess years of all‐India monsoon rainfall. The correlation coefficients (CC) between the all‐India monsoon rainfall series and the SOIs of summer monsoon (JJA), autumn (SON) and winter (DJF) minus spring (MAM) seasons are significant at the 1 per cent level. The correlations have been examined by dividing the series into two equal halves of 23 years and different sliding window widths of 10, 20 and 30 years. The least squares fit line is represented by the equation y (all‐India monsoon rainfall) =85.9 ‐ 2.7x (DJF minus MAM, SOI), the variance explained by this line is about 13 per cent. In view of the large spatial variability of the summer monsoon rainfall the correlations are examined for the rainfall series of various meteorological subdivisions of the country. The CC between the monsoon rainfall of the subdivisions north of 16°N and west of 80°E and the SOI series of DJF minus MAM is significant at the 5 per cent level or above.Potentialities of the SOI of DJF minus MAM, an important premonsoon circulation parameter, are examined for the seasonal prediction of Indian summer monsoon rainfall, and the limitations of single parameter prediction models ar

ISSN:0196-1748    

DOI:10.1002/joc.3370050404

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractPrincipal component analysis has been used to group the European Mediterranean stations into homogeneous regions. The annual rainfall records used were from 90 stations distributed all over the European Mediterranean countries.Major components were selected by a dominant‐variance selection rule, called rule N. The most important component corresponds to a fairly uniform field, the second marks the climatological distribution of cyclonic disturbances, the third shows a gradient from north‐east to south‐west and the fourth exhibits the existence of two centres of anomalies with a negative ridge and a positive value on each side.A cluster analysis based on these major eigenvectors shows the existence of five climatic regions. A subjective method, using the zero‐line characterizing the significant eigenvectors, shows similar

ISSN:0196-1748    

DOI:10.1002/joc.3370050405

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractSatellite infrared imagery for three years (1980, 1981, 1982) are analysed using a colour enhancement technique to derive a cloud climatology of the southwest United States summer ‘monsoon’. Diurnally‐stratified and weekly statistics are obtained for different cloud levels and used as an index of the monsoon intensity in each year. Strong diurnal variations in cloudiness, related to surface heating, are identified for July and August, as are marked interannual differences. These regional‐scale cloud variations are found to correlate more closely with the 700mb wind direction than with the height of the 700 mb pressure surface when considered for a representative station (Winslow, Arizona). A satellite‐based definition of ‘monsoon’ best considers variations of the total cloud rather than of any individual cloud level(s).Several surface and 700 mb synoptic circulation indices are identified and related statistically to the intraseasonal cloudiness changes. The most significant association is found for the variations in latitude of the Bermuda high pressure ridge that presumably relates to changes in subsidence. However, the sign of this relationship may reverse in years when other circulation systems, notably the North Pacific anticyclone, also influence the desert Southwest. Consideration of the zonal westerly index between 45 and 65°N tends to improve the correlation between the Bermuda ridge and summer monsoon cloudiness over the region. Such cloud‐circulation studies have implications not only for climate dynamics but also for ongoing solar energy research in the Am

ISSN:0196-1748    

DOI:10.1002/joc.3370050406

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractAn upper‐air climatology of tropical South America is presented using objectively analysed geopotential height, temperature and wind data from various radiosonde stations for the common period 1970‐1974.In the lower troposphere the South Atlantic high dominates the geopotential height patterns extending deeply into interior Brazil in Southern winter. In the upper troposphere, contour gradients are concentrated around the subtropical region in winter. Temperature analysis shows the steep meridional gradient in winter. In summer, the Peruvian‐Bolivian Altiplano heating effect is manifested in the mid‐tropospheric temperature fields and also in the thickness field.Lower‐tropospheric flow throughout the year is marked by an anticyclonic turning of easterlies over much of eastern Brazil. Easterlies originating from the South Atlantic high penetrate further inland in Southern winter. Upper‐tropospheric flow changes dramatically from mainly westerly in winter to a well‐defined anticyclone over the Altiplano and a trough downstream over northeast Brazil in summer. Thickness and temperature patterns indicate that the upper anticyclone is maintained by a warm‐core system whereas the trough is marked by a relatively cold temperature. Upper tropospheric flows are equivalent barotropic in nature over tropical South America. The map discussion of summer and winter circulation is complemented by cross‐sections of meridional wind component along a

ISSN:0196-1748    

DOI:10.1002/joc.3370050407

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe observed meridional temperature gradients in the middle and high latitudes of the southern hemisphere are much higher than the critical gradients necessary for the manifestation of baroclinic instability in a two‐level quasi geostrophic model. This is in contrast to the ‘baroclinic adjustment’ observed in the northern hemisphere by Stone (

ISSN:0196-1748    

DOI:10.1002/joc.3370050408

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractThis paper describes a dynamic parameterization for a simple global climate model that is based on the planetary boundary layer equations of horizontal motion. This new parameterization resolves many of the problems associated with other representations of the general circulation in simple climatic models. The model developed in this study accurately simulates the presently observed zonally‐averaged temperature and wind field patterns. Sensitivity tests demonstrate that a model with the new dynamic parameterization meets or exceeds the performance levels of other one‐dimensional energy balance global climate models. By solving many of the problems associated with the available alternative circulation parametcrizations, the new circulation representation based on the equations of motion appears to improve the quality of the popular simple climate mod

ISSN:0196-1748    

DOI:10.1002/joc.3370050409

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe paper demonstrates the relevance of sky view factor analysis in urban canyons to thermal features of the surface and air in the urban canopy layer at night. The result of the study, made in the city of Malmö (population about 230,000) in southern Sweden, indicates, among other things, that the street geometry and its regional distribution within the city area plays a fundamental role in generating the street surface temperature pattern of the city, its 'surface heat island, The paper also demonstrates a digital image processing technique of determining the sky view factor from fish‐eye lens photograp

ISSN:0196-1748    

DOI:10.1002/joc.3370050410

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractThis study reviews the investigations on the radiation budget in the Alps at elevations above 1500 m a.s.l. Regarding outgoing radiation, only that from snow and ice is considered. Physical relationships between radiation and variables such as elevation, month and cloud amount are discussed. The individual components of the radiation budget are analysed first, and then an attempt is made to synthesize radiation balances.Elevation dependencies between 2000 and 3500 m a.s.l. in the canton of Valais (south‐western Switzerland) in summer (June to August) for average cloud conditions (1931‐1960) are as follows: the cloud amount increases from 0.507 to 0.582. The maxima occur in June. Global radiation increases from 22.7 to 23.6 MJm−2d−1. The maxima occur in June. Counter‐radiation decreases from 25.8 to 21.9 MJm−2d−1. The maxima occur in July. For average albedo, the radiation balance of horizontal glacier surfaces decreases from 15.3 to 5.3 MJm−2d−1, with the maxima occurring in July. For albedo conditions after snowfall, the radiation balance decreases from 2.7 to 1.3 MJm−2dd−1, the maxima occurring in June or July.The study has the following applications, among others: it can (1) contribute to the understanding of the genesis of the climate of the Alps, (2) assist in the development of runoff models for heavily glacierized basins and (3) be helpful in th

ISSN:0196-1748    

DOI:10.1002/joc.3370050411

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY