摘要:

AbstractThe International Satellite Cloud Climatology Project (ISCCP) C2 data from 1984 to 1987 are used to form average extreme season zonal means and global climatologies of cloud parameters. The total cloud amount, in general, agrees well with previous cloud climatologies. The level of agreement between the zonal total cloud climatology of Warrenet al.and the ISCCP C2 data is extremely good. The main features of the general circulation of the atmosphere are observed in the global climatology, notably the equatorial maximum associated with the Inter Tropical Convergence Zone, the subtropical minima, and mid‐latitude maxima. The polar regions are areas of large disagreement with previous cloud climatologies. For both poles the ISCCP C2 data show that maximum cloudiness occurs in the winter, whereas most previous cloud climatologies indicate that maximum cloudiness occurs in summer. The ISCCP data indicate that Antarctica is an area of relatively small cloud amounts, which concurs with most previous climatologies. However, the amount and season of minimum cloudiness is in disagreement. Results from the amount of cloud types also show features that can be related to the general circulation of the atmosphere. Low clouds are found to be the most common cloud type over the ocean. Large amounts of low cloud are found on the west coasts of subtropical continents, consistent with the presence of marine stratocumulus. The subtropical high pressure zones are areas with small amounts of middle and high cloud types. The Indian south‐west monsoon is easily visible by an increase in the amount of high cloud in the region during Northern Hemisphere summer. The total water‐path results highlight the difficulties of cloud retrieval over permanent snow or ice cover. At present the water path results are unrel

ISSN:0899-8418    

DOI:10.1002/joc.3370130602

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractConcurrent pyranometer and GMS (Japanese Geostationary Meteorological Satellite) data were collected for the western tropical Pacific during a 21‐month period in 1987 and 1988. Data from 10 pyranometer stations in 1987 were used to build a satellite insolation model. Such processes as surface albedo, narrow band to broad band conversion, and depletion by water vapour and aerosols were taken into account. The model was then tested with an independent pyranometer data set comprising 9 months in 1988.Results show that aerosol depletion is site‐specific, with typical long‐term values ranging from 19·8 per cent of the extraterrestrial value for Kuala Lampur, to 4·8 per cent for Willis Island. Monthly insolation may be mapped over the oceanic regions of the study area assuming that the Willis Island aerosol depletion values apply. The model gave root‐mean‐square (RMS) errors of 14·08 W m−2when tested against all monthly average pyranometer data for 1988. Corresponding RMS errors are 11·67 W m−2when only Willis Island data are used. Sources of errors are discussed, as are suggestions fo

ISSN:0899-8418    

DOI:10.1002/joc.3370130603

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractAlong the south‐eastern seaboard of Africa, a drought‐prone area is found between the humid subtropics and a deser. Convective mid‐summer precipitation in the north‐east is contrasted with stratiform winter rains in the west. Mean annual precipitation is2000 mm. According to time series analysis of rainfall records, dry spells recur at intervals of 3·5 and 18·2 years, most notably in the period 1940–1970. By contrast, excessive rainfall characterized the mid‐1970s. Extreme dry and wet years are analysed for circulation, convection and sea‐temperature differences. Below‐normal sea temperatures to the south‐west and east of the study area are associated with drought in the eastern Cape. Circulation differences indicate that low‐level westerly winds sweep across the region, in association with a stationary subtropical westerly wave of wavelength 3000 im and amplitude 1500 km. A positive outgoing longwave radiation anomaly indicative of reduced cloudiness and water vapour is noted in a north‐west—southeast band extending from Namibia across the eastern Cape watershed. Anticyclonic vorticity anomalies of the order of 10−5s−1across the subtropics of southern Africa are common in dry years. Lower divergence to upper convergence anomalies of the order of 2 × 10−6s−1are the driving forces of subsidence over the eastern Cape. The analysis of climatic patterns associated with dry spells will assist in forcasting seasonal rainfall, planning agricultural producti

ISSN:0899-8418    

DOI:10.1002/joc.3370130604

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractChanges in streamflow volumes resulting from climatic change can affect the management of water resources. However, the detection of a statistically significant trend can be difficult because of the large interannual variability and the relatively short period of instrumental record. In this paper, five statistical tests are applied to the historical annual streamflow series of 30 unregulated Australian rivers, located in protected natural catchments, in order to detect trends or changes in the means. The Studentt‐statistic is also used to describe the relationship between interannual variability and the magnitude of change and length of data required to identify a statistically significant trend. The analysis indicates that, with the current data set, there is no clear evidence to suggest that the greenhouse effect is impacting on Australian streamflow volumes. The change required to identify a statistically significant change in the mean is directly proportional to the interannual variability, and less dependent on the length of data available. The interannual variability of Australian streams is twice that of Northern Hemisphere streams, therefore, a greater change is required in Australian flow volumes before a statistically significant change can be identified. The analysis of available historical records, however, indicates that statistically significant trends can be detected in the future flow volumes if the scenarios predicted by the G'CMs are realize

ISSN:0899-8418    

DOI:10.1002/joc.3370130605

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractAn objective scheme, initially developed by Jenkinson and Collison, is used to classify daily circulation types over the British Isles, along the lines of the subjective method devised by Lamb. The scheme uses daily grid‐point mean sea‐level pressure data for the region. The results of the analysis over the period 1881–1989 are compared with ‘true’ Lamb weather types. The frequencies of objectively developed types are highly correlated with traditional Lamb types, especially so for synoptic (cyclonic and anticyclonic) types, although still good for wind directional types. Comparison of the two classification schemes reveals negligible differences between the correlations of the counts of circulation types and regional temperature and rainfall. The major difference between the two classification schemes is that the decline of the westerlies since 1940 is less evident with the objecti

ISSN:0899-8418    

DOI:10.1002/joc.3370130606

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractMaximum entropy spectrum analysis of six fish catch series, seven series giving dates of wine harvest, and forty four height of sea‐level records from Europe yields evidence for two peaks with periods 18–19 and 10–11 years, the same terms recently reported in European tree‐ring chronologies. For each series the two wavetrains are obtained by bandpass filters, summed, superimposed on the trend‐like components of the raw data, and plotted against the raw data. The contribution, on average, of the waves to total variance in the raw data varies from a high of 50 per cent for fish catches to a low of 14 per cent for dates of wine harvest (the mean contribution for height of sea‐level is 18 per cent). The peaks are identified as the 18·6‐year luni‐solar, Mn, and 10–11‐year solar cycle, Sc, signals, which also have been reported recently in other climate variables, such as air temperature, air pressure, in rain‐gauge and tree‐ring data from North and South America, South Africa, Tasmania, and New Zealand; and in sea‐surface temperature as well as in American crop yield and other economic data. Further experiments show that with 110 years, or more, of data the Yule‐Walker method of spectrum analysis has sufficient resolution to resolve both signals. It is also shown that failure to apply a properly designed digital high‐pass filter to climate records prior to spectrum analysis usually leads to

ISSN:0899-8418    

DOI:10.1002/joc.3370130607

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractA 14‐year (1977–1990) record of global solar radiation measurements performed in Athens, Greece, has been utilized to determine the distribution of radiant energy in the various wavelength bands. The monthly mean values of the irradiation ratios in the spectral intervals, blue (0·380–0·525 μm), green‐orange (0·525–0·630 μm), red (0·630–0·710 μm), and photosynthetically active radiation (PAR) (0·380–0·710 μm) and the global irradiation (0·3–2·8 μm) compare favourably with values reported in the literature for different locations over a wide geographical area.The irradiation ratios exhibit seasonal variations attributable to changes in local air‐mass climatology. It is observed that the proportion of the radiant energy in the various spectral bands relative to the global solar irradiation increases as sky conditions change from ‘clear’ to ‘partly cloudy’. Finally, the observed seasonal dependence of the broad‐band spectral energy distribution is essentially caused by changes in the composition of the air masses (turbidity, airborne pollutants, clouds) in residence at the

ISSN:0899-8418    

DOI:10.1002/joc.3370130608

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

ISSN:0899-8418    

DOI:10.1002/joc.3370130609

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

ISSN:0899-8418    

DOI:10.1002/joc.3370130601

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY