摘要:

AbstractA numerical simulation study of the influence of surface albedo on July circulation in semi‐arid regions, using the general circulation model (GCM) of the Goddard Laboratory of Atmospheric Sciences (GLAS) is presented. The results are based on two 47‐day integrations. In the first integration, called the control run, the surface albedo was normally prescribed, whereas in the second integration, called the anomaly run, the surface albedo was modified in four regions: the Sahel in Africa, the western Great Plains in the United States, the Thar Desert border in the Indian subcontinent, and northeast Brazil in South America. This experiment is similar to that of Charneyet al.(1977); however, it was performed with the GLAS model with vastly different boundary forcings and several changes in the physical parameterizations.Each run was started from observed initial conditions for 15 June 1979, based on NMC analysis. An analysis of the two simulations shows that in the Sahel, and the Thar Desert border regions the current results again show reduced precipitation with increased surface albedo in accordance with Charneyet al.(1977) and Charney (1975). The semi‐arid northeast Brazil region, which had a winter circulation, also conforms with Charney's (1975) hypothesis. However, the Great Plains region was an exception. There the total precipitation in two simulations was unchanged, as was the total cloudiness. In this region, the convective precipitation was reduced somewhat, while the large‐scale precipitation compensated this decrease by approximately the same amount. The lack of albedo impact on precipitation in the Great Plains region could be due to the influence of the Rocky Mountains in generating variations in the large‐scale flow.The purpose of repeating Charney's albedo experiment was to test the sensitivity of his earlier results with the current GLAS GCM which has substantially modified physical parameterizations, particularly the planetary boundary layer (PBL), crucially important for such impact studies. Taking into account that both the GCM and the initial conditions of the atmosphere were different, it is worth noting that this experiment still provides support for Charney's hypothesis (1975) regarding the influence of surface albedo on mean‐monthly climatology in the subtropical desert margin regions.Another important influence noted was the variability of mean monthly simulation in areas far away from the albedo anomaly regions. Because the differences occur in regions of high observed climatological variability, it is necessary to separate the contribution of albedo anomalies as opposed to the model variability. The influence of surface albedo changes to produce large changes in the mean montly circulation elsewhere is very intriguing and needs further in

ISSN:0196-1748    

DOI:10.1002/joc.3370020202

出版商:John Wiley&Sons, Ltd.    

年代:1982

数据来源: WILEY

摘要:

AbstractA coarse‐mesh (8° latitude × 10° longitude), global domain climate model is shown to produce useful simulations of the sea‐level pressure and the precipitation distribution over south Asia during spring and early summer. Although the computations produce excessively fast development of the monsoon trough, the trend of increasing rainfall over the Indian subcontinent finds expression in the simulations. The model precipitation increases seasonally too early over southern India but the pattern by July correctly depicts a maximum south of the Tibetan plateau.Four pairs of simulations during the model onset month tested the sensitivity of the onset to small arbitary differences in atmospheric stale. The results suggest that the timing of Indian precipitation may not be predictable from consideration of antecedent measurable atmospheric para

ISSN:0196-1748    

DOI:10.1002/joc.3370020203

出版商:John Wiley&Sons, Ltd.    

年代:1982

数据来源: WILEY

摘要:

AbstractNocturnal measurements of air, temperature and longwave radiation were taken in aEucalyptus delegatensisshelterwood and in a clearfelled control site. On average the shelterwood exhibited temperatures between 1°C and 2°C warmer. Longwave radiation correlated well with percentage sky view as determined from fish eye lens photographs. The shelterwood seems to decrease the radiation loss by an average figure of 21 per cent on a cloudless night. The Brunt cooling theory is used to relate the air temperature and radiation figure

ISSN:0196-1748    

DOI:10.1002/joc.3370020204

出版商:John Wiley&Sons, Ltd.    

年代:1982

数据来源: WILEY

摘要:

AbstractPrincipal component analysis is applied to annual weather type frequencies for the British Isles. The results objectively define characteristic relationships between the different types, and are used to determine changes in the atmospheric circulation in the region of the British Isles over the period 1861 to 1980. It is shown that, as far as annual frequencies are concerned, only six (of the 27) weather types are needed to define and monitor changes in the atmospheric circulation.The component amplitudes are correlated with temperature and rainfall data, and physically reasonable relationships are identified. The analysis is extended to the period 1781 to 1785, and similarities are found between the extremes experienced during that period and during the 1970s.

ISSN:0196-1748    

DOI:10.1002/joc.3370020205

出版商:John Wiley&Sons, Ltd.    

年代:1982

数据来源: WILEY

摘要:

AbstractMonthly and annual values are calculated of a zonal index based on surface pressure at 35°N and 55°N between 60°W and 10°W. The period under study, 1873‐1972, is divided into three sub‐periods which approximate with three epochs proposed by Lamb (1972). A comparison of our indices with Lamb's results is followed by a discussion of our monthly index, and the rarity of easterly flow in the 100‐year period is noted. The results are subjected to a trend and a power spectrum analysis and the latter indicates a number of periodicities some of which are not easily e

ISSN:0196-1748    

DOI:10.1002/joc.3370020206

出版商:John Wiley&Sons, Ltd.    

年代:1982

数据来源: WILEY

摘要:

AbstractDuring the winter of 1981 the mean snow covered area in the Northern Hemisphere was less than any other year in the 15‐year record (1966‐1981) except 1970. For North America, the mean snow cover area was the lowest on record, and for Eurasia the mean snow cover area was the second lowest since records began in 1966. It has been observed that the average winter snow cover in both North America and Eurasia for both 1980 and 1981 decreased from that of the previous year, the first time this has been observed in the 15‐year period of record. Assessment of any long term climatic trends must wait extension of the snow cover data

ISSN:0196-1748    

DOI:10.1002/joc.3370020207

出版商:John Wiley&Sons, Ltd.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe main field experiments and climatological calculations of the surface energy balance on the arctic tundra are reviewed, following the historical development of theories and instruments. The scientific significance and problem areas of individual studies are discussed and the present status of understanding the energy balance on the arctic tundra is described.

ISSN:0196-1748    

DOI:10.1002/joc.3370020208

出版商:John Wiley&Sons, Ltd.    

年代:1982

数据来源: WILEY

ISSN:0196-1748    

DOI:10.1002/joc.3370020210

出版商:John Wiley&Sons, Ltd.    

年代:1982

数据来源: WILEY

ISSN:0196-1748    

DOI:10.1002/joc.3370020212

出版商:John Wiley&Sons, Ltd.    

年代:1982

数据来源: WILEY

ISSN:0196-1748    

DOI:10.1002/joc.3370020213

出版商:John Wiley&Sons, Ltd.    

年代:1982

数据来源: WILEY