摘要:

AbstractA series of sensitivity experiments has been conducted using a version of the NCAR Community Climate Model (CCM) and a complementary zero‐dimensional land‐surface model in order to invesligate the sensitivity of the models to surface process parameterizations in northern high latitudes. The study was motivated by anomalously high surface temperatures at these latitudes in a control simulation with the CCM. The effects of perturbing the maximum vegetation cover, distribution of the roots within the active soil layer, the depth of the active soil layer, soil albedo, and of maintaining a fully saturated upper and active soil layer were explored. Little response occurred in either model when the depth of the soil or the root distribution was altered. Increasing the percentage of ground covered by vegetation increased the canopy air temperature but generally reduced soil temperatures in the zero‐dimensional model. However, in the CCM integration the surface air temperature increased over most of the region for this change. This response seems to be due to the high level of precipitation during the three‐dimensional integration and is similar to one of the zero‐dimensional computations in which a large rainfall event was prescribed on the second day of the 10 day integration. Maintaining the moisture contents of both soil layers at their capacity caused a decrease in soil temperatures at most locations in the CCM and in the zero‐dimensional model once the soil in the control began to dry out. Increasing the soil albedo also produced soil and surface air cooling in both models. All the integrations underlined the considerable sensitivity of the land‐surface parameterization scheme to the instantaneous and preceding soil moisture conditions. Reduction in surface temperatures achieved was significantly less than the original discrepancy between CCM temperatures and observations. Part of the discrepancy could be caused by unrepresentative observational data and a model bias toward high levels of net surface radiation. In addition, preliminary calculations suggest that explicit inclusion of permafrost may be necessary before a fully satisfactory representation of the tundra land‐surface climate can be achieved. This conclusion may be important for CO2‐induced clima

ISSN:0196-1748    

DOI:10.1002/joc.3370070402

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe interannual variability of the Indian monsoon (June–September) rainfall has been examined in relation to the monthly zonal wind anomaly for 10‐mb (30km) and 30‐mb (24km) at Balboa for the 28‐year period 1958–85. The fluctuations in the zonal wind anomalies in January at 10‐mb appear to be highly related to the monsoon rainfall, with rainfall tending to be less (more) than normal during easterly (westerly) anomaly, suggesting some predictive value for the Indian monsoon rainfall. The zonal wind anomalies at 10‐mb lead those at 30‐mb by 6 months. This lead time is consistent with the well‐known downward phase propagation with a speed of 1 km/month in the QBO of tropical stratospheric wind. Large‐scale flood never occurred during easterly wind anomalies, and drought almost never during westerly anomalies in January at 10‐mb. This suggests that useful probability forecasts of droughts or flo

ISSN:0196-1748    

DOI:10.1002/joc.3370070403

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractSeveral characteristics of (he south‐west monsoon rainfall of the low latitude stations of Cochin (coastal) and Minicoy (island) have been studied using the hyetograms of these stations for the ten year period 1973–1982. Both stations exhibit diurnal variations of rainfall with maximum activity in the post‐midnight hours and minimum in the afternoon hours. The amplitude of the diurnal variation increases for rain events of increasing intensities. The integrated duration of the seasonal rainfall is about 250 h at Cochin and 110 h al Minicoy. Half the total rain from heavy falls is received in a fifth of the total duration; half the total duration accounts for only a fifth of the total rain from light falls.The association between cumulative percentage rainfall (x) and cumulative percentage rain duration (y) is found to be of the form x = ay exp (byc) wherea,bandcare empirical constants. The average rain intensity varies from about I mm/h to 25 mm/h along this rainfall curve. An equation of the same form also gives a satisfactory representation of the variation of cumulative percentages of rain amount/rain‐duration/rain hours with rain events of increasing

ISSN:0196-1748    

DOI:10.1002/joc.3370070404

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractA maximum entropy analysis of winter and summer flood records of the Nile from ad 622 to 1490 shows evidence for periodic lunar nodal 18′6‐year(as well as weaker 10–11 year cyclic) induced drought/flood in regions of Africa drained by this river. This supports the results of Hameed (1984) who analyzed the same records using the Fourier transform method, and of Hameed and Currie (1985) who studied the summer flood records of the modern period (ad 1690–1962) using the maximum entropy method. The nodal term exhibits bistable phasing with respect to dates or epochs of maximum in the nodal tide, a phenomenon previously found in drought/flood proxy data in South America (Currie, 1983), in India (Currie, 1984a), in North America (Currie, 1984c), in China (Currie and Fairbndge, 1985), and in precipitation data for the northeastern United States (Currie, 1987c). Evidence for the 10–11 year solar cycle term in the Nile records is also discussed. Tyson (1980,1981) found terms near 19‐ and 11‐years in South African rainfall data, with the former exhibiting a bistable switch in phase at the beginning of our century, which is in agreement with results of Hameed and Currie (1985) for the moder

ISSN:0196-1748    

DOI:10.1002/joc.3370070405

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe 510‐year, 120‐stalion proxy precipitation records published by the State Meteorological Administration of the People's Republic of China were used to study the large‐scale climate patterns, including the climate regions and interregional relationships. In this paper, we present a study of the sensitivity of the climate patterns of recent years (1950–1979) to choice of stations and statistical techniques. First, the original highly inhomogeneous 120‐station network is reduced to a quasi‐uniform network comprising 93 stations. Next, based on the reduced network, two new networks arc derived‐a47‐station network with the same spatial domain and a 29‐station network with half the domain. The climate patterns for these station networks are compared by use of two different statistical procedures, principal component analysis/cluster analysis and factor analysis with orthogonal and oblique rotations. It is found that the climate patterns remain similar when the density and domain of the 120‐station network are systematically reduced. It is also found that similar climate patterns are obtained using either of the chosen statistical techniques, although factor analysis appears to be more sensitive to changes in the network than principal component/cluster analysis. Examination of measurement data also reveals large‐scale climate patterns similar to those derived from the proxy data. Finally, the climate patterns are shown to be consistent wit

ISSN:0196-1748    

DOI:10.1002/joc.3370070406

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

ISSN:0196-1748    

DOI:10.1002/joc.3370070407

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

ISSN:0196-1748    

DOI:10.1002/joc.3370070401

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY