摘要:

AbstractAutoregressive time series models are used to make forecasts of stratospheric zonal wind and temperature at Kwajalein Island near the equator in the northern Pacific Ocean. The tropical stratosphere is dominated by the quasi‐biennial oscillation (QBO). Because the QBO has a varying period, an autoregressive model is more appropriate than a mixture of sinusoids. The data for 11 levels are efficiently represented by principal components, and univariate and multivariate autoregression models are fitted to six of the principal components. The autoregressive models are used for estimation of variance density spectra and for forecasting. The multivariate model is found to perform better in both detecting and forecasting the quasi‐biennial oscillation than either univariate models of the principal components or autoregressive models of the data set its

ISSN:0196-1748    

DOI:10.1002/joc.3370040402

出版商:John Wiley&Sons, Ltd.    

年代:1984

数据来源: WILEY

摘要:

AbstractThe response of the 200 mb tropical wind field to the Southern Oscillation and central equatorial Pacific sea surface temperature is examined with correlation and regression analyses on a seasonally stratified basis. Although there are differences in magnitude, all seasons are found to exhibit the following set of responses: during periods of low Southern Oscillation Index and high equatorial sea surface temperature there are easterly anomalies of the equatorial zonal wind and westerly anomalies in the adjacent subtropics. These anomalies are consistent with the circulations in simple models of the Walker circulation in which the longitudinal scale of equatorial heating is increased, resulting in reduced zonal overturning at the equator (weakened Walker circulation) and increased meridional overturning and acceleration of the subtropical westerlies in a region slightly to the west of the anomalous heating centre. The correlation and regression results also show that central Pacific equatorial sea surface temperature is an excellent index of the heating anomalies.Theoretical results have predicted that the importance of remote forcing from the tropics in higher latitudes is dependent upon the strength of the intervening zonal wind field. Season‐to‐season differences are particularly apparent in the northern hemisphere responses of the zonal wind field to the Southern Oscillation: remote responses are relatively strong when the mean zonal winds over the Pacific region and corresponding values of standing wave group velocity are relatively large and vice versa. A similar correspondence is not found south of the equator as the correlation results do not vary as strongly with season. This may be due to greater equatorial trapping of Southern Oscillation anomalies in the same season when subtropical winds are more favourable for meridional coupl

ISSN:0196-1748    

DOI:10.1002/joc.3370040403

出版商:John Wiley&Sons, Ltd.    

年代:1984

数据来源: WILEY

摘要:

AbstractIn this study, two 47‐day simulations were made with the general circulation model of the Goddard Laboratory for Atmospheric Sciences starting from the observed initial conditions for 15 June (00Z) 1979 as produced by NMC analysis. In the first simulation, the soil moisture was normally initialized and then allowed to vary by the model generated surface water balance. In the second simulation, the evaporation was prescribed and maintained zero in four chosen semi‐arid regions: the Sahel, the Thar Desert border in the Indian subcontinent, the Great Plains in North America and north‐east Brazil in South America. Elsewhere the soil moisture was calculated as in the first simulation. The two runs were identical in all other respects.The local climatology simulated by the GCM was analysed in the four anomaly regions. The mean July precipitation increased slightly in the Great Plains and Sahel regions, while it increased substantially (∼70 per cent) in the Thar Desert border region. However, in the north‐east Brazil region it decreased slightly. Relative thermal lows were created in each region, along with enhanced rising motion. There was also an increase in the mean monthly diabatic heating in all four regions. An analysis of the vertical structure of the moisture convergence field revealed that there was an increase in the low level moisture convergence in all of the anomaly regions. This compensated for the local moisture deficit created by the lack of evaporation.These results are based on one set of simulations representing the month of July. Further simulations would be required in order to evaluate their statistical sig

ISSN:0196-1748    

DOI:10.1002/joc.3370040404

出版商:John Wiley&Sons, Ltd.    

年代:1984

数据来源: WILEY

摘要:

AbstractAn analysis of northern, low and southern latitude temperature trends of the past century, along with available atmospheric CO2concentration and industrial carbon production data, suggests that the true climatic effect of increasing the CO2content of the atmosphere may be to cool the Earth and not warm it, contrary to most past analyses of this phenomenon. A physical mechanism is thus proposed to explain how CO2may act as aninversegreenhouse gas in Earth's atmosphere. However, a negative feedback mechanism related to a lowering of the planet's mean surface albedo, due to the migration of more mesic‐adapted vegetation onto arid and semi‐arid lands as a result of the increased water use efficiency which most plants experience under high levels of atmospheric CO2, acts to counter this inverse greenhouse effect. Quantitative estimates of the magnitudes of both phenomena are made, and it is shown that they are probably compensatory. This finding suggests that we will not suffer any great climatic catastrophe but will instead reap great agricultural benefits from the rapid increase in atmospheric CO2which we are currently experiencing and which is projected to continue for perhaps another century or two into the fut

ISSN:0196-1748    

DOI:10.1002/joc.3370040405

出版商:John Wiley&Sons, Ltd.    

年代:1984

数据来源: WILEY

摘要:

AbstractThe broad characteristics of the North‐west Australian Cloud Band, frequently observed across the Australian continent, are outlined. The cloud in the Band is most frequently first apparent within approximately 5° latitude and 17° longitude of 12DS 100°E, and may extend from there for several thousand kilometres, typically towards the east‐south‐east. It is found to be most in evidence during the winter months. Various atmospheric features associated with the development of the Cloud Band are d

ISSN:0196-1748    

DOI:10.1002/joc.3370040406

出版商:John Wiley&Sons, Ltd.    

年代:1984

数据来源: WILEY

摘要:

AbstractAn index is defined for the date of onset of the north Australian wet‐season, based on rainfalls observed at ten stations across tropical Australia. The index is shown to be reasonably representative of wet‐season onset throughout the area of interest. Some suggestion of bimodality is found in the frequency distribution of onset dates. An operationally feasible method for predicting the probability that the wet‐season will commence late is presented, building on earlier published work which has established the feasibility of prediction of seasonal rainfall near the date of onset of the wet. The forecast method uses the linear logistic equation and Darwin pressures observed in months prior to the onset to make predictions. Acceptable forecasts can be issued four months prior to onset. Two examples of the use of the method are pro

ISSN:0196-1748    

DOI:10.1002/joc.3370040407

出版商:John Wiley&Sons, Ltd.    

年代:1984

数据来源: WILEY

摘要:

AbstractIn an attempt to study weather and climatological conditions in the Thessaloniki area during the winter period, a weather‐type classification is proposed according to principles first adopted by Russian authors. The methods of factorial analysis are used for this weather‐type classification. A study of the monthly and yearly frequencies of good, unpleasant, cloudy or overcast weather allows us to better understand the area's ‘atmospheric quality’ affecting man's lif

ISSN:0196-1748    

DOI:10.1002/joc.3370040408

出版商:John Wiley&Sons, Ltd.    

年代:1984

数据来源: WILEY

摘要:

AbstractAn expression is derived for the equivalent number of independent values obtained by partial sampling of a coherent, i.e. autocorrelated, time‐series or spatial series of data. The expression is a function of both the coherence of the data values and the coherence of the sampling, i.e. the non‐randomness of the distribution of available data. For a data series with high autocorrelation the distribution of the sampling in time or space is more important than for a relatively incoherent data series. Meteorological data are used as illustrative examples. The derived expression can be used in estimating the variance of sample me

ISSN:0196-1748    

DOI:10.1002/joc.3370040409

出版商:John Wiley&Sons, Ltd.    

年代:1984

数据来源: WILEY

ISSN:0196-1748    

DOI:10.1002/joc.3370040410

出版商:John Wiley&Sons, Ltd.    

年代:1984

数据来源: WILEY

ISSN:0196-1748    

DOI:10.1002/joc.3370040411

出版商:John Wiley&Sons, Ltd.    

年代:1984

数据来源: WILEY