摘要:

AbstractMaps of cloud cover over the Arctic have been prepared from manual interpretation of Defense Meteorological Satellite Program images at 3‐day intervals for April, May and June, 1979,1980. Additional maps were prepared for selected dates to give a 10‐day sample for each of eight synoptic MSL pressure pattern types over the same area. Synoptic and monthly cloud distributions are compared with previous estimates. A large bias in our low cloud estimates for April may be caused by springtime Arctic have layers. The identification of substantial geographical and interannual variability of cloud amounts suggests that synoptic controls are important at this sea

ISSN:0196-1748    

DOI:10.1002/joc.3370070502

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractRecent variations of circulation and climate can be studied by investigating even rather short periods of time as far as they display different modes or anomalies which may also act on larger timescales as more persistent ones. Thus a period of 10 years (September 1966 to August 1976) which could be covered by daily sets of 500hPa airflow data in the Atlantic‐European region and of precipitation data at 101 Mediterranean stations was chosen to examine the variable distribution patterns of upper troughs in the Mediterranean area and their corresponding patterns of precipitation anomalies. After the outline of trough axis distribution to eight successive longitudinal bands and of the different percentages of trough precipitation at various trough axis positions for the whole period of 10 years a subdivision into individual years was made to show some of the operative deviations both of the upper trough distribution and of the corresponding precipitation pattern in relation to the overall mean situation. Together with some circulation indices (zonal index, geopotential anomaly, measure of (he relative vorticity, specifications about the Westerlies' main branch) which have been calculated for the crucial upstream region of the North Atlantic, some basic tendencies concerning different circulation patterns and their consequences for the Mediterranean region could be outlined. Considering within‐type changes and the variations of further cyclonic elements this might serve for estimating climatological effects on larger time‐scales of more persistent anomalies of circul

ISSN:0196-1748    

DOI:10.1002/joc.3370070503

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractMean growing season (April‐September) precipitation series at 407 stations in the Interior Plains of North America, dating back to 1985 in some stations, are used to derive a Bhalme and Mooley‐type drought index for the region. Linear trend, representing first order non‐stationarity, is first removed from the drought series. Then the periodogram via the Fast Fourier Transform (FFT), Maximum Entropy (ME) and Non‐Integer (NI) spectral techniques are applied to search for significant periodicities in the temporal characteristics of the drought series. Cross‐spectral technique is also used to characterize the extent of spectral coherence in the drought series.It is found that no significant power in drought is present at periods greater than about 6 years. Spectra of drought in the Interior Plains are dominated by three peaks in the quasi‐biennial, quasi‐triennial and quasi‐5‐year oscillations. The periodic 186‐year lunar nodal cycle obtained by others for the Drought Area Index (DAI) for the region is completely absent in the spectra of the analysed drought index series. Also the well‐known 11‐year sunspot cycle is only evident in the drought index series for a few of the stations. In general there is an ill‐defined drought recurrence interval.Moreover the areal extent of peaks contained within these oscillations do not indicate any significant spatial coherence. These periodicities can be evident at one station while being absent at another a few hundred kilometres away. On the basis of the spectral results, it is concluded that obtained significant periodicities are only short‐lived time variabilities in drought as recorded by individual stations and do not represent any persistent drought characteristics over a broad geographical region. A cross‐spectral analysis of the drought series with sunspot numbers shows no evidence to indicate a significant relation between drought and the single sunspot cycle. In general, the growing season drought series in the Interior Plains displays only what appears to be a random variation, with the possible superimposition of t

ISSN:0196-1748    

DOI:10.1002/joc.3370070504

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractModel calculations of incident shortwave radiation were performed for the Mount Kenya massif with the objectives of: (i) exploring the major factors controlling the ice distribution in the peak region: and (ii) determining the primary forcings that led to the differential retreat of the various glaciers.The ice distribution on Mount Kenya, characterized by largest glaciers lo the south and east, is primarily controlled by the precipitation pattern. By contrast, the radiation pattern is unconducive to maintaining this ice distribution, as insolation tends to be higher on these largest glaciers. Spatial variability in the incident radiation is mostly due to shading effects, with cloudiness however being more important in reducing absolute values. Steep slopes, essentially above 5,100 m, and higher temperatures below 4,600 m are further limiting factors.A drastic glacier recession is borne out by mappings of the ice extent in 1899 and 1963. Over this time span, the number of glaciers diminished from 18 to 11, and another disappeared since 1978. Of the eight defunct ice entities, six were small. By far the largest glacier to disappear since the turn of the century was the Kolbe, in a precipitation‐abundant but radiationally very exposed location on the eastern flank of the mountain. The largest and now easternmost ice body, the Lewis, which occupies the radiationally most exposed location of all the glaciers, has experienced the greatest ice wastage.The model calculations indicate that the drastic ice recession since the late 1800s is largely due to an increase in absorbed shortwave radiation accompanying, and in part brought about by, changes in cloudiness, precipitation, and temperature. In addition to the consequences for the overall ice amount, the spatial distribution of radiation totals, as influenced by topographical shading, appears to account for the remarkably diverse shrinkage of the glaciers on Mount Keny

ISSN:0196-1748    

DOI:10.1002/joc.3370070505

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractA recent paper by Richman (1986) provides a very useful review of the ideas of rotation in principal component analysis, in the context of climatology. However, the paper also raises a number of points which are open to discussion. The present note comments on a number of these points, and aims to give a balanced view of the usefulness of principal component analysis, both with and without rotation, in climatology.

ISSN:0196-1748    

DOI:10.1002/joc.3370070506

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractJolliffe's comments raise some interesting and important points concerning both unrotated principal component analysis and rotated principal component analysis that deserve further consideration. These are examined herein, with particular attention to my original review of rotation.

ISSN:0196-1748    

DOI:10.1002/joc.3370070507

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

ISSN:0196-1748    

DOI:10.1002/joc.3370070508

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

ISSN:0196-1748    

DOI:10.1002/joc.3370070509

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

ISSN:0196-1748    

DOI:10.1002/joc.3370070510

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

ISSN:0196-1748    

DOI:10.1002/joc.3370070501

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY