摘要:

AbstractSpectrum analysis of 59 South African rain‐gauge records yields evidence for two peaks with periods 18.2·1.4 years (57 out of 59 series covering virtually the entire country) and 10.3·0.5 years (in 37 series covering almost all except easternmost South Africa). They are identified as the luni‐solar 18.6‐year Mnand 10–11‐year solar cycle Scsignals in climate; their phases and amplitudes are non‐stationary with respect to both time and geography and, in particular, 180° phase changes in wave polarity are observed. These phase changes occurred in the early part of the century and by mid‐epochs 1964.0 and 1982.6 (mid‐epochs are dates of minimum in Mntidal forcing) a unipolar cell of drought encompassed virtually the entire nation. Constructive interference by the Scwave, which reached a minimum near 1981, exacerbated the droughts of mid‐epoch 1982.6 which were more severe than even those of the 1960s. The results confirm and extend in many respects those found by P. D. Tyson and his co

ISSN:0899-8418    

DOI:10.1002/joc.3370130302

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe potential for using satellite outgoing longwave radiation (OLR) and passive microwave data as a proxy for rainfall over sub‐equatorial Africa and adjacent oceans is explored. Correlations between anomalies of field OLR and a summer rainfall index are −0.67 to −0.93 over central southern Africa, where the amplitude of interannual fluctuation in the decade 1975–1984 is largest. OLR‐rainfall correlations decline to −0.42 over Madagascar owing to a less homogeneous distribution of rainfall. Over South Africa during the winter dry season the correlation becomes positive except over the eastern seaboard where sea‐surface temperatures remain high.Satellite microwave estimates of cloud liquid water (LW) over the oceans surrounding southern Africa are presented for selected months during 1988 and 1989. Agreement is found between coastal rainfall and adjacent oceanic LW patterns. Contrasting distributions of interior and coastal rains in January and October 1989, respectively, are associated with the positioning of standing troughs evident in concentrated areas of high LW values in the mid‐latitudes. The advance and structure of the Inter Tropical Convergence Zone (ITCZ) over the tropical South‐west Indian Ocean is illustrated in m

ISSN:0899-8418    

DOI:10.1002/joc.3370130303

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractComparisons between years of below average rainfall over West Africa, sea‐surface temperatures (SST) over the Atlantic Ocean and the world ocean, and latitudinal positions of the Inter Tropical Convergence Zone (ITCZ) over the Atlantic Ocean show that the relationships depend mainly on the rainfall anomaly patterns. The well‐known SST dipole (cold northern ocean and warm equatorial and southern ocean) is only apparent during those August months with below average Sudano‐Sahelian rainfall and above average Guinean rainfall (rainfall type ‘−/+’) and an abnormal southward position of the ITCZ. In contrast, those August months that experience rainfall deficits over the whole of West Africa (rainfall type ‘−/−’) are associated with warm SST anomalies over the eastern Pacific Ocean, cold persistant SST anomalies over the equatorial Atlantic Ocean and a more northward position of the ITCZ. Those patterns first appear in northern spring before the Sahelian rainy season.The composite SST differences for the ‘−/+’ and ‘−/+’ rainfall types computed with August or July‐September amounts have a good resemblance with each other. Comparison of results related to the reverse July‐September rainfall patterns (the ‘+/−’ and ‘+/+’ patterns) during the 1950s shows that the SST anomalies were globally colder when, on average, the Sahelian rainy seasons experienced significant excesses while th

ISSN:0899-8418    

DOI:10.1002/joc.3370130304

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThis study attempts to determine the relationship between the curvature of the coastline and the filling (increase in central pressure) of hurricanes and tropical storms by comparing both the rate of filling and the total filling for storms striking convex, concave, and linear coastlines. The USA and Mexican coastline was approximated by a subjective smoothing procedure, and the coastal curvature corresponding to each landfalling Atlantic tropical cyclone from 1900 to 1979 was measured and grouped into one of the three curvature categories. Storm‐filling rates and total amounts of filling were determined before and after landfall by computing the change in wind speed for various Saffir‐Simpson hurricane intensity categories. The averages of these variables within each strength and curvature grouping were compared in order to determine if they were statistically different. Storms were also compared in order to determine if stronger storms fill a greater total amount than weaker storms, regardless of the coastline's curvature.Concave coasts were found to be associated with storms filling both more rapidly and by a greater amount than convex coasts for weak hurricanes and strong tropical storms, and they were associated with storms that filled by a greater amount for hurricanes of moderate strength. This most likely results from the lower water‐to‐land ratios associated with storms striking concave coasts and the reduction in latent and sensible heat fluxes from the surface. Also, stronger storms were found to fill more rapidly and by a greater total amount than weaker storms, and storms striking the East Coast generally filled more rapidly and by a greater total amount than storms striking the Gulf Coast or

ISSN:0899-8418    

DOI:10.1002/joc.3370130305

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

ISSN:0899-8418    

DOI:10.1002/joc.3370130306

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

ISSN:0899-8418    

DOI:10.1002/joc.3370130307

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractUsing monthly‐mean temperature data over Japan, the monthly‐mean temperature anomaly (MMTA) is investigated with special reference to its spatial scale. Relationship between occurrence probability of the MMTA and distance indicates that the occurrence probability is almost constant up to around 800 km and then rapidly decreases in magnitude. However, re‐examination of the relationship reveals that the MMTA has a spatial scale of around 1600 km as a minimum, which corresponds to the macro β or α scale. In addition to this principal investigation, seasonal dependence and temporal changes of the MMTA are also inves

ISSN:0899-8418    

DOI:10.1002/joc.3370130308

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

ISSN:0899-8418    

DOI:10.1002/joc.3370130309

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

ISSN:0899-8418    

DOI:10.1002/joc.3370130310

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

ISSN:0899-8418    

DOI:10.1002/joc.3370130301

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY