Periodicities, ENSO effects and trends of some South African rainfall series: an update
The precipitation data for some regions in South Africa were studied for the period 1900 - 1998. From the 11 regions examined, 8 in South Africa had maximum precipitations in the austral summer months (December, January, February, March), while 3 had maxima in autumn and winter. Annual values showed...
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| Format: | Article |
| Language: | English |
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Academy of Science of South Africa
2010-01-01
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| Series: | South African Journal of Science |
| Online Access: | http://192.168.0.121/index.php/sajs/article/view/10083 |
| _version_ | 1818644297061236736 |
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| author | R. Kane |
| author_facet | R. Kane |
| author_sort | R. Kane |
| collection | DOAJ |
| description | The precipitation data for some regions in South Africa were studied for the period 1900 - 1998. From the 11 regions examined, 8 in South Africa had maximum precipitations in the austral summer months (December, January, February, March), while 3 had maxima in autumn and winter. Annual values showed considerable year-to-year fluctuations (50% to 200% of the mean), while five-year running means showed long-term fluctuations (75% to 150% of the mean). A spectrum analysis indicated periodicities in the ranges 2 - 3 (quasi-biennial oscillation, QBO), 3 - 4 (quasi-triennial oscillation, QTO), 6 - 11, 17 - 21, 23 - 26, 32 - 35 and 55 - 66 years, some common to, and some different in different regions. The QBO and QTO accounted for a substantial fraction (30 - 50%) of the total variance. In five-year running means, the effects of QBO and QTO were suppressed considerably. The plots showed distinct peaks, but the spacings varied in a wide range, indicating that predictions based on extrapolation of single peaks are not likely to come true even for decadal averages. El Niño effects for the giant event of 1982/83 were as expected but those for 1997/98 were obscure, almost absent. Running means over 21 years did not indicate linear trends, upwards or downwards. Instead, considerable oscillations were seen, with magnitudes different in different regions (5 - 25%). On average, high values during 1915/16 decreased considerably (5 - 8%) up to 1935, oscillated upwards thereafter and recouped by 1980, but decreased considerably thereafter. |
| first_indexed | 2024-12-17T00:12:36Z |
| format | Article |
| id | doaj.art-55db6e62439246a3b633838560f2e45f |
| institution | Directory Open Access Journal |
| issn | 1996-7489 |
| language | English |
| last_indexed | 2024-12-17T00:12:36Z |
| publishDate | 2010-01-01 |
| publisher | Academy of Science of South Africa |
| record_format | Article |
| series | South African Journal of Science |
| spelling | doaj.art-55db6e62439246a3b633838560f2e45f2022-12-21T22:10:48ZengAcademy of Science of South AfricaSouth African Journal of Science1996-74892010-01-011055/6Periodicities, ENSO effects and trends of some South African rainfall series: an updateR. Kane0Instituto Nacional de Pesquisas Espaciais, Caixa Postal 515, 12245-970 - São José dos Campos, SP, Brazil.The precipitation data for some regions in South Africa were studied for the period 1900 - 1998. From the 11 regions examined, 8 in South Africa had maximum precipitations in the austral summer months (December, January, February, March), while 3 had maxima in autumn and winter. Annual values showed considerable year-to-year fluctuations (50% to 200% of the mean), while five-year running means showed long-term fluctuations (75% to 150% of the mean). A spectrum analysis indicated periodicities in the ranges 2 - 3 (quasi-biennial oscillation, QBO), 3 - 4 (quasi-triennial oscillation, QTO), 6 - 11, 17 - 21, 23 - 26, 32 - 35 and 55 - 66 years, some common to, and some different in different regions. The QBO and QTO accounted for a substantial fraction (30 - 50%) of the total variance. In five-year running means, the effects of QBO and QTO were suppressed considerably. The plots showed distinct peaks, but the spacings varied in a wide range, indicating that predictions based on extrapolation of single peaks are not likely to come true even for decadal averages. El Niño effects for the giant event of 1982/83 were as expected but those for 1997/98 were obscure, almost absent. Running means over 21 years did not indicate linear trends, upwards or downwards. Instead, considerable oscillations were seen, with magnitudes different in different regions (5 - 25%). On average, high values during 1915/16 decreased considerably (5 - 8%) up to 1935, oscillated upwards thereafter and recouped by 1980, but decreased considerably thereafter.http://192.168.0.121/index.php/sajs/article/view/10083 |
| spellingShingle | R. Kane Periodicities, ENSO effects and trends of some South African rainfall series: an update South African Journal of Science |
| title | Periodicities, ENSO effects and trends of some South African rainfall series: an update |
| title_full | Periodicities, ENSO effects and trends of some South African rainfall series: an update |
| title_fullStr | Periodicities, ENSO effects and trends of some South African rainfall series: an update |
| title_full_unstemmed | Periodicities, ENSO effects and trends of some South African rainfall series: an update |
| title_short | Periodicities, ENSO effects and trends of some South African rainfall series: an update |
| title_sort | periodicities enso effects and trends of some south african rainfall series an update |
| url | http://192.168.0.121/index.php/sajs/article/view/10083 |
| work_keys_str_mv | AT rkane periodicitiesensoeffectsandtrendsofsomesouthafricanrainfallseriesanupdate |