














“I-SSTs”sirhunyezo esaziwako ukusukela ngo 1997 ngesikhathi sedumo labendaba nababika ngesehlakalo se El Niño.  Ngendlela elungileko, nangonobangela wokuvuma kwabososayensi kobana imimoya yelwandle (SSTs) ayibinomthelela wokunisa izulu enarheni yekhethu, kodwana ngelitjhwa kunengi okusaseleko…

I-Sewula Afrika iyinarha ethloga amanzi wezulu nge-Sub-tropics, izombelezwe malwandle ekungiwo adlala indima eqakathekileko ekuniseni izulu ngokuya kweenkathi zonyaka. Amalwandle athumela imimoya ebujameni bokuna kwezulu begodu abanemithelela mayelana neendlela zobujamo bezulu obungaraga ubujamo lobu buye phambili, namkha bususwe enarheni.

Ukwahlukana kokuna kwezulu kungabangela ekutheni kube namatjhuguluko ebujameni bemimoya yezulu engaphezulu (isib. Imimoya yelwandle) emalwandle azombelezileko, namkha umthelela wobujamo bezulu obukhulu njenge El Niño/La Niña, namkha ezenzweni ezenziwa mumuntu namkha ekuhlanganisweni kwazo zoke izenzo lezi. Nasitjhejisisa kuhle, sitjheja ukudlalwa kwendima malwandle abomakhelwana we-Indiya ne-Atlantiki mayelana nokuna kwezulu e-Sewula Afrika.

Ilwandle le-Indiya

Kudala kwaziwa kobana amakhaza adlula isimedo se SSTs ngepulanga yeSewula Afrika ahlanganiswa nokuna kwezulu okungathabisiko ngepumalanga yeSewula Afrika. Nasingezelela, ukufuthumala okudlula isimedo se SSTs ngesifundeni setlhagwini ye Madagascar ngesikhathi sehlobo kanengi kungahlanganiswa nesomiso ngemfundeni ezisepumalanga netlhagwini zenarha. Kwagadesi, kunobufakazi obuncani bokobana imimoya yelwandle le-Indiya ibanemithelela ekuniseni izulu lebusika endaweni ezisesewula netjhingalanga yenarha.

Kuneembangela ezinengi zokutjhuguluka kweendlela ze SSTs (isib. Amatjhuguluko wokutjhisa ukwedlula isimedo namakhaza adlula isimedo se SSTs. Kesinye isikhathi amatjhuguluko enzeka ngonobangela we El Niño. Ngesikhathi se El Niño, ukutjhisa okudlula isimedo se SSTs ngelwandle letrophikhali ye-Indiya kuvamile kobana kuvele ngesikhathi sebusika bekulandele ukuvela kwe El Niño phakathi kwelwandle lephasafiki. Ngesikhathi sehlobo elilandelako, iindawo ezitjhisako nemalwandle 
we-I-ndiya nephasafiki zezitjhise ngokudluleleko; leso sikhathi sonyaka lapho singalindela ubujamo besomiso bonyana bubhebhetheke.

I- La Niña, ngakwelinye ihlangothi, kuvamile kobana ibemakhaza ukudlula isimedo se SSTs ngetrophikhali yelwandle le-Indiya kodwana kufuthumale ukwedlula isimedo se SSTs ngesewula yenarha yeSewula Afrika; kungakho, iimfunda lapho kuna khona izulu ehlobo kuvamile kobana kube nesomiso esidlula isimedo ngesikhathi se La Niña, Nanyana amatjhuguluko wemimoya nokuna kwezulu ngeendaweni eziselwandlwe le-Indiya nenarheni ye-Afrika zithanda ukwehluka kancani namkha khulu nje ngesikhathi se le La Niña, azibuyeli emuva zoke njengobana ilwandlwe nemimoya kukhambisana ngendlela ezinengi.

Nasingezelela ku El Niño ne La Niña, ilwandlwe le-Indiya kesinye isikhathi libonisa iindlela ze SST ekukholwakala kobana ziba nomthelela ekuneni kwezulu lehlobo eSewula Afrika. Indlela eqakathekileko yokuna kwezulu okungehla kumumethe isifunda esikhulu esifuthumeleko ukudlula isimedo semimoya yelwandlwe kufikela ngesewula-mpumalanga ye Madagascar ngaso lesosikhathi kunye neendawo zelwandlwe ezingetjhingalanga yetjhingalanga ye Australia zikhombisa ukubamakhaza ukwedlula isimedo. Lendlela yobujamo bezulu nayibuyekezwako, ukuna kwezulu okungaphasi kwesimedo kuthanda ukwenzeka eSewula Afrika, Zimbabwe, ne Zambia.

Janabari, Febrebari-Matjhi ziinyanga eziqakathekileko zesikhathi sokuna kwezulu eenarheni ezisethlagwini-pumalanga zeSewula Afrika. Leziimbonelo ezimbili zibonisa imithelela ye SSTs elwandle le-Indiya mayelana nokuna kwezulu eenarheni ezisepumalanga ye Sewula Afrika.


Isibonelo1 : Janabari-Febrebari 2000
Amaphesente wokuna kwezulu elijwayelekileko
Janabari kufikela ngoMatjhi 2000








Hlaza kwesibhakabhaka: ngaphezulu   125% yokuna kwezulu elijwayelekileko
Hlaza kotjani: 75% kufikela ku 125% yokuna kwezulu elijwayelekileko
Braweni: Ngaphasi kwe 75 % yokuna kwezulu elijwayelekileko
Umebhe (ngesinceleni) ukhombisa ukuna kwezulu kilesisikhathi.
I-SSTs esifundeni setlhagwini pumalanga ye Madagascar besimakhaza ukudlula isimedo nanyana bekufuthumele ukwedlula isimedo se SSTs esikhona ngepumalnga ye Sewula Afrika. Ubujamo obukhulu bokuna kwezulu obujwayelekileko bubonakala ngeemfundeni ezisepumalanga ye Sewula Afrika.
Ubujamo be-La Niña, bubonakale elwandle lephasafiki.










Isibonelo 2: Janabari- Febrebari 2002
Amaphesente wokuna kwezulu elijwayelekileko
Janabari kufikela ngoMatjhi 2002











Hlaza kwesibhakabhaka: ngaphezulu   125% yokuna kwezulu elijwayelekileko
Hlaza kotjani: 75% kufikela ku 125% yokuna kwezulu elijwayelekileko
Braweni: Ngaphasi kwe 75 % yokuna kwezulu elijwayelekileko
Umebhe (ngesinceleni) ukhombisa ukuna kwezulu kilesisikhathi.

I-SSTs esifundeni setlhagwini pumalanga ye Madagascar besifuthumele ukudlula isimedo nakobana bekumakhaza ukwedlula isimedo se SSTs esikhona ngepumalnga ye Sewula Afrika. Ubujamo obukhulu bokuna kwezulu obujwayelekileko bubonakala ngeemfundeni ezisethlagwini- pumalanga yeSewula Afrika.

Ubujamo obuphakathi (be El Niño namkha La Niña)  bubonakale ngelwandle lephasafiki



 Ilwandle le-Atlantiki

Umthelela welwandle le-Antantiki ekuneni kwezulu lehlobo eemfundeni lisungulwe ngokungalapheleli. Ukwenzeka kokufuthumala khulu ukwedlula isimedo se SSTs phakathi kwe gwi lelwande le Angola netlwagwini ye Namibia ngesikhathi sehlobo (esibizwa nge Benguela Niño) laziwa ngokobana lizihlanganise nezulu elihle ngeemfundeni zetjhingalanga zenarhezo.  Amazinga wokufuthumala/nokubamakhaza ngeendaweni ezinge Angola Benguela athanda ukuhluma ngesikhathi sika Matjhi no Apreli. Nakwenzakala, Isimedo esingehla sokuna kwezulu zingadlulela eenarheni ezingasiseduze nelwandle bezithelele ithlagwini pumalanga ye Sewula Afrika.

Ngakwelinye ihlangothi, ukwehlukahlukana kwe SSTs ngelwandle leSewula ye Atlantiki (phakathi kwelathitjhudi engaba yi-25oS ne 45oS) zaziwa ngokobana zisondelene nokuna kwezulu lebusika esifundeni se tlhagwini kapa.

Ukwahlukahlukana kobujamo belwandle kungarholela ekutheni kube ne-El Niño/La Niña, kodwana kwesinye isikhathi zivela kweminye imimoya ezombelezako kilelilwandle.

Ukuswaphelisa 

Kafitjhazana, ukwahlukahlukana kwemimoya yamalwandle angePhasafiki, Indiya ne Sewula ye-Atlantiki kuba nomthelela wokuna kwezulu eSewula Afrika. Lezi akuzizenzakalo ezibanga ukuna kwezulu okuhlukahlukeneko kwaphela ngalokho amatjhuguluko we SSTs angabonisa amatshwayo angehla namkha angaphasi kwesimedo sokuna kwezulu endaweni ezinabileko zenarha ngesikhathi seenkhathi zonyaka.

Nanyana kunjalo, nakuneminingwana efaneleko mayelana nemimoya yelwandle efakwe emakhompyutheni ngaphambi kobana kufike isikhathi esithile sonyaka, Iindlela zekhompyutha lezi kanengi zingakhombisa amatshwayo anembako wobujamo bezulu esikhathini esizako kobana sizakuba nezulu namkha isomiso. Ukuthuthukisa inembo elizako mayelana neendlela ezisetjenziswa yikhompyutha kumsebenzi oragela phambili eKorweni YoBujamo BeZulu yeSewula Afrika kunye nezinye iinhlangano zikarhulumende eziphathelene nobujamo bezulu kunye namayunivesithi ephasini mazombe begodu kuthenjelwe kibososayensi ekufumaneni lokho ekwenzeka ngamalanga emalwandle wephasini kunye nemimoya yakhona.




About the Authors:

Chris Reason is professor in Oceanography at the University of Cape Town.
Anna Bartman has been involved in long-range forecasting at the SA Weather Service for the past 12 years.
