Te Tikanga o te Āhuatanga La Niña
Ko La Niña tētahi o ngā āhuatanga āhuarangi o te ao e tino pā ana ki ngā āhuarangi i ngā rohe maha o te ao, tae atu ki a Indonesia. Ko tēnei āhuatanga he wāhanga o tētahi huringa taiao e mōhiotia ana ko te ENSO (El Niño–Southern Oscillation), arā, ko te taunekeneke matatini i waenga i te āhuarangi me te moana i te Moana-nui-a-Kiwa pārūrū. Ahakoa he rite a El Niño ki te whakamahana i ngā pāmahana o te mata o te moana i te Moana-nui-a-Kiwa waenganui-mā-rāwhiti, ko La Niña te ritenga kē, arā, he āhuatanga ka mātao ake ngā pāmahana o te mata o te moana i te rohe i te mea noa. Kāore tēnei huringa pāmahana e puta takitahi ana, engari ka puta he raupapa tauhohenga mekameka i roto i te hau, te pēhanga hau, te hanganga kapua, me te ua. He mea nui te mārama ki te tikanga o La Niña kia taea ai e te hapori me te kāwanatanga te matapae i ōna pānga, pērā i te pikinga o te ua, te waipuke, me ngā whakararuraru ki ngā rāngai ahuwhenua me te hī ika.
1. Ko La Niña hei Wāhanga o te Pūnaha ENSO
Ko te ENSO he pūnaha o ngā wiri (te pikinga me te hekenga) e puta ana i ia wā, i ia 2–7 tau te nuinga. I raro i ngā āhuatanga noa (koretake), he āhua pumau te āhua o te tohanga o te Moana-nui-a-Kiwa: ko te Moana-nui-a-Kiwa ki te hauauru (e tata ana ki Initonīhia me Ahitereiria) he mahana ake, ko te Moana-nui-a-Kiwa ki te rawhiti (e tata ana ki Amerika ki te Tonga) he mātao ake nā te pupū ake (te pikinga ake o te wai matao mai i raro i te moana). Ina pāngia tēnei pūnaha e ngā rerekētanga nui, ka puta he wāhanga El Niño, La Niña rānei.
Ko ngā āhuatanga o La Niña e whai ake nei:
– Te whakamatao i ngā āhuatanga rerekē o te pāmahana o te mata o te moana (SST) i te Moana-nui-a-Kiwa o waenganui me te rawhiti.
– Te kaha ake o ngā hau hokohoko mai i te rawhiti ki te hauauru.
– Ngā panonitanga o ngā tauira pēhanga hau e pā ana ki te tohanga o te hau, inā koa te Walker Circulation.
– Te nekehanga o te pokapū whakawhiti hau (te hanganga o ngā kapua ua) ki te rohe uru o Te Moana-nui-a-Kiwa.
2. Te Tūranga o te Pāmahana o te Mata o te Moana: Te Tīmatanga o te Mekameka Hurihanga
Ko te tikanga o La Niña ka tīmata i ngā panonitanga o te pāmahana o te mata o te moana i te Moana-nui-a-Kiwa pārūrū. Ka puta tēnei whakamatao i te rohe e mōhiotia ana ko Niño 3.4 (huri noa i te Moana-nui-a-Kiwa waenga), e whakamahia ana hei tohu matua. Ina heke te pāmahana o tēnei rohe mā te 0,5°C, neke atu rānei, i raro iho i te tikanga mō ētahi marama karapīpiti, ka tīmata ngā āhuatanga ki te neke ki La Niña.
He mea nui tēnei whakamatao nā te mea ko ngā moana te "kaituku pūngao" mō te āhuarangi. Ka whakaitihia e te wai moana mātao te mimiti, ka whakaitihia te nui o te mamaoa wai e piki ake ana ki te āhuarangi i te Moana-nui-a-Kiwa waenga-mā-rāwhiti. Nō reira, ka ngoikore te hanganga o ngā kapua me te ua i tēnei rohe, engari ko te Moana-nui-a-Kiwa uru he kaha ake te hanga i ngā kapua convective nā te mea he mahana tonu te pāmahana o te moana, he mahana ake rānei i te toharite.
3. Te Whakakaha o ngā Hau Pākihi me te Pānga "Pana" o te Wai Moana
Ko tētahi o ngā kī ki te La Niña ko ngā hau hokohoko rawhiti e pupuhi ana mai i te takutai o Amerika ki te Tonga ki Āhia ki te Tonga-mā-rāwhiti. I ngā wā o La Niña, ka kaha ake ēnei hau hokohoko. E rua ngā pānga nui o te kaha ake o ngā hau hokohoko:
1. Te pana i te wai mahana ki te hauauru
Ka panaia te wai mahana ki runga, ka kohia ki te taha hauauru o te Moana-nui-a-Kiwa (huri noa i a Initonīhia, Papua Niu Kini, me te raki o Ahitereiria). Mā tēnei kohi ka nui ake te rerekētanga o te taumata moana: ki teitei ake i te hauauru, ki raro iho i te rawhiti.
2. Te whakapakari i te puea ake i te rawhiti
I te panaia atu o te wai mata mahana mai i te takutai o Amerika ki te Tonga, ka whakakapia te wāhi takoto kau i te mata e te wai matao, whai matūkai mai i ngā paparanga o raro. Ka kiia tēnei tukanga ko te upwelling, ā, koinei te take matua e matao ai te rawhiti o te Moana-nui-a-Kiwa i te wā o La Niña.
Nā te mea ka kaha ake ngā hau hokohoko me te puea ake o te hau, ka roa te whakamatao i te rawhiti, ā, ka toro atu ki waenganui o te Moana-nui-a-Kiwa.
4. Te Hurihanga o Walker: Te Mīhini Āhuarangi e Huri ana i ngā Tauira
He hononga tata a La Niña ki ngā panonitanga o te Walker Circulation, arā, te tohanga hauāuru ki te rawhiti i te Moana-nui-a-Kiwa ekueta. He māmā noa iho, ko te mahi a te Walker Circulation penei:
– Ka piki ake te hau wera me te hau makuku (convection) i ngā wāhi he mahana te moana → ka hanga kapua me te ua.
– I te āhuarangi o runga, ka neke te hau ki te rawhiti.
– Ka heke te hau ki runga i ngā wāhi makariri, maroke.
– I te mata o te whenua, ka hoki te hau ki te hauauru hei hau hokohoko.
Ina puta te La Niña, ka mahana haere te moana i te taha hauauru o te Moana-nui-a-Kiwa, ka mātao haere te moana i te taha rawhiti o te Moana-nui-a-Kiwa. Nā reira:
– Ka piki ake te ua me te hauātanga i te taha hauauru o te Moana-nui-a-Kiwa (tae atu ki Initonīhia).
– Ka kaha ake te heke o te hau i waenganui–rāwhiti o te Moana-nui-a-Kiwa, ka maroke ake te rohe.
– Ka kaha ake ngā hau hokohoko, ka nui ake te mātao me te puea ake.
He tauira tēnei o tētahi tikanga urupare pai rongonui i roto i te ENSO, e mōhiotia whānuitia ana ko te urupare Bjerknes: te whakamatao o te moana → te kaha ake o ngā hau hokohoko → te pikinga o te puea ake → te whakamatao kaha ake.
5. Te Tūranga o te Thermocline: Te "Rohe" e Whakatau ana i te Pūmautanga o La Niña
Kei raro i te mata o te moana tētahi paparanga whakawhiti pāmahana e kiia nei ko te thermocline, he rohe e wehe ana i te wai mahana i runga me te wai matao i raro. He nui te pānga o te hohonutanga o te thermocline ki te ngāwari, ki te uaua rānei o te putanga ake o te wai matao ki runga.
I te wā o La Niña:
– He pāpaku ake te wāhi werawera i te rawhiti o te Moana-nui-a-Kiwa, ā, ka māmā ake te piki ake o te wai matao ki te mata.
– He hohonu ake te pāmahana wera i te taha hauauru o te Moana-nui-a-Kiwa, e tohu ana i te nui haere o te wai mahana.
Ko te rerekētanga o te pari thermocline (e anga whakarara ana mai i te hauauru hōhonu ki te rawhiti pāpaku) he āhuatanga o ngā āhuatanga La Niña kaha, ā, ka pumau ake ai tēnei āhuatanga mō ētahi wā.
6. Ngā Ngaru o te Moana me ngā Whakaoho Tuatahi (Kelvin rāua ko Rossby)
Haunga ngā hau me ngā thermocline, ka uru atu hoki ngā ngaru moana nui ki ngā āhuatanga o La Niña, inā koa:
– Ngā ngaru Kelvin (e neke ana ki te rawhiti i te taha o te ekueta)
– Ngā ngaru o Rossby (e neke ana ki te hauauru)
Ka taea e ngā panonitanga o ngā hau o te ekueta te whakaoho i ēnei ngaru, ka whakarerekē i te hohonutanga o te thermocline me te tohatoha wera o raro i te mata. Ina kaha ake te kaha o ngā ngaru e ārahi ana ki te whakamatao, ka piki ake te tūponotanga o La Niña. Arā, ehara a La Niña i te "raruraru mata" anake, engari kei roto hoki ko te rokiroki me te whakawhiti wera i roto i ngā paparanga moana hohonu.
7. Pānga ki te Ua: He aha i maha ai te makuku o Initonīhia?
I te neke me te kaha haere o te pokapū whakawhiti i te taha hauauru o te Moana-nui-a-Kiwa, ka pāngia a Initonīhia e:
– He ua nui ake i te noa, inā koa i ētahi wāhi e pāngia ana e ngā hau ua me ngā āhuatanga o te moana e karapoti ana.
– Te pikinga ake o te auau o te ua nui, ka taea ai e tēnei te waipuke me te horo whenua.
– Ngā huringa o ngā wā, hei tauira, he roa ake te wā ua, he kaha ake rānei te tihi.
Heoi, kāore i te ōrite tonu te pānga o La Niña ki Indonesia. Ko ētahi atu āhuatanga ā-rohe pērā i te Indian Ocean Dipole (IOD), te pāmahana o te moana i ngā wai o Indonesia, me ngā āhuatanga o te hau marangai o Āhia-Ahitereiria ka kaha ake, ka ngoikore rānei i ngā pānga o La Niña.
8. Te Mutunga o te Huringa La Niña
Kāore a La Niña e mau tonu ake ake. Ka ngoikore haere ina:
– Kei te tīmata ngā hau hokohoko ki te hoki ki te āhua noa, ki te ngoikore rānei.
– Ka heke te pupū ake i te rawhiti.
– Kei te hoki anō te pāmahana o te mata o te moana i waenganui-mā-rāwhiti o te Moana-nui-a-Kiwa ki te tata ki te toharite.
I ētahi wā, ka roa pea te La Niña neke atu i te tau (La Niña maha-tau) mēnā ka kaha tonu te urupare a te moana ki te āhuarangi, ā, kāore e ranea te rahui wera o raro i te mata hei whakamahana anō i te Moana-nui-a-Kiwa waenganui-rāwhiti.
Whakamutunga
Ko te tikanga o La Niña he hua o ngā taunekeneke tata i waenganui i te moana me te āhuarangi i te Moana-nui-a-Kiwa pārūrū. Ko te whakamatao i ngā pāmahana mata moana i waenganui-mā-rāwhiti o te Moana-nui-a-Kiwa ka whakaoho i te kaha o ngā hau hokohoko, ka kaha ake te pupū ake, ka huri i te pari thermocline, ka whakapakari ake i te Walker Circulation. Ka hangaia e tēnei tukanga he porowhita urupare pai e taea ai e La Niña te noho mō ngā marama ki te neke atu i te tau. He whānui te pānga: ko te taha hauauru o te Moana-nui-a-Kiwa, pērā i a Indonesia, he nui ake te makuku, ko te taha rawhiti o te Moana-nui-a-Kiwa me ētahi wāhanga o Amerika he maroke ake. Mā te mārama ake ki te tikanga o La Niña, ka taea te whakatakoto tika ake i ngā mahi whakaiti me te urutau, inā koa hei whakaiti i te mōrearea o ngā aituā wai me te pupuri i te haumarutanga kai.
Ki te hiahia koe, ka taea e au te whakarerekē i tēnei tuhinga kia putaiao ake (me ngā tohutoro hautaka), kia rongonui ake rānei mō ngā kaipānui kura, me te tāpiri atu hoki i ngā raraunga mō te pānga o La Niña ki Initonīhia.
