Tsinkaye na shekaru goma na Pacific

Pacific decadal oscillation (PDO) mai ƙarfi ne, tsarin maimaitawa na canjin yanayi na teku da ke tsakiya a tsakiyar tsakiyar yankin Pacific. Ana gano PDO a matsayin ruwan dumi ko sanyi a cikin Tekun Pacific, arewacin 20 ° N. A cikin ƙarni da ya gabata, girman wannan yanayin yanayi ya bambanta ba bisa ka'ida ba a sikelin lokaci na shekara-shekara zuwa shekaru-shekaru (ma'ana lokutan lokaci na 'yan shekaru zuwa kusan lokutan lokaci da yawa). Akwai shaidar juyawa a cikin polarity mai yawa (ma'ana canje-canje a cikin ruwan sanyi da ruwan dumi a cikin yankin) na oscillation da ke faruwa a kusa da 1925, 1947, da 1977; juyawa biyu na ƙarshe sun dace da sauye-sauye masu ban mamaki a cikin Tsarin samar da salmon a Arewacin Tekun Pacific. Wannan yanayin yanayi kuma yana shafar yanayin teku na bakin teku da yanayin iska na nahiyar daga Alaska zuwa California.

A lokacin "mai dumi", ko "mai kyau", lokaci, yammacin Pacific ya zama mai sanyi kuma wani ɓangare na gabashin teku yana dumi; a lokacin "mai sanyi", ko "matsayi", lokaci, akasin haka yana faruwa. Steven R. Hare ne ya ba da sunan oscillation na shekaru goma na Pacific, wanda ya lura da shi yayin da yake nazarin sakamakon samar da salmon a shekarar 1997. 

Alamar oscillation na Pacific decadal ita ce babbar aikin orthogonal (EOF) na yanayin zafin jiki na teku na kowane wata (SST-A) a Arewacin Pacific (poleward na 20 ° N) bayan an cire matsakaicin zafin teku na duniya. Wannan alamar PDO ita ce daidaitattun jerin lokuta. An sake gina 'signal' na PDO har zuwa 1661 ta hanyar jerin lokuta na bishiyoyi a yankin Baja California.

 Hanyoyin da ake amfani da su 
Bincike da yawa sun nuna cewa za'a iya sake gina alamar PDO a matsayin ƙaddamar da tilasta wa wurare masu zafi da kuma matakai na wurare masu zafi. Don haka, ba kamar El Niño-Southern Oscillation (ENSO) ba, PDO ba yanayin jiki ɗaya ne na bambancin teku, amma jimlar matakai da yawa tare da asali daban-daban.

A ma'auni na lokaci-shekara ana sake gina alamar PDO a matsayin jimlar bazuwar da ENSO ya haifar da bambancin a cikin Aleutian Low, yayin da a kan ma'aunin lokaci na ENSO, tilasta yanayin yanayi da canje-canje a cikin Yankin Tekun Arewacin Pacific suna ba da gudummawa kusan daidai. Bugu da ƙari, Yanayin zafin jiki na teku yana da wasu hunturu zuwa hunturu saboda tsarin sake fitowa.

 Tasirin 

Tsarin sararin samaniya na PDO da tasirin suna kama da waɗanda ke da alaƙa da abubuwan da suka faru na ENSO. A lokacin da ya dace, lokacin hunturu na Aleutian Low yana zurfafawa kuma ya koma kudu, iska mai dumi / mai zafi yana gudana tare da gabar yammacin Arewacin Amurka kuma yanayin zafi ya fi na yau da kullun daga Arewa maso Yammacin Pacific zuwa Alaska amma a ƙasa da al'ada a Mexico da Kudu maso gabashin Amurka. Ruwan sama na hunturu ya fi na yau da kullun a cikin Alaska Coast Range, Mexico da Kudu maso Yammacin Amurka amma ya ragu a kan Kanada, Gabashin Siberia da Australia  McCabe et al. ya nuna cewa PDO tare da AMO suna da tasiri sosai ga tsarin fari na shekaru da yawa a Amurka, ana inganta yawan fari a yawancin Arewacin Amurka a lokacin PDO mai kyau da kuma Kudu maso Yammacin Amurka a yayin mummunan PDO a lokuta biyu idan PDO yana da alaƙa da AMO mai kyau. Hakanan yana shafar ruwan sama na Asiya, ana lura da ruwan sama da raguwar zafin lokacin rani a kan yankin Indiya a lokacin mummunan lokaci.
Alamun PDOMatsayi mai kyau na PDOMataki mara kyau na PDOYanayin zafiPacific Northwest, British Columbia, da AlaskaSama da matsakaiciDa ke ƙasa da matsakaiciMexico zuwa Kudu maso Gabashin AmurkaDa ke ƙasa da matsakaiciSama da matsakaiciRuwan samaYankin bakin teku na AlaskaSama da matsakaiciDa ke ƙasa da matsakaiciMexico zuwa Kudu maso Yammacin AmurkaSama da matsakaiciDa ke ƙasa da matsakaiciKanada, Gabashin Siberia da OstiraliyaDa ke ƙasa da matsakaiciSama da matsakaiciLokacin bazara na IndiyaDa ke ƙasa da matsakaiciSama da matsakaici

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