本文選題：PDO + NPGO　； 參考：《南京大學(xué)》2015年碩士論文

【摘要】：中緯度氣候存在著顯著的年代際信號。在北太平洋最主要的年代際信號有太平洋年代際振蕩(PDO)和北太平洋渦旋振蕩(NPGO),對應(yīng)大氣中的阿留申低壓模態(tài)(AL)和北太平洋振蕩(NPO)。太平洋年代際信號的產(chǎn)生與維持同中緯度海氣相互作用有密切的關(guān)系。中緯度海表面溫度(SST)異常一方面通過直接熱力強(qiáng)迫引起大氣環(huán)流異常,另一方面還可以通過海洋鋒區(qū)影響天氣尺度渦旋的形成和發(fā)展,天氣尺度渦旋的非線性作用對低頻流產(chǎn)生強(qiáng)迫,后者的作用尤為重要。本文利用1948-2010年北半球冬季NCEP再分析資料診斷了與PDO和NPGO信號相關(guān)的大氣環(huán)流異常和天氣尺度瞬變活動異常特征,討論了海洋鋒區(qū)天氣尺度波與低頻流相互作用在大氣環(huán)流對PDO以及NPGO對應(yīng)的SST異常響應(yīng)中的貢獻(xiàn),并建立簡單理論模型描述中緯度海洋和大氣的耦合過程。本文主要得出以下結(jié)論：PDO暖位相時(shí)北太平洋海盆區(qū)為SST冷異常,對應(yīng)的SST異常的南北梯度在北太平洋是一個(gè)偶極的結(jié)構(gòu)。在北太平洋有兩條海洋鋒區(qū)：副熱帶鋒區(qū)和副極地鋒區(qū),PDO暖位相時(shí),副極地鋒區(qū)南移,加強(qiáng)了副熱帶鋒區(qū)。伴隨著副極地鋒區(qū)的南移和副熱帶鋒區(qū)的加強(qiáng),風(fēng)暴軸的活動也隨著南移增強(qiáng)。天氣尺度瞬變渦旋的渦度輸送和熱力輸送共同作用使得阿留申低壓增強(qiáng)并向東南偏移,急流增強(qiáng)。NPGO暖位相時(shí)北太平洋SST異常呈現(xiàn)偶極型結(jié)構(gòu),約以40℃N為界,40℃N以北為冷異常,40℃N以南為暖異常,對應(yīng)的是副極地鋒區(qū)的增強(qiáng)和副熱帶鋒區(qū)的北移,風(fēng)暴軸增強(qiáng)。瞬變渦旋的非線性強(qiáng)迫使得阿留申低壓和夏威夷上空副熱帶高壓都增強(qiáng),急流向北移動。對于PDO和NPGO,大尺度環(huán)流場都是相當(dāng)正壓結(jié)構(gòu),溫度場都是斜壓結(jié)構(gòu)。使用理論模型模擬的結(jié)論表明,海氣耦合的結(jié)果就是被強(qiáng)迫的海洋Rossby波,最不穩(wěn)定的波長大約10000km,對應(yīng)的時(shí)間尺度基本是年代際時(shí)間尺度,與PDO以及NPGO的時(shí)間尺度相近。在這個(gè)海氣耦合過程中,影響SST的主要作用是洋流對SST的南北輸送作用,洋流對SST的南北輸送使得所有波段都產(chǎn)生不穩(wěn)定,而洋流異常導(dǎo)致的夾卷作用異常會抑制短波的不穩(wěn)定,增加長波的不穩(wěn)定,但作用比平流項(xiàng)弱。
[Abstract]:There are significant Interdecadal signals in the mid-latitude climate. The most important Interdecadal signals in the North Pacific are the Pacific Interdecadal Oscillation (PDO) and the North Pacific Vortex Oscillation (NPGOG), corresponding to the Aleutian low pressure mode (ALL) in the atmosphere and the North Pacific Oscillation (NPO). The generation of the Pacific Interdecadal signal is closely related to the maintenance of mid-latitude sea-air interaction. On the one hand, the SST-anomaly in mid-latitude sea surface temperature can cause the atmospheric circulation anomaly through direct thermal forcing, on the other hand, it can also influence the formation and development of synoptic scale vortices through the oceanic frontal region. The nonlinear action of synoptic vortex forces low frequency flow, the latter is especially important. In this paper, the characteristics of atmospheric circulation anomalies and synoptic scale transient anomalies associated with PDO and NPGO signals are diagnosed by using the NCEP reanalysis data from 1948-2010 in the Northern Hemisphere. The contribution of synoptic scale waves and low-frequency currents in ocean frontal region to the response of atmospheric circulation to SST anomaly corresponding to PDO and NPGO is discussed, and a simple theoretical model is established to describe the coupling process between mid-latitude ocean and atmosphere. In this paper, we draw the following conclusions: the North Pacific basin is a SST cold anomaly during the warm phase of the North Pacific Ocean, and the North and South gradient of the corresponding SST anomaly is a dipole structure in the North Pacific Ocean. There are two ocean fronts in the North Pacific: the subtropical front and the subpolar front. When PDO is warm, the subpolar front moves southward and strengthens the subtropical front. Along with the southward movement of the subpolar front and the strengthening of the subtropical front, the activity of the storm track increases with the southward shift. The vorticity transport and thermal transport of synoptic scale transient vortices make Aleutian low pressure increase and shift to the southeast. The SST anomaly in the North Pacific shows dipole structure during the warm phase of jet enhancement. The north of 40 鈩，

本文編號：1836372