北半球冬季風(fēng)暴軸與熱帶外海洋的相互作用
發(fā)布時間：2018-04-27 14:24
本文選題：中緯度海—?dú)怦詈?/strong> + 風(fēng)暴軸�。� 參考：《中國海洋大學(xué)》2014年博士論文
【摘要】：風(fēng)暴軸代表了強(qiáng)烈的中緯度天氣尺度瞬變渦動活動，在中緯度天氣和氣候系統(tǒng)中具有十分重要的地位。不僅如此，從中緯度海-氣相互作用的角度來講，風(fēng)暴軸對熱帶外海表面溫度（SST）異常響應(yīng)所產(chǎn)生的非線性反饋在大尺度海-氣耦合過程中起著重要的調(diào)控作用。因此，認(rèn)識和理解風(fēng)暴軸在不同時間尺度上的變化及其與下墊面SST異常的關(guān)系對理解熱帶外氣候變化及其可預(yù)測性具有重要的科學(xué)意義。然而，關(guān)于風(fēng)暴軸異常與中緯度SST異常之間的耦合關(guān)系以及風(fēng)暴軸的長期變化趨勢，目前還缺乏清晰的認(rèn)識。風(fēng)暴軸的長期變化很可能在一定程度上預(yù)示中緯度海氣耦合的變化。 本文利用百年時間長度的海洋同化資料和20世紀(jì)大氣再分析資料（20CRv2），，結(jié)合超前-滯后的最大協(xié)方差分析（MCA）等多種統(tǒng)計分析方法，闡明了北太平洋和北大西洋冬季風(fēng)暴軸異常分別與其下墊面SST異常之間的季節(jié)和年際耦合關(guān)系。對于北太平洋而言：①在季節(jié)時間尺度上，秋季副極地海區(qū)的海盆尺度SST冷異常能夠使早冬時期的風(fēng)暴軸在30°N以北產(chǎn)生海盆尺度的正異常響應(yīng)，從而使風(fēng)暴軸活動向北加強(qiáng)。秋季這種海盆尺度SST冷異常實(shí)際上能夠向北加強(qiáng)早冬大氣的斜壓性和斜壓能量轉(zhuǎn)換，這很可能導(dǎo)致相應(yīng)的風(fēng)暴軸活動加強(qiáng)。然而，風(fēng)暴軸的這種響應(yīng)模態(tài)與早冬風(fēng)暴軸對SST的強(qiáng)迫模態(tài)完全不同，后者表現(xiàn)為：向南移動并加強(qiáng)的風(fēng)暴軸能夠在北太平洋中西部誘導(dǎo)產(chǎn)生SST冷異常，而在北美西海岸沿岸產(chǎn)生SST暖異常。②在年際時間尺度上，研究發(fā)現(xiàn)在冬季（DJF）中緯度海區(qū)，類似太平洋年代際振蕩（PDO）模態(tài)的馬蹄型SST異常（其中北太平洋中西部海區(qū)表現(xiàn)為SST暖異常）與40°N以北海盆尺度的風(fēng)暴軸正異常之間存在相互加強(qiáng)的正反饋效應(yīng)。該耦合模態(tài)具有顯著的年代際變化特征。進(jìn)一步分析發(fā)現(xiàn)：上述風(fēng)暴軸異常響應(yīng)與由SST異常變化引起的大氣低層斜壓性的增強(qiáng)密切相關(guān)；風(fēng)暴軸的異常變化則主要通過引起異常的表面凈熱通量和Ekman平流輸運(yùn)來誘導(dǎo)產(chǎn)生SST異常。 對于北大西洋而言：①在季節(jié)時間尺度上，早冬時期中緯度海區(qū)的經(jīng)向偶極子型SST異常（冷異常中心位于紐芬蘭外東南部；暖異常中心位于副熱帶海區(qū)西部）能夠使早春時期的風(fēng)暴軸活動顯著增強(qiáng)。早冬時期的這種經(jīng)向偶極子型SST異常實(shí)際上能夠顯著加強(qiáng)早春大氣的斜壓性和斜壓能量轉(zhuǎn)換，這很可能導(dǎo)致相應(yīng)的風(fēng)暴軸活動加強(qiáng)。然而與北太平洋不同的是，風(fēng)暴軸的這種響應(yīng)模態(tài)與早春風(fēng)暴軸對SST的強(qiáng)迫模態(tài)非常類似。②在年際時間尺度上，研究發(fā)現(xiàn)在冬季（JFM）中緯度海區(qū)，單極子型的SST暖異常（異常中心位于紐芬蘭以東和以南海區(qū)）與類似緯向偶極子型的風(fēng)暴軸異常（以下游區(qū)域中的負(fù)異常為主導(dǎo)）之間存在相互加強(qiáng)的正反饋效應(yīng)。該耦合模態(tài)具有顯著的年代際變化特征。進(jìn)一步研究發(fā)現(xiàn)：單極子型的SST暖異常能夠使低層大氣斜壓性在40°N-50°N緯度帶顯著減弱，這很可能導(dǎo)致風(fēng)暴軸活動減弱；風(fēng)暴軸的異常變化則主要通過引起向下的異常凈熱通量和異常Ekman暖平流輸運(yùn)進(jìn)而誘導(dǎo)產(chǎn)生單極子型的SST暖異常。 基于20CRv2資料提供的56個集合樣本數(shù)據(jù)集，本文還系統(tǒng)地揭示了北半球冬季風(fēng)暴軸的百年變化趨勢。研究發(fā)現(xiàn)，20世紀(jì)北半球冬季風(fēng)暴軸在對流層高層和低層具有不同的百年變化趨勢特征。在對流層高層，由天氣尺度的瞬變渦動運(yùn)動能（EKE）以及位勢高度場標(biāo)準(zhǔn)差表征的北太平洋和北大西洋風(fēng)暴軸均在其北部以及下游區(qū)域呈現(xiàn)出顯著增強(qiáng)的趨勢。這表明在20世紀(jì)后半葉，北半球冬季風(fēng)暴軸顯著向東北方向擴(kuò)展。此外，在北太平洋以及美國上空的高層大氣中，瞬變渦動對西風(fēng)動量的經(jīng)向輸送也同樣顯著增強(qiáng)。然而，在對流層低層，風(fēng)暴軸活動（尤其體現(xiàn)在EKE以及瞬變渦動對熱量的經(jīng)向輸送）在北太平洋副極地海區(qū)的中西部上空以及北大西洋風(fēng)暴軸上游地區(qū)呈現(xiàn)出顯著減弱的趨勢。進(jìn)一步分析發(fā)現(xiàn)，在對流層高層（低層），風(fēng)暴軸的增強(qiáng)（減弱）與大氣斜壓不穩(wěn)定的增大（減�。┟芮邢嚓P(guān)。 在上述分析基礎(chǔ)上，我們以中緯度大氣對黑潮-親潮延伸體（KOE）區(qū)SST異常的響應(yīng)為切入點(diǎn)，揭示了北太平洋中緯度海-氣耦合在全球變暖背景下的變化。研究發(fā)現(xiàn)，早冬時期（NDJ）大氣位勢高度對KOE區(qū)SST暖異常的響應(yīng)在阿留申低壓區(qū)呈現(xiàn)出相當(dāng)正壓結(jié)構(gòu)的脊響應(yīng)特征。在20世紀(jì)中，這種暖SST-準(zhǔn)正壓脊響應(yīng)具有顯著增強(qiáng)的趨勢，這很可能由全球變暖所致。IPCC-AR4多氣候模式試驗(yàn)結(jié)果也進(jìn)一步證實(shí)：在全球變暖場景下，暖SST-準(zhǔn)正壓脊響應(yīng)顯著增強(qiáng)。這表明全球變暖使早冬時期的北太平洋中緯度海-氣耦合顯著加強(qiáng)。
[Abstract]:The storm axis represents a strong mid latitude synoptic transient eddy activity, which is very important in mid latitude weather and climate systems. In addition, from the angle of mid latitude sea air interaction, the nonlinear feedback generated by the storm axis on the anomalous response of the tropical sea surface temperature (SST) is coupled with the large scale sea air coupling. Therefore, the understanding and understanding of the variation of the storm axis at different time scales and its relation to the SST anomaly of the underlying surface have important scientific significance for understanding the changes in the extratropical climate and its predictability. However, the coupling relationship between the anomaly of the storm axis and the anomaly of the mid latitude SST and the storm axis Long term change trend is still lacking in clear understanding. The long-term variation of storm axis is likely to predict the mid latitude air sea coupling to a certain extent.
In this paper, the seasonal and interannual coupling relationship between the anomalous winter storm axis in the North Pacific and the North Atlantic and its underlying surface SST anomalies in the North Pacific and North Atlantic is illustrated by using the oceanic assimilation data of a hundred years and the twentieth Century atmospheric reanalysis data (20CRv2) and the maximum covariance analysis (MCA). North Pacific: (1) on the seasonal time scale, the basin scale SST cold anomaly in the subpolar region of the autumn can cause the early winter storm axis to produce a positive abnormal response to the basin scale in the north of 30 N, so that the activity of the storm axis strengthens northward. In autumn, the basin scale SST cold anomaly can actually strengthen the early winter atmosphere in the north. However, this response mode of the storm axis is completely different from the forced mode of the early winter storm axis for SST, which shows that the Southward Moving and strengthened storm axis can induce SST cold anomalies in the Midwest of the North Pacific, while on the west coast of North America. On the interannual time scale, the study found that in winter (DJF) mid latitude sea area, the anomaly of horseshoe type SST similar to the Pacific interdecadal oscillation (PDO) mode (including the SST warm anomaly in the Midwest Pacific region of the North Pacific) and the positive feedback effect of 40 degree N to the positive anomaly of the wind storm axis of the Beihai basin scale. The coupling mode has significant interdecadal characteristics. Further analysis shows that the abnormal response of the storm axis is closely related to the enhancement of the low atmospheric baroclinic caused by the abnormal change of SST. The abnormal changes of the storm axis are mainly induced by the abnormal surface net heat flux and the Ekman advection transport to induce the SST anomaly.
For the North Atlantic: (1) on the seasonal time scale, the meridional dipole type SST anomalies in the mid latitudes of the early winter period (the cold anomaly center is located in the southeastern part of Newfoundland and the warm anomaly center in the west of the subtropical sea area) can significantly increase the activity of the storm axis in the early spring period. This meridional dipole type in early winter is different from that of the early winter. In fact, the baroclinic and baroclinic energy conversion in early spring can actually be significantly enhanced, which may lead to a corresponding enhancement of the corresponding storm axis activity. However, unlike the North Pacific, this response mode of the storm axis is very similar to the forced mode of the early spring storm axis for SST. There is a positive feedback effect between the latitude sea area, the monopole type SST warm anomaly (the anomaly center is located in the east of Newfoundland and the South China Sea) and the zonal dipole type storm axis anomaly (the negative anomaly in the downstream region). The coupling mode has the characteristic of the decadal variation. The SST warm abnormality of the polar subtype can weaken the low atmospheric baroclinic at 40 degrees N-50 degree N latitude, which may lead to the weakening of the activity of the storm axis, and the abnormal change of the storm axis is mainly induced by the downward anomalous net heat flux and the abnormal Ekman warm advection, which induces the SST warm anomaly of the monopole type.
Based on the 56 set sample data sets provided by the 20CRv2 data, this paper also systematically reveals the Centennial trend of the winter storm axis in the northern hemisphere. It is found that the winter storm axis in the northern hemisphere has a different Centennial trend in the upper troposphere and low layer in the northern hemisphere in twentieth Century. In the upper troposphere, the transient eddy motion energy of the synoptic scale (E KE) and the North Atlantic and North Atlantic storm axes, characterized by the standard deviation of the potential height field, showed a significant trend in the north and downstream regions. This indicates that the northern hemisphere winter storm axis expanded significantly in the northern hemisphere in the late twentieth Century. In addition, the transient vorticity in the North Pacific and the upper atmosphere over the United States. The meridional transport of the westerly momentum is also significantly enhanced. However, in the lower troposphere, the activity of the storm axis (especially the meridional transport of the EKE and the transient vortices) in the Midwest over the northern Pacific subpolar sea area and the upstream of the North Atlantic storm axis. The enhancement (weakening) of storm axis is closely related to the increase of atmospheric baroclinic instability.
On the basis of the above analysis, we take the response of the middle latitude atmosphere to the SST anomaly in the Kuroshio tidal extension (KOE) region as a breakthrough point, and reveal the changes of the mid latitude sea air coupling in the North Pacific under the global warming background. It is found that the response of the early winter (NDJ) atmospheric potential to the SST warm anomaly in the KOE region appears in the Aleutian low pressure region. In twentieth Century, this warm SST- quasi positive ridge response has a significant increasing trend in twentieth Century, which is likely to be further confirmed by the results of the.IPCC-AR4 multi climate model test caused by global warming: the warm SST- quasi positive pressure ridges should be significantly enhanced in the global warming scenario. This indicates that global warming makes early winter. The mid latitude Northern Pacific Ocean Atmosphere coupling is significantly enhanced.
【學(xué)位授予單位】：中國海洋大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2014
【分類號】：P732;P433
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相關(guān)期刊論文 前3條
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2 朱偉軍,孫照渤;冬季北太平洋風(fēng)暴軸的年際變化及其與500hPa高度以及熱帶和北太平洋海溫的聯(lián)系[J];氣象學(xué)報;2000年03期
3 朱偉軍;李瑩;;冬季北太平洋風(fēng)暴軸的年代際變化特征及其可能影響機(jī)制[J];氣象學(xué)報;2010年04期
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