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Tropical Pacific neutral for remainder of summer
在南半球夏季的餘下時間, 熱帶太平洋會維持中性(18-12-2012)
The tropical Pacific Ocean remains neutral - neither El Niño nor La Niña. The central to eastern Pacific has cooled somewhat over the past month, with sea surface temperatures (SSTs) now close to their long-term average. Atmospheric indicators of ENSO, such as the Southern Oscillation Index (SOI), trade winds and cloudiness near the Date Line have shown some fluctuations recently, but have also continued at neutral levels. Further falls are expected in the SOI over the coming days, as a result of the tropical weather system which spawned TC Evan. Large fluctuations in the SOI over summer due to tropical weather systems are not uncommon.
熱帶太平洋繼續維持中性--即不是厄爾尼諾或拉尼娜狀態. 過去一個月, 太平洋中部-東部稍為轉冷, 現時其海洋表層溫度(SSTs)已經接近長期平均值. 最近, 各項ENSO的大氣指標(例如南方濤動指數(SOI), 信風和換日線附近的雲量)稍有波動, 但是它們仍然在中性的水平. 本局預期在未來一段日子, SOI會持續下跌. 這是由產生熱帶氣旋\"伊雲\"的熱帶天氣系統所致. 受到熱帶天氣系統的影響, 夏季期間SOI出現的大幅波動, 並非異常的現象.
Climate models surveyed by the Bureau of Meteorology indicate that the tropical Pacific is likely to remain ENSO neutral through the southern hemisphere summer. This means that in contrast to the two prior summers, Australian rainfall and temperatures are unlikely to be strongly influenced by ENSO. Given current conditions and outlooks, this will be the first ENSO-neutral summer since 2005–06.
氣象局參考的氣候模式表示, 在南半球的夏季以內, 熱帶太平洋會維持在ENSO中性狀態. 這意味著, 和過去兩年的夏季不同, 今年澳洲的夏季將不會受到ENSO的嚴重影響. 基於現在的情況和展望, 這將會是2005-2006年度以來首個ENSO中性的夏季.
The influence of the Indian Ocean Dipole (IOD) on Australian rainfall is limited during summer and autumn, though near-record ocean temperatures off the northwest Australian coast may have at least a local influence.
雖然澳洲西北部沿海出現的、接近歷史鋒值的海溫或會對該區有一定的影響, 但是在夏季和秋季期間, 印度洋偶極子(IOD)對澳洲降水的影響有限.
Sea Surface Temperatures
海洋表層溫度
Monthly sea surface temperatures:
每月海洋表層溫度:
When compared to that for the previous month, the sea-surface temperature (SST) anomaly map for November shows the focus of warm SST anomalies in the tropical Pacific Ocean has shifted westward. SSTs are slightly above average in the western half of the equatorial Pacific, while in the east anomalies have all but disappeared. The warmest anomalies remain west of the Date Line, where an area of water is more than 1 °C warmer than usual. Warm SST anomalies also remain around Australia’s northwest and western coast.
11月的海洋表層溫度(SST)距平圖顯示, 和上月相比之下, 熱帶中太平洋的SST暖距平中心, 已經有所西移. 赤道太平洋的西半部的SST稍為高於平均值, 而東半部的距平區已完全消失. 最大的暖距平區仍在換日線以西, 其水溫高於平均值超過1度. 在澳洲西北部和西部海岸, 仍然存在著SST暖距平.
Index | October | November | Temperature change | NINO3 | +0.3 | +0.2 | 0.1 °C cooler | NINO3.4 | +0.4 | +0.2 | 0.1 °C cooler | NINO4 | +0.8 | +0.8 | no change |
Baseline period 1961–1990. |
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Weekly sea surface temperatures:
每周海洋表層溫度:
SST anomalies in the tropical Pacific have changed little over the past fortnight. Very weak warm anomalies remain along the equator west of about 170°W (see the SST anomaly map for the week ending 16 December below). SSTs in the central and eastern tropical Pacific are generally close to average, although some small areas of cool water are present adjacent to the South American coast. Warm SST anomalies remain in the region to Australia’s northwest, while those in the south Pacific have weakened compared to two weeks ago.
過去兩星期, 熱帶太平洋的SST距平有輕微的轉變. 在西經約170度以西的赤道上, 仍然有著十分微弱的暖距平(詳見直到12月16日為止的每週SST距平圖, 如下). 儘管南美洲沿岸附近出現了零碎的冷水區, 熱帶太平洋中部和東部的SST大致接近正常. 澳洲西北部仍然有著SST暖距平區, 而南太平洋的SST暖距平區, 則較兩星期前為弱.
[table=100%]IndexPreviousCurrentTemperature change
(2 weeks)NINO3+0.1+0.00.1 °C coolerNINO3.4+0.3+0.10.2 °C coolerNINO4+0.6+0.6no change
Baseline period 1961–1990.
Sub-surface Pacific Ocean temperatures
太平洋地區的次表層海溫
Monthly sub-surface:
每月次表層海溫:
The four-month sequence of sub-surface temperature anomalies (to November) shows water across the entire equatorial Pacific Ocean was cooler than average at about 150 meters of depth. The anomalies reached more than 2 °C below average in places, while closer to the surface weak warm anomalies were present.
直到11月為止、過去4個月的赤道太平洋次表層海溫距平序列指出, 整個赤道太平洋、水深約150米的水域, 皆較平均值為冷. 該區的負距平已經超過2度, 而在接近表層的水域, 則出現了弱暖距平.
Weekly sub-surface:
每周次表層海溫:
Compared to two weeks ago, sub-surface temperature anomalies in the eastern equatorial Pacific have cooled. The map for the 5 days ending 16 December shows very weak warm anomalies 50 to 150 m beneath the surface of the central equatorial Pacific, while weak cool anomalies are present in the eastern and western equatorial Pacific at greater depth, and also close to the surface in the far eastern equatorial Pacific.
和兩星期前相比, 赤道東太平洋的次表層海溫距平有所轉冷. 直到12月16日為止的5天距平圖顯示, 在赤道中太平洋表層以下50-150米的水域, 有著十分微弱的暖距平, 同時, 在赤道太平洋東部和西部以下、更深的次表層水域, 以及遠東赤道太平洋、接近表層的水域, 出現了微弱的冷距平.
Southern Oscillation Index:
南方濤動指數:
The Southern Oscillation Index (SOI) has dropped sharply over the past week and a half, but remains within neutral values. The latest (16 December) 30-day SOI value is −7.5. This is primarily due to a low pressure trough which formed near Tahiti in the second week of December, and which spawned several tropical lows including TC Evan. During the southern hemisphere summer, it is not unusual to have large deviations of the SOI on a weekly scale due to transient weather systems.
過去1.5星期, 南方濤動指數(SOI)急劇下跌, 但是仍在中性範圍. 最新(12月16日)的30天SOI數值是-7.5。這主要是因為在12月的第二週, 大溪地附近有一低壓槽形成, 其中生成了數個熱帶低壓(包括熱帶氣旋\"伊雲\"). 在南半球的夏季期間, 由於有短期性的天氣系統存在, SOI在一週內出現大幅偏差的情況並非不正常.
Sustained positive values of the SOI above +8 may indicate a La Niña event, while sustained negative values below −8 may indicate an El Niño event. Values of between about +8 and −8 generally indicate neutral conditions.
SOI持續在+8以上,可能意味著拉尼娜事件的發生;而SOI持續在-8以上,可能意味著厄爾尼諾事件的發生。SOI在+8和-8之間維持的話,通常表示情況為中性。
Trade winds:
信風:
The anomaly map for the 5 days ending 16 December shows trade winds are near average across the eastern half of the tropical Pacific and weaker than average across the western half; westerly winds are present near the equator over the far western tropical Pacific.
直到11月18日為止的最新一幅5天風力距平圖顯示, 熱帶太平洋東半部的信風接近正常, 而西半部則較平均值為弱; 在遠西太平洋、接近赤道的區域, 出現了偏西信風.
During La Niña events, there is a sustained strengthening of the trade winds across much of the tropical Pacific, while during El Niño events there is a sustained weakening of the trade winds.
在拉尼娜事件下,赤道太平洋地區的大部分地區的信風會持續增強;而在厄爾尼諾事件下,信風會持續減弱。
Cloudiness near the Date Line:
換日線附近的雲量:
During the past two weeks, cloudiness near the Date Line was somewhat below average before becoming slightly above average.
過去兩星期, 換日線附近的雲量稍為低於平均值, 其後轉為稍高於平均值.
Cloudiness along the equator, near the Date Line, is an important indicator of ENSO conditions, as it typically increases (negative OLR anomalies) near and to the east of the Date Line during an El Niño event and decreases (positive OLR anomalies) during a La Niña event.
換日線附近的赤道地區雲量,是ENSO狀況的重要指標之一,因為在厄爾尼諾事件下,換日線附近和以東的雲量通常會增加(OLR負距平),而在拉尼娜事件下則會減少(OLR正距平)。
Climate Models:
氣候模式:
International climate models surveyed by the Bureau indicate that SSTs in the equatorial Pacific Ocean are expected to remain in the neutral range for the austral summer 2012–13 and into the following autumn.
本局參考的國際氣候模式指出,在2012-2013年度澳洲的夏季, 以及接續的秋季, 赤道太平洋的SST會維持在中性範圍以內.
Indian Ocean Dipole:
印度洋偶極子:
The Indian Ocean Dipole (IOD) is currently neutral, with the latest IOD index value at +0.4°C for the week ending 16 December. The IOD typically has limited influence on Australia during the summer.
現時印度洋偶極子(IOD)為中性. 直到12月16日為止的一週, 最新的IOD指數數值為+0.4度. 一般來說, IOD對澳洲夏季的影響有限.
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