The Relationship Between the Interannual Variation of Earth’s Rotation and El Niño Events
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Variation (astronomy)
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Earth surface
Abstract The sea surface temperature (SST) and surface enthalpy flux response to tropical cyclones (TCs) in the Kuroshio are investigated using 18‐year observational datasets. The statistical results show that the maximum TC‐induced SST cooling and its occurrence time, recovery time, spatial patterns of the SST anomaly, and the surface enthalpy flux anomaly between the Kuroshio and the warm core eddies (WCEs) and typical oceanic water (i.e., eddy‐free and Kuroshio‐free, TOW) varies considerably. Specifically, the Kuroshio suppresses TC‐induced SST cooling more so than the WCE. The Kuroshio can make the maximum SST cooling occur approximately half a day sooner than that in the WCE and TOW. The recovery time is also shorter in the presence of the Kuroshio and is more pronounced with increasing SST reduction. Compared to the cold wake in the TOW, the composited SST decrease exhibits a long strip with a width of approximately 2° in the presence of the Kuroshio, rather than having a circular distribution of SST decrease as in the WCE. In the recovery period, the negative SST anomaly propagates leftward slowly under TOW conditions, whereas the negative SST anomaly shifts rightward gradually in the Kuroshio condition. Similarly, the air‐to‐sea flux anomaly propagates rightward slowly in the Kuroshio, which moves leftward in the WCE and TOW. These results emphasize that the impact of the Kuroshio on the tropical cyclone‐induced SST anomaly and the surface enthalpy flux anomaly cannot be ignored.
Anomaly (physics)
Eddy
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Using the data of Tropical Cyclones (TCs) series for the 56-yr period of 1949—2004, we studied the statistical characteristics of the multi-year variation of the frequency of TCs activity over the western North Pacific and the relationship with sea surface temperature (SST). The results show that the frequency of TCs activity over the area has interannual and interdecadal variability, which differs with the intensity of TCs but tends to decrease with time and TCs do not increase significantly due to global warming. Three areas are identified in this study to discuss the influence of SST. The results show that the increase of TCs frequency is caused by negative SST anomaly in the equatorial eastern Pacific. The positive anomaly of TCs frequency will result in negative SST anomaly in the western North Pacific based on an existing lead-lag correlation. The more severe the TCs, the earlier they are influenced by SST and large frequency of TCs will in turn result in negative SST anomaly in western North Pacific. The stronger the TCs, the shorter the period for which they produce negative anomaly. The SST of central North Pacific is much positively correlated with the frequency of TCs, which shows that an intense vortex wind field of TCs can result in local mixing in the upper layers of the ocean and the Pacific Meridional Mode (PMM) for air-sea coupling can affect TCs.
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Long-term observations indicate that the Indian Ocean displays significant low-frequency variability in mean sea-level pressure, near-surface wind, cloud and sea-surface temperature (SST). A general circulation model is used to study the response of the atmosphere to an idealized SST anomaly pattern (warm in southern mid-latitudes, cool in southern tropics) that captures the essence of observed multidecadal SST variability as well as that associated with ENSO in the South Indian Ocean. The major objectives are to investigate air–sea interaction mechanisms potentially associated with the variability and whether the atmospheric response to the SST is likely to lead to maintenance or damping of the original SST anomaly pattern, and on what time scale. Two types of experiment are performed to tackle these objectives. An ensemble of roughly 1-year-long integrations suggests that the seasonal-scale response of the atmosphere to the imposed SST anomaly includes reduced genesis and density of cyclones in the mid- to higher latitudes, and an indication of a shift in their tracks relative to climatology. It is argued that these changes together with those to the near-surface winds could be expected to lead to variations in surface fluxes that would tend to reinforce the original SST anomaly pattern on seasonal scales. A 21 year integration of the model with the SST anomaly pattern imposed throughout indicates that a low is generated near, and downstream of, the warm mid-latitude anomaly. On decadal/multidecadal scales, the associated changes to the surface winds are argued as being likely to lead to changes in surface fluxes and in the strength of the South Indian subtropical gyre that would oppose the original anomaly. The current and previous model results together with the observations then support the idea that the observed multidecadal variability in atmospheric circulation and SST of the South Indian Ocean during the past century may have arisen through a combination of basin scale atmosphere–ocean interaction and a remotely forced component. © 1998 Royal Meteorological Society
Anomaly (physics)
Middle latitudes
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Anomaly (physics)
Tropical Atlantic
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Based on reanalysis data from 1979 to 2016, this study focuses on the sea surface temperature (SST) anomaly of the tropical North Atlantic (TNA) in El Niño decaying years. The TNA SST exhibits a clear warm trend during this period. The composite result for 10 El Niño events shows that the TNA SST anomaly reaches its maximum in spring after the peak of an El Niño event and persists until summer. In general, the anomaly is associated with three factors—namely, El Niño, the North Atlantic Oscillation (NAO), and a long-term trend, leading to an increase in local SST up to 0.4°C, 0.3°C, and 0.35°C, respectively. A comparison between 1983 and 2005 indicates that the TNA SST in spring is affected by El Niño, as well as the local SST in the preceding winter, which may involve a long-term trend signal. In addition, the lead–lag correlation shows that the NAO leads the TNA SST by 2–3 months. By comparing two years with an opposite phase of the NAO in winter (i.e., 1992 and 2010), the authors further demonstrate that the NAO is another important factor in regulating the TNA SST anomaly. A negative phase of the NAO in winter will reinforce the El Niño forcing substantially, and vise versa. In other words, the TNA SST anomaly in the decaying years is more evident if the NAO is negative with El Niño. Therefore, the combined effects of El Niño and the NAO must be considered in order to fully understand the TNA SST variability along with a long-term trend. 摘要 基于1979年到2016年多种再分析资料, 本文分析了El Niño衰减年热带北大西洋的海温异常. 结果表明, 热带北大西洋海温在此期间呈显著变暖趋势. 10次El Niño事件的合成结果表明热带北大西洋海温异常在El Niño事件峰值之后的春季达到最大值, 并持续到夏季. 一般而言, 这种异常与三个因子有关, 即El Niño, 北大西洋涛动和长期趋势, 能分别导致局地海温上升0.4°C, 0.3°C和0.35°C. 1983年和2005年的对比分析表明, 尽管El Niño强度对春季北大西洋海温起到决定性作用, 与长期趋势密切相关的前冬海温也很重要. 此外, 超前-滞后相关结果表明北大西洋涛动超前海温约2–3个月. 比较两个冬季相反位相北大西洋涛动的年份 (即1992年和2010年) , 表明北大西洋涛动也能调制北大西洋海温异常. 冬季负位相北大西洋涛动能显著增强El Niño的强迫影响, 反之亦然. 换言之, 如果北大西洋涛动与El Niño位相相合, 衰减年北大西洋海温异常才更为显著. 因此, 为全面理解热带北大西洋海温变化, 除长期趋势外, 还必须考虑El Niño和北大西洋涛动的综合影响.
Anomaly (physics)
Forcing (mathematics)
Tropical Atlantic
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This study investigates the evolution of the sea surface temperature (SST) over the cold tongue (CT) region in the central South China Sea (SCS) during various El Niño events. A significant and distinct double-peak warming evolution can occur during EP El Niño and CP El Niño events, with the former being more remarkable and robust than the latter. Further analyses show that the weak and insignificant CT SST anomaly in CP El Niño events is influenced by some CP El Niño events in which the warm sea surface temperature anomaly (SSTA) is located west of 175° E (WCP El Niño). The response of CT SSTA mainly depends on the warm SSTA location of CP El Niño. The different corresponding mechanisms in winter, spring and summer are discussed respectively in this work. Further analysis reveals that the weak and insignificant SST anomaly over the CT region in CP El Niño events is caused by the faint SSTA response during the WCP El Niño events. The results of this study call attention to the response of the SCS climate in both atmosphere and ocean to the diversity of ENSO, especially the CP El Niño.
Anomaly (physics)
Surface air temperature
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The tropical Pacific,the tropical Indian Ocean and the tropical Atlantic are the most prominent areas in terms of Ocean Atmosphere interaction on earth.To probe into some features about the local Ocean Atmosphere interaction,new satellite data for the Sea Surface Temperature(SST) anomaly and Cloud Liquid Water(CLW) have been analysed statistically by correlation analysis in the three tropical oceans in this paper.It is discovered that the synchronous correlation coefficients of SST anomaly and CLW anomaly are always positive within 5 weeks of lead or lag time,which means there is a positive feedback mechanism between SST anomaly and CLW anomaly in the equatorial Pacific and Atlantic;When the SST anomaly leads the CLW anomaly by one week,the positive correlation coefficient is maximum,which means that the SST variation could lead the CLW variation in the west tropical Indian Ocean;Contrary to this,the synchronous correlation coefficient is negative in cold sea surfaces,such as the extra-equatorial southeast and northeast Pacific and extra-equatorial south Atlantic,where the CLW variation could lead to the SST variation.In the tropical northwest pacific,which is in the east of the Philippines,the CLW variation could also lead to the SST variation;In the east equatorial Indian Ocean,the SST increase(decrease) could lead to CLW increase(decrease) in some periods,and CLW increase(decrease) could also conduce to SST decrease(increase) in other periods.Those results will be useful for understanding tropical ocean-atmosphere interaction and improving the parameterization scheme of ocean-atmosphere interaction.
Anomaly (physics)
Lead (geology)
Tropical Atlantic
Sea-surface height
Variation (astronomy)
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Four perpetual January integrations of an atmospheric general circulation model have been performed, in each of which a different sea surface temperature (SST) anomaly was specified in the North Pacific. The observed SST anomaly for the 1976/77 winter was chosen as the basic anomaly, and 1200-day runs were carded out in which this anomaly was multiplied by ±1 and ±2. A fifth run was performed which combined the basic midlatitude SST anomaly from 1976/77 with a tropical Pacific SST anomaly representative of the mature phase of a warm El Niño/Southern Oscillation (ENSO) episode. An ensemble of eight, independent 90-day averaged realizations was extracted from each simulation. Maps of ensemble-mean differences from the model climatology are presented in this paper, together with estimates of the statistical significance of some of the features which appear on these maps. The model response to the basic SST anomaly and to twice the basic SST anomaly is a midiatitude teleconnection pattern, the Pacific/North American (PNA) pattern, which has been found in previous experiments which used tropical Pacific SST anomalies. The amplitude of the model response increases at a slower than linear rate as the magnitude of the SST anomaly is increased. The model response to the basic midlatitude SST anomaly is compared with the model response to tropical Pacific SST anomalies. When the basic midlatitude anomaly is combined with a tropical Pacific SST anomaly, such as commonly occurs during the mature phase of warm ENSO episodes, we find that the model response to the combined SST anomalies is approximately equal to the sum of the model responses produced by the SST anomalies acting separately. The model response to the basic SST anomaly times –1 and times –2 is not a previously described teleconnection pattern. Over the North Pacific, the model response in the upper troposphere is weak, but below 700 mb. the response in heights and temperatures is the opposite of that produced for SST anomalies of the opposite sign. There is also a positive anomalous zonal wind over the southern United States and a negative height anomaly over the eastern United States.
Anomaly (physics)
Teleconnection
Middle latitudes
Forcing (mathematics)
Walker circulation
Atmospheric Circulation
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