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QIN Sisi,ZHANG Qilong,YIN Baoshu. 2015. Seasonal variability in the thermohaline structure of the Western Pacific Warm Pool. Acta Oceanologica Sinica, 34(7):44-53
Seasonal variability in the thermohaline structure of the Western Pacific Warm Pool
西太平洋暖池热盐结构的季节变化
Received:June 18, 2014  Revised:November 21, 2014
DOI:10.1007/s13131-015-0696-6
Key words:Western Pacific Warm Pool  thermohaline structure  barrier layer  mixed layer  seasonal variability
中文关键词:  西太平洋暖池  热盐结构  障碍层  混合层  季节变化
基金项目:
Author NameAffiliationE-mail
QIN Sisi Key Laboratory of Ocean Circulation and Waves, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China
University of Chinese Academy of Sciences, Beijing 100049, China 
 
ZHANG Qilong Key Laboratory of Ocean Circulation and Waves, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China qlzhang@qdio.ac.cn 
YIN Baoshu Key Laboratory of Ocean Circulation and Waves, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China  
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Abstract:
      Using the 28℃ isotherm to define the Western Pacific Warm Pool (WPWP), this study analyzes the seasonal variability of the WPWP thermohaline structure on the basis of the monthly-averaged sea temperature and salinity data from 1950 to 2011, and the dynamic and thermodynamic mechanisms based on the monthly-averaged wind, precipitation, net heat fluxes and current velocity data. A △T=-0.4℃ is more suitable than other temperature criterion for determining the mixed layer (ML) and barrier layer (BL) over the WPWP using monthly-averaged temperature and salinity data. The WPWP has a particular thermohaline structure and can be vertically divided into three layers, i.e., the ML, BL, and deep layer (DL). The BL thickness (BLT) is the thickest, while the ML thickness (MLT) is the thinnest. The MLT has a similar seasonal variation to the DL thickness (DLT) and BLT. They are all thicker in spring and fall but thinner in summer. The temperatures of the ML and BL are both higher in spring and autumn but lower in winter and summer with an annual amplitude of 0.15℃, while the temperature of the DL is higher in May and lower in August. The averaged salinities at these three layers are all higher in March but lower in September, with annual ranges of 0.41-0.45. Zonal currents, i.e., the South Equatorial Current (SEC) and North Equatorial Counter Current (NECC), and winds may be the main dynamic factors driving the seasonal variability in the WPWP thermohaline structure, while precipitation and net heat fluxes are both important thermodynamic factors. Higher (lower) winds cause both the MLT and BLT to thicken (thin), a stronger (weaker) NECC induces MLT, BLT, and DLT to thin (thicken), and a stronger (weaker) SEC causes both the MLT and BLT to thicken (thin) and the DLT to thin (thicken). An increase (decrease) in the net heat fluxes causes the MLT and BLT to thicken (thin) but the DLT to thin (thicken), while a stronger (weaker) precipitation favors thinner (thicker) MLT but thicker (thinner) BLT and DLT. In addition, a stronger (weaker) NECC and SEC cause the temperature of the three layers to decrease (increase), while the seasonal variability in salinity at the ML, BL, and DL might be controlled by the subtropical cell (STC).
中文摘要:
      以28℃等温线作为西太平洋暖池的边界, 基于1950至2011年的月平均温盐数据, 本文分析了暖池热盐结构的季节变化特征, 并通过月平均的风场, 流场, 降水和净热通量数据分析了该季节变化特征的动力及热力机制。得到结论如下:在利用月平均网格资料计算暖池的混合层和障碍层时, ΔT 选-0.4℃更合适;西太平洋暖池在垂向上可分为三层, 从上至下依次为:混合层, 障碍层和深层。其中障碍层的厚度最厚, 混合层最薄。这三层厚度的季节变化一致, 均为春季厚而夏季薄。混合层和障碍层的温度均为春秋季高而冬夏季低, 其最大年差为0.15℃, 而深层的温度则在5月最高而8月最低。三层盐度均在3月最高9月最低, 其最大年差为0.41~0.45;暖池热盐结构季节变化在动力方面主要受风和水平流特别是SEC与NECC的作用, 在热力方面降水和净热通量都是其变化的主要因素。强(弱)风往往会使得混合层和障碍层增厚(变薄), 而当NECC增强(减弱)时, 三层均变薄(增厚), SEC增强(减弱)时, 混合层和障碍层增厚(变薄)而下层变薄(增厚)。同时, 当净热通量增加(减少)时, 往往会使得混合层和障碍层增厚(变薄), 下层变薄(增厚), 而强(弱)降水则会使得混合层变薄(增厚), 障碍层和深层增厚(变薄)。除此之外, 当NECC及SEC增强时(减弱)时, 三层的温度下降(升高), 而三层盐度的季节变化则可能主要受副热带环流圈(STC)的影响。
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