考虑飞沫影响的拖曳系数方案对台风条件下上层海洋海温数值模拟的影响
作者简介:刘霄燕(1991—), 女, 新疆维吾尔自治区乌鲁木齐市人, 在读物理海洋学方向研究生。E-mail: liu_xiaoyan_sophie@126.com
收稿日期: 2016-10-20
要求修回日期: 2017-04-13
网络出版日期: 2017-09-22
基金资助
国家重点基础研究计划(“973”)项目(2013CB430305)
The influence of a new drag coefficient scheme considering sea spay on numerical simulation of upper-ocean temperature response to tropical cyclone
Received date: 2016-10-20
Request revised date: 2017-04-13
Online published: 2017-09-22
Supported by
National Program on Key Basic Research Project (973) Program (2013CB430305)
Copyright
为了提高对上层海洋的模式模拟准确性, 为台风海气耦合模式提供更加合理的动量交换耦合方案, 文章应用一个分粒径段的海洋飞沫函数给出一个新的海面拖曳系数CD计算方案, 它体现了台风高海况条件下海洋飞沫层使海面拖曳系数数值减小特点。论文以2014年第15号台风“海鸥”经过南海强化观测区域时段作为个例, 应用POM(Princeton Ocean Model)三维海洋环流模式进行数值模拟试验, 结果发现低风速情况下, 考虑海洋飞沫因素后的CD与传统计算方案数值相近, 在高风速情况下, 考虑海洋飞沫因素后的CD方案与模式传统计算方案不同, 表现出随风速增长趋缓, 直至随风速略有下降现象。与传统拖曳系数方案相比, 采用新的拖曳系数方案后, 模拟的台风条件下上层海洋的温度降温幅度、混合层深度加深幅度、温跃层强度减弱程度都略有减弱, 这些模拟特征与观测事实更加接近。
刘霄燕 , 李永平 , 段自强 . 考虑飞沫影响的拖曳系数方案对台风条件下上层海洋海温数值模拟的影响[J]. 热带海洋学报, 2017 , 36(5) : 24 -32 . DOI: 10.11978/2016103
To improve model forecast of upper ocean and offer a more proper momentum exchange scheme for an air-sea coupling model, a new drag coefficient scheme of CD considering sea spay layer on the surface is established and is used in the three-dimensional oceanic circulation model of the Princeton Ocean Model (POM). A case of tropical cyclone Kalmaegi in 2014 is selected, which passed through the center of a buoys array set up by our field experiment in the northern South China Sea. Observation data were collected for both atmosphere and ocean in the process, and are used to verify the model simulation. It is found that the drag coefficient CD under low wind condition is consistent with the traditional CD scheme. However, they are different from each other under high wind condition with CD increasing slowly, even decreasing slightly, if sea spay process is considered by the new CD scheme. Furthermore, numerical experiments are conducted using the POM. The results show that the responses of upper ocean on temperature are more reasonable with a weaker cooling rate of ocean temperature and thermocline strength, and smaller deepening of mixed layer depth in the upper ocean if the new drag coefficient scheme is used.
Fig. 1 Buoy array in the South China Sea and track of Typhoon Kalmaegi. represents the center of typhoon, and●represents the locations of the buoys图1 南海浮标观测阵列及2014年“海鸥”台风路径 |
Fig. 2 Averaged ocean temperature standard deviation between simulation in EXP2 and Argo observations图2 EXP2模式模拟海温与西北太平洋Argo观测海温的标准差 |
Fig. 3 Ocean temperature profiles with depth before Typhoon Kalmaegi passing the locations of B2 (a), B4 (b) and B5 (c). Short dashed line: buoy observations; and solid line: simulated ocean temperature by EXP1图3 9月10日18时(台风影响前)浮标B2(a)、浮标B4(b)和浮标B5(c)海温随深度的变化廓线 |
Fig. 4 Sea surface wind field used by the model at 06:00 on Sep. 15 in 2014. represents the center of typhoon, and●represents locations of buoys图4 2014年9月15日06时的模式强迫海面风场 |
Fig. 5 The observed wind speed (dotted line) and model wind speed (solid line) at B2, B4 and B5 buoy sites, from Sep. 10 to Sep. 19图5 B2(a)、B4(b)和B5(c)浮标所在位置上的2min平均风速的观测(虚线)和模式强迫风速(实线)时间序列 |
Fig. 6 Variation of drag coefficient CD with wind speed and sea spray concentration |
Fig. 7 Difference of sea surface temperature before and after Typhoon Kalmaegi: a) satellite observations; b) EXP1; and c) EXP2图7 “海鸥”台风经过浮标观测列阵前后的SST变化 |
Fig. 8 Time series of SST for EXP1, EXP2 and observations, respectively, at B2 (a) and B5 (b)图8 海表面温度SST随时间变化 |
Tab. 1 SST decreases in EXP1, EXP2 and observed by buoys (Units: ℃)表1 EXP1、EXP2和观测的SST降温幅度(单位: ℃) |
浮标 | EXP1 | EXP2 | OBS(观测) |
---|---|---|---|
B1 | 2.17 | 1.88 | 1.87 |
B2 | 2.02 | 1.90 | 1.44 |
B3 | 1.61 | 1.31 | 1.24 |
B4 | 1.96 | 1.67 | 1.80 |
B5 | 1.05 | 0.97 | 0.62 |
Fig. 9 Ocean temperature profiles with depth before and after Typhoon Kalmaegi: i) OBS; ii) EXP1; and iii) EXP2. a) Buoy 2; and b) Buoy 4. Solid line: before typhoon passage; and dashed line: after typhoon passage图9 台风影响前后观测(i)、EXP1(ii)和EXP2(iii)海温随深度的变化廓线 |
The authors have declared that no competing interests exist.
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