【作者】 涂静；

【导师】 张苏平；

【作者基本信息】 中国海洋大学 ， 气象学， 2011， 硕士

【摘要】 海洋大气边界层高度对于污染物的扩散、海气能量的交换以及海雾的产生和海上层云、积云对流的发展都有着重要的影响,本文利用2005～2008年大连、青岛和台州5325个高分辨率L波段二次测风雷达探空资料、地面观测资料以及再分析资料,对沿海台站以及整个黄东海边界层高度时空变化特征进行了分析,主要结论如下:(1)青岛和台州傍晚的边界层高度略高于清晨,多为稳定和中性状态,青岛在春季稳定边界层最多,与4～7月的季节性逆温相对应;台州稳定边界层分布在秋冬季节,受地面辐射逆温影响,并且逆温高度要高于青岛。(2)青岛边界层高度存在日变化,在01、07、13和19LST四个时刻的计算结果中,午后13LST最高,傍晚19LST要高于清晨,高度变化程度介于内陆和海洋之间;通过小波分析发现,九月边界层高度日变化最为显著,这是由于7、8月份青岛盛行偏南风,受到海洋的调节,昼夜温差减小,同时7、8月多云和阴雨天气较多,热力因素对边界层的日变化影响明显减小,边界层的日变化减弱;通过典型天气的个例分析发现,热力对流占优势时边界层高度日变化比动力剪切占优势时明显。(3)分别用位温梯度法和干绝热法计算混合层高度,与观测的正午边界层高度对比,干绝热法计算结果更接近实际观测值;通过比较,沿海台站的边界层高度的季节变化与内陆台站不同,在夏季(6月)最低,秋季(9、10月)最高。在沿海台站,春、夏季海气温差小甚至为负值,下垫面相对稳定,浮力热通量最小,约920 hPa暖平流导致的低层季节性稳定大气层的建立以及夏季小的风切变都使得边界层高度在春、夏季节较低;相反的,在秋冬季节,下垫面不稳定,浮力热通量大,以及大的风剪切都有利于湍流的发展,形成更高的边界层。此外,台州秋冬季节近地面辐射逆温对当日混合层的发展没有影响;(4)通过小波分析,发现沿海台站边界层高度有显著的2～4天天气尺度振荡,10～20天准双周振荡以及30～60天的准40天振荡。天气尺度周期和准双周振荡的显著时域在春秋季节,台州较另外两个台站约延迟一个月;大连和青岛准40天振荡在夏季最为明显,而台州在1、2月最明显,说明这种季节内的振荡与地域分布有关;(5)黄东海大部分海区边界层高度季节变化呈现夏季低、冬季高的单峰结构,和东高西低、南高北低的空间分布。与陆地边界层高度的季节变化主要收到太阳辐射强度的影响不同,在海洋上空,由于海气温差和风速的季节变化,从而产生与陆地相反的感热通量和潜热通量的季节变化,是海洋上空大气边界层高度季节变化与陆地相反的主要原因。边界层高度在11、12月份有明显的东西分布,而在夏季(6、7月)主要表现为南北分布。边界层高度季节变化在黄海北部最为明显,在东海海域季节变化约700m,黄海海域可达约1000m。更多还原

【Abstract】 The Atmospheric Boundary Layer Height (ABLH) over Sea can have an important influence on the spread of pollution, the exchange between oceanic and atmospheric energy, the generation of sea fog, and the development of cumulus convection. In this paper, we analyzed the temporal and spatial variation of ABLH using the daily high-resolution L-band radar sounding data of Dalian Qingdao and Taizhou from 2005 to 2008. The main conclusions are as follows.(1) The boundary height in the evening in Qingdao and Taizhou is a little higher than that in the morning, and they are mostly in a stable and neutral condition. As for Qingdao, the highest ABLH occurs in the spring, which is related to the April-to-July seasonal inversion. As for Taizhou, the stable boundary layer occurs in the fall and winter, and it is influenced by the radiation inversion with an inversional height higher than that of Qingdao. However, the convectional boundary layer over Taizhou most occurs in summer, for it is influenced by the seasonal variation of the time of sunset and sunrise.(2) On the daily variation of ABLH of Qingdao, among the results of 01, 07, 13 and 19 LST, the highest boundary layer occurred at 13 LST, while the 19 LST one was a little higher than that of early morning, and the amplitude was situated between the land and the ocean. Wavelet analyses show that the daily variation of boundary layer is most dominant in September, which is because the prevailing wind in July and August in Qingdao is south wind and the temperature difference during day and night is decreased due to the effect of the ocean. Meanwhile, there is more cloudy and rainy weather in July and August, so the daily variation accounted for by thermal factors is decreased. Through the analyses of typical cases, the ABLH which was caused mainly by convection was found to be higher than that was caused mainly by dynamic shears.(3) The dry adiabatic method (DAM) and potential temperature gradient method (TGM) were both used to calculate the height of mixing layer. Compared with observational noon boundary layer height, the DAM is closer to the real. The seasonal variation of coastal stations, which is different from that of inland stations, has a lowest boundary layer in summer and a highest in fall. The boundary layer height of coastal stations in fall and winter is similar to that of the inland stations, but significantly lower in spring and summer. In spring, the seasonal stable stratification is the main factor of preventing the development of turbulence. In summer, due to the effect of the ocean, the temperature difference between day and night at coastal stations are obviously less than inland, resulting a lower mixing layer height. In that of Taizhou, the boundary layer height is lower due to the descend airflow caused by subtropical high; However, in the fall and winter, the prevailing wind is north wind with dry air mass from mainland; the daily variation caused by thermal factors increases, and the strengthened wind shear is also good for the development of turbulence; they are all contributing factors to higher boundary layer height; In fall and winter, the radiation inversion contributes less to the development of the mixing layer.(4) Wavelet analyses found that the ABLH at coastal stations have a 2-4 day weather scale oscillation, 10-20 day quasi-two-week oscillation, and 30-60 day quasi-40-day oscillation. The dominant time of the former two is the spring and fall. Taizhou is later than the other two stations by 1 month. The quasi-40-day oscillation in Dalian and Qingdao was dominant in summer, while winter for Taizhou. So the intraseasonal oscillation is regionally different.(5) The ABLH of the Yellow-East China Sea has significant seasonal variation -- the lowest in the summer and the highest in the autumn, its space distribution is lower in the northwest and higher in the southeast. The most important influence on the seasonal variation of ocean ABLH is SST-SAT and wind seasonal variations, which is different from the inland ABLH. Deeply exposed to this influence, the sensible and latent heat fluxes also make the same changes, and have an opposite phase compared to those inland. The east-west distribution of ABLH in the Yellow Sea is most obvious in November and December, significant north-south distribution of ABLH is obvious in the summer. The region which has the most distinct seasonal variation is the north yellow sea, which has a boundary layer up to 1000m, in contrast with the East China Sea with 700m boundary layer height.更多还原