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TRAMS_RUC_1 km模式初始场和侧边界方案的改进研究
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国家重点研究发展专项课题2018YFC1506900,国家自然科学基金项目41705035,广东省科技计划项目2017A020219005


Revised Initial Field and Lateral Boundary Condition Scheme for the TRAMS_RUC_1 km Model
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    摘要:

    本文从垂直分辨率、时间更新频率和要素完整性三个方面,对水平网格距为1 km的华南区域短时临近预报模式(TRAMS_RUC_1 km: Tropical Region Assimilation Model for South China Sea_The Rapid Update Cycle_1 km)中的初始场和侧边界方案进行改进研究。首先选择一次华南飑线个例进行敏感性试验,研究结果表明:(1)提高初始场和侧边界的垂直分辨率以后,模式对飑线内部中小尺度对流系统引起的强降水中心的模拟结果明显更加接近实况,而增加中低层的垂直分辨率对预报的改进起到了主要作用。(2)将模式侧边界时间更新频率从6 h一次提高到1 h一次以后,模式侧边界要素场的逐小时剧烈变化信息可以比较完整的保留下来。在使用高时间分辨率的侧边界条件进行模拟时,粤西沿海地区的水汽辐合明显加强,这对原来模式预报飑线移速偏慢现象会有改善作用。(3)当模式侧边界条件具有较高的时空分辨率时,进一步补充垂直速度和云微物理变量的侧边界条件对于飑线模拟结果的影响并不明显。总的来说,提高初始场和侧边界的垂直分辨率以及增加侧边界更新的时间分辨率,对于区域高分辨率模式对这次华南飑线预报效果的改进具有重要意义,而忽略垂直速度和云微物理量的侧边界条件则是一种可以接受的简化。在个例研究的基础上,利用改进后的初、边界条件进行为期一个月(2019年4月份)的批量试验,评估结果表明新方案对于逐小时降水空间分布和日变化特征的模拟均有明显改善。

    Abstract:

    In the TRAMS_RUC_1 km (Tropical Region Assimilation Model for South China Sea_The Rapid Update Cycle_1 km), the initial field and lateral boundary condition scheme, including its vertical resolution, time update frequency, and completeness, were revised and tested with a typical squall line case. Preliminary analysis revealed the following aspects: (1) The mesoscale character of precipitation in the squall line was better simulated after increasing the vertical resolutions of the initial field and lateral boundary, with the increase in the vertical resolutions of the middle and low layers playing the most critical role. (2) The diurnal change of lateral boundary forcing became more accurate after increasing its time update frequency. The squall line moved south after using the high update frequency of the lateral boundary condition because of the strengthened convergence of moist flux along the coastline. (3) With the high vertical resolution and high update frequency of the lateral boundary condition, lateral forcing of the vertical speed and cloud particle had no obvious effect on the forecasting of the squall line. In general, the vertical resolutions of the initial field and lateral boundary needed to be increased. The time update frequency also needed to be increased. Meanwhile, the lateral forcing of the vertical speed and cloud particle could be omitted. The effect of the new scheme was verified against observations in April 2019 (which lasted for a month). The distribution pattern and diurnal cycle of the mean hourly precipitation were significantly improved with the revised initial field and lateral boundary condition scheme.

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徐道生,陈德辉,张邦林,吴乃庚. TRAMS_RUC_1 km模式初始场和侧边界方案的改进研究.大气科学,2020,44(3):625~638 XU Daosheng, CHEN Dehui, ZHANG Banglin, WU Naigeng. Revised Initial Field and Lateral Boundary Condition Scheme for the TRAMS_RUC_1 km Model. Chinese Journal of Atmospheric Sciences (in Chinese),2020,44(3):625~638

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  • 收稿日期:2019-07-15
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  • 在线发布日期: 2020-05-26
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