排序方式： 共有4条查询结果，搜索用时 15 毫秒
1
1.
2.
Mesoscale convective systems (MCSs) are severe disaster-producing weather systems. Previous attempts of MCS census are made by examining infrared satellite imageries artificially, with subjectivity involved in the process unavoidably. This method is also inefficient and time-consuming. The disadvantages make it impossible to do MCS census over Asia and western Pacific region (AWPR) with an extended span of time, which is not favorable for gaining a deeper insight into these systems. In this paper, a fire-new automatic MCS identification (AMI) method is used to capture four categories of MCSs with different sizes and shapes from numerical satellite infrared data. 47,468 MCSs are identified over Asia and western Pacific region during the warm season (May to October) from 1995 to 2008. Based on this database, MCS characteristics such as shape, size, duration, velocity, geographical distribution, intermonthly variation, and lifecycle are studied. Results indicate that the number of linear MCSs is 2.5 times that of circular MCSs. The former is of a larger size while the latter is of a longer duration. The 500 hPa steering flow plays an important role in the MCS movement. MCSs tend to move faster after they reach the maximum extent. Four categories of MCS have similar characteristics of geographical distribution and intermonthly variation. Basically, MCSs are zonally distributed, with three zones weakening from south to north. The intermonthly variation of MCSs is related to the seasonal adjustment of the large-scale circulation. As to the MCSs over China, they have different lifecycle characteristics over different areas. MCSs over plateaus and hill areas, with only one peak in their lifecycle curves, tend to form in the afternoon, mature at nightfall, and dissipate at night. On the other hand, MCSs over plains, which have several peaks in their lifecycle curves, may form either in the afternoon or at night, whereas MCSs over the oceans tend to form at midnight. Affected by the sea-land breeze circulation, MCSs over coastal areas of Guangdong and Guangxi always come into being at about 1500 or 1600 (local time), while MCSs over the Sichuan Basin, affected by the mountain-valley breeze circulation, generally initiate nocturnally. 相似文献
3.
4.
对流温度在局地热对流降水预报中的应用 总被引：1，自引：0，他引：1
热对流降水是副热带高压控制下常见的一种天气现象,突发性强且时空尺度小,是目前天气预报业务中的难点。本文尝试使用对流温度（Tc）预报热对流降水。首先改进了 MICAPS3中Tc 的算法。然后使用2004—2013年7—8月南京站的探空和地面观测资料,探讨了在副热带高压控制下时使用Tc 预报热对流降水的可行性。结果表明,南京站热对流降水发生的气候平均概率约为1／6;热对流降水的发生概率随日最高温度（Tmax ）与Tc 的差值先增大后减小;当Tmax比Tc 低0．5℃以上时,发生概率低于平均概率;当Tmax比Tc 高0．5～1．5℃时,热对流降水的发生概率最大,达到了40％。Tmax＞30℃、Tmax－Tc＞－3．5℃是副热带高压控制下的热对流降水发生的两个必要条件。另外,对34个热对流降水的统计表明,热对流降水主要出现在每日13—18时,平均持续时间为50 min,平均降水量为7．8 mm。 相似文献
1