几种风压场中强降水临近预报的探讨

AN ANALYSIS OF NOWCASTING HEAVY PRECIPITATION IN SEVERAL KINDS OF WIND AND PRESSURE FIELD

通过简化的降水率公式、散度方程和运动学公式,在强降水上空满足风压场,(分别为高,低层地转偏差;分别为高、低层实际风)条件下,分别导出与天气尺度运动正相对散度中心对应的强降水加强,减弱及移动的判别式。并提出以此判别式作为临近预报的依据。讨论表明:在天气尺度运动正相对散度中心对应的强降水上空,满足上述条件下,高层,高、低层及低层非地转运动在地转涡度平衡态(fζ=▽2φ)附近摆动,通过高层强辐散、高层强辐散同时低层强辐合或低层强辐合引起正相对散度中心的变化,影响强降水加强、减弱。

Based on the simplificd formula of precipitation rate and the divergence equation by the kinematis method, a set of formulas for discriminating intensification, weakening and movcment of heavy precipitation area, which is associated with the center of large scale motion is derived under the condition that v' 2 and v'1 are geostrophic departure,v2 and v1 actual winds in both the upper and lower troposphere) respectively. It is put forward that nowcasting is based on this formula of discrimination. It is indicated in the discussion that, under the above-mentioned condition' the ageostrophie motion fluctuates abou the equilibrium state of geostrophic vorticity and affects the heavy procipitation area by the variation of the positive center of relative divergence caused by the upper strong divergence, lower strong convergence when it occurs or lower strong convergence itself in the upper, upper-lowcr and lower tropo-sphcre.