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Analysis of the Characteristics of Inertia-Gravity Waves during an Orographic Precipitation Event

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Advances in Atmospheric sciences 2018年第5期35卷 604-620页

作者： Lu LIU lingkun ran {2. {3. state key {2. of Severe Weather Chinese Academy of Meteorological Sciences Beijing 100081 China Institute of atmosphere physics Chinese Academy Sciences Beijing 100029 China Heavy Rain and Drought-Flood Disasters in Plateau and Basin key laboratory of Sichuan Province Chengdu 610072 China Plateau atmosphere and Environment key {2. of Sichuan Province Sichuan 610103 China

A numerical experiment was performed using the Weather Research and Forecasting（WRF） model to analyze the generation and propagation of inertia-gravity waves during an orographic rainstorm that occurred in the Sichuan area on 17 August 2.14. To examine the spatial and temporal structures of the inertia-gravity waves and identify the wave types, three wavenumber-frequency spectral analysis methods（Fourier analysis, cross-spectral analysis, and wavelet cross-spectrum analysis）were applied. During the storm, inertia-gravity waves appeared at heights of 10-14 km, with periods of 80-100 min and wavelengths of 40-50 km. These waves were generated over a mountain and propagated eastward at an average speed of 15-2. m s^（-1）. Meanwhile, comparison between the reconstructed inertia-gravity waves and accumulated precipitation showed there was a mutual promotion process between them. The Richardson number and Scorer parameter were used to demonstrate that the eastward-moving inertia-gravity waves were trapped in an effective atmospheric ducting zone with favorable reflector and critical level conditions, which were the primary causes of the long lives of the waves. Finally, numerical experiments to test the sensitivity to terrain and diabatic heating were conducted, and the results suggested a cooperative effect of terrain and diabatic heating contributed to the propagation and enhancement of the waves.

关键词： inertia-gravity waves orographic precipitation Fourier analysis wavelet cross-spectrum analysis

Evolution of Instability before and during a Torrential Rainstorm in North china

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Advances in Atmospheric sciences 2016年第1期33卷 110-120页

作者： Lu LIU lingkun ran {2. {3. Institute of Atmospheric physics Chinese Academy Sciences Beijing 100029 Graduate University of chinese academy of sciences Beijing 100040 state key {2. of Severe Weather Chinese Academy of Meteorological Sciences Beijing 100081

NCEP-NCAR reanalysis data were used to analyze the characteristics and evolution mechanism of convective and symmetric instability before and during a heavy rainfall event that occurred in beijing on 2. July *** twelve hours before the rainstorm,the atmosphere was mainly dominated by convective instability in the lower level of 900-800 *** strong southwesterly low-level jet conveyed the moist and warm airflow continuously to the area of torrential rain,maintaining and enhancing the unstable *** the precipitation occurred,unstable energy was released and the convective instability ***,due to the baroclinicity enhancement in the atmosphere,the symmetric instability strengthened,maintaining and promoting the subsequent torrential *** the convective instability tendency equation demonstrated that the barotropic component of potential divergence and the advection term played a major role in enhancing the convective instability before the *** of the tendency equation of moist potential vorticity showed that the coupled term of vertical vorticity and the baroclinic component of potential divergence was the primary factor influencing the development of symmetric instability during the *** the effects of these factors on convective instability and symmetric instability showed some correlation.

关键词： convective instability symmetric instability torrential rain potential divergence

Potential Deformation and Its Application to the Diagnosis of Heavy Precipitation in Mesoscale Convective Systems

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Advances in Atmospheric sciences 2017年第7期34卷 894-908页

作者： Na LI lingkun ran Linna ZHANG {2. {3. key laboratory of Cloud-Precipitation {2. and Severe Storms Institute of Atmospheric Physics Chinese Academy of Sciences BeOing 100029 China state key {2. of Severe Weather Chinese Academy of Meteorological Sciences Beijing 100081 China beijing Meteorological Bureau Beijing 100089 China

Many observational studies have shown that deformation, like vertical vorticity and divergence, is closely related to the occurrence and distribution of strong precipitation. In this paper, to involve deformation in precipitation diagnosis, a new parameter called potential deformation（PD） is derived and then applied to precipitation detection within a simulated mesoscale convective system（MCS）. It is shown that PD includes both stretching deformation and shearing deformation and shares similar characteristics with deformation insofar as it does not change with the rotating coordinate. Diagnosis of the simulated MCS reveals that PD performs well in tracing the MCS＇ precipitation. In terms of their distributional pattern, the large-value areas of PD are similar to the precipitation in the different development stages of the MCS. A detailed analysis of the physical processes contained within the PD shows that it can reflect the three-dimensional moisture variation,vertical wind shear and wind deformation within the MCS. These structures are usually a comprehensive reflection of the characteristics of the surface cold pool, rear inflow jet, downward cold air flow and upward warm moist flow within the precipitating convective cells. For this reason, the PD shows much stronger anomalies in the precipitating atmosphere than the non-precipitating atmosphere, which implies considerable potential for its application in detecting heavy precipitation within MCSs.

关键词： Precipitation convective vorticity moisture divergence mesoscale observational stretching downward coordinate