Analysis of Convectively Induced Turbulence (CIT) within the Shallow Convections in Seoul, South Korea

Turbulence that directly affect aircraft near the convective system is regarded as the Convectively Induced Turbulence (CIT). Although it is possible for pilots to tactically avoid the possible CIT regions by looking at the on-board radar echoes, it is necessary to aware which areas have more hazardous CIT within the clouds. On October 28, 2018, moderate-or-greater (MOG) CIT with a sudden variation in vertical acceleration (g) between +0.6 g and +1.6 g is occurred at z = 2.2 km within the shallow convection bands near Seoul (37.59"° N, 126.63°E) right after aircraft took off. 1-Hz sampling rate of flight data and 5-min frequency of ground-based radar data are used to understand the environmental condition responsible for this MOG CIT.

Using the flight data, we estimate the cube root of Eddy Dissipation Rate (EDR; m^2/3 s^-1) by finding the best fit of the Kolmogorov scale (k^-5/3) on the wind spectra for every 1-min interval, which shows this CIT has about 0.4 m^2/3 s^-1 of EDR corresponding to the MOG intensity at the incident time (0542 UTC). From the radar data, reflectivity (dBZ) confirms that the shallow convective bands have higher dBZ near the surface and their tops are about 4 km above the ground. Spectral Width (SW; m s^-1) observed by the Doppler radar indicates the scattering degree of wind velocity in a given scanning volume, inferring the magnitudes of atmospheric turbulence. In this case, SW showed the highest value (~ 4 m s^-1) in the upper part of the shallow convection, which is consistent with the accident location.