A Detection of Convectively Induced Turbulence Using in Situ Aircraft and Radar Spectral Width Data

Jung-Hoon Kim,Soo-Hyun Kim,Seungwoo Baek,Gyuwon Lee,Ja-Rin Park,Eunjeong Lee,Jeonghoe Kim

doi:10.3390/rs13040726

Abstract

A commercial aircraft, departing from Seoul to Jeju Island in South Korea, encountered a convectively induced turbulence (CIT) at about z = 2.2 km near Seoul on 28 October 2018. At this time, the observed radar reflectivity showed that the convective band with cloud tops of z = 6–7 km passed the CIT region with high values of spectral width (SW; larger than 4 m s–1). Using the 1 Hz wind data recorded by the aircraft, we estimated an objective intensity of the CIT as a cube root of eddy dissipation rate (EDR) based on the inertial range technique, which was about 0.33–0.37 m2/3 s−1. Radar-based EDR was also derived by lognormal mapping technique (LMT), showing that the EDR was about 0.3–0.35 m2/3 s−1 near the CIT location, which is consistent with in situ EDR. In addition, a feasibility of the CIT forecast was tested using the weather and research forecast (WRF) model with a 3 km horizontal grid spacing. The model accurately reproduced the convective band passing the CIT event with an hour delay, which allows the use of two methods to calculate EDR: The first is using both the sub-grid and resolved turbulent kinetic energy to infer the EDR; the second is using the LMT for converting absolute vertical velocity (and its combination with the Richardson number) to EDR-scale. As a result, we found that the model-based EDRs were about 0.3–0.4 m2/3 s−1 near the CIT event, which is consistent with the estimated EDRs from both aircraft and radar observations.

Highlights

Atmospheric turbulence in the free atmosphere is one of the most dangerous aviation weather hazards, as it can cause in-flight injuries and fatalities, and structural damage, shortening the longevity of aircraft and causing flight delays and fuel losses [1,2,3]
As a baseline study for the development of a convectively induced turbulence (CIT) forecast system in South Korea, we examined the CIT event on 28 October 2018 in South Korea, and estimated the eddy dissipation rate (EDR) using in situ aircraft data, Doppler radar-based spectral width (SW) data, and convection-permitting numerical simulation results
Were interested in larger values of SW, which are responsible for stronger turbulence, so we focused on the range of the probability density function (PDF) fitting on the right side of the histogram [3,27,51,52 we focused on the range of the PDF fitting on the right side of the histogram [3,27,51,52]

Summary

Introduction

Atmospheric turbulence in the free atmosphere is one of the most dangerous aviation weather hazards, as it can cause in-flight injuries and fatalities, and structural damage, shortening the longevity of aircraft and causing flight delays and fuel losses [1,2,3]. Turbulence directly affecting aircraft in the free atmosphere is classified into three types depending on its generation mechanism and location: Clear-air turbulence (CAT), mountain wave turbulence (MWT), and convectively induced turbulence (CIT) [2,3,4,5,6,7]. CAT can be induced by shear instability above and below the upper-level jet core [8,9,10], inertia instability in anticyclonic shear and curved flows [11,12,13], and inertia gravity waves and their subsequent triggers near the exit region of the jet or above the jet core [14,15]. Convective gravity waves (CGWs) can generate out-of-cloud CIT, which is referred to as near-cloud turbulence (NCT), both above or laterally away from the main convection through the CGW propagation, critical-level

Methods

Discussion

Conclusion