Comparison of Doppler LIDAR Observations of Severe Turbulence and Aircraft Data

A total of 31 aircraft reported encountering turbulence at the Hong Kong International Airport (HKIA) during the passage of Typhoon Imbudo on 24 July 2003. Of these, 15 were severe or moderate to severe turbulence reports.

A Doppler LIDAR was installed at HKIA in mid-2002 to enhance the detection and warning of wind shear under clear-air conditions. This paper examines the feasibility of using the LIDAR for turbulence detection in an operational setting based on data collected for the above-mentioned turbulence episode. The LIDAR imageries reveal the presence of small-scale wind disturbances with length scale of only a few hundred metres across associated with the terrain-induced turbulence (see Figures 1 and 2).

The paper will present comparison results of Doppler velocity variance and spectral widths versus aircraft recorded wind and accelerometer readings during the turbulence episode. Altogether a total of 82 sets of flight data have been examined. Areas for further enhancement of operational turbulence detection will be discussed.

Figure 1. LIDAR PPI imagery of Doppler radial velocity at 02:36 UTC on 24 July 2003 at 1.0 degree elevation (small-scale wind disturbances can be clearly identified within the dotted circle)

Figure 2. LIDAR RHI imagery of Doppler radial velocity at 02:36 UTC on 24 July 2003 towards 258 degrees azimuth (small-scale wind disturbances can be clearly identified within the dotted circle)