Windshear detection by Terminal Doppler Weather Radar during Tropical Cyclone Mujigae in 2015

Meteorological Applications

Tse

Lee

et al. 2020

Self Cite

This paper reports on a waterspout presiding over the Pearl River Estuary near Zhuhai, China. It is observed mainly using the terminal Doppler weather radar in Hong Kong. A slanting radar reflectivity core and airflow circulating around was seen in the vertical cross-section across the mesoscale/microscale cyclone associated with the waterspout. The vertical wind profile associated with the cyclone was analysed and found to exhibit characteristics similar to those of a tornado reported in the region in a previous study. The primary characteristic of the waterspout was a circulating flow stronger at higher levels (approximately a few kilometres above ground) than at lower levels. In terms of nowcasting, the performance of a convection-permitting numerical weather prediction model (2 km horizontal resolution) was analysed. It was found to demonstrate reasonable simulation skill for the mesoscale/microscale cyclone, although the slanting feature was not well predicted. The results of this study can serve as a useful reference for similar studies of waterspouts/tornadoes worldwide. K E Y W O R D Snumerical simulation, waterspout, weather radar

Section: Methodsmentioning

confidence: 99%

Analysis of a waterspout at Zhuhai, China, on June 12, 2019

Meteorological Applications

Tse

Lee

et al. 2020

Self Cite

“…Weather radars are the major analysis tools of this paper. There are 5 microwave weather surveillance radars in Hong Kong. In the present analysis, two of them would be used: the long-range (512 km), S-band, dual polarization radar on the top of the mountain Tate's Cairn (about 500 m above mean sea level; Kong and Chan, 2018); and the C-band Terminal Doppler Weather Radar (TDWR) at Brother's Point (Tse et al, 2019).…”

Section: Surface-based Meteorological Observationsmentioning

confidence: 99%

A rare winter thunderstorm event near Hong Kong

Hon

2020

ATM

“…Beam blockage would be too great if the SRL were placed to the south of those buildings. That said, the use of raw radial velocities containing “mixtures” of crosswind and headwind components is not unheard of—detection principles based on PPI scans would tend to consider the full Doppler velocities and avoid decomposing further along the desired directions (Newell and Cullen, 1993; Choy et al ., 2004; Tse et al ., 2019). It must be stressed that the current SRL configuration specializes in capturing building‐disrupted airflow, which, for the case of corridor 25RA of HKIA, is predominantly crosswind changes near the final 1 nm.…”

Section: Verification Results and Discussionmentioning

confidence: 99%

Alerting of hectometric turbulence features atHongKongInternationalAirport using a short‐rangeLIDAR

Hon

Meteorological Applications

2020

Small-scale, fast-evolving airflow disturbances, possibly due to upstream building clusters, are known to affect aircraft landing at corridor 25RA of Hong Kong International Airport (HKIA), China, under southerly or southwesterly winds. The paper presents a new algorithm, based on the concept of coherent integrated differential velocity (CIDV), for the automatic alerting of such hectometric (scale of hundreds of metres) turbulence features using short-range LIDAR (SRL) scans at 30 m radial resolution and an observation frequency of around every 20 s by Hong Kong Observatory (HKO). The CIDV identifies the cumulative effect of coherent patches of radial velocity changes occurring along the landing flight path by comparing two consecutive subminute SRL scans. Verification was conducted between June and September 2017 against a selection of relevant pilot reports, with a positive skill level observed over the whole range of the CIDV thresholds considered. When simulating a realistic setting where the SRL would issue alerts in conjunction with HKO's operational Windshear and Turbulence Warning System (WTWS), the CIDV algorithm would bring a gain in hit rate between 5% and 25%, with a corresponding increase in alert duration between 0.4% and 20%. The chosen CIDV threshold of 0.4 mÁs −1 nautical mile (nm) can be physically interpreted as an average radial velocity change of 4.0 mÁs −1 sustained over a distance of < 200 m (or between 2 and 3 s of flight), which agrees with reported values of crosswind changes considered significant for a landing aircraft and also pilots' perception of the characteristics of such events.