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Understanding the fluid dynamics and thermodynamics in the urban atmospheric boundary layer (ABL) is of great practical importance. Based on one-year observations from two advanced remote sensing instruments, namely, the wind lidar and the microwave radiometer, this study investigates the urban ABL structure in a densely built downtown area of Hong Kong. Atmospheric stability, ABL height, wind shear, and wind veer are statistically analyzed. The interconnections among wind speed profiles, wind direction profiles, ABL stability, and ABL height are comprehensively examined. Some features of the wind and thermodynamic structure are observed, such as the prevalence of unstable conditions in the urban ABL and the increase in wind shear and veer with ABL stability. The research outcomes are expected to contribute to the understanding of urban meteorology and offer scientific insights into the influences of urban terrain on the ABL and the vertical and temporal structure of wind and thermodynamic properties in the urban ABL. [ABSTRACT FROM AUTHOR]

Since 2011, routine reconnaissance has been carried out whenever there is a tropical cyclone (TC) entering the Flight Information Region of Hong Kong that may pose a threat to the territory. In October 2022, Typhoon Nesat entered the northern part of the South China Sea and aircraft reconnaissance flights were conducted for the storm. This paper presents these interesting data for the meteorological and wind engineering communities. The presented observations would be beneficial for other studies of this cyclone, such as numerical simulations of Nesat for comparison with actual observations. [ABSTRACT FROM AUTHOR]

Figure 2 shows the location of the radars and the position of the circulation at 04:53:30 when it most likely produced a waterspout, based on the appearance of a small-scale couplet in the velocity data of the nearest radar (Hengqin). ([10]) studied the ability of numerical simulations to predict waterspouts by comparing simulated and observed radar data from a storm producing a weak waterspout near Hong Kong airport. Observational analysis of a waterspout sighted in Macao, China, on 1 June 2021 Waterspout in Macao on 1 June 2021 (provided by radio station of Macao). [Extracted from the article]

(2020), and axisymmetric tropical cyclone boundary layer structure was analysed by compositing dropsonde data from multiple tropical cyclones. For the purpose of this study, forecast wind and thermodynamic profiles from the AAMC-WRF at locations corresponding to the dropsonde observations of the tropical cyclones concerned will be generated in the form of "simulated dropsondes". The dropsonde data were not assimilated into the model, but serve as an independent source of data to check the performance of the AAMC-WRF in the forecast of the tropical cyclone, at least in regards to the vertical profiles of the wind and thermodynamic properties of each cyclone. [Extracted from the article]

On 4 July 2005, many observatories around the world and in space observed the collision of Deep Impact with comet 9P/Tempel 1 or its aftermath. This was an unprecedented coordinated observational campaign. These data show that (i) there was new material after impact that was compositionally different from that seen before impact; (ii) the ratio of dust mass to gas mass in the ejecta was much larger than before impact; (iii) the new activity did not last more than a few days, and by 9 July the comet's behavior was indistinguishable from its pre-impact behavior; and (iv) there were interesting transient phenomena that may be correlated with cratering physics., The Deep Impact mission was designed so that much of the mission-critical science would be done from Earth-based telescopes. These facilities would observe the comet before, during, and after impact [...]

Horizontal interpolation (along the direction of the cross-section) has been applied to enhance visualisation along this direction. gl GLO:65TF/01jan22:wea3878-fig-0007.jpg PHOTO (COLOR): 7 Vertical cross-sections along C-D in Figure 6(a) showing (a) radial velocity, (b) horizontal speed, and (c) vertical velocity. gl Mountain waves over the central part of the airport island In addition to the western and eastern regions, mountain waves may also occur over the central part of the island, though it is rather rare. Topographic map showing the Hong Kong International Airport (HKIA). Mountain waves to the west of the airport island There are two incidents of mountain waves to the west of the airport island. Mountain waves near Hong Kong International Airport: observations and high-resolution model analysis. [Extracted from the article]