Data Fusion of GEO FY4A GIIRS and LEO Hyperspectral Infrared Sounders with Surface Observations: A Hong Kong Case Study

2021 ◽  
Keyword(s):  
Hong Kong ◽  
Water Vapor ◽  
Weather Prediction ◽  
Coastal Region ◽  
Sampling Interval ◽  
Surface Data ◽  
Accurate Temperature ◽  
Rapid Transition ◽  
Surface Observations

Abstract Hyperspectral infrared satellite observations from geostationary platforms allow for the retrieval of temperature and water vapor measurements with higher temporal and vertical resolution than was previously available. The Chinese satellite, FY-4A includes the Geostationary Interferometric Infrared Sounder (GIIRS) which has the ability to measure vertical profiles of temperature and water vapor from space at times when ground-based upper air soundings are not available and can fill an important need in short-range weather prediction. In this study, CAPE and LI, which are used for forecasting atmospheric instability, were computed using the SHARPpy algorithm used by the NWS Storm Prediction Center. However, remote infrared and microwave sensing is lacking detailed information in the boundary layer, so the addition of the NOAA MADIS surface data may be necessary in order to get accurate temperature and moisture measurement near the surface. This study uses May 10-16, 2019 in the coastal region near Hong Kong for evaluating the use of hourly surface observations combined with satellite soundings from FY4A GIIRS at two hour intervals. The GIIRS plus MADIS surface-based CAPE and LI estimates are compared to estimates derived from low earth orbiting (LEO) SNPP and NOAA20 from NOAA, METOP from EUMETSAT, NWP reanalysis, and local radiosondes. In the case study, the two-hour sampling interval of the GIIRS geostationary sounder was able to capture the rapid transition (16 hours) from stable to unstable atmosphere in both CAPE and LI. The use of surface observations with satellite soundings gave mixed results, possibly due to the complex terrain near Hong Kong.

scholarly journals A comparison between the GNSS tomography technique and the WRF model in retrieving 3D wet refractivity field in Hong Kong

2018 ◽  
Author(s):  
Zhaohui Xiong ◽  
Bao Zhang ◽  
Yibin Yao
Keyword(s):  
Hong Kong ◽  
Water Vapor ◽  
Weather Prediction ◽  
Wrf Model ◽  
Vertical Direction ◽  
Lower Troposphere ◽  
Reanalysis Data ◽  
Radiosonde Data ◽  
Rainy Period ◽  
Lower Accuracy

Abstract. Water vapor plays an important role in various scales of weather processes. However, there are limited means to monitor its 3-dimensional (3D) dynamical changes. The Numerical Weather Prediction (NWP) model and the Global Navigation Satellite System (GNSS) tomography technique are two of the limited means. Here, we conduct an interesting comparison between the GNSS tomography technique and the Weather Research and Forecasting (WRF) model (a representative of the NWP models) in retrieving Wet Refractivity (WR) in Hong Kong area during a rainy period and a rainless period. The GNSS tomography technique is used to retrieve WR from the GNSS slant wet delay. The WRF Data Assimilation (WRFDA) model is used to assimilate GNSS Zenith Tropospheric Delay (ZTD) to improve the background data. The WRF model is used to generate reanalysis data using the WRFDA output as the initial values. The radiosonde data are used to validate the WR derived from the GNSS tomography and the reanalysis data. The Root Mean Square (RMS) of the tomographic WR, the reanalysis WR that assimilate GNSS ZTD, and the reanalysis WR that without assimilating GNSS ZTD are 6.50 mm/km, 4.31 mm/km and 4.15 mm/km in the rainy period. The RMS becomes 7.02 mm/km, 7.26 mm/km and 6.35 mm/km in the rainless period. The lower accuracy in the rainless period is mainy due to the sharp variation of WR in the vertical direction. The results also show that assimilating GNSS ZTD into the WRFDA model only slightly improves the accuracy of the reanalysis WR and that the reanalysis WR is better than the tomographic WR in most cases. However, in a special experimental period when the water vapor is highly concentrated in the lower troposphere, the tomographic WR outperforms the reanalysis WR in the lower troposphere. When we assimilate the tomographic WR in the lower troposphere into the WRFDA model, the reanalysis WR is improved.

scholarly journals Real-Time GNSS-Derived PWV for Typhoon Characterizations: A Case Study for Super Typhoon Mangkhut in Hong Kong

2019 ◽  
Vol 12 (1) ◽  
pp. 104 ◽  
Author(s):  
Qimin He ◽  
Kefei Zhang ◽  
Suqin Wu ◽  
Qingzhi Zhao ◽  
Xiaoming Wang ◽  
...  
Keyword(s):  
Time Series ◽  
Hong Kong ◽  
Water Vapor ◽  
Wind Speed ◽  
Real Time ◽  
Global Navigation Satellite Systems ◽  
International Gnss Service ◽  
China Meteorological Administration ◽  
Super Typhoon

Typhoons can be serious natural disasters for the sustainability and development of society. The development of a typhoon usually involves a pre-existing weather disturbance, warm tropical oceans, and a large amount of moisture. This implies that a large variation in the atmospheric water vapor over the path of a typhoon can be used to study the characteristics of the typhoon. This is the reason that the variation in precipitable water vapor (PWV) is often used to capture the signature of a typhoon in meteorology. This study investigates the usability of real-time PWV retrieved from global navigation satellite systems (GNSS) for typhoons’ characterizations, and especially, the following aspects were investigated: (1) The correlation between PWV and atmospheric parameters including pressure, temperature, precipitation, and wind speed; (2) water vapor transportation during a typhoon period; and (3) the correlation between the movement of a typhoon and the transportation of water vapor. The case study selected for this research was Super Typhoon Mangkhut that occurred in mid-September 2018 in Hong Kong. The PWV time series were obtained from a conversion of GNSS-derived zenith total delays (ZTDs) using observations at 10 stations selected from the Hong Kong GNSS continuously operating reference stations (CORS) network, which are also located along the path of the typhoon. The Bernese GNSS Software (ver. 5.2) was used to obtain the ZTDs; and the root mean square (RMS) of the differences between the GNSS-ZTDs and International GNSS Service post-processed ZTDs time series was less than 8 mm. The RMS of the differences between the GNSS-PWVs (i.e., the ZTDs converted PWVs) and radiosonde-derived PWVs (RS-PWVs) time series was less than 2 mm. The changes in PWV reflect the variation in wind speed during the typhoon period to a certain degree, and their correlation coefficient was 0.76, meaning a significant positive correlation. In addition, a new approach was proposed to estimate the direction and speed of a typhoon’s movement using the time difference of PWV arrival at different sites. The direction and speed estimated agreed well with the ones published by the China Meteorological Administration. These results suggest that GNSS-derived PWV has a great potential for the monitoring and even prediction of typhoon events, especially for near real-time warnings.

scholarly journals Competition and Sustainability Development of a Multi-Airport Region: A Case Study of the Guangdong–Hong Kong–Macao Greater Bay Area

2019 ◽  
Vol 11 (10) ◽  
pp. 2958 ◽  
Author(s):  
Wang Liao ◽  
Xiaoshu Cao ◽  
Shengchao Li
Keyword(s):  
Hong Kong ◽  
Urban Areas ◽  
Coastal Region ◽  
Asia Pacific ◽  
Asia Pacific Region ◽  
Airline Competition ◽  
New Era ◽  
Tourist Destinations ◽  
Bay Area

A new era in the development of multi-airport regions (MARs) has been in China, especially in the construction of global urban areas such as the Guangdong–Hong Kong–Macao Greater Bay Area (GBA). In order to better understand competition and provide significant advice to support sustainable development of Chinese MARs, this paper takes the GBA-MAR as an example, and then explores the competition between airports in this multi-airport region based on route level and its impact on passenger airport choice using three liner models. According to our findings, competition is concentrated on a few air routes in the Northeast–East Coastal region and the Asia-Pacific region, in which all three airports operate. Although the domestic market of the GBA-MAR has been relatively mature, the international air transport market is still left with considerable room, which is also reflected in connections to the world’s cities and tourist destinations. In addition, the research also found that different airport brands created by route type significantly affected passenger airport choice. Overall, the study revealed that whether from a supply or demand aspect, competition between airports in a multi-airport region—not just airline competition in a single airport—is an important topic.

scholarly journals Near real-time water vapor tomography using ground-based GPS and meteorological data: long-term experiment in Hong Kong

2014 ◽  
Vol 32 (8) ◽  
pp. 911-923 ◽  
Author(s):  
P. Jiang ◽  
S. R. Ye ◽  
Y. Y. Liu ◽  
J. J. Zhang ◽  
P. F. Xia
Keyword(s):  
Hong Kong ◽  
Water Vapor ◽  
Real Time ◽  
Time Window ◽  
Meteorological Data ◽  
Weather Prediction ◽  
Radiosonde Data ◽  
Double Difference ◽  
Statistical Measures ◽  
Term Experiment

Abstract. Water vapor tomography is a promising technique for reconstructing the 4-D moisture field, which is important to the weather forecasting and nowcasting as well as to the numerical weather prediction. A near real-time 4-D water vapor tomographic system is developed in this study. GPS slant water vapor (SWV) observations are derived by a sliding time window strategy using double-difference model and predicted orbits. Besides GPS SWV, surface water vapor measurements are also assimilated as real time observations into the tomographic system in order to improve the distribution of observations in the lowest layers of tomographic grid. A 1-year term experiment in Hong Kong was carried out. The feasibility of the GPS data processing strategy is demonstrated by the good agreement between the time series of GPS-derived Precipitable Water Vapor (PWV) and radio-sounding-derived PWV with a bias of 0.04 mm and a root-mean-square error (RMSE) of 1.75 mm. Using surface humidity observations in the tomographic system, the bias and RMSE between tomography and radiosonde data are decreased by half in the ground level, but such improved effects weaken gradually with the rise of altitude until becoming adverse above 4000 m. The overall bias is decreased from 0.17 to 0.13 g m−3 and RMSE is reduced from 1.43 to 1.28 g m−3. By taking the correlation coefficient and RMSE between tomography and radiosonde individual profile as the statistical measures, quality of individual profile is also improved as the success rate of tomographic solution is increased from 44.44 to 63.82% while the failure rate is reduced from 55.56 to 36.18%.

scholarly journals Diagnosis and modelling of a summer convective storm over Mediterranean Pyrenees

2005 ◽  
Vol 2 ◽  
pp. 273-277 ◽  
Author(s):  
A. Callado ◽  
R. Pascual
Keyword(s):  
Weather Prediction ◽  
Coastal Region ◽  
Local Maximum ◽  
Numerical Weather Prediction Model ◽  
Sea Breezes ◽  
Convective Storms ◽  
Surface Data ◽  
Radar Imagery ◽  
Convergence Zones ◽  
Weak Pressure Gradient

Abstract. Over the Mediterranean Pyrenees and near coastal region there is a high frequency of convective storms during summertime. This fact determines a local maximum of precipitation at this season unlike the normal and general minimum over Mediterranean basin. The common synoptic and mesoscale patterns associated to convective phenomena are briefly analyzed and diagnosed with radar imagery, surface pressure and isobaric level fields and surface data. They usually involves a little distant through at medium levels, very weak pressure gradient at the surface and not significant instability, but a preferred Planetary Boundary Layer low-level convergence zones tied to the orography. As a result of this analysis two different kinds of circulations associated to recurrent convergence zones have been recognized: upvalley/upslope winds and sea breezes. High resolution simulations from a Numerical Weather Prediction model for a case study have carried out to analyze the role of the main key components, i.e. the orography, the sea and valley breeze and their influence to generate local convergence zones. Furthermore, the skills of the model to simulate the location and the intensity of the precipitation of these summer Mediterranean storms have been discussed.

Public space in the old derelict city area – a case study of Mong Kok, Hong Kong

2001 ◽  
Vol 6 (1) ◽  
pp. 15-31 ◽  
Author(s):  
Charlie Q L Xue ◽  
Kevin K Manuel ◽  
Rex H Y Chung
Keyword(s):  
Hong Kong ◽  
Public Space ◽  
City Area

scholarly journals Coping with English for Academic Purposes Provision during COVID-19

2021 ◽  
Vol 13 (15) ◽  
pp. 8642
Author(s):  
Lucas Kohnke ◽  
Andrew Jarvis
Keyword(s):  
Hong Kong ◽  
Collaborative Learning ◽  
Online Teaching ◽  
Qualitative Case Study ◽  
English For Academic Purposes ◽  
Teacher Perspectives ◽  
Case Study Approach ◽  
Study Approach ◽  
University Studies

COVID-19 and the shift to online teaching necessitated a change in approach for English for Academic Purposes (EAP) teachers in preparing their students for university studies. This study explored how EAP instructors coped with and adapted their provision for emergency remote teaching. The study was conducted at an English-medium university in Hong Kong and a qualitative case study approach was adopted. The results revealed two overarching themes of opportunity and challenge. While the sudden shift to online teaching forced innovation and fostered collaborative learning and feedback, teachers experienced difficulties in communicating with students and monitoring their learning. The study voices teacher perspectives in delivering EAP courses online and highlights important implications for the successful delivery of future online EAP provisions.

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