Abstract
Compared to conventional data, radar observations have an advantage of high spatial and temporal resolutions, and Doppler radars are capable of capturing detailed characteristics of flow fields, including typhoon circulation. In this study, the possible improvement of short-term typhoon predictions near Taiwan, particularly with regard to related rainfall forecasts over the mountainous island, using Doppler radial wind observations is explored. The case of Typhoon Aere (2004) was chosen for study, and a series of experiments were carried out using the Penn State University/National Center for Atmospheric Research (PSU/NCAR) Mesoscale Model Version 5 (MM5) with its three-dimensional variational (3D-VAR) data assimilation system. The results show that once the Doppler radial velocities were assimilated into the model, the typhoon's circulation intensified within one hour. However, when Typhoon Aere approached from the east and only the western half of its core area could be observed by the radar, the assimilation caused the typhoon to deflect southward due to the incomplete and uneven data coverage. In another experiment in which Doppler radar data assimilation did not start until Typhoon Aere moved closer, such that its entire core region could be observed. A similar track deflection was avoided. Overall, the assimilation of Doppler radial velocity data reduced the intensity error (in wind speed) by about 25%. Furthermore, the improvements in location, intensity, and circulation structure of Typhoon Aere lead to better rainfall prediction over the island of Taiwan.
Highlights
Typhoons are the most disastrous weather systems affecting Taiwan
Because the typhoon center was still far away from Taiwan during the first 2 cycles, the radar located on WuFen Mountain (RCWF) radar only observed the western part of typhoon Aere
From the results of the simulation experiments, we found that the limited coverage of radar observations affects the impact of radar data assimilation on typhoon predictions
Summary
Typhoons are the most disastrous weather systems affecting Taiwan. Three to four typhoons strike Taiwan annually, causing great loss of life and damage to the economy. A typhoon track forecast with wind and rain distribution is very important for disaster mitigation. The complicated topography of the Central Mountain Range (CMR) in Taiwan makes typhoon prediction a challenging task, especially when typhoon circulation interacts with the CMR. The difficulties involved in predicting typhoons near Taiwan have been discussed extensively in the literature. Wu and Kuo (1999) pointed out that the major problems of typhoon prediction are caused by: (1) inadequate observa-
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
