Wei-Yu Chang

National Central University | NCU · Department of Atmospheric Sciences

The drop size distribution (DSD) and drop shape relation (DSR) characteristics that were observed by a ground-based 2D video disdrometer and retrieved from a C-band polarimetric radar in the typhoon systems during landfall in the western Pacific, near northern Taiwan, were analyzed. The evolution of the DSD and its relation with the vertical develo...

This study evaluates the simulated cloud properties, especially the simulated raindrop size distribution, by the Chinese Academy of Meteorological Sciences bulk microphysics scheme (CAMS BMS) and two other two-moment microphysics schemes (Morrison and WDM6) in the Weather Research and Forecasting model (WRF v3.1). Measurements from a mesoscale conv...

An Observing System Simulation Experiment (OSSE) was developed and conducted to assess the potential impact of different observing strategies of field experiments on analysis and short-term forecasts. A Mei-Yu front rainfall case study, occurring in 2003 in southeastern Asia, was utilized to demonstrate the OSSE application to field experiments. Da...

A variational algorithm for estimating measurement error covariance and the attenuation of X-band polarimetric radar measurements is described. It concurrently uses both the differential reflectivity Z(DR) and propagation phase Phi(DP). The majority of the current attenuation estimation techniques use only Phi(DP). A few of the Phi(DP)-based method...

Dual-Doppler, polarimetric radar observations and precipitation efficiency (PE) calculations are used to analyze subtropical heavy rainfall events that occurred in southern Taiwan from 14 to 17 June 2008 during the Southwest Monsoon Experiment/Terrain-Influenced Monsoon Rainfall Experiment (SoWMEX/TiMREX) field campaign. Two different periods of di...

This study selected three heavy-rainfall events of different types in Taiwan’s Mei-yu season for high-resolution simulations at a grid size of 1 km and assessed the model’s capability to reproduce their morphology and characteristics. The three cases include a pre-frontal squall line, a mesoscale convective system (MCS) embedded in southwesterly fl...

To evaluate the hygroscopic cloud seeding in reality, this study develops a hybrid microphysics scheme using a Weather Research and Forecasting (WRF) model, WDM6-NCU (WDM6 modified by National Central University), which involves 43 bins of seeded cloud condensation nuclei (CCN) in the WDM6 bulk method scheme. This scheme can describe the size distr...

To evaluate the hygroscopic cloud seeding in reality, this study develops a hybrid microphysics scheme on WRF model, WDM6–NCU, which involves 43 bins of seeded cloud condensation nuclei (CCN) in the WDM6 bulk method scheme. This scheme can describe the size distribution of seeded CCNs and explain the process of the CCN imbedding, cloud and raindrop...

Quantitative precipitation estimates (QPE) can be further improved using estimation algorithms derived from localized raindrop size distribution (DSD) observations. In this study, DSD measurements from two disdrometer stations within Metro Manila during the Southwest monsoon (SWM) period were used to investigate the microphysical properties of rain...

This study introduces a recent field experiment investigating the multi‐scale terrain‐circulation‐precipitation interactions. When the synoptic‐scale northeasterly wind prevails under the active East Asian winter monsoon, stratocumulus cloud decks with severe rainfall exceeding 100 mm·d‐1 frequently occur in the northeastern plain area and adjacent...

This study assessed the long-term radar reflectivity ( $Z$ ) biases of collocated S- and C-band dual-polarization radars. The systematic bias, wet-radome effect (WRE), and attenuation effect were investigated. The algorithm of self-consistency utilizes $Z$ , differential reflectivity ( $Z_{\mathrm{ dr}}$ ), and a specific differential phase ( $...

The current study summarizes the raindrop size distributions (RSDs) characteristic of the North Indian Ocean (NIO) tropical cyclones (TCs) measured with ground-based disdrometers installed at the coastal (Thiruvananthapuram, 8.5335°N, 76.9047°E) and inland (Kadapa, 14.4742°N, 78.7098°E) stations in south India. The NIO TCs observed at the coastal s...

The study analyzed the raindrop size distribution (DSD) measured by an optical Parsivel disdrometer in Southern Luzon, Philippines and utilized it to generate dual-pol relations for the nearby Tagaytay radar. The relations were generated using two methods (Method 1 - gamma-based and Method 2 - linear fitting), four time-integration steps (1-, 2-, 5...

The key factors, namely, the radar data quality, raindrop size distribution (RSD) variability, and the data integration method, which significantly affect radar-based quantitative precipitation estimation (QPE) are investigated using the RCWF (S-band) and NCU C-POL (C-band) dual-polarization radars in northern Taiwan. The radar data quality control...

The long-term assessment of reflectivity (𝑍𝐻𝐻) biases using a S-band dual-polarimetric radar (RCWF), operated by the Central Weather Bureau (CWB) of Taiwan (121.77 °E, 25.07 °N) was analyzed in this study. The biases including systematic bias and wet-radome effect (WRE) along with the attenuation effect from RCWF were investigated. The differential...

中央氣象局建置C波段雷達網能夠提供高時空間解析度的定量降水估計，但C波段降雨雷達資料易受到硬體端的系統性偏差、濕天線罩效應與回波衰減效應所影響。故本研究以2020年5月21-22梅雨個案為例設計一套針對高雄林園雷達(RCLY)的資料品管流程，流程中使用雷達波束徑向連續點上的相關係數、差異反射率、差異相位差的標準差之間的搭配做為門檻值，能夠比僅利用相關係數作為門檻值更能夠有效地濾除地形雜波。 並以中央大學測站10年以上的撞擊式雨滴譜儀資料依月份分降雨型態並進行T-matrix散射模擬雷達參數，進一步求得各降雨型態的衰減校正係數以及系統性偏差係數進行修正。 結果顯示經由品質控管可以有效地修正經衰減效應和濕天線罩效應低估的雷達資料，並降低在濕天線罩效應影響期間的回波變異性。而藉由計算整體回波偏差...

Four types (2D-video disdrometer: 2DVD; precipitation occurrence sensor system: POSS; micro-rain radar: MRR; and Joss–Waldvogel disdrometer: JWD) of sixteen instruments were collocated within a square area of 400 m2 from 16 April to 8 May 2008 for intercomparison of drop size distribution (DSD) of rain. This unique dataset was used to study the inh...

Overall Science Plans for TAHOPE project

This study investigates the impacts of different types of Cloud Condensation Nuclei (CCN) on the extreme of precipitation and updraft (above the 99th percentile threshold) of a mesoscale convection system occurred over the southwest coast of Taiwan Island under the moist southwesterly monsoon environment using cloudpermitting simulations. The conve...

In the present work, long-term (10 years) raindrop size distribution (RSD) measurements from Joss-Waldvogel Disdrometer (JWD) installed at National Central University (NCU, 24°58'6"N 121°11'27"E), Taiwan and vertical profile of radar reflectivity were used to analyze the variations in gamma parameters of six seasons (winter, spring, meiyu, summer,...

Coordinated TLE (transient luminous event) optical observations in Taiwan have been heldsince 2011, with an aim to achieve triangulation. Currently, there are four observation stations withbaselines varying from 100 to 400 km between them. The system recorded eight gigantic jets (GJs) thatwere recorded by at least two stations on the night of 20 Au...

The accuracy of rain rate estimation using polarimetric radar measurements has been improved as a result of better characterization of radar measurement quality and rain microphysics. In the literature, a variety of power-law relations between polarimetric radar measurements and rain rate are described due to dynamic or varying nature of rain micro...

Data collected by the National Center for Atmospheric Research S-band polarimetric radar (S-Pol) during the Terrain-Influenced Monsoon Rainfall Experiment (TiMREX) in Taiwan are analyzed and used to infer storm microphysics in the ice phase of convective storms. Both simultaneous horizontal (H) and vertical (V) (SHV) transmit polarization data and...

In this paper, experimental X-band polarimetric radar data fromsimultaneous transmission of horizontal (H) and vertical (V) polarizations (SHV) are shown, modeled, and microphysically interpreted. Both range-height indicator data and vertical-pointing X-band data from the Taiwan Experimental Atmospheric Mobile-Radar (TEAM-R) are presented. Some of...

The precipitation mechanisms of typhoon Naru (2001) revealed by radar observation was studied. A quality control sequence was applied to 12 hrs raw disdrometer data to get the drop size distribution. The disdrometer, integrated sounding system, rain gage network and dual-Doppler radar data were collected during Nari's landfall. The terrain followin...