Multilocalization data assimilation for predicting heavy precipitation associated with a multiscale weather system. (13th July 2017)

• Record Type: Journal Article
• Authors: Yang, Shu‐Chih; Chen, Shu‐Hua; Kondo, Keichii; Miyoshi, Takemasa; Liou, Yu‐Chieng; Teng, Yung‐Lin; Chang, Hui‐Ling
• Is Part Of: Journal of advances in modeling earth systems. Volume 9:Number 3(2017)
• Page Start: 1684
• Page End: 1702
• Publication Date: 2017-07-13
• Subjects: dual‐localization data assimilation -- EnKF -- heavy rainfall prediction; Geological modeling -- Periodicals; Climatology -- Periodicals; Geochemical modeling -- Periodicals; 551.5011
• DOI: 10.1002/2017MS001009
• Languages: English
• ISSNs: 1942-2466

Abstract

Abstract: High‐resolution numerical simulations are regularly used for severe weather forecasts. To improve model initial conditions, a single short localization is commonly applied in the ensemble Kalman filter when assimilating observations. This approach prevents large‐scale corrections from appearing in a high‐resolution analysis. To improve heavy rainfall forecasts associated with a multiscale weather system, analyses must be accurate across a range of spatial scales, a task that is difficult to accomplish using a single localization. This study is the first to apply a dual‐localization (DL) method to improve high‐resolution analyses used to forecast a real‐case heavy rainfall event associated with a Meiyu front on 16 June 2008 in Taiwan. A Meiyu front is a multiscale weather system characterized by storm‐scale convection, a mesoscale front, and large‐scale southwesterly monsoonal flow. The use of the DL method to produce the analyses was able to correct both the synoptic‐scale moisture flux transported by southwesterly monsoonal flow and the mesoscale low‐level convergence offshore of southwestern Taiwan. As a result, the forecasted amount, pattern, and temporal evolution of the heavy rainfall event were improved. Key Points: Improving large‐scale moisture transport and small‐scale convergence are critical to Meiyu rainfall forecasts A multiscale weather system needs multiscale corrections in high‐resolution EnKF analysis EnKF with dual localizations improves the intensity and time variation of the short‐lasting, intense heavy rainfall prediction