Summertime Convective Initiation Nowcasting over Southeastern China Based on Advanced Himawari Imager Observations

• Published in: Journal of the Meteorological Society of Japan Vol. 96; no. 4; pp. 337 - 353
• Main Authors: ZHUGE, Xiaoyong, ZOU, Xiaolei
• Format: Journal Article
• Language: English
• Published: Meteorological Society of Japan 01.01.2018
• Subjects: AHI; convective initiation; nowcasting
• ISSN: 0026-1165; 2186-9057
• DOI: 10.2151/jmsj.2018-041

Convective initiation (CI) nowcasting often has a low probability of detection (POD) and a high false-alarm ratio (FAR) at subtropical regions where the warm-rain processes often occur. Using the high spatial and temporal resolution and multispectral data from the Advanced Himawari Imager (AHI) on board Japanese new-generation geostationary satellite Himawari-8, a standalone CI nowcasting algorithm is developed in this study. The AHI-based CI algorithm utilizes the reflectance observations from channels 1 (0.47 μm) and 7 (3.9 μm); brightness temperature observations from infrared window channel 13 (10.4 μm), the dual-spectral differences between channels 10 (7.3 μm) and 13, 13, and 15 (12.4 μm), and a tri-spectral combination of channels 11, 15, and 13, as CI predictors without relying on any dynamic ancillary data (e.g., cloud type and atmospheric motion vector products). The proposed AHI-based algorithm is applied to CI cases over Fujian province in the Southeastern China. When validated by S-band radar observations, the CI algorithm produced a POD as high as 93.33 %, and an FAR as low as 33.33 % for a CI case day that occurred on August 1, 2015, over Northern Fujian. For over 216 CI events that occurred in a 3-month period from July to September 2015, the CI nowcasting lead time has a mean value of ∼ 64 min, with a longest lead time over 120 min. It is suggested that false-alarm nowcasts that occur in the presence of capping inversion require further investigation and algorithm enhancements.