- 著者
- GENG Biao KATSUMATA Masaki TANIGUCHI Kyoko
- 出版者
- Meteorological Society of Japan
- 雑誌
- 気象集誌. 第2輯 (ISSN:00261165)
- 巻号頁・発行日
- pp.2020-026, (Released:2020-02-06)
- 被引用文献数
- 4
This study investigated the impact of mixed Rossby-gravity waves (MRGWs) on the diurnal cycle of precipitation over the southwestern coastal area of Sumatra using data captured during a pilot field campaign of the Years of the Maritime Continent (YMC) Project. The study focused on a 19-day period from 24 November to 12 December 2015, using data from intensive surface observations, radiosondes, a C-band polarimetric radar collected onboard the research vessel Mirai at 4.067°S, 101.900°E, and data from global objective analysis. The results indicated a relationship between oscillations with periods of several days in the intensity of diurnal precipitation and the wind field. Wind oscillations were attributed to several westward-propagating MRGWs traversing the study site. Diurnal convection and precipitation over the land and ocean were enhanced (suppressed) when MRGW-induced offshore (onshore) wind perturbations dominated. Large-scale low-level convergence and upper-level divergence, stronger sea-breeze flow, and colder land-breeze flow were also observed with the intensification of MRGW-induced offshore wind perturbations. However, diurnal precipitation displayed a similar well-defined phase and propagation pattern over the land and ocean, coherent with the regular evolution of sea- and land-breeze circulations, regardless of wind perturbations induced by MRGWs. The results suggest that local convergence induced by the land-sea contrast is mainly responsible for driving the diurnal cycle. Notwithstanding, MRGWs exert a significant impact on the amplitude of diurnal convection and precipitation by modulating the large-scale dynamic structure of the atmosphere and the intensity of local sea- and land-breeze circulations.
- 著者
- GENG Biao KATSUMATA Masaki
- 出版者
- Meteorological Society of Japan
- 雑誌
- 気象集誌. 第2輯 (ISSN:00261165)
- 巻号頁・発行日
- pp.2020-031, (Released:2020-03-17)
- 被引用文献数
- 5
In this study, an algorithm is developed to detect the spurious differential phase ΦDP and specific differential phase KDP in the rain for application following the removal of gate-to-gate ΦDP fluctuations. The algorithm is a threshold filter that is designed based on the empirical relationship between the KDP and radar reflectivity factor at horizontal polarization ZH for raindrops. The construction and validation of the algorithm was conducted using the data observed by the C-band polarimetric radar on board the research vessel Mirai near Sumatra from 23 November to 17 December 2015, when a pilot field campaign of the Years of the Maritime Continent (YMC) project was conducted. Perturbations exist in the ΦDP and associated spurious values of KDP on a 10-km scale in the range direction, which are mainly induced by second-trip echoes and nonuniform beam filling. These perturbed ΦDP values and the positively and negatively biased KDP values can be efficiently detected by this new algorithm. The standard deviation of the KDP in areas with relatively low ZH is also significantly reduced by applying the algorithm. Simultaneously, the rain rate estimation from the filtered KDP has been greatly improved. The results indicate that the algorithm developed in this study can efficiently manage the quality of the data observed not only in the open ocean but also in coastal areas of the Maritime Continent.