2:15 PM - 2:30 PM
[AAS06-03] Case Study of Precipitable Water Vapor on Snow Season in Central Japan based on GNSS Observations
Keywords:GNSS Meteorology, JPCZ
1. Introduction
The monsoon from Eurasia and the Tsushima Current flowing over the Sea of Japan sometimes cause heavy snowfall on the Sea of Japan side in winter. On the other hand, the monsoon loses water vapor when it crosses the mountains of Japan, making the Pacific side drier than the Sea of Japan side. However, in general, the Nobi Plain is possible to make snowfall than other areas along the Pacific side. Uehara et al. (2008) pointed out that Precipitable Water Vapor (PWV) around the Nobi Plain is bigger than the other area along the Pacific Ocean sides. There are other causes besides the aforementioned geographical factors. In this study, we estimate the spatiotemporal distribution of PWV in Central Japan during winter pressure patterns using GNSS observations and attempt to elucidate the cause of the large PWV in the Nobi Plain.
2. Data and Methodology
In this study, PWV is estimated by GNSS observations using the phenomenon that microwaves are delayed when they pass through the atmosphere. The GNSS observation data are from December 25 to 28, 2021, using GSI's GEONET and the SoftBank original reference sites (GEONET: 1313 sites nationwide, the SoftBank original reference sites: 498 sites in the central Japan region). We analyze resampling every 5 minutes GNSS observation data using RTKLIB ver. 2.4.3.
3. Results and Discussion
The spatiotemporal distribution of PWV on the Sea of Japan side has higher than on the Pacific side. And also, the PWV around the Nobi Plain is higher than in other areas along the Pacific side. The difference of PWV between Wakasa Bay and the Nobi Plain is almost the same values during the snowfall in the Nobi Plain (December 27). It suggests a water vapor supply system between the Nobi Plain and Wakasa Bay. To verify these assumptions, we introduce WVC index, which is the convergence and the divergence of PWV. The WVC index suggests the convergence zone of water vapor between Wakasa Bay and the Nobi Plain (Wakasa-Nobi Convergence Zone: WNCZ). The WNCZ may relate to topography, such as the Ibukiyama Mountains located on the east side of the WNCZ.
On the other hand, the western side of WNCZ has no characteristic mountainous terrain. So, WNCZ may relate to the wider water vapor convergence by the Japan sea Polar air mass Convergence Zone (JPCZ).
Acknowledgments
The SoftBank's GNSS observation data used in this study was provided by SoftBank Corp. and ALES Corp. through the framework of the "Consortium to utilize the SoftBank original reference sites for Earth and Space Science".
The monsoon from Eurasia and the Tsushima Current flowing over the Sea of Japan sometimes cause heavy snowfall on the Sea of Japan side in winter. On the other hand, the monsoon loses water vapor when it crosses the mountains of Japan, making the Pacific side drier than the Sea of Japan side. However, in general, the Nobi Plain is possible to make snowfall than other areas along the Pacific side. Uehara et al. (2008) pointed out that Precipitable Water Vapor (PWV) around the Nobi Plain is bigger than the other area along the Pacific Ocean sides. There are other causes besides the aforementioned geographical factors. In this study, we estimate the spatiotemporal distribution of PWV in Central Japan during winter pressure patterns using GNSS observations and attempt to elucidate the cause of the large PWV in the Nobi Plain.
2. Data and Methodology
In this study, PWV is estimated by GNSS observations using the phenomenon that microwaves are delayed when they pass through the atmosphere. The GNSS observation data are from December 25 to 28, 2021, using GSI's GEONET and the SoftBank original reference sites (GEONET: 1313 sites nationwide, the SoftBank original reference sites: 498 sites in the central Japan region). We analyze resampling every 5 minutes GNSS observation data using RTKLIB ver. 2.4.3.
3. Results and Discussion
The spatiotemporal distribution of PWV on the Sea of Japan side has higher than on the Pacific side. And also, the PWV around the Nobi Plain is higher than in other areas along the Pacific side. The difference of PWV between Wakasa Bay and the Nobi Plain is almost the same values during the snowfall in the Nobi Plain (December 27). It suggests a water vapor supply system between the Nobi Plain and Wakasa Bay. To verify these assumptions, we introduce WVC index, which is the convergence and the divergence of PWV. The WVC index suggests the convergence zone of water vapor between Wakasa Bay and the Nobi Plain (Wakasa-Nobi Convergence Zone: WNCZ). The WNCZ may relate to topography, such as the Ibukiyama Mountains located on the east side of the WNCZ.
On the other hand, the western side of WNCZ has no characteristic mountainous terrain. So, WNCZ may relate to the wider water vapor convergence by the Japan sea Polar air mass Convergence Zone (JPCZ).
Acknowledgments
The SoftBank's GNSS observation data used in this study was provided by SoftBank Corp. and ALES Corp. through the framework of the "Consortium to utilize the SoftBank original reference sites for Earth and Space Science".