1:45 PM - 2:00 PM
[AOS18-07] Analysis of winter precipitation along the Sea of Japan using the 10-year reanalysis dataset of the MOVE/MRI.COM-JPN
Keywords:Sea of Japan, MOVE/MRI.COM-JPN, MGDSST, AMeDAS
Precipitation on the Sea of Japan side in winter is produced by the cold northwest monsoon, which transports water vapor supplied by the sea surface of the Sea of Japan (Figure 1). Higher sea surface temperatures (SST) increase the amount of water vapor supplied to the atmosphere, which affects precipitation. The Tsushima Warm Current (TWC) flowing into the Sea of Japan, which branches off from the Kuroshio Current, flows in through the Tsushima Strait (about 150m depth), and flows out through the Tsugaru Strait and the Soya Strait. TWC flows about 200 m thick due to the topography of the straits and land shelf, causing high temperature and high salinity conditions in the surface layer of the southern Sea of Japan. A discontinuity between water temperature and salinity is formed around 40°N, with relatively cold water to the north and warm water to the south. In warm-water areas, TWC flows generally parallel to the shore.
Previous studies have shown impacts on winter precipitation from SST and TWC volume transport several months earlier, but the analysis summarizes the winter period, and the detailed spatial distribution for each month is not clear. In this study, the data were analysed at a relatively higher spatial and temporal resolution than in previous studies. I investigated the possible effect of SST and the ocean heat content (OHC) in the Sea of Japan on monthly precipitation in winter.
The atmospheric data used were from the Japan Meteorological Agency (JMA)'s AMeDAS on monthly total precipitation from October to February from 1982 to 2018 and the daily sea-level pressure difference between Fukuoka and Nemuro as an indicator of the winter monsoon. Monthly precipitation, which has a positive correlation with the pressure difference, was used for validation with oceanographic data. SST data used JMA's Merged satellite and in-situ data Global Daily Sea Surface Temperature (MGDSST) (Kurihara et al. 2006) from 1982 to 2018. The ocean interior data used were the 10-year reanalysis data obtained with an operational system for monitoring and forecasting the status of costal and open-ocean waters around Japan (JPN) (Hirose et al. 2020) from the Meteorological Research Institute. From JPN data, the east-west strait volume transport in the Tsushima Strait and OHC from the sea surface to 100 m depth were used from 2008 to 2018.
In the analysis, monthly mean values of SST and OHC were analysed in clusters and separated into five areas with similar trends from north to south. The mean of SST and OHC calculated from each areas and compared for the interannual variability. A correlation analysis was then performed between precipitation deviations from December to February and SST and OHC deviations in each sea area from the same month of precipitation to two months before. Monthly mean of TWC were taken from the same month as the precipitation month up to three months prior.
The cluster analysis showed that SST in each area showed an increase for the period from 1982 to 2018, but a decrease for the period from 2008 to 2018, depending on the period of analysis. OHC also showed a similar decrease as SST during the same period. The correlation between monthly precipitation deviations and OHC or SST deviations was then shown. Correlation analysis with precipitation deviations in February showed significant positive correlations with December TWC west-side volume transport deviations and January east and west volume transport deviations in the Tohoku region, and with January east-side volume transport deviations in the Chugoku region. The correlation between precipitation and TWC volume transport by east-west showed differences in the distribution of AMeDAS by month and by region.
Previous studies have shown impacts on winter precipitation from SST and TWC volume transport several months earlier, but the analysis summarizes the winter period, and the detailed spatial distribution for each month is not clear. In this study, the data were analysed at a relatively higher spatial and temporal resolution than in previous studies. I investigated the possible effect of SST and the ocean heat content (OHC) in the Sea of Japan on monthly precipitation in winter.
The atmospheric data used were from the Japan Meteorological Agency (JMA)'s AMeDAS on monthly total precipitation from October to February from 1982 to 2018 and the daily sea-level pressure difference between Fukuoka and Nemuro as an indicator of the winter monsoon. Monthly precipitation, which has a positive correlation with the pressure difference, was used for validation with oceanographic data. SST data used JMA's Merged satellite and in-situ data Global Daily Sea Surface Temperature (MGDSST) (Kurihara et al. 2006) from 1982 to 2018. The ocean interior data used were the 10-year reanalysis data obtained with an operational system for monitoring and forecasting the status of costal and open-ocean waters around Japan (JPN) (Hirose et al. 2020) from the Meteorological Research Institute. From JPN data, the east-west strait volume transport in the Tsushima Strait and OHC from the sea surface to 100 m depth were used from 2008 to 2018.
In the analysis, monthly mean values of SST and OHC were analysed in clusters and separated into five areas with similar trends from north to south. The mean of SST and OHC calculated from each areas and compared for the interannual variability. A correlation analysis was then performed between precipitation deviations from December to February and SST and OHC deviations in each sea area from the same month of precipitation to two months before. Monthly mean of TWC were taken from the same month as the precipitation month up to three months prior.
The cluster analysis showed that SST in each area showed an increase for the period from 1982 to 2018, but a decrease for the period from 2008 to 2018, depending on the period of analysis. OHC also showed a similar decrease as SST during the same period. The correlation between monthly precipitation deviations and OHC or SST deviations was then shown. Correlation analysis with precipitation deviations in February showed significant positive correlations with December TWC west-side volume transport deviations and January east and west volume transport deviations in the Tohoku region, and with January east-side volume transport deviations in the Chugoku region. The correlation between precipitation and TWC volume transport by east-west showed differences in the distribution of AMeDAS by month and by region.