1 / 16

SOLA: Scientific Online Letters on the Atmosphere (Met. Soc. Japan) Cited 22 times

SOLA: Scientific Online Letters on the Atmosphere (Met. Soc. Japan) Cited 22 times Keywords: Korea strait volume transport, rain/snowfall, winter monsoon. Introduction. Importance of precipitation forecasting. Worst predictable variable. Ignored ocean’s variability. Winter monsoon.

joann
Download Presentation

SOLA: Scientific Online Letters on the Atmosphere (Met. Soc. Japan) Cited 22 times

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. SOLA: Scientific Online Letters on the Atmosphere (Met. Soc. Japan) Cited 22 times Keywords: Korea strait volume transport, rain/snowfall, winter monsoon

  2. Introduction Importance of precipitation forecasting Worst predictable variable Ignored ocean’s variability Winter monsoon Plenty of moisture in the ocean Snowfall Concerning of heavy snows Effort to prediction Example of subsurface current measurements for the prediction of snowfall

  3. Data - Monthly volume transport through Korea Strait obtained by integrating the observed velocity from the ADCP mounted under a ferryboat since Feb. 1997 (Takikawa et al. 2005) - Monthly JMA precipitation data at NW stations marked in blue crosses Corr=0.767 C: ASON transport (Sv) P: DJF precipitation (mm)

  4. Autumn current and winter precipitation Large amount of warm water transport in autumn Spread over the southern East sea Enhances evaporation at the surface in winter ASON transport (0.804) Remote-sensing NDJ SST (97-05) DJF precipitation (0.822) Above scenario is justified

  5. And winter monsoon Many studies already clarified the heavy snowfall generated by the monsoonal outbreak MOI = SLP difference between Irkutsk, Russia (52°16´N,104°21´E) and Nemuro, Japan (43°20´N,145°35´E) SLP was taken from NCEP1 Winter monsoon is still a principal factor determining the regional precipitation Precipitation (snowfall) = warm TWC + cold dry outbreak

  6. Current, Precipitation, and Monsoon C: ASON transport (Sv) P: DJF precipitation (mm) M: Monsoon index (hPa) Corr=0.767, rmse=40.7mm Corr=0.906, rmse=27.0mm If the warm ocean current were negligible and the northerly wind stopped, the winter precipitation should be hardly expected The subsurface ocean measurement certainly improves the precipitation estimate Ocean currents leads the monsoon. The reason is not clear yet.

  7. Discussion and conclusion Winter snowfall in Japanese NW region can be predicted by the ocean current observation in autumn Monsoon index and SST have shown even stronger correlation, but only short or negligible time lag to predict Based on the transport data, they predicted less snow in 2005/2006 than that in 2004/2005, and it was right (530 mm for 2005/2006, 596 mm in previous winter, although there was disastrous snow in Dec. 2005) Short-term variability is highly determined by the meteorological condition, the long-term variation may be strongly affected by the oceanic conditions Subsurface conditions in oceans change slowly and often lead to long term changes in the atmosphere due to their large heat capacity

  8. Cited 9 times Keywords: Korea strait volume transport, WP teleconnection pattern

  9. Introduction Volume transport of the TWC can be a good predictor of the seasonal precipitation (Hirose and Fukudome, 2006) TWC fluctuation impacts not only the local coastal area, but possibly a broader climate system (remember that current leads monsoon) ENSO PNA WP Controlling winter climate over the North Pacific There are also active roles of regional ocean variability in determining the atmospheric conditions (Isobe and Beardsley 2007; Frankignoul and Sennechael 2007; Frankignoul et al. 2011 <- not in this paper :D) Extended study of the previous research in terms of the data period and area coverage to find more strong and broad evidence of atmosphere-ocean interaction

  10. Correlation analysis DJF precipitation (1976/77 ~ 2005/06) SON TWC transport measured by Ferryboat ADCP (1997/98 ~ 2005/06) SON TWC transport estimated from tide gauge (from 1960s) Corr btw transport and precipitation measured estimated Positive correlation region: Large TWC in autumn carries more heat into the East Sea and thus the high water temperature strengthens evaporation and precipitation in winter (Hirose and Fukudome, 2006) => How can we explain the negative correlations?

  11. Negative correlations The northwesterly winter monsoon is not likely to be the direct cause : moisture is lost in the mountains (even it is an opposite sign) Precipitation brought to the Pacific coast by the southerly winds? : Not related to East Sea Close relationship between the transport in SON and topospheric variation in the DJF : Large transport leads to the development of a weak westerly jet (Z500 large in south) : The dipoles are resembles WP pattern Not yet explained…. DJF Z500 corr. to SON TWC

  12. Comparison with WP WP index: rotated principal component of Z500 (NCEP) Corr=0.90 with measured 0.57 with estimated The seasonal lag is important in predicting the WP pattern (maximum in 3 month lags) TWC does not appear to affect the other dominant structure of the PNA ENSO, major controlling factor of PNA, WP? : insignificant correlation, no lag dependency : Tropical influence probably has a large-scale and long-term effect…? : TWC, additional sharp local predictor of WP

  13. For your information… The tropical influence decreases recently ENSO’s interannual signal dominates its seasonal signals (not shown here) => Probably no lag dependence Pak et al. in revision Negative correlation, again Lau (1988) and Ueno (1993) : High probability of rain/snow on the Pacific side during a negative phase of WP Takano et al. (2008) : Convective activity over the East Sea is correlated with the WP index Strong TWC -> positive WP (Kam. Pos.) -> low precipitation => Negative correlation between TWC and Pacific side precipitation in Japan

  14. Discussion Ocean-to-atmosphere feedback in the extratropics : wind-driven ocean variation may affect the climate teleconnection pattern TWC is only a part of the western boundary current system : TWC solely controls the WP pattern? : What TWC represents for? 1976/77 to 2005/06 ND SST (Reynolds + Minobe’s SST) Warm anomalies eastern East Sea Cold anomaly in the Yellow Sea -> Large transport may be counter-balanced with a small transport of Yellow Sea Warm Current This variation possibly contributes to the activity of the WP pattern… Covariances between ND SST and SON TWC

  15. Discussion Cold Yellow Sea + Warm eastern East Sea => Positive (Kam. Pos.) WP pattern Similar pattern… yes Large TWC (small YSWC) -> Cold Yellow Sea + Warm eastern East Sea -> Positive WP -> Low precipitation in Pacific side …. Covariances between ND SST and DJF WP But, large-scale negative covariance with subtropical region could not be explained by the TWC transport : Related to subropical gyre? (weak correlation with TWC) : Related to Kuroshio and TWC transport? (-0.32 with 4 month lag +-0.2 with WP…) => TWC variation in autumn may be related to the subarctic variation

  16. Concluding remarks Autumn transport of TWC can be an excellent predictor of the WP teleconnection pattern associated with the precipitation pattern in the Japanese region in the following winter : The 3-month lag may be an indicator of ocean-to-atmosphere feedback in extratropics

More Related