On Relationship Between Pacific-japan Teleconnection And Sea Fogs Over The Northwestern Pacific

In this paper, the sea fog observation data in Chinese coastal station, ICOADS(International Comprehensive Ocean-Atmosphere Data Set) visibility data, GPCPprecipitation data and the NCEP-CFSR reanalysis data are used to study the effects ofPacific-Japan teleconnection pattern(P-J pattern) in July on sea fog in sea area east ofKuril Islands and the relationship between the phenomenon of sea fog frequencysuddenly drops from July to August over entire Yellow sea and the P-J pattern phaseshift. Finally, the changing trend of sea fog over Western North Pacific(WNP) underglobal warming is projected combined with the CMIP5models.The correlation analysis indicates that the correlation coefficient is highest inJuly between Sea Fog Index of East of Kuril Islands(SFIEKI) and P-J index, about0.62exceeding99%significance level. The Ocean-Atmosphere conditions in P-Jpositive phase are conducive to formation of sea fog. Composite analysis shows thatin the positive phase anomalies (the standardized P-J index is much higher thannormal), the position of Western North Pacific Subtropical High(WNPSH) is northand east, which cause a stronger south wind and moisture convergence over sea areaeast of Kuril Islands. Southerly is mainly horizontal wind in positive phase years,while vertical motion is obvious in the negative phase years. It is conducive to depressthe marine atmosphere boundary layer height in the background circulation. Inaddition, The warmer temperature advection at950hPa contribute to form strongthermal inversion layer. It is a possible reason of different geopotential height field,that the different distribution of vorticity advection characters of meridionaltransportation in positive phase years and zonal transportation in negative phase year.The structure of south cloud and north fog maybe influenced by the area and heightof anomalous circulation of P-J pattern and forced by the Kuroshio extension SSTfront. P-J teleconnection pattern considered as a atmospheric bridge contacts tropicand midlatitude area, which affect the sea fog east of Japan through influence atmospheric circulation.The analysis of P-J phase intraseasonal shift shows that P-J pattern is theanomalous atmospheric circulation leading mode over WNP in Summer with asignificant intraseasonal variation and a4pentads half period. The positionintraseasonal variation of WNPSH contributes to the formation of P-J pattern. TheRossby wave energy northwestward propagate in Philippine sea impels negativevorticity area westward extend from east of Japan, together with enhanced mid-highlatitude surface geopotentical height strengthen the east wind component in Bo hai seaand Yellow sea. In the past30years, atmospheric circulation variation over WNPduring July and August trends to happen in advance, which may cause P-J patternphase shift in advance about2pentads. Therefore, the sea fog frequency decrease inChina offshore in July and August may affected by this change.The projection refer to geopotential height, wind, specific humidity, cloud watercontent and so on from15models in CMIP5suggest that occurrence frequency ofnegative phase of P-J pattern may increase in the second half of the21st century.Northwestward extend of WNPSH could be one of the possible reasons of theincrease. The negative phase anomalous atmospheric circulation will change manyoceanic and meteorological conditions, which may lead to sea fog frequency decreaseover east of Japan and high value area northward.