The Connectivity of the Winter North Atlantic …...Journal of the Meteorological Society of Japan, Vol. 82, No. 3, pp. 905--913, 2004 905 The Connectivity of the Winter North Atlantic

Journal of the Meteorological Society of Japan, Vol. 82, No. 3, pp. 905--913, 2004 905

The Connectivity of the Winter North Atlantic Oscillation (NAO)

and the Summer Okhotsk High

Masayo OGI

Frontier Research System for Global Change, Yokohama, Japan

Yoshihiro TACHIBANA

Liberal Arts Education Center, Tokai University, Hiratsuka, JapanInternational Arctic Research Center, Frontier Research System for Global Change, Yokohama, Japan

and

Koji YAMAZAKI

Graduate School of Environmental Earth Science, Hokkaido University, Sapporo, JapanInternational Arctic Research Center, Frontier Research System for Global Change, Yokohama, Japan

(Manuscript received 25 June 2003, in final form 25 February 2004)

Abstract

We statistically investigated winter-summer climatic connectivity between the winter North AtlanticOscillation (NAO), and the summer Okhotsk High. We found that the winter NAO persistently influen-ces the surface air temperature, snow cover over the Eurasia continent, sea ice and SST around theBarents Sea region from winter to summer. The warm air temperature anomalies in East Siberia makea preferable condition for upper-level blocking. Warm signals around the Barents Sea region excite theRossby wave propagating toward the Sea of Okhotsk. In addition, regional persistency of the wintertimelocal phenomena, and their possible influence on the summertime Okhotsk High is examined. The neg-ative phase of the winter NAO is related to the winter and spring heavy sea ice in the Sea of Okhotsk.The heavy spring sea ice in the Sea of Okhotsk brings about the cold SST around the Sea of Okhotsk.However, since the Okhotsk High does not have correlation with the SST around the Sea of Okhotsk inthe previous month, the local connection of the sea ice in the Sea of Okhotsk with the summer OkhotskHigh is unlikely. Associated with an enhanced Okhotsk High, cold SST anomalies appear to the east ofJapan. This cold SST anomaly is a response to the cold air advection associated with the Okhotsk High.We suggest that the winter NAO remotely regulates both the winter sea ice, and the summer OkhotskHigh.

1. Introduction

In early summer, the climate around the Seaof Okhotsk is characterized by the occurrence

of the Okhotsk High, and its interannual vari-ability is very large. The occurrence of theOkhotsk High brings about thick fog and coolwet weather conditions in northern Japan (Ku-doh 1984; Kato 1985; Kawano 1989). In addi-tion, the Okhotsk High regulates the Asiansummer monsoon and plays an important rolein influencing the associated Baiu/Meiyu sta-tionary front (e.g., Ninomiya and Mizuno 1985,

Corresponding author: Masayo Ogi, Frontier Re-search System for Global Change, Yokohama 236-0001, Japan.E-mail: [email protected]( 2004, Meteorological Society of Japan

(V7 14/6/04 14:51) Ga/J J-1095 J. Meteor 82:3 PMU: WSL 20/05/04 AC1: WSL 28/05/04 (NewCenturySchlbk) (0).3.04.05 pp. 905-913 006_P (p. 905)

1987; Wang 1992). Therefore, understandingthe interannual variation of the Okhotsk Highis important for not only regional-scale, butalso large-scale climates. Recently, Ogi et al.(2003a, 2003b) found that summertime large-scale atmospheric circulations are connectedto the North Atlantic Oscillation (NAO) of theprevious winter. They pointed out that inthe year of a positive phase of the winter NAO,the summertime 500 hPa geopotential heightanomaly field in the mid-latitudes is overallpositive, especially over the Sea of Okhotsk,central Siberia, the British Isles and NorthAmerica. Their result suggests the existenceof a winter-summer large-scale remote con-nection with the climate around the Sea ofOkhotsk. In their study, however, the relationof the winter NAO to the atmosphere over theSea of Okhotsk is barely mentioned, becausethe scope of the study did not concentrate onthe Sea of Okhotsk, but instead addressedhemispheric scale atmosphere. A study on therelationship between the sea ice in the Sea ofOkhotsk and the Amur River discharge con-ducted by Ogi et al. (2001), also suggested theexistence of the winter-to-summer connection.They showed that the summertime river dis-charge, which is influenced by summertimeatmospheric patterns, is closely related to thewintertime sea-ice variation, which is relatedto the wintertime atmosphere. This good cor-relation between the winter ice and the sum-mer river discharge might be due to the atmo-spheric winter-to-summer connection.

In the present paper, large-scale winter-to-summer atmospheric connectivity, influenc-ing the summertime climate around the Sea ofOkhtosk is investigated. To deduce this, corre-lation and linear regression analyses amongthe atmospheric circulation, SST, sea ice andsnow cover from winter through summer, areapplied. In addition, regional persistency of thewintertime local phenomena, such as sea iceand SST around the Sea of Okhotsk, and theirpossible influence on the summertime OkhotskHigh is examined.

2. Data

Atmospheric data used in this study arefrom the National Center for EnvironmentalPrediction/National Center for AtmosphericResearch (NCEP/NCAR) monthly mean re-

analysis dataset, with a 2:5� � 2:5� regularlatitude-longitude grid (Kalnay et al. 1996;Kistler et al. 2001). The monthly mean sea-icearea and SST in the Arctic Ocean, issued bythe Global Sea Ice Coverage and Sea SurfaceTemperature Data (GISST2.3b) with a 1� � 1�

resolution from 1971 to 2000, are also used.The snow cover frequency is based on the digi-tal NOAA-NESDIS Weekly Northern Hemi-sphere Snow Charts from 1971 to 1995, com-piled by Robinson et al. (1993). The NAO indexis defined as the SLP difference between Styk-kisholmur, Iceland and Ponta Delgada, Azoresby Hurrell (1995) from 1971 to 2000. TheOkhotsk High index is apply to the area-averaged monthly sea level pressure (SLP)within the Sea of Okhotsk. The averaging areais from 50–60�N through 140–160�E. The seaice data of the Sea of Okhotsk, issued by theJapan Meteorological Agency (JMA) from 1971to 2000 are used. Information about the JMAdata is mentioned in Yamazaki (2000) in detail.The JMA data is manually analyzed every 5days, using the GMS, the NOAA satellite im-ages, the SSM/I data and other available ob-servations.

3. The remote connection betweenwinter NAO and summer OkhotskHigh

To confirm NAO’s inter-seasonal connection,we calculated the regression/correlation co-efficient of the SLP field in June, with theNAO index in January (Fig. 1). A high posi-tive correlation/regression area over the Sea ofOkhotsk is obvious in this figure. This NAO’sinter-seasonal connection with the summertimeatmospheric pattern is in agreement with Ogiet al. (2003a, 2003b), in which the wintertimeNAO is related to the summertime atmo-spheric annular pattern in the troposphere.They showed that the wintertime NAO is re-lated to the summertime hemispheric north-south geopotential seesaw between the Arcticand circumpolar ring, in which strong signa-tures are in the Sea of Okhotsk, central Siberiaand the British Isles.

Ogi et al. (2003a) pointed out that the winterNAO index does not have a significant auto-correlation after March. The signal of the win-ter NAO can be memorized in the snow-cover,sea ice and surface oceans, and the anomalies

Journal of the Meteorological Society of Japan906 Vol. 82, No. 3


memorized in them, then influence the sum-mertime atmospheric circulations. To deter-mine the ground hydrological and oceanic pro-cesses related to both the summertime OkhotskHigh and the wintertime NAO, we calculatedthe correlation coefficients of variables relatedto the surface processes.

The correlation/regression of the surfacetemperature at 2-m in June correlating withthe winter NAO (Fig. 2a), displays large val-ues over the mid-latitudes over northern Eur-asia and northern North America, especiallyover central Siberia and the northern Sea ofOkhotsk. Figure 2b shows the correlation co-efficients of the NAO in January, with the SST,sea-ice, and snow cover in June. The warmcolor in the figure denotes a warmer SST, lesssea-ice and less snow cover for the positiveNAO index in winter. The snow cover and sur-face air temperature over eastern Siberia showsignificant correlations with the NAO in Janu-ary. The positive NAO in January is associated

with less snow and warm surface air tempera-ture over eastern Siberia in June, which tendsto reduce the upper-level westerly over the Seaof Okhotsk through thermal wind relationshipand produce positive height anomalies there(see Fig. 2 in Ogi et al. 2003a). In addition, thesea-ice over the Barents Sea is negatively cor-related with the NAO in January, and the SSTsover the Barents Sea are also positively corre-lated with the NAO in January. Fig. 2 possiblyindicates that the influence of the winter NAOis memorized in these regions, and that someof these memorized anomalies affect the inter-annual variation of the Okhotsk High.

To illustrate the inter-seasonal persistentsignal in the surface temperature anomaly thatis influenced by the winter NAO, we show theinter-seasonal variation of the surface temper-ature regressed with the winter NAO. Figure 3shows the lag correlation of the surface tem-perature at 2-m along the latitude of 70�N withthe NAO index in January. When the NAO isin a positive phase, the Eurasia continent is, asa whole, persistently warmer through March.This wintertime warm temperature over Eura-sia is in agreement with previous studies (e.g.,Hurrell 1996; Xie et al. 1999; Wu and Wang2002; Ogi et al. 2003a, 2003b). Moreover, thewarm anomaly persists through spring aroundthe Atlantic region. Especially over the BarentsSea (20�E–60�E) region, warmer anomaliespersist until July. Wu and Wang (2002) pointedout that the winter AO influences the wintersurface air temperature in the high latitudesof the Asian Continent and the Barents Sea.In addition, this persistency is in agreementwith the persistency of other surface processesshown by Ogi et al. (2003a), who showed thatanomalies of the Eurasian snow cover, BarentsSST and Barents sea ice, persist from springthrough summer.

Figure 4 shows the correlation/regression co-efficient map, between the winter NAO indexand the geopotential height at 500 hPa in June.Over the Sea of Okhotsk region, a positive highcorrelation, which corresponds to the OkhotskHigh, is obvious, and a wave-like pattern fromcentral Siberia to eastern Siberia can be seen.Wang (1992), and Wang and Yasunari (1994)pointed out that eastward Rossby wave propa-gation from the west of East Siberia, mightbe one of the possible factors for forming the

Fig. 1. The maps of the correlation andregression coefficients of the monthlymean sea level pressure (SLP) in June,with the NAO in January from 1971through 2000. Areas of light, middlelight, and heavy shading indicate thatcorrelation coefficients exceed the 90%,95%, 99% confidence levels, respectively.The confidence limit is based on a two-sided Student’s t-test. The contour in-terval is 0.5 hPa.

M. OGI, Y. TACHIBANA and K. YAMAZAKI 907June 2004


Fig. 2. (a) The correlation and the regression coefficients of the surface temperature at 2-m in Junewith the NAO index in January. The shadings are the same as those in Fig. 1. (b) Correlation andregression coefficients of the SST, sea ice and snow cover in June with the NAO index in January.Contours over oceans are correlations of the SST. Solid (red) and broken (blue) lines represent thepositive and negative correlations, respectively. The shadings over oceans are correlations of thesea-ice. The shadings over land are correlations of snow cover. The denotations of the shadingareas are reversed to Fig. 1 (red denotes negative, blue denotes positive).

Fig. 3. Lag correlation of the monthlysurface temperature at 2-m along thelatitude of 70�N with the NAO index inJanuary. The shadings are the same asthose in Fig. 1.

Fig. 4. The correlation/regression of themonthly geopotential height at 500 hPain June, with the NAO index in Janu-ary. Arrows indicate the wave-activityflux (m2s�2) at 300 hPa, formulated byTakaya and Nakamura (1997, 2001).The shadings are the same as those inFig. 1.



Okhotsk High. However, they did not clearlypoint out the source region of the Rossbywaves. The wave-like pattern in Fig. 4 suggeststhat the Rossby wave excited over central Sibe-ria propagates toward the Sea of Okhotsk,and possibly influences the atmospheric circu-lation around the Sea of Okhotsk. Arrows su-perimposed in Fig. 4 are the wave activity fluxformulated by Takaya and Nakamura (1997,2001) at the 300-hPa level. The arrows clearlyexhibit the eastward flux mainly emanatingfrom the southern coast of the Barents Sea,in which the sea ice, SST and surface tempera-ture anomalies are significant (see Fig. 2) to-ward the north of the Sea of Okhotsk. Thiswave activity flux pattern suggests that thesurface anomalies around the Barents Sea,which are attributed to the variation of thewinter NAO, excite the Rossby wave propagat-ing in a downwind direction toward the Sea ofOkhotsk, and then enhance the Okhotsk High.From the Okhtosk region, the wave propagatesto the North Pacific and the Arctic, generatingnegative anomalies. The negative anomalies inthe North Pacific are located at the eastwardextension of the Baiu frontal zone.

4. A possibility of regional sea iceinfluence on the Okhotsk High

Our main findings is that the wintertimeNAO has a linkage to the following summer-time Okhotsk High. We suggest that the signalof the wintertime NAO is memorized in thesnow over Eurasia and the sea ice, SST overthe Barents Sea. Along with this remote influ-ence, the sea ice in the Sea of Okhotsk maylocally influence the atmosphere around theSea of Okhotsk, through the summer SST in,and around, the Sea of Okhotsk. The Sea ofOkhotsk is covered by sea ice from Novemberthrough May, and the interannual variabilityof the Okhotsk sea ice is quite large (e.g.,Tachibana et al. 1996). Many previous studieson the wintertime environmental atmosphericconditions have pointed out that the wintersea-ice in the Sea of Okhotsk, is associated withwintertime large-scale atmospheric anomalies(e.g., Cavalieri and Parkinson 1987; Parkinson1990; Tachibana et al. 1996). Yamazaki (2000)pointed out that the winter NAO, and the seaice extent in the Sea of Okhotsk, has a nega-tive correlation of �0.46. On the other hand,

the extreme change of the sea-ice is suggestedto influence large-scale atmosphere as well aslocal atmosphere (Honda et al. 1996, 1999).In addition, because the auto-correlation of thesea-ice has a large persistency from winter tospring (Yamazaki 2000), the spring sea-ice, aswell as the winter sea-ice, must be regulatedby wintertime atmospheric patterns. Table 1shows the auto-correlation of the sea-ice inthe Sea of Okhotsk from December throughMay. The correlation coefficients among all themonths are positive. Due to the absorption ofthe latent heat during melting periods, spring-time ice may prevent the SST from rising.Therefore, there is the possibility that the localvariations of the SST in the Sea of Okhotskin late spring and early summer may influencethe Okhotsk High. To examine the relationshipamong the interannual variations of the sea icein the Sea of Okhotsk in spring (April–May),the monthly mean SST and the SLP fromspring to summer. We calculate the correlation/regressions coefficients among them. First, therelationship between the spring (April–May)sea ice in the Sea of Okhotsk, and the SSTfrom April to June is shown in Figs. 5a, 5b, and5c. The simultaneous correlation/regression forApril and May (Figs. 5a and 5b) shows that theregression coefficients in the southeast Sea ofOkhotsk, northern North Pacific and the Be-ring Sea are overall negative, and that the cor-relation coefficients in these areas exceed thestatistically significant level of 99%. The largenegative correlation area in the northern NorthPacific, moreover, persists through June (Fig.5c). This high correlation/regression area forJuly, however, becomes narrower (not shown).This represents the fact that after the heavyspring ice cover in the Sea of Okhotsk, thenegative SST anomaly in the northwestern

Table 1. The auto-correlation coefficientsof the sea ice in the Sea of Okhotsk.

Dec Jan Feb Mar Apr May

Dec 1.0 0.70 0.44 0.24 0.47 0.55Jan 1.0 0.76 0.32 0.46 0.55Feb 1.0 0.65 0.57 0.44Mar 1.0 0.74 0.51Apr 1.0 0.81May 1.0



North Pacific persists through the early sum-mer. However, no persistent signal of the SSTcan be seen within the Sea of Okhotsk. In Fig.5c, the positive SST anomalies east of Japanare enhanced in June, which can be interpretedas the effect of the Okhotsk High, and will bediscussed later.

Figures 5d, 5e and 5f show the correlation/regression of the SLP from April to June withthe spring sea ice in the Sea of Okhotsk. Pat-terns in April (Fig. 5d) show a positive correla-tion over the Sea of Okhotsk, whose statisticalsignificance is, however, weak. In May (Fig. 5e),no significant correlation signal can be seenin and around the Sea of Okhotsk. However,in June, negative correlation/regression coeffi-cients over and around the Sea of Okhotsk aresignificantly high, and the high correlation areacovers most of the Sea of Okhotsk, and thewestern Bering Sea. In July, the statisticallysignificant area mostly disappears (not shown).The results shown in Fig. 5 indicate that when

the sea ice in the Sea of Okhotsk is heavierthan normal, the persistency of the SST in theSea of Okhotsk is small, but in contrast, in thenorthwestern North Pacific, the persistency isquite large.

In addition, we examine the correlation coef-ficient between the surface temperature at 2-m,the SST and the Okhotsk High index, whichis defined as the area-averaged SLP over theregion 50–60�N, 140–160�E in June, are shownin Fig. 6. The contour lines over the ocean inthe figure denote SST correlation with theOkhotsk High, the shadings over the ocean aresea ice correlation with the Okhotsk High, andthe contour lines over the land are the sur-face temperature correlation with the OkhotskHigh. The simultaneous correlation of thesurface temperature with the Okhotsk High(Figure 6b), shows a positive correlation areaover the land north of the Sea of Okhotsk, andthe land south of the Barents Sea. A negativecorrelation of sea ice is found in the Barents

Fig. 5. The maps of the correlation and regression coefficients of the monthly mean sea surfacetemperature (SST) (Fig. 5a: April, 5b: May, 5c: June), and the monthly mean sea level pressure(SLP) (Fig. 5d, 5e, 5f ), with the sea-ice extent index averaged from April through May over theOkhotsk Sea (OSI) from 1971 through 2000. The shadings are the same as those in Fig. 1. Thecontour interval is 0.1 K in Fig. 5a, 5b, 5c and 0.5 hPa in Fig. 5d, 5e, 5f.



Sea. The positive correlation over the northernEurasia area is the same areas as those of thepositive relationship between the surface tem-perature in June, and the winter NAO index(Fig. 2a). These results further support thatthe winter NAO influences surface temperatureand snow cover, and these memorized anoma-lies affect the Okhotsk High. An elongated neg-ative area is seen from Lake Baikal to thenorthwestern Pacific. The strong Okhotsk Highis associated with warmer surface air temper-atures to the north and colder temperatures tothe south. This meridional gradient of low-leveltemperatures implies a weakening of upper-level westerly flow through the thermal windrelationship, and it is consistent with the factthat the Okhotsk High is usually accompaniedby an upper level blocking.

In the northwestern Pacific, although thenegative values persist through the followingmonth (July), they do not appear in the previ-ous month (May). This fact suggests that theSST anomalies in the northwestern Pacific isnot a cause of the Okhotsk High, rather theyare generated by the atmospheric circulationanomalies associated with the strong OkhotskHigh. The northerly cold air advection to theeast and south of the Okhotsk High, may causethe cold SST anomalies in the northwesternpart of the North Pacific. Arrows in Fig. 7 showthe regressed surface wind at 10-m in June

with the Okhotsk High index, and contours inFig. 7 show the climatology of the surface airtemperature at 2-m in June. The cold advectionis obvious over the negative SST region, whichlies to the east of Japan shown in Fig. 6(b).Figures 8(a) and (b) respectively show theregressions of the latent and sensible heatfluxes in June, with the Okhotsk High indexin June. Both are positive in the region to theeast of Japan, indicating that the ocean losesheat through sensible and latent heat fluxes.These results are consistent with the notionthat the northerly cold wind associated withthe Okhotsk High, generates the cold SST in

Fig. 6. The correlation coefficients between the Okhotsk High index (50–60�N, 140–160�E) in Juneand the SST and the surface temperature at 2-m in (a) May (b) June (c) July. Contours over theocean are SST correlation with the Okhotsk High, the shadings over the ocean are sea ice negativecorrelation with the Okhotsk High, and the contour lines over land are the surface temperatureat 2-m correlation with the Okhotsk High. Contour and shading indicate correlations of r > 0:3.The denotations of the shading areas are reversed to Fig. 1 (red denotes negative, blue denotespositive).

Fig. 7. The regression coefficients of thesurface wind at 10-m in June with theOkhotsk High index in June (Arrows).The contours are the climatology of thesurface air temperature at 2-m in June,from 1971 through 2002.



the region to the east of Japan. In this re-spect, the SST anomalies associated with springsea ice in the Sea of Okhotsk (Fig. 5a, 5b) donot affect the formation of the Okhotsk High.Rather, the Okhotsk High causes the SSTanomalies in the region to the east of Japan.In Fig. 5c, which shows correlations betweenspring sea-ice and SST, the positive SSTanomalies east of Japan are enhanced in June.This can also be interpreted as the effect of theOkhotsk High.

7. Conclusions

This study has examined connectivity be-tween the wintertime NAO and the summer-time Okhotsk High in the interannual timescale. When the NAO in January is in a posi-tive (negative) phase, the Okhotsk High inJune is stronger (weaker) than normal. Thewintertime NAO leaves strong memories insnow in Eurasia, in the sea ice and the SSTover the Barents Sea. These strong memoriespersist through summer. In addition, the mem-orized surface anomalies excite the stationaryRossby wave in the Barents region, and propa-gate eastward to the Sea of Okhotsk. As a re-sult, the wintertime NAO has good connectivitywith the summertime Okhotsk High in the in-terannual time scale.

From the local inter-seasonal point of view,springtime anomalous light coverage of the seaice over the Okhotsk Sea is connected with thestrong Okhotsk High. The Okhotsk high corre-lates the SST in the Barents Sea, the surfacetemperature of the southern continent of theBarents Sea and the northern continent ofthe Sea of Okhotsk. The Barents area is influ-enced by the winter NAO influence. The good

correlation between the springtime sea icein the Sea of Okhotsk, and the summertimeOkhotsk High, is not the direct physical rela-tion. Both variations are caused by the winterNAO.

Our findings suggest that the winter NAOis a predictor for the summertime OkhotskHigh, which strongly influences the summer-time Asian monsoon (e.g., Ninomiya and Miz-uno 1987). Therefore, the finding in this paperhas an important implication for forecastingthe summertime East Asia climate.

Acknowledgments

We would like to thank Dr. Honda in Fron-tier Research System for valuable discussionsand for his advice on the usage of the programs.We also have had fruitful discussion with Dr.Takeuchi in Frontier, Dr. Ukita in ColumbiaUniv. and Dr. Tanimoto in Hokkaido Univ.,who provided perceptive insight into the ice,SST and the ocean variations. Dr. Minobein Hokkaido Univ. and the reviewers providedhelpful comments and suggestions. Further-more, we thank Mr. Kaneko in JMA whowillingly provided us the sea-ice data over theOS. The Grid Analysis and Display System(GrADS) was used for drawing the figures.

References

Cavalieri, D.J. and C.L. Parkinson, 1987: On therelationship between atmospheric circulationand fluctuations in the sea ice extents of theBering and Okhotsk seas. J. Geophys. Res., 92,7141–7162.

Honda, M., K. Yamazaki, Y. Tachibana, and K.Takeuchi, 1996: Influence of Okhotsk sea-iceextent on atmospheric circulation. Geophys.Res. Lett, 23, 3595–3598.

Fig. 8. The regression coefficients between the Okhotsk High index in June and (a) the Latent heatflux, (b) the Sensible heat flux (Wm�2).



———, ———, H. Nakamura, and K. Takeuchi,1999: Dynamic and thermodynamic character-istics of atmospheric response to anomaloussea-ice extent in the Sea of Okhotsk. J. Cli-mate, 12, 3347–3358.

Hurrel, J.W., 1995: Decadal trends in the North At-lantic Oscillation: Regional temperatures andprecipitation. Science, 269, 676–679.

———, 1996: Influence of variations in extratropicalwintertime teleconnections on Northern Hemi-sphere temperature. Geophys. Res. Lett., 23,665–668.

Kalnay, E., M. Kanamitsu, R. Kistler, W. Collins,D. Deaven, L. Gandin, M. Iredell, S. Saha,G. White, J. Woollen, Y. Zhu, M. Chelliah, W.Ebisuzaki, W. Higgins, J. Janowiak, K.C. Mo,C. Ropelewski, J. Wang, A. Leetmaa, R. Rey-nolds, Roy Jenne, and Dennis Joseph, 1996:The NCEP/NCAR 40-year reanalysis project.Bull. Amer. Meteor. Soc., 77, 437–471.

Kistler, R., E. Kalnay, W. Collins, S. Saha, G. White,J. Woollen, M. Chelliah, W. Ebisuzaki, M.Kanamitsu, V. Kousky, H. van den Dool, R.Jenne, and M. Fiorino, 2001: The NCEP-NCAR50-year reanalysis: Monthly means CD-ROMand documentation. Bull. Amer. Meteor. Soc.,82(2), 247–267.

Kato, K., 1985: Heat budget in the atmosphere andthe variation of the air temperature in thelower layer over the Okhotsk Sea (A case studyduring the Baiu Season in 1979). Tenki, 32,425–433 (in Japanese).

Kawano, H., 1989: Heat and moisture budgets in thelayer containing fog, stratus or stratocumulusover the sea of the southeast of Hokkaido.Tenki, 36, 369–375 (in Japanese).

Kudoh, T., 1984: Characteristics of Okhotsk air massduring the typical Yamase period (1981.6.18–21). Tenki, 31, 411–419 (in Japanese).

Ninomiya, K. and H. Mizuno, 1985: Anomalouslycold spell in summer over northeastern Japancaused by northeasterly wind from polar mari-time airmass. Part 1. EOF analysis of temper-ature variation in relation to the large-scalesituation causing the cold summer. J. Meteor.Soc. Japan, 63, 845–857.

———, 1987: Variations of Baiu precipitation overJapan in 1951–1980 and large-scale charac-teristics of wet and dry Baiu. J. Meteor. Soc.Japan, 65, 115–127.

Norris, J.R., Y. Zhang, and J.M. Wallace, 1998:Role of low clouds in summertime atmosphere-ocean interactions over the North Pacific. J.Climate, 11, 2482–2490.

Ogi, M., Y. Tachibana, F. Nishio, and M.A. Dan-chenkov, 2001: Does the fresh water supply

from the Amur river flowing into the Sea ofOkhotsk affect sea ice formation? J. Meteor.Soc. Japan, 79, 123–129.

——— and K. Yamazaki, 2003a: Impact of thewintertime North Atlantic Oscillation (NAO)on the summertime atmospheric circulation.Geophys. Res. Lett., 30(13), 1704, doi:10.1029/2003GL017280.

Ogi, M., K. Yamazaki, and Y. Tachibana, 2003b:Solar cycle modulation of the seasonal linkageof the North Atlantic Oscillation (NAO). Geo-phys. Res. Lett., 30(22), 2170, doi:10.1029/2003GL018545.

Okawa, T., 1973: Growth mechanism of the Okhotskhigh. J. Meteor. Res., 25, 65–77 (in Japanese).

Parkinson, C.L., 1990: The impact of the Siberianhigh and Aleutian low on the sea-ice coverof the sea of Okhotsk. Ann. Glacial, 14, 226–229.

Robinson, D.A., K.F. Dewey, and R.R. Heim, Jr,1993: Global snow cover monitoring: an up-date. Bull. Amer. Meteor. Soc., 74, 1689–1696.

Tachibana, Y., M. Honda, and K. Takeuchi, 1996:The abrupt decrease of the sea ice over thesouthern part of the Sea of Okhotsk in 1989and its relation to the recent weakening of theAleutian low. J. Meteor. Soc. Japan, 74, 579–584.

Takaya, K. and H. Nakamura, 1997: A formulationof a wave-activity flux for stationary Rossbywaves on a zonally varying basic flow. Geophys.Res. Lett., 24, 2985–2988.

———, 2001: A formulation of a phase-independentwave-activity flux of stationary and migratoryquasi-geostrophic eddies on a zonally varyingbasic flow. J. Atmos. Sci., 58, 608–627.

Wang, Y., 1992: Effects of blocking anticyclones inEurasia in the rainy season (Meiyu/Baiu sea-son). J. Meteor. Soc. Japan, 70, 929–951.

——— and T. Yasunari, 1994: A diagnostic analy-sis of the wave train propagating from high-latitudes to low-latitudes in early summer. J.Meteor. Soc. Japan, 72, 269–279.

Wu, B. and J. Wang, 2002: Winter Arctic Oscillation,Siberian High and East Asian winter monsoon.Geophys. Res. Lett., 29(19), 1897, doi:10.1029/2002GL015373.

Xie, S.-P., H. Noguchi, and S. Matsumura, 1999:A hemispheric-scale quasi-decadal oscillationand its signature in northern Japan. J. Meteor.Soc. Japan, 77, 573–582.

Yamazaki, K., 2000: Interaction between the winter-time atmospheric circulation and the variationin the sea ice extent of the Sea of Okhotsk.Seppyo, 62, 345–354 (text in Japanese, ab-stract and figures in English).



Documents

The Connectivity of the Winter North Atlantic …...Journal of the Meteorological Society of Japan, Vol. 82, No. 3, pp. 905--913, 2004 905 The Connectivity of the Winter North Atlantic