Vol. 28, issue 01, article # 7

Abstract:

The composite analysis of average for July pressure and wind fields in the strong and weak East Asian summer monsoon (EASM) periods was carried out using ECMWF ERA-40 and ERA-Interim data. The study showed that the strong EASM periods are characterized by increased meridional flows over East Asia, especially in the area of the monsoon and mid-latitude circulation interaction, where an increased cyclonicity zone appeares. Over large parts of Asia, the atmospheric pressure is higher in the weak EASM periods. In the weak EASM periods, the polar vortex is weak; however, troughs over the Kara Sea, the Sea of Okhotsk, and Hudson Bay are clearly developed. In the Aleutian depression area, the pressure is also reduced. The strongest and most significant long-term changes in the pressure field, indicating weakening of the meridional exchange in recent decades, are characteristic for areas of convergence of the meridional flows of the East Asian and African monsoon.

Keywords:

East Asian summer monsoon, general atmospheric circulation, weakening of monsoon, geopotential, wind velocity field, meridional flows, tropospheric trough

References:

1. Li J., Cook E.R., Chen F., Davi N. Summer monsoon moisture variability over China and Mongolia during the past four centuries // Geophys. Res. Lett. 2009. V. 36, N 22. L22705.
2. Qian W., Hu Q., Zhu Y., Lee D.-K. Centennial-scale dry-wet variations in East Asia // Clim. Dyn. 2003. V. 21, N 1. P. 77–89.
3. Shen C., Wang W.-C., Peng Y., Xu Y., Zheng J. Variability of summer precipitation over Eastern China during the last millennium // Clim. Past. 2009. V. 5, N 2. Р. 129–141.
4. Zhu C., Wang B., Qian W., Zhang B. Recent weakening of northern East Asian summer monsoon: A possible response to global warming // Geophys. Res. Lett. 2012. V. 39, N 9. P. 4.
5. Wang H. The weakening of the Asian monsoon circulation after the end of 1970's // Adv. Atmos. Sci. 2001. V. 18, N 3. P. 376–386.
6. Zhou T.-J., Gong D.-Yi., Li J., Li Bo. Detecting and understanding the multi-decadal variability of the East Asian summer monsoon – recent progress and state of affairs // Meteorol. Zeitschrift. 2009. V. 18, N 4. P. 455–467.
7. Ding Yi.-H., Wang Z., Sun Y. Inter-decadal variation of the summer precipitation in East China and its association with decreasing Asian summer monsoon. Part I: Observed evidences // Int. J. Climatol. 2008. V. 28, N 9. P. 1139–1161.
8. Berezhnyh T.V., Marchenko O.Ju., Abasov N.V., Mordvinov V.I. Izmenenie cirkuljacii atmosfery nad Vostochnoj Aziej i formirovanie dlitel'nyh malovodnyh periodov v bassejne reki Selengi // Geogr. i prirod. resursy. 2012. N 3. P. 61–68.
9. Li H., Dai A., Zhou T., Lu J. Responses of East Asian summer monsoon to historical SST and atmospheric forcing during 1950–2000 // Clim. Dyn. 2010. V. 34, N 4. P. 501–514.
10. Zeng G., Sun Zh., Wang W.-Ch., Min J. Inter-decadal variability of the East Asian summer monsoon and associated atmospheric circulations // Adv. Atmos. Sci. 2007. V. 24, N 5. P. 915–926.
11. Ding Yi.-H., Wang Z., Sun Y. Inter-decadal variation of the summer precipitation in East China and its association with decreasing Asian summer monsoon. Part II: Possible causes // Int. J. Climatol. 2009. V. 29, N 13. P. 1926–1944.
12. Pedelabord P. Mussony. M.: Izdatelstvo inostr. literatury, 1963. 195 p.
13. Hromov S.P. Mussony v sisteme obshhej cirkuljacii atmosfery // A.I. Voejkov i sovremennye problemy klimatologii. L.: Gidrometeoizdat, 1956. С. 84–108.
14. Chen S.J., Zhang P.-Z. Climatology of Deep Cyclones over Asia and the Northwest Pacific // Theor. Appl. Climatol. 1996. V. 54, N 3–4. P. 139–146.
15. Wang X., Zhai P., Wang C. Variations in Extratropical Cyclone Activity in Northern East Asia // Adv. Atmos. Sci. 2009. V. 23, N 3. P. 471–479.
16. Wang B., Wu Z., Li J., Liu J., Chang C.-P., Ding Y., Wu G.-X. How to measure the strength of the East Asian summer monsoon? // J. Clim. 2008. V. 21, N 17. P. 4449–4463.
17. Kalnay E., Kanamitsu M., Kistler R. The NCEP/NCAR 40-year reanalysis project // Bull. Amer. Meteorol. Soc. 1996. V. 77, N 3. P. 437–471.
18. Gibson J.K., Kalberg P., Uppala S. The ECMWF reanalysis (ERA) Project // ECMWF Newslett. 1996. N 73. P. 7–17.
19. Inoue T., Matsumoto J. A Comparison of Summer Sea Level Pressure over East Eurasia between NCEP-NCAR Reanalysis and ERA-40 for the Period 1960–1999 // J. Meteorol. Soc. Jap. 2004. V. 82, N 3. P. 951–958.
20. Han J.-P., Wang H.-J. Features of interdecadal changes of the East Asian summer monsoon and similarity and discrepancy in ERA-40 and NCEP/NCAR reanalysis data // Chin. J. Geophys. 2007. V. 50, N 6. P. 1444–1453.
21. Sterl A. On the (in-)homogeneity of reanalysis products // J. Clim. 2004. V. 17, N 19. P. 3866–3873.
22. Dee D.P., Uppala S.M., Simons A.J., Berrisford P., Poli P., Kobayshi S., Andrae U., Balmaseda M.A., Balsamo G., Bauer P., Bechtold P., Beljoars A.C.M., Berg L., Bidlot J., Bormann N., Delsol C., Dragani R., Fuentes M., Geer A.J., Haimberger L., Healy S.B., Hersback H., Hólm E.V., Isaksen L., Kalberg P., Kohler H., Matricardi M., McNally A.P., Monge-Sanz B.M., Morcrette J.-J., Park B.-K., Peubey C., Rosnay P., Tarolato C., Thépaut N., Vitart F. The ERA-Interim reanalysis: Configuration and performance of the data assimilation system // Quart. J. Roy. Meteorol. Soc. 2011. V. 137, N 656. P. 553–597.
23. URL: http://www.emc.ncep.noaa.gov/gmb/bkistler/ psfc/psfc.html
24. Drozdov O.A., Vasil'ev V.A., Kobysheva N.V., Raevskij A.N., Smekalova L.K., Shkol'nyj E.P. Klimatologija. L.: Gidrometeoizdat, 1989. 568 p.
25. Ren B., Lu R., Xiao Z. A possible linkage in the interdecadal variability of rainfall over North China and the Sahel // Adv. Atmos. Sci. 2004. V. 21, N 5. P. 699–707.
26. Quan X.W., Diaz H.F., Fu C.B. Interdecadal change in the Asia–Africa summer monsoon and its associated changes in global atmospheric circulation // Glob. Planet. Change. 2009. V. 37, N 3. P. 181–188.
27. Huang G., Liu Y., Huang R. The interannual variability of summer rainfall in the arid and semiarid regions of Northern China and its association with the northern hemisphere circumglobal teleconnection // Adv. Atmos. Sci. 2011. V. 28, N 2. P. 257–268.
28. Hao L., Min J., Ding Y.-H., Wang J. Relationship between reduction of summer precipitation in North China and atmospheric circulation anomalies // J. Water Resource and Protection. 2010. V. 2, N 6. P. 569–576.