The dynamic plateau monsoon index and its association with general circulation anomalies

Based on monthly ECMWF reanalysis-Interim (ERA-Interim) reanalysis data, along with monthly precipitation and temperature data, the Dynamic Plateau Monsoon Index (DPMI) is defined. The results of a contrast analysis of the DPMI versus the Traditional Plateau Monsoon Index (TPMI) are described. The response of general circulation to northern Qinghai-Xizang Plateau summer monsoon anomalies and the correlation of the DPMI with general circulation anomalies are investigated. The results show that, the DPMI reflected meteorological elements better and depicted climate variation more accurately than the TPMI. In years when the plateau summer monsoon is strong, the low over the plateau and the trough near the eastern coast of Asia are deeper and higher than normal over South China. This correlation corresponds to two anomalous cyclones over the plateau and the eastern coast of Asia and an anomalous anticyclone in South China. The plateau and its adjacent regions are affected by anomalous southwesterly winds that transport more moisture to South China and cause more precipitation. The lower reaches of the Yangtze River appear to receive more precipitation by means of the strong westerly water vapor flow transported from the “large triangle affecting the region”. In years when the plateau summer monsoon is weak, these are opposite. The plateau monsoon is closely related to the intensity and position of the South Asian high, and the existence of a teleconnection pattern in the mid-upper levels suggests a possible linkage of the East Asian monsoon and the Indian monsoon to the plateau summer monsoon.

[1]  Guoxiong Wu,et al.  Comparisons of soil moisture datasets over the Tibetan Plateau and application to the simulation of Asia summer monsoon onset , 2010 .

[2]  J. Jouzel,et al.  Tibetan Plateau summer monsoon northward extent revealed by measurements of water stable isotopes , 2001 .

[3]  I. Trigo.  Climatology and interannual variability of storm-tracks in the Euro-Atlantic sector: a comparison between ERA-40 and NCEP/NCAR reanalyses , 2006 .

[4]  P. Ruti,et al.  Discrepancies in Southern Hemisphere Mid-latitude Atmospheric Variability of the NCEP-NCAR and ECMWF Reanalyses , 2005 .

[5]  J. Srinivasan,et al.  Rossby waves in May and the Indian summer monsoon rainfall , 1999 .

[6]  P. Webster,et al.  Monsoons: Processes, predictability, and the prospects for prediction , 1998 .

[7]  Hongxu Zhao,et al.  On the relationship between Tibetan snow cover, the Tibetan plateau monsoon and the Indian summer monsoon , 2004 .

[8]  C. Fu,et al.  The role of land-sea distribution and orography in the asian monsoon. Part I: Land-sea distribution , 2010 .

[9]  J. Chan,et al.  A Unified Monsoon Index for South China , 1999 .

[10]  Bai Hu.  The Principal Feature of QinghaiXizang Plateau Monsoon Variation in 40 Years , 2001 .

[11]  C. Fu,et al.  The role of land-sea distribution and orography in the Asian monsoon. Part II: Orography , 2010 .

[12]  Maocang Tang,et al.  Plateau monsoons of the northern hemisphere: a comparison between North America and Tibet , 1984 .

[13]  Chen Jing,et al.  Climatic Change of Qinghai-Xizang Plateau Region in Recent 40-year Reanalysis and Surface Observation Data——Contrast of Observational Data and NCEP, ECMWF Surface Air Temperature and Precipitation , 2004 .

[14]  R. Lu,et al.  A teleconnection pattern in upper-level meridional wind over the North African and Eurasian continent in summer , 2002 .

[15]  LI Dong-liang,et al.  The Principal Feature of Qinghai-Xizang Plateau Monsoon Variation in 40 Years , 2001 .

[16]  Peter J. Webster,et al.  Monsoon and Enso: Selectively Interactive Systems , 1992 .

[17]  Takeshi Enomoto.  Interannual variability of the bonin high associated with the propagation of Rossby waves along the Asian jet , 2004 .

[18]  T. Terao.  The zonal wavelength of the quasi-stationary Rossby waves trapped in the westerly jet , 1999 .

[19]  A. Betts,et al.  Comparison of river basin hydrometeorology in ERA-Interim and ERA-40 reanalyses with observations , 2009 .

[20]  P. Guest,et al.  A comparison of surface layer and surface turbulent flux observations over the Labrador Sea with ECMWF analyses and NCEP reanalyses , 2000 .

[21]  K. Kumar,et al.  Indian summer monsoon rainfall and 200‐mbar meridional wind index: Application for long‐range prediction , 2007 .

[22]  Richard H. Johnson,et al.  A Report of the Field Operations and Early Results of the South China Sea Monsoon Experiment (SCSMEX) , 1999 .

[23]  Hayashi spectra of the northern hemisphere mid-latitude atmospheric variability in the NCEP–NCAR and ECMWF reanalyses , 2005, physics/0509145.

[24]  D. Bromwich,et al.  Strong Trends in the Skill of the ERA-40 and NCEP–NCAR Reanalyses in the High and Midlatitudes of the Southern Hemisphere, 1958–2001* , 2004 .

[25]  Gao Wen-liang,et al.  Relationship between Interannual Change over Qinghai-Xizang Plateau Monsoon and Climate Changein Upper Reach of Changjiang River , 2003 .

[26]  J. Slingo,et al.  The mean evolution and variability of the Asian summer monsoon: comparison of ECMWF and NCEP/NCAR reanalyses , 1999 .