Tropospheric biennial oscillation and south Asian summer monsoon rainfall in a coupled model

Journal of earth system science

J S Chowdary^1¹  Gopinadh Konda^1,2²  G Srinivas^1,2³ 

[1] Department of Meteorology and Oceanography, Andhra University, Visakhapatnam 530 003, India.^2;Indian Institute of Tropical Meteorology (IITM), Pune 411 008, India.^1;King Abdullah University of Science and Technology (KAUST), Thuwal 23955, Saudi Arabia.^3

关键词: Tropospheric biennial oscillation;    monsoon;    ENSO;    sea surface temperature;    coupled models;   

DOI  :  

学科分类：天文学(综合)

来源: Indian Academy of Sciences

【 摘 要 】

In this study Tropospheric Biennial Oscillation (TBO) and south Asian summer monsoon rainfall are examined in the National Centers for Environmental Prediction (NCEP) Climate Forecast System (CFSv2) hindcast. High correlation between the observations and model TBO index suggests that the model is able to capture most of the TBO years. Spatial patterns of rainfall anomalies associated with positive TBO over the south Asian region are better represented in the model as in the observations. However, the model predicted rainfall anomaly patterns associated with negative TBO years are improper and magnitudes are underestimated compared to the observations. It is noted that positive (negative)TBO is associated with La Ni~na (El Ni~no) like Sea surface temperature (SST) anomalies in the model. This leads to the fact that model TBO is El Ni˜no-Southern Oscillation (ENSO) driven, while in the observations Indian Ocean Dipole (IOD) also plays a role in the negative TBO phase. Detailed analysissuggests that the negative TBO rainfall anomaly pattern in the model is highly influenced by improper teleconnections allied to IOD. Unlike in the observations, rainfall anomalies over the south Asian region are anti-correlated with IOD index in CFSv2. Further, summer monsoon rainfall over south Asian region is highly correlated with IOD western pole than eastern pole in CFSv2 in contrast to the observations. Altogether, the present study highlights the importance of improving Indian Ocean SST teleconnections to south Asian summer rainfall in the model by enhancing the predictability of TBO. This in turn would improve monsoon rainfall prediction skill of the model.

【 授权许可】

CC BY