Abstract:
The northern hemisphere (NH) stationary Circumglobal teleconnection (CGT) pattern in boreal summer season was identified and discussed in previous studies. The evidences were also found that the tropical thermal forcing can modulated this pattern. It is conceivable that warming in the eastern and central Pacific Ocean may influence the CGT pattern. The impacts of two types of El Niño on NH at 200 hPa height (H 200) have been investigated in this study. The observed data analysis revealed that the H200 anomalies are opposite in polarity during two types of El Niño Southern Oscillations (ENSO) i.e. Warm pool (WP) El Niño and Cold Tongue (CT) El Niño. During WP (El Niño), a zonal wave train is observed with phase opposite to that of well known CGT pattern in boreal summer season. During CT (El Niño) the Eurasian part is similar to the CGT pattern and opposite to that observed in WP El Niño. These contrasting impacts may be attributed to the different patterns of tropospheric warming and upper air divergence related to different convection centers in the Pacific Ocean during two types of El Niño. Moreover, negative anomaly of the central Asian High was observed during WP (El Niño), which may result in weaker summer monsoon over the south Asian region, especially over Pakistan and northwest India. A coupled general circulation model also simulated upper air wave patterns related to the two types of El Niño, which confirms our findings based on observed data analysis.
Page(s):
53-60
DOI:
DOI not available
Published:
Journal: Pakistan Journal of Meterology, Volume: 11, Issue: 21, Year: 2014