Impact of South Asian High Variability on Monsoon Precipitation in Pakistan

Maida Z., G Rasul

Abstract


The South Asian High (SAH) variability is known to have significant contribution in the success
and failure of summer monsoon precipitation (JAS) of Pakistan situated within South Asia. This
study aims to analyze the impact of South Asian High (SAH) variability on the summer monsoon
precipitation in Pakistan. The principal component analysis shows strong positive temporal
correlation coefficient between SAH (200 hPa) and monsoon (JAS) precipitation i.e. 0.7 for the
period 1980-2010. The streamline and precipitation analysis shows that Pakistan receives heavy
precipitation during strong SAH years (1988, 1992, 1994, 2010) due to westward (70°E-80°E)
movement of SAH from its mean position and experience suppress precipitation during weak SAH
year (1987, 1997, 2004, 2009) due to eastward (90°E-110°E) oscillation of SAH. The isotherms
analysis shows negative anomalies in strong SAH years and positive anomalies in weak SAH
years over most parts of Pakistan. The minimum values of divergence of moisture flux (DMF) at
850 hPa in strong SAH years and nil DMF in weak SAH years has been observed over western
parts of Pakistan. The wind field (850 hPa) analysis has shown the evident stimulation of moisture
from Arabian Sea incase of strong SAH years and quite minute stimulation of moisture in weak
SAH years. Hence, it is evident from the study that the strength and oscillation of SAH and
summer monsoon precipitation (JAS) in Pakistan are strongly inter-reliant upon each other. It is
anticipated that climate change can lead the country towards extreme droughts and extreme
flooding. This study will be helpful for the forecasters who can use the behavior of SAH (Tibetan
High) as an indicator for prediction of intense and weak summer monsoon rainfall.


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