Impact of Siberian High on rainfall variability over Northern part of Indo-Pak region
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ORIGINAL PAPER
Impact of Siberian High on rainfall variability over Northern part of Indo-Pak region M. J. Iqbal & S. M. Fahad Riaz & Badar M. K. Ghauri
Received: 15 October 2011 / Accepted: 8 May 2012 / Published online: 31 May 2012 # Saudi Society for Geosciences 2012
Abstract Anticyclones dominate the weather over most of the eastern and the southern Asia during the winter season. This study examines the impact of Siberian High on winter rainfall variability over South Asia. In this paper, the teleconnections between the Siberian High and winter precipitation that cover the northern part of Indo-Pak region have been discussed. The objective indices of area-weighted pressure and area-weighted latitudinal and longitudinal movements high are used to find out the linkage between the winter rainfall in the mentioned region and the Siberian High. The analysis shows that rainfall pattern is significantly correlated with latitudinal displacement of the Siberian High. We have constructed a linear model of the winter rainfall using Siberian High latitude and Nino34 which explains 27 % variance of the winter precipitation for the region under study. The article also explains the physical mechanisms to establish the relationships between the Siberian High and regional rainfall. Keywords Siberian high . Winter rainfall . Centers of action (COA)
M. J. Iqbal (*) Institute of Space and Planetary Astrophysics, University of Karachi, Karachi, Pakistan e-mail: [email protected] M. J. Iqbal : S. M. F. Riaz Department of Mathematics, University of Karachi, Karachi, Pakistan B. M. K. Ghauri NCRG, Institute of Space and Technology, Karachi, Pakistan
Introduction North Atlantic Oscillation (NAO) and El Niño-Southern Oscillation (ENSO) play significant role in determining the winter rainfall variability over Southwest Asia (Syed et al. 2006; Cullen et al. 2002; Eshel et al. 2000). In particular, a positive precipitation anomaly is found in correspondence of positive NAO phase and warm ENSO phase over subregion encompassing the northern Pakistan, Afghanistan, Tajikistan, and the southern Uzbekistan. NAO explains only 10 % of the variability of winter rainfall. This paper will find new predictors which can be used to improve the model of the winter rainfall. Figure 1 shows the distribution of sea level pressure in the Indian Ocean and the continent of Asia during winter (December–February) over 1961–2000. The pressure pattern in South Asia indicates the influence of Indian Ocean High to the south and the Siberian High to the north. Siberian High (SH) is associated with the coldest and densest air masses in the Northern Hemisphere (Lydolf 1977). It is a semipermanent and quasistationary atmospheric center of action, dominant in the boreal winter season. The location of SH is shown in Fig. 1. SH forms generally in October mainly in response to strong and continuous radiative cooling in the lower troposphere above the snow-covered surface of Asia and persists until around the end of April. Lydolf (1977) considered the SH to be a shallow
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