Connection between Anomalous Zonal Activities of the South Asian High and Eurasian Summer Climate Anomalies

Abstract

Using the daily mean anomalies of atmospheric variables from the NCEP Reanalysis-1 (NCEP R1), this study reveals the connection between anomalous zonal activities of the South Asian high (SAH) and Eurasian climate anomalies in boreal summer. An analysis of variance identifies two major domains with larger geopotential height variability located in the eastern and western flanks of the SAH at around 100 and 150 hPa, respectively. For both eastern and western domains, extreme events are selected during 1981–2014 when normalized height anomalies are greater than 1.0 (less than −1.0) standard deviation for at least 10 consecutive days. Based on these events, four SAH modes that include strong and weak Tibetan modes (STM and WTM, respectively) and strong and weak Iranian modes (SIM and WIM, respectively) are defined to depict the zonal SAH features. The positive composite in the eastern (western) domain indicates the STM (SIM) manifests a robust wavelike pattern with an anomalous low at 150 hPa, and surface cold and wet anomalies over Mongolia and northern China (Kazakhstan and western Siberia) are surrounded by three anomalous highs at 150 hPa and surface warm and dry anomalies over Eurasia. Opposite distributions are also evident in the negative composites of the two domains (WTM and WIM). The surface air temperature anomalies are the downward extension of an anomalous air column aloft while the precipitation anomalies are directly associated with the height anomalies above the air column.

Antarctic sea‐ice variation associated with vertical geopotential height and temperature anomalies

“…These centres illustrated from Figures descript the linkage of SIC‐temperature anomalies. Similar vertical connection between GPH‐temperature anomalies and surface dry‐wet anomalies was also observed from the persistent event analysis of anomalous zonal activities of the South Asian High (Shi and Qian, ).…”

“…The height and temperature anomalies satisfy the hydrostatic balance, meaning that the temperature anomalies can be vertically derived from the height anomalies (Shi and Qian, ; Qian, ). Thus, the SAT anomalies and SIC anomalies are the downward extension of temperature anomalies beneath the height anomalies at the middle to upper troposphere.…”

Subseasonal intensity variation of the South Asian high in relationship to diabatic heating: observation and CMIP5 models

“…The observed second EOF mode displays a positive center of anomalous Z100 over East Asia and a negative one over the IP. It represents the subseasonal zonal oscillation of the SAH, which has been intensively studied (Zhang et al 2002;Ren et al 2015;Shi and Qian 2016;Yang and Li 2016;Chen and Zhai 2016). We focus on the EOF1 in this study.…”

“…As a member of the Asian summer monsoon system, the SAH's spatiotemporal variability and impacts on the weather and climate over Asia and beyond have been investigated (Zhang et al 2002(Zhang et al , 2005(Zhang et al , 2016Liu et al 2004Liu et al , 2007Liu et al , 2013Duan and Wu 2005;Randel and Park 2006;Zarrin et al 2010;Huang et al 2011;Jiang et al 2011;Qu and Huang 2012;Wei et al 2014;Yang et al 2014;Ren et al 2015;Wu et al 2015;Chen and Zhai 2016;Shi and Qian 2016;Yang and Li 2016). Especially, variations of the SAH on subseasonal time scale have attracted more attention in recent years.…”

“…Zhang et al (2002) suggested the bimodality of the SAH at 100 hPa and identified them as the Iranian pattern and the Tibetan pattern, respectively. Further investigations have studied the features of subseasonal zonal shift of the SAH and its connection with precipitation and diabatic heating over eastern Asia Shi and Qian 2016;Yang and Li 2016). Other literature mentioned about the SAH's subseasonal intensity variation.…”