Relationship between the Indian summer monsoon and the large-scale circulation variability over the Mediterranean

Abstract

In this study the impact of the Indian summer monsoon on the large scale variability of the atmospheric circulation over the Mediterranean is investigated on an inter-annual time scale. Composite and correlation analysis results are presented, outlining different circulation patterns in the upper and lower troposphere for strong and weak monsoon years respectively. For this purpose ERA-40 Reanalysis monthly mean data at various isobaric levels together with the standardized All India Rainfall Index for boreal summer (June-July-August-September) of a 44-year period were employed. During strong monsoon years many atmospheric circulation systems appear strengthened over Eurasia, resembling a well-organized Rossby wave train over the area. In the upper troposphere a meridional shift of the jet streams over the examined area was also identified during extreme monsoon years. On the other hand, in the lower troposphere enhanced northerlies (Etesians) appear to dominate over Eastern Mediterranean along with intensified subsidence during strong monsoon years.

Analysis of recent changes in maximum and minimum temperatures in Pakistan

“…Teleconnection patterns can affect vast areas (such as the Northern Hemisphere) and explain much of the variability and trends in precipitation and temperature at the regional scale (Trigo and Palutikof 2001;Vicente-Serrano et al 2006;López-Bustins et al 2008;Rizou et al 2015, Rios-Cornejo et al 2015. Some studies in Asia have also focused on the relationship between climate and patterns in recent decades: Tatli (2007) in the region 50ºW-120ºE, 0º-80ºN; Syed et al (2010) in Central -Southwest Asia; Villafuerte and Matsumoto (2015) in Southeast Asia; Khan et al (2008), Saaed et al (2011), Revadekar et al (2012) and Azfal et al (2013) in Pakistan; Khalili (2006, 2008) in Iran; Türkes and Erlat (2009) The main goal of the present study is to contribute to the existing knowledge of trends (sign and magnitude) in Tmax and Tmin in Pakistan in recent decades.…”

Etesians and the summer circulation over East Mediterranean in Coupled Model Intercomparison Project Phase 5 simulations: Connections to the Indian summer monsoon

“…During summer, dry hot weather is the main climatic characteristic for the Aegean basin. Etesians contribute to the decrease of surface temperature in order to moderate the summer heat and control the appearance of heat wave events during summer as results of the mid‐tropospheric decent and the cool advection in the lower levels (Metaxas and Bartzokas, ; Ziv et al ., ; Tyrlis et al ., ; Rizou et al ., ). Etesians contribute to the reduction of pollution events, enhancing pollutant dispersion and improve air quality (Metaxas and Bartzokas, ; Melas et al ., ; Ziomas, ; Giakoumi et al ., ; Poupkou et al ., ; Tyrlis et al ., ); on the other hand, strong Etesians can enhance the fast spread of fires in the Aegean islands (Kotroni et al ., ; Amraoui et al ., ) and can cause difficulties with sea transport and sailing (Metaxas and Bartzokas, ; Koletsis et al ., ; Koletsis et al ., ).…”

“…In general, Etesians can be classified as a monsoon type wind system (Poupkou et al ., ). Previous studies focused on the connection between the Etesians and the South Asia monsoon system (Tyrlis et al ., ; Tyrlis and Lelieveld, ; Rizou et al ., ; Dafka et al ., ). According to Tyrlis et al ., , the subsidence over the EMED–Middle East and the Etesian circulation over the Aegean are connected to the large‐scale ascent over the South Asian monsoon region via the westwards propagating Rossby waves (Rodwell and Hoskins, ; Tyrlis et al ., ).…”

“…Past studies have analysed the Etesians and the linkage between EMED and ISM region (shown in Figure ) during the extended summer based on observations and reanalysis data (Ziv et al ., ; Tyrlis et al ., ; Rizou et al ., ; Dafka et al ., ; Rizou et al ., ). However, there is no previous study investigating the long‐term variability of Etesians and the linkage of atmospheric circulation between EMED and Bay of Bengal (ΒoΒ)/west Indian summer monsoon (wISM) using ESMs simulations participating to Coupled Model Intercomparison Project Phase 5 (CMIP5).…”

Changes in the future summer Mediterranean climate: contribution of teleconnections and local factors

“…Ziv et al (2004) have shown these two factors to be significantly correlated, pointing to the Asian summer monsoon, which exerts an influence on the Mediterranean surface, middle, and upper troposphere dynamics. The possible mechanism behind this linkage was explored in a framework of the Rossby wave pattern response to the diabatic heating of the monsoon convection, i.e., the monsoondesert mechanism (Rodwell and Hoskins, 1996;Tyrlis et al, 2013;Rizou et al, 2015;Cherchi et al, 2014Cherchi et al, , 2016. Additionally, Rodwell and Hoskins (2001) explained changes in Etesian winds as a direct result of changes in the subsidence over the eastern Mediterranean, which via Sverdrup's equation controls the low-level northerly flow.…”