ENSO influence on summer temperature over Arabian Peninsula: role of mid-latitude circulation

Abstract

This study discusses the interannual variability of the summer (June–August) season surface air temperature (SAT) over the Arabian Peninsula and its relationship to the global circulation patterns under the influence of El Nino Southern Oscillation (ENSO). A composite analysis based on the above (below) normal summer SAT over the Arabian Peninsula reveals a wavelike pattern resembling the mid-latitude Circumglobal Wave Train (CGT). The positive (negative) phase of the CGT is associated with above (below) normal SAT anomalies over the Arabian Peninsula. Further, the Arabian Peninsula summer SAT is also found to be associated with ENSO and this association has strengthened in recent decades as compared to before 1980s. The ENSO induced upper level circulation patterns resemble the CGT pattern. The ENSO warm phase over the central and eastern Pacific is associated with anomalous low pressure anomalies over the Eurasian region while the cold phase associated with anomalous high pressure. This favours the above normal SAT anomalies over the Eurasian region including the northern parts of the Peninsula during the cold phase of ENSO and below normal temperature during the warm phase. The weakening of upper level low-pressure anomalies over central Asia during the positive phase of CGT also favours the extension of the Eurasian high over the Arabian Peninsula. Additionally, the climate model simulations experiments performed with newly developed Saudi-KAU Atmospheric Global Climate Model (AGCM) also support the observed findings.