Regional impact of the Armenian highland as an elevated heat source: ERA-Interim reanalysis and observations

Abstract

The heat-driven plain–plateau circulation producing strong summertime winds in Yerevan has been examined. The study indicates that the formation of plain–plateau circulation over the Armenian Highland is the combined product of large-scale and local circulations. There is significant enhancement of the westerly subtropical jet over the study region, Caspian Sea and further to the east in the upper troposphere in days with severe wind gusts in Yerevan. Further, the influence of major monsoon systems (Indian and African) on the plain–plateau circulation over the Armenian Highland is considered in this study. Both observations and ERA-Interim reanalysis data show the existence of intense heat source over the southeastern and southern parts of the Armenian Highland which produces an extra daytime warming exceeding 2.1 °C on average at the ground surface during days with severe gusts in Yerevan. This warm center is maintained through 700 hPa level and it disappears in the middle and upper troposphere. The plateau atmospheric boundary layer can extend beyond 4,000 m above mean sea level (up to the middle troposphere) during the afternoon. By contrast, exposed mountain ranges stretching along the Black and Caspian seas are characterized by significant negative temperature differences. It should be noted that ERA-Interim reanalysis data strongly underestimate the significant negative differences in mean daytime temperatures over northeastern, southeastern parts of Armenia and over Sevan Lake basin found in observed data. The results suggest intensification of the plain–plateau circulation over the Armenian Highland induced by recent surface warming over the study region. Temperature projections over the study region for the twenty-first century show that the enhancement of the plain–plateau circulation can be expected under future climate conditions.