Spatial patterns and regimes of daily precipitation in Iran in relation to large-scale atmospheric circulation

摘要: The relationships between large-scale atmospheric circulation types and seasonal regimes of daily precipitation over Iran are assessed using from a high-resolution gridded dataset provided by the Asian Precipitation-Highly Resolved Observational Data Integration Towards Evaluation Water Resources (APHRODITE) Project. Regional spatial modes variability were identified S-mode Principal Component Analysis (PCA) with Varimax rotation, applied to subset days when at least 10% all grid-points received ≥ 5 mm. study refers period 1961–2004 is carried out for each season (excluding summer) separately. To characterize dynamical features associated regional regime (PR), composites fields computed only averaging rotated PCA scores 1.5 (strong positive phase). In autumn winter, divided into five PRs, while four PRs in spring. Results suggest that distribution largely governed geographical position both mid-tropospheric trough Middle East Arabian anticyclone. fact, almost trough, as pre-conditioning factor, leads regional-scale ascending motions, whereas anticyclone induces low-tropospheric moisture transports southern water bodies cyclonic systems near Iran, triggering rain-generating conditions. Copyright © 2011 Royal Meteorological Society