ORIGINAL PAPER Moderate to heavy cold-weather precipitation occurrences in Tehran and the associated circulation types Sakineh Khansalari 1 & Tayeb Raziei 2 & Ali Reza Mohebalhojeh 1,3 & Farhang Ahmadi-Givi 1 Received: 16 February 2016 /Accepted: 22 December 2016 # Springer-Verlag Wien 2017 Abstract Large-scale atmospheric circulations associated with 133 moderate to heavy cold-weather precipitation events recorded at Mehrabad station in Tehran, Iran, during the peri- od 1951–2013 are analysed. To this end, the performance of un-rotated, orthogonally rotated and obliquely rotated solu- tions of T-mode principal component analysis (PCA) is exam- ined in classifying the atmospheric circulations into a few representative circulation types (CTs). The T-mode PCAs were applied to the 500-hPa geopotential height for the events in a domain from 10 ∘ E to 70 ∘ E and from 20 ∘ N to 50 ∘ N. The first six leading principal components were retained and then orthogonally and obliquely rotated using varimax and promax solutions, respectively. Statistical inter-comparison of the CTs obtained using the three solutions suggests that the obliquely rotated solution is the better choice for circulation classifica- tion in the present study. The six CTs obtained using the oblique rotation were then linked to the daily total precipita- tion and daily mean temperature variability at Tehran station as well as to the standardized anomalies of the daily total precipitation and mean daily temperature of a dense network of stations distributed across Iran. It is found that the CTs identified, though generally comparable in producing signifi- cant precipitation in Tehran, vary in their potential to bring cold weather and generate snowfall in Tehran specifically and in the country in general. While the first three CTs give rise to regional patterns of standardized precipitation anomalies centred in Tehran, the next three CTs leave a pronounced precipitation signature almost across the whole country. As regards the standardized temperature anomalies, with the ex- ception of one CT that causes deep and widespread negative standardized anomalies over most parts of the country, the other CTs are characterized with a dipolar structure of a deep intrusion of cold weather to the west and prevailing warm weather to the east of the country. Keywords Synoptic climatology . Circulation types . T-mode PCA . Heavy precipitation events . Iran 1 Introduction In a changing climate with severely constrained water re- sources, the space–time variability analysis of precipitation is becoming ever more important. Among the large spectrum of problems encountered in such analysis, there is the question of the link between the temporal variation of precipitation in a given region and the large-scale atmospheric circulation. In the daily time scale, weather events of significant precipitation generally occur under certain large-scale circulation types re- ferred to by CTs hereafter. Therefore, it is not surprising that a large body of research has been devoted to the identification of atmospheric circulations responsible for significant precipita- tion occurrences in various regions across the globe (see, for example, Corte-Real et al. 1998; Kilsby and Cowpertwait 1998; Cavazos 1999; Romero et al. 1999; Wibig 1999; Kidson 2000; Xoplaki et al. 2000; Santos et al. 2005, 2007; Raziei et al. 2012a, 2012b, 2013a). In Iran, the factor directly controlling precipitation variabil- ity is the complex orography (Fig. 1a) which is involved in * Ali Reza Mohebalhojeh amoheb@ut.ac.ir 1 Space Physics Department, Institute of Geophysics, University of Tehran, Tehran, Iran 2 Soil Conservation and Watershed Management Research Institute (SCWMRI), Tehran, Iran 3 Institute of Geophysics, University of Tehran, Po Box 14155-6466, Tehran, Iran Theor Appl Climatol DOI 10.1007/s00704-016-2026-0