ORIGINAL PAPER Temporal and spatial analysis of precipitation patterns in an Andean region of southern Ecuador using LAWR weather radar Fernando On ˜ ate-Valdivieso 1 • Andreas Fries 1 • Katherine Mendoza 1 • Victor Gonzalez-Jaramillo 1 • Franz Pucha-Cofrep 1 • Ru ¨ tger Rollenbeck 2 • Jo ¨rg Bendix 2 Received: 8 September 2016 / Accepted: 17 May 2017 Ó Springer-Verlag Wien 2017 Abstract This paper focuses on the analysis of precipita- tion patterns, using a Local Area Weather Radar to collect information about the precipitation distribution in an Andean region of southern Ecuador (cities of Loja, Zamora and Catamayo). 54 representative events were selected to develop daily precipitation maps and to obtain their rele- vant characteristics, which were related to the topography and the season. The results showed that a strong correlation between the areas covered by precipitation (R A coefficient) and the season exists. In general, humid air masses come from the east (Amazon Basin), but during the main rainy season (December to April), humidity also frequently enters the study region from the west (Pacific Ocean). The rainy season is characterized by convective precipitation, associated with higher evaporation rates during austral summer. The relatively dry season is formed between May and November, but considerable precipitation amounts are registered, too, due to advective moisture transport from the Amazon Basin, a result of the predominant tropical easterlies carrying the humidity up the eastern escarpment of the Andes, generally following the natural course of the drainage systems. 1 Introduction The knowledge of the spatiotemporal distribution and dynamics of rainfalls in the tropical Andes remains insuf- ficient, due to the spare operational meteorological station network (e.g., Barry 2008). Furthermore, the complex topography makes reliable estimation of the spatiotemporal precipitation distribution highly challenging (Gabella and Notarpietro 2004; Germann et al. 2006, 2009; Villarini and Krajewski 2010). Nevertheless, precipitation data from meteorological stations have been widely used to investi- gate rainfall formation processes even in complex terrain (e.g., Espinoza et al. 2015), although this information has great uncertainties, including measurement errors, espe- cially in windy environments and exposed positions (Rol- lenbeck and Bendix 2006). However, rain gauge measurements facilitate point data accurately (Jensen and Pedersen 2005), but these data must be extrapolated to obtain areawide precipitation maps to analyze the rainfall distribution. The accuracy of these maps depends highly on the density of the existing station network, because climate conditions change considerably within short distances, especially in the Andes of southern Ecuador (Rollenbeck and Bendix 2011; Fries et al. 2014). In general, the rainfall distribution and amounts in mountain areas depend on the atmospheric flow and the local topography, because the mountain ridges act as bar- riers and modify the spatial and temporal rainfall distri- bution (e.g., Johansson and Chen 2005). Furthermore, the precipitation distribution is linked to the stability condi- tions, wind speed, perpendicularity of the flow to the ter- rain, and the height of the mountain ridges (Foresti and Pozdnoukhov 2012). Under unstable conditions (convec- tive cloud formation), the rainfall distribution depends on whether the convection is thermally induced or caused by Responsible Editor: C. Simmer. & Fernando On ˜ate-Valdivieso fronate@utpl.edu.ec 1 Departamento de Geologı ´a, Minas e Ingenierı ´a Civil (DGMIC), Hidrologı ´a y Climatologı ´a Working Group, Universidad Te ´cnica Particular de Loja, Loja, Ecuador 2 Laboratory for Climatology and Remote Sensing (LCRS), Faculty of Geography, University of Marburg, Marburg, Germany 123 Meteorol Atmos Phys DOI 10.1007/s00703-017-0535-8