High-resolution Radar analysis of precipitation extremes in Ecuador and North Peru and implications of the ENSO-dynamics

• Applicant: Privatdozent Dr. Rütger Rollenbeck
• Subject Area: Physical Geography
• Term: from 2018 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 398620920

The aim of this research is the observation and analysis of regional precipitation extremes and the associated atmospheric dynamics of circulation in the meteorologically complex transition zone from the coastal plains of southern Ecuador and northern Peru across the Andes to the eastern foot zone of the mountains. A longer time series from 2014 to 2020 of the weather radar systems of RadarNetSur (www. Radarnetsur.gob.ec) allows to identify and explain relevant spatio-temporal patterns like persistent, transient end episodic cycles. The diurnal cycle is shaped by small-scale local circulation systems like the mountain-valley-, the land-sea-breeze or the confluence of synoptical flows and katabatic winds. They lead to a characteristic pattern of precipitation genesis, which cannot be registered by point observations. In Radar imagery they show up in detail and their spatial distribution will be visible. This enables to understand the high heterogeneity of the diurnal cycle and the occurrence of extremes as dependent on the topography. Dependent on the synoptic wind situation such patterns also change their location. This superordinate control in its spatial extent can only be observed by weather radar by deriving typical spatio-temporal patterns in relation to the larger-scale weather situation. As a result, detailed maps of the diurnal and annual cycle of precipitation and areas with a high potential for extreme events are generated. The arid climate of the coastal regions is caused by large scale subsidence, but episodically deep convection occurs. Convective cells with extreme precipitation are propagating eastwards and cause local flooding, more frequently in the southern sub-regions. Genesis and typical pathways are analyzed by using profiles of precipitation intensity and associated dynamic convergence zones, which form during such events. The movement profile of such dynamic convergence zones is indicative for the relation of their genesis to the synoptical and spatial context and shows areas of elevated risk for extreme events. Also, regional differences of the whole study region caused by topography and general exposition are shown. Regional differences are also an important aspect of the longer-term influence on the genesis of extreme precipitation. For each sub-region the effect of temperature anomalies of the costal (El-Niño-region 1+2) and central pacific (EN-region 3+4) will be analysed, especially their modifying influence on local precipitation enhancement by topographic and synoptic factors.

• DFG Programme: Research Grants