Analysis of intense rainfall events on Madeira Island during the 2009/2010 winter

Abstract

Abstract. This paper constitutes a step towards the understanding of some characteristics associated with high rainfall amounts and flooding on Madeira Island. The high precipitation events that occurred during the winter of 2009/2010 have been considered with three main goals: to analyze the main atmospheric characteristics associated with the events; to expand the understanding of the interaction between the island and the atmospheric circulations, mainly the effects of the island on the generation or intensification of orographic precipitation; and to evaluate the performance of high resolution numerical modeling in simulating and forecasting heavy precipitation events over the island. The MESO-NH model with a horizontal resolution of 1 km is used, as well as rain gauge data, synoptic charts and measurements of precipitable water obtained from the Atmospheric InfraRed Sounder (AIRS). The results confirm the influence of the orographic effects on precipitation over Madeira as well as the tropical-extratropical interaction, since atmospheric rivers were detected in six out of the seven cases analyzed, acting as a low level moisture supplier, which together with the orographic lifting induced the high rainfall amounts. Only in one of the cases the presence of a low pressure system was identified over the archipelago.

Numerical modelling of heavy rainfall event over Madeira Island in Portugal: sensitivity to different micro physical processes

“…An official report from the National Weather Service (Guttman, 2010) showed that the heavy rainfall was associated with a plume of deep moisture (Figure 2(a)) which came across the Atlantic Ocean with strong southwesterly flow and passed over Madeira. The plume of moisture is visible in the total precipitable water (Figure 2(a)) obtained from the Atmospheric InfraRed Sounder (AIRS), as explained in Couto et al (2012). It was reported that the precipitable water (PW) anomalies over 42 mm from the 'rum-runner express' were of the order of 4-5 standard deviations above normal (Figure 2(b)).…”

“…They showed that strong humidity convergence at lower levels (at and below 700 hPa) was an important dynamical ingredient that contributed to enhancing upward movements and higher precipitation generation. Couto et al (2012) analysed these events together with the other extreme precipitations events which occurred in the 2009/2010 winter. The authors found that in six out of the seven cases analysed the passage of a cold front and the presence of atmospheric rivers, acting to increase moisture in the lower atmospheric levels, together with the orographic lifting, induced the heavy precipitation events.…”

A dependence modelling study of extreme rainfall in Madeira Island

“…The amount of rainfall increases with altitude and the northern slopes are more humid than the southern ones (Prada et al, 2009). Madeira's location, topography and natural vegetation originate a variety of micro-climates, and this Portuguese island has essentially a Mediterranean climate with mild summers and winters (Couto et al, 2012). Some exceptions are found at the highest altitudes, where the mean annual air temperature can decrease to 8 + C, while in the coastal regions it ranges between 18 + C and 19 + C (Lima and Lima, 2009).…”

“…During the summer season, the rainfall regime is also affected by the Azores anticyclone (Couto et al, 2012). The island's mountain streams have a high seasonal, torrential flow regime, with high waters during the months of October to March/April (Shahin, 2012) and very low flows during the rest of the year.…”

Semiautomated object-based classification of rain-induced landslides with VHR multispectral images on Madeira Island

“…On 20 February 2010 an extreme rainfall event followed a prolonged precipitation period (Luna et al, 2011;Couto et al, 2012;Fragoso et al, 2012;Teixeira et al, 2014). In the first hours of the morning rainfall values reached more than the double of the monthly average, triggering landslides and exceptionally strong flash floods that affected severely the municipalities of Funchal (home to half of the island population) and Ribeira Brava (Lira et al, 2013).…”