Time filter

Source Type

Arias-Hidalgo M.,ESPOL Polytechnic University | Neupauer R.M.,ESPOL Polytechnic University | Neupauer R.M.,University of Colorado at Boulder | Villa-Cox G.,ESPOL Polytechnic University | Barcia J.L.,Instituto Nacional Of Meteorologia E Hidrologia Inamhi
World Environmental and Water Resources Congress 2016: Watershed Management, Irrigation and Drainage, and Water Resources Planning and Management - Papers from Sessions of the Proceedings of the 2016 World Environmental and Water Resources Congress | Year: 2016

In this paper, two alternatives for a useful description of streamflow time patterns in Ecuadorian lowlands are proposed. In that region, streamflow rates are influenced by precipitation, which varies seasonally due to annual climate patterns, spatially due to small-scale weather patterns, and temporally over longer periods due to longer-period climate fluctuations. Using wavelet coefficients, different periodicities were identified throughout the series, with a dominant one-year frequency (annual cycle). Nevertheless, other frequencies are noteworthy. For instance, during the period 2005-2012, the frequency of 2 year suggested a larger difference between the highest peaks during the rainy season (usually from December to April), and the lowest valleys of the dry period (rest of the year), otherwise difficult to perceive using only the raw data. In addition, the filter Baxter-King has been successfully applied for seasonal separation, including extreme years (El Niño events of 1982-1983, and 1997-1998). Hence, the use of wavelets may open opportunities for further research, including gap analysis, and cross-wavelet analysis between river stations belonging to different subbasins, but sharing similar features. © ASCE.

Le Pennec J.-L.,CNRS Magmas and Volcanoes Laboratory | Ruiz G.A.,National Polytechnic School of Ecuador | Ramon P.,National Polytechnic School of Ecuador | Palacios E.,Instituto Nacional Of Meteorologia E Hidrologia Inamhi | And 2 more authors.
Journal of Volcanology and Geothermal Research | Year: 2012

Repeated ash fall events have occurred during the 1999-ongoing eruption of Tungurahua volcano, Ecuador, notably during the late 1999 and August 2001 eruptive phases. While the eruptive styles were similar, these two phases had different impacts on nearby rural and urban Andean populations: ash falls in late 1999 had limited effects on human health and farming, whereas the 2001 phase resulted in medical problems, death of animals in livestock, and damages to houses and crops. Here we investigate the origin of this difference by estimating the size of the August 2001 event (VEI, magnitude, intensity), and by comparing monitoring information of the 1999 and 2001 phases (duration, explosion rate, column height, SO 2 output rate). The results show that both phases ranked at VEI 3, although the longer 1999 phase was likely larger than the 2001 phase. Mass magnitude (M) and intensity (I) indexes calculated for the 2001 phase reach M≈2.7 and I≈6.5 when based on ash fall layer data, but increase to M≈3.2 and I≈7.0 when ballistic products are included. We investigated the influence of rain fall and wind flow regimes on ash dispersion, sedimentation and remobilization. The analysis indicates that the harmful effect of the 2001 phase resulted from unfavorable conditions that combined volcanological and seasonal origins, including: a) a low elevation of the ash plume above rural regions owed to a usually bent-over column, b) ash sedimentation in a narrow area west of the volcano under sub-steady wind directions, c) anticipated ash settling by frequent rain flushing of low intensity, and d) formation of a wet cohesive ash coating on buildings and harvests. Conversely, the stronger 1999 phase injected a large amount of ash at higher elevation in the dry season; the ash was widely disseminated across the whole Ecuadorian territory and beyond, and was frequently removed by rain and winds. In summary, our study illustrates the influences of eruption size and weather conditions on the impact of volcanic activity in a tropical setting and puts emphasis on the necessity to merge volcanological and meteorological monitoring duties for hazard assessment and alert level definition, in order to mitigate the effect of ash falls in the Andes and elsewhere. © 2011 Elsevier B.V.

Armijos E.,Instituto Nacional Of Meteorologia E Hidrologia Inamhi | Armijos E.,University of the State of Amazonas | Laraque A.,French National Center for Scientific Research | Barba S.,National University of Costa Rica | And 12 more authors.
Hydrological Sciences Journal | Year: 2013

Water discharge and suspended and dissolved sediment data from three rivers (Napo, Pastaza and Santiago) in the Ecuadorian Amazon basin and a river in the Pacific basin (Esmeraldas) over a 9-year period, are presented. This data set allows us to present: (a) the chemical weathering rates; (b) the erosion rates, calculated from the suspended sediment from the Andean basin; (c) the spatio-temporal variability of the two regions; and (d) the relationship between this variability and the precipitation, topography, lithology and seismic activity of the area. The dissolved solids load from the Esmeraldas basin was 2 × 106 t year-1, whereas for the Napo, Pastaza and Santiago basins, it was 4, 2 and 3 × 106 t year-1, respectively. For stations in the Andean piedmont of Ecuador, the relationship between surface sediment and the total sediment concentration was found to be close to one. This is due to minimal stratification of the suspended sediment in the vertical profile, which is attributed to turbulence and high vertical water speeds. However, during the dry season, when the water speed decreases, sediment stratification appears, but this effect can be neglected in the sediment flux calculations due to low concentration rates. The suspended sediment load in the Pacific basin was 6 × 106 t year-1, and the total for the three Amazon basins was 47 × 106 t year-1. The difference between these contributions of the suspended sediment load is likely due to the tectonic uplift and the seismic and volcanic dynamics that occur on the Amazon side. © 2013 © IAHS Press.

Skansi M.D.L.M.,Servicio Meteorologico Nacional | Brunet M.,Rovira i Virgili University | Brunet M.,University of East Anglia | Sigro J.,Rovira i Virgili University | And 13 more authors.
Global and Planetary Change | Year: 2013

Here we show and discuss the results of an assessment of changes in both area-averaged and station-based climate extreme indices over South America (SA) for the 1950-2010 and 1969-2009 periods using high-quality daily maximum and minimum temperature and precipitation series. A weeklong regional workshop in Guayaquil (Ecuador) provided the opportunity to extend the current picture of changes in climate extreme indices over SA.Our results provide evidence of warming and wetting across the whole SA since the mid-20th century onwards. Nighttime (minimum) temperature indices show the largest rates of warming (e.g. for tropical nights, cold and warm nights), while daytime (maximum) temperature indices also point to warming (e.g. for cold days, summer days, the annual lowest daytime temperature), but at lower rates than for minimums. Both tails of night-time temperatures have warmed by a similar magnitude, with cold days (the annual lowest nighttime and daytime temperatures) seeing reductions (increases). Trends are strong and moderate (moderate to weak) for regional-averaged (local) indices, most of them pointing to a less cold SA during the day and warmer night-time temperatures.Regionally-averaged precipitation indices show clear wetting and a signature of intensified heavy rain events over the eastern part of the continent. The annual amounts of rainfall are rising strongly over south-east SA (26.41. mm/decade) and Amazonia (16.09. mm/decade), but north-east Brazil and the western part of SA have experienced non-significant decreases. Very wet and extremely days, the annual maximum 5-day and 1-day precipitation show the largest upward trends, indicating an intensified rainfall signal for SA, particularly over Amazonia and south-east SA. Local trends for precipitation extreme indices are in general less coherent spatially, but with more general spatially coherent upward trends in extremely wet days over all SA. © 2012 Elsevier B.V.

Discover hidden collaborations