Abstract
Since April of 2015, the ash dispersion and ash fallout due to Vulcanian eruptions at Tungurahua, one of the most active volcanoes in Ecuador, have been forecasted daily. For this purpose, our forecasting system uses the meteorological Weather Research and Forecasting (WRF) and the FALL3D models. Previously, and based on field data, laboratory, and numerical studies, corresponding eruption source parameters (ESP) have been defined. We analyzed the historically forecasted results of the ash fallout quantities over four years (April 2015 to March 2019), in order to obtain the average isomass and probability maps for three-month periods: February–March–April (FMA), May–June–July (MJJ), August–September–October (ASO), and November–December–January (NDJ). Our results indicate similar ash fallout shapes during MJJ and ASO, with a clear and defined tendency toward the west of the volcano; this tendency is less defined during NDJ and FMA. The proximal region west of the volcano (about 100 km to the west) has the highest probability (>70%) of being affected by ash fallout. The distant region to the west (more than 100 km west) presented low to medium probabilities (10%–70%) of ash fallout. The cities of Guaranda (W, 60% to 90%), Riobamba (SW, 70%), and Ambato (NW, 50% to 60%) have the highest probabilities of being affected by ash fallout. Among the large Ecuadorian cities, Guayaquil (SW, 10% to 30%) has low probability, and Quito (N, ≤5%) and Cuenca (SSE, <5%) have very low probabilities of being affected by ash fallout. High ash clouds can move in different directions, compared to wind transport near the surface. Therefore, it is possible to detect ash clouds by remote sensing which, in Ecuador, is limited to the layers over the meteorological clouds, which move in a different direction than low wind; the latter produces ash fallout over regions in different directions compared to the detected ash clouds. In addition to the isomass/probability maps and detected ash clouds, forecasting is permanently required in Ecuador.
Highlights
Due to the impact of volcanic activity on air pollution, damage to buildings and crops, and air traffic closures [1,2,3], potentially affected regions require information on ash dispersion trajectories and ground deposition patterns [4,5]
It is possible to detect ash clouds by remote sensing which, in Ecuador, is limited to the layers over the meteorological clouds, which move in a different direction than low wind; the latter produces ash fallout over regions in different directions compared to the detected ash clouds
The east to west direction has been reported as the main direction of ash clouds, Figure 2 and the figures in Appendix A highlight that the ash fallout can affect areas located in diverse directions from the vent, and even that ash clouds at different Flight Levels (FLs) can move in different directions, compared to wind near the surface
Summary
Due to the impact of volcanic activity on air pollution, damage to buildings and crops, and air traffic closures [1,2,3], potentially affected regions require information on ash dispersion trajectories and ground deposition patterns [4,5]. Ecuador hosts about 85 volcanoes, about 25 of which are currently erupting, active, or potentially active. Over the last 20 years, five volcanoes have produced small to large explosive eruptions with. Atmosphere 2020, 10, x FOR PEER REVIEW eruptions ash with significant ash plumes. Tungurahua, El Reventador, and significant plumes (Pichincha, Sangay, (Pichincha, Tungurahua,Sangay, and Cotopaxi). Since April of 2015, the ash dispersion and ash fallout due to Vulcanian eruptions at Tungurahua Research into the dispersion and research intoTherefore, the dispersion and forecasting of volcanic ashforecasting is a priorityofinvolcanic
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