Validation of Kriging to Understand ‘Volcanic Eruption Event Temperature Profiles’ To Improve Gradients in Numerical Weather Prediction Models

Abstract

When volcanoes erupt explosively, the ash gets airborne and reaches till stratosphere vertically, and then spreads laterally to synoptic scales due to wind. Detecting the presence of ash in the atmosphere accurately is a challenge. Although several remote, in-situ, and near-sensing techniques exist, due to the variety and complexity of the physical and chemical properties of ash, that get ejected, even within between spells of the eruption of a given volcanic event, it is hard to distinguish it from other aerosols such as desert sand, ice clouds, etc. The false positives in the detection render these solutions unreliable and inconsistent. As a result, weather parameters are explored as an alternative strategy to predict the presence of ash. In specific, the temperature variable is identified as the proxy variable to study the spatial distribution of ash in the atmosphere. There are several beneficial reasons to study temperature because the values do not vary randomly, low-cost equipment suffice to gather the data, the diurnal variations can be accounted for easily, the ability to convert scales from negative to positive metrics for numerical calculations does not vary significantly with ash type, etc. For this research, the eruption of the Icelandic volcano, Eyjafjallajokull is chosen, due to the severe negative impact it created on the economy across Europe in April and May 2010. World Meteorological Organisation (WMO) and International Civil Aviation Authority (ICAO) together have created Volcanic Ash Advisory Center (VAAC) to model the concentration and simulate the transportation of ash to inform the hazards of ash fall to various stakeholders across the world. The London VAAC used a VAFTDM known as Numerical Atmosphericdispersion Modeling Environment (NAME) to model the ash spread. This theoretical model had several limitations, chief of them being related to the accuracy of the Numerical Weather Prediction (NWP) models that were supported for ash modeling. The UK Met Office dealing with the NWP associated with the NAME model supported and offered multiple models such as Unified Model (UM), ECMWF, and a few others to predict the weather variables. Since each VAAC uses its own NWP model that varies spatially and temporally, a benchmarking exercise was conducted to compare the Volcanic Ash Forecast Transport and Dispersion (VAFTD) models. The benchmarking allowed the use of either NCEP or ECMWF NWP. For this research, NCEP NWP was chosen for analysis since 6 out of 12 VAFTD models used this NWP.