Volcanic ash cloud detection from space: a comparison between the RSTASH technique and the water vapour corrected BTD procedure

Volcanic eruptions can inject large amounts (Tg) of gas and particles into the troposphere and, sometimes, into the stratosphere. Besides the main gases (H2O, CO2, SO2 and HCl), volcanic clouds contain a mix of silicate ash particles in the size range from 0.1 μm to 1 mm or larger. The interest in volcanic ash detection is high, particularly because it represents a serious hazard for air traffic. Particles with dimensions of several millimetres can damage the aircraft structure (windows, wings, ailerons), while particles less than 10 μm may be extremely dangerous for the jet engines and are undetectable by the pilots during night or in low visibility conditions. Furthermore, ash detection represents a critical step towards quantitative retrievals of plume parameters. In this paper two different satellite techniques for volcanic cloud detection and tracking are compared, namely a water vapour corrected version of the brightness temperature difference (BTD-WVC) procedure and an implementation of the robust satellite technique, specifically configured for volcanic ash (RSTASH). The BTD method identifies volcanic ash clouds on the basis of the brightness temperature difference measured in two infrared spectral bands at around 11 and 12 μm. To account for the atmospheric water vapour differential absorption in the 11–12 μm spectral range, which tends to reduce (and in some cases completely mask) the BTD signal, a water vapour correction procedure has been developed (BTD-WVC), based on measured or synthetic atmospheric profiles. RSTASH instead, is based on the analysis of a time series of satellite records, aimed at identifying signal anomalies through an automatic unsupervised change detection step. To assess the performance of the BTD-WVC and RSTASH methods in detecting volcanic ash clouds, some eruptive events of Mt Etna, observed by the Advanced Very High Resolution Radiometer (AVHRR) sensor, have been analysed. The obtained results show a good agreement between the BTD-WVC and RSTASH techniques for all the considered images, in terms of pixels detected as ‘ash affected’ (i.e. the ash cloud area). In particular, compared to the traditional BTD procedure, the BTD-WVC and RSTASH techniques significantly improve volcanic ash cloud detection, both in daytime and night-time data, especially in the case of low ash loading.

[1]  P. Zettwoog,et al.  Eruptive and diffuse emissions of CO2 from Mount Etna , 1991, Nature.

[2]  William I. Rose,et al.  Use of GOES thermal infrared imagery for eruption scale measurements, Soufrière hills, Montserrat , 2000 .

[3]  Teodosio Lacava,et al.  Assessing RAT (Robust AVHRR Techniques) performances for volcanic ash cloud detection and monitoring in near real-time : The 2002 eruption of Mt. Etna (Italy) , 2007 .

[4]  A. Berk.  MODTRAN : A moderate resolution model for LOWTRAN7 , 1989 .

[5]  I. M. Watsona,et al.  Thermal infrared remote sensing of volcanic emissions using the moderate resolution imaging spectroradiometer , 2004 .

[6]  Lieven Clarisse,et al.  Observations of the eruption of the Sarychev volcano and simulations using the HadGEM2 climate model. , 2010 .

[7]  Fred Prata,et al.  An evaluation of volcanic cloud detection techniques during recent significant eruptions in the western 'Ring of Fire' , 2004 .

[8]  C.M.R. Platt,et al.  Nocturnal effects in the retrieval of land surface temperatures from satellite measurements , 1993 .

[9]  I. Barton,et al.  An AVHRR investigation of surface emissivity near Lake Eyre, Australia , 1986 .

[10]  Teodosio Lacava,et al.  Improving volcanic ash cloud detection by a robust satellite technique , 2004 .

[11]  Alfred J Prata,et al.  Infrared radiative transfer calculations for volcanic ash clouds , 1989 .

[12]  J. Simpson,et al.  Response to “Comments on ‘Failures in detecting volcanic ash from a satellite-based technique’” , 2001 .

[13]  Takashi Yamanouchi,et al.  Detection of clouds in Antarctica from infrared multispectral data of AVHRR , 1987 .

[14]  T. Casadevall,et al.  The 1989–1990 eruption of Redoubt Volcano, Alaska: impacts on aircraft operations , 1994 .

[15]  Daniele Andronico,et al.  A multi-disciplinary study of the 2002–03 Etna eruption: insights into a complex plumbing system , 2005 .

[16]  Donald W. Hillger,et al.  Principal Component Image Analysis of MODIS for Volcanic Ash. Part I: Most Important Bands and Implications for Future GOES Imagers , 2002 .

[17]  Valerio Tramutoli,et al.  Assessment and validation in time domain of a Robust Satellite Technique (RSTASH) for ash cloud detection , 2011 .

[18]  S. Hook,et al.  The ASTER spectral library version 2.0 , 2009 .

[19]  Gary K. Davis,et al.  History of the NOAA satellite program , 2007 .

[20]  Dominik Brunner,et al.  Monitoring volcanic ash from space, ESA-EUMETSAT workshop on the 14th April to 23rd May eruption of Eyjafjöll volcano, South Iceland , 2010 .

[21]  Boris Behncke,et al.  The July–August 2001 eruption of Mt. Etna (Sicily) , 2003 .

[22]  Arlin J. Krueger,et al.  Early evolution of a stratospheric volcanic eruption cloud as observed with TOMS and AVHRR , 1999 .

[23]  Dynamics of volcanic and meteorological clouds produced on 26 December (Boxing Day) 1997 at Soufrière Hills Volcano, Montserrat , 2002, Geological Society, London, Memoirs.

[24]  Simona Scollo,et al.  The 2002–03 Etna explosive activity: Tephra dispersal and features of the deposits , 2008 .

[25]  Thorvaldur Thordarson,et al.  Contamination of water supplies by volcanic ashfall: A literature review and simple impact modelling , 2006 .

[26]  Donald W. Hillger,et al.  Improved detection of airborne volcanic ash using multispectral infrared satellite data , 2003 .

[27]  W. Brutsaert,et al.  Satellite remote sensing of land surface temperatures: Application of the atmospheric correction method and split-window technique to data of ARM-SGP site , 2002 .

[28]  P. Baxter,et al.  The respiratory health hazards of volcanic ash: a review for volcanic risk mitigation , 2006 .

[29]  William I. Rose,et al.  Anatomy of 1986 Augustine volcano eruptions as recorded by multispectral image processing of digital AVHRR weather satellite data , 1991 .

[30]  I. F. Grant,et al.  Determination of mass loadings and plume heights of volcanic ash clouds from satellite data , 2001 .

[31]  V. Tramutoli,et al.  AVHRR automated detection of volcanic clouds , 2005 .

[32]  William I. Rose,et al.  Retrieval of sizes and total masses of particles in volcanic clouds using AVHRR bands 4 and 5 , 1994 .

[33]  D. C. Robertson,et al.  MODTRAN: A Moderate Resolution Model for LOWTRAN , 1987 .

[34]  Teodosio Lacava,et al.  On the Exportability of Robust Satellite Techniques (RST) for Active Volcano Monitoring , 2010, Remote. Sens..

[35]  Donald W. Hillger,et al.  Principal Component Image Analysis of MODIS for Volcanic Ash. Part II: Simulation of Current GOES and GOES-M Imagers , 2002 .

[36]  David C. Pieri,et al.  Operational implications of airborne volcanic ash , 2000 .

[37]  Stefano Corradini,et al.  Mt. Etna tropospheric ash retrieval and sensitivity analysis using moderate resolution imaging spectroradiometer measurements , 2008 .

[38]  Luca Merucci,et al.  Retrieval of SO 2 from thermal infrared satellite measurements: correction procedures for the effects of volcanic ash , 2009 .

[39]  A. Cracknell.  advanced very high resolution radiometer AVHRR , 1997 .

[40]  Simona Scollo,et al.  The 4–5 September 2007 lava fountain at South-East Crater of Mt Etna, Italy , 2008 .

[41]  Daniela Mele,et al.  The analysis of the influence of pumice shape on its terminal velocity , 2005 .

[42]  Alfred J Prata,et al.  Observations of volcanic ash clouds in the 10-12 μm window using AVHRR/2 data , 1989 .

[43]  G. Malvasi,et al.  A Robust Multitemporal Satellite Technique for Volcanic Activity Monitoring: Possible Impacts on Volcanic Hazard Mitigation , 2007, 2007 International Workshop on the Analysis of Multi-temporal Remote Sensing Images.

[44]  Arlin J. Krueger,et al.  Comparison of TOMS and AVHRR volcanic ash retrievals from the August 1992 eruption of Mt. Spurr , 1999 .

[45]  David C. Pieri,et al.  Failures in detecting volcanic ash from a satellite-based technique , 2000 .

[46]  William I. Rose,et al.  Atmospheric correction for satellite‐based volcanic ash mapping and retrievals using “split window” IR data from GOES and AVHRR , 2002 .