This is a database of eruption source parameters, quantitative satellite retrievals, and numerical meteorology that can be used to validate numerical models of volcanic ash transport and dispersion. This database builds on compilations of the IAVCEI Commission on Tephra Hazard Modeling intended for validating models of tephra sedimentation (e.g. http://dbstr.ct.ingv.it/iavcei/results.htm); except that this database focuses on tephra transport and dispersal, particularly in ash clouds. We define ash cloud here as the cloud of ash that moves horizontally in the atmosphere and distinguish it from the column or “plume” which ascends vertically above the vent. The database includes (1) a summary table of source parameters; (2) detailed background information on source parameters with references to original sources; (3) links to numerical wind fields; and (4) links to processed satellite data with quantities such as cloud mass load that can be directly compared with model output. For this version of the database, we present data for the 18 May, 1980 eruption of Mount St. Helens, Washington (USA); (2) the “beta” (b) phase of the Chaitén (Chile) eruption on 6 May, 2008; (3) the 2008 Kasatochi (Alaska, USA) eruption; and (4) phase I of the Eyjafjallajökull (Iceland) eruption lasting from April 14-18, 2010.

This is not meant to be an exhaustive compilation. Rather, it is a compilation of a few eruptions for which we, as authors, can provide data. Eruption data are also being archived by other groups, including the Norwegian Institute for Air Research (NILU) VAST project, and projects within the German National Aeronautics and Space Research Center (DLR).

Please note: We ask that users acknowledge the source of this information when presenting it in publications or talks. Please note also that we are not responsible for the use or misuse of these data.

2. Numerical Meteorology

Numerical meteorology, including wind fields, for these eruptions have been generated by Arnau Folch at the Barcelona Supercomputer Center using the Weather Research and Forecasting (WRF) Model. The data can be accessed using a web browser at ftp://uPGzFy0h:3DIW%21nmT@bts.bsc.es, or, at the command line, by typing “ftp bts.bsc.es” and logging in with the username “uPGzFy0h” and password “3DIW!nmT”. The “namelist.input” and “namelist.wps” files in subdirectories at that location gives details on grid location, density, and time intervals for the model output, although some familiarity with WRF parameter names may be required to understand the files. A user’s guide to the WRF model and its output is available at the University Corporation for Atmospheric Research web page. The model output contains a single model domain at 20-km resolution for each eruption, with one hour between each forecast interval. Details on the model setup, on the parameters included in the output, and on other issues are explained in documents at that repository.

3. Satellite Data

Satellite data have been processed by Mike Pavolonis for the 2008 Kasatochi eruption. Data for additional eruptions will be available soon. Data may be downloaded by anonymous ftp from ftp://ftp.ssec.wisc.edu/pub/geocat/noaa_ash_retv/kasatochi. They include processed MODIS data of brightness temperature difference, cloud height, ash effective radius, total cloud mass, ash mass load, and several other parameters. Details on file structure, on the type of data they contain, and on file formats are explained in the Appendix.

4. Summary table

Below is a summary of the duration, plume height, and erupted mass for these eruptions. “VE” in the second column gives the vent elevation. “D” and “H” in the fourth and fifth columns give eruption duration in hours and plume height in km above sea level.

Volcano	lon	lat	VE km	Start time UTC	D hrs	H km	Mass Tg
Mount St. Helens 18 May, 1980	46.20	-122.18	2.0	1980-05-18 15:30 1980-05-18 16:00 1980-05-18 16:36 1980-05-18 17:30 1980-05-18 18:15 1980-05-18 18:45 1980-05-18 19:15 1980-05-18 19:45 1980-05-18 20:15 1980-05-18 21:15 1980-05-18 22:30 1980-05-18 23:30 1980-05-19 00:30 1980-05-19 01:30	0.25 0.11 0.9 0.75 0.5 0.5 0.5 0.5 1 1.25 1 1 1 1	30 15 14 15 16 17 17 14 15 15 16 19 8 6	176.5 3.2 18.9 21.9 19.9 26.5 26.5 10.5 29.3 36.6 39.8 89.1 1.2 0.2
Chaitén, 2008	-72.65	-42.83	0.5	2008-05-06 12:20	0.9	20	225
Kasatochi, 2008	-175.51	52.18	0.1	2008-08-07 22:01 2008-08-08 01:50 2008-08-08 04:35	1 0.5 10	14 14 18	1.5 0.7 42.8
Eyjafjallajökull, 2010 phase I	-19.62	63.63	1.7	2010-04-14T12:00 2010-04-14T15:00 2010-04-14T18:00 2010-04-14T21:00 2010-04-15T00:00 2010-04-15T03:00 2010-04-15T06:00 2010-04-15T09:00 2010-04-15T12:00 2010-04-16T06:00 2010-04-16T09:00 2010-04-16T12:00 2010-04-16T15:00 2010-04-16T18:00 2010-04-16T21:00 2010-04-17T00:00 2010-04-17T03:00 2010-04-17T06:00 2010-04-17T09:00 2010-04-17T12:00 2010-04-17T15:00 2010-04-17T18:00 2010-04-17T21:00 2010-04-18T00:00 2010-04-18T03:00 2010-04-18T06:00 2010-04-18T09:00	3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3	8.5 8.8 8.5 5.6 5.5 5.4 5.6 5.8 5.8 4.3 5.2 5.6 5.5 5.7 5.8 8.1 8 8 8.1 5.3 5.1 5 5.1 5.2 5.2 5.1 4	21.92 26.22 21.92 2.18 1.96 1.75 2.18 2.69 2.69 0.41 1.39 2.18 1.96 2.42 2.69 17.05 15.97 15.97 17.05 1.57 1.24 1.09 1.24 1.39 1.39 1.24 0.24
Eyjafjallajökull, 2010 phase III	-19.62	63.63	1.7	2010-05-04T15:00 2010-05-04T18:00 2010-05-04T21:00 2010-05-05T00:00 2010-05-05T03:00 2010-05-05T06:00 2010-05-05T09:00 2010-05-05T12:00 2010-05-05T15:00 2010-05-05T18:00 2010-05-05T21:00 2010-05-06T00:00 2010-05-06T03:00 2010-05-06T06:00 2010-05-06T09:00 2010-05-06T12:00 2010-05-06T15:00 2010-05-06T18:00 2010-05-06T21:00 2010-05-07T00:00 2010-05-07T03:00 2010-05-07T06:00 2010-05-07T09:00 2010-05-07T12:00 2010-05-07T15:00 2010-05-07T18:00 2010-05-07T21:00 2010-05-08T00:00 2010-05-08T03:00 2010-05-08T06:00 2010-05-08T09:00 2010-05-08T12:00 2010-05-08T15:00 2010-05-08T18:00 2010-05-08T21:00 2010-05-09T00:00 2010-05-09T03:00 2010-05-09T06:00 2010-05-09T09:00 2010-05-09T12:00 2010-05-09T15:00 2010-05-09T18:00 2010-05-09T21:00 2010-05-10T00:00 2010-05-10T03:00 2010-05-10T06:00 2010-05-10T09:00 2010-05-10T12:00 2010-05-10T15:00 2010-05-10T18:00 2010-05-10T21:00 2010-05-11T00:00 2010-05-11T03:00 2010-05-11T06:00 2010-05-11T09:00 2010-05-11T12:00 2010-05-11T15:00 2010-05-11T18:00 2010-05-11T21:00 2010-05-12T00:00 2010-05-12T03:00 2010-05-12T06:00 2010-05-12T09:00 2010-05-12T12:00 2010-05-12T15:00 2010-05-12T18:00 2010-05-12T21:00 2010-05-13T00:00 2010-05-13T03:00 2010-05-13T06:00 2010-05-13T09:00 2010-05-13T12:00 2010-05-13T15:00 2010-05-13T18:00 2010-05-13T21:00 2010-05-14T00:00 2010-05-14T03:00 2010-05-14T06:00 2010-05-14T09:00 2010-05-14T12:00 2010-05-14T15:00 2010-05-14T18:00 2010-05-14T21:00 2010-05-15T00:00 2010-05-15T03:00 2010-05-15T06:00 2010-05-15T09:00 2010-05-15T12:00 2010-05-15T15:00 2010-05-15T18:00 2010-05-15T21:00 2010-05-16T00:00 2010-05-16T03:00 2010-05-16T06:00 2010-05-16T09:00 2010-05-16T12:00 2010-05-16T15:00 2010-05-16T18:00 2010-05-16T21:00 2010-05-17T00:00 2010-05-17T03:00 2010-05-17T06:00 2010-05-17T09:00 2010-05-17T12:00 2010-05-17T15:00 2010-05-17T18:00 2010-05-17T21:00	3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3	5.3 5.3 5.7 5.6 5.6 5.5 5.5 5.7 6.7 6.3 8.4 5.2 5.2 5.2 5.2 5.3 5.5 5.5 5.4 5.3 5.2 5.3 5.3 5.3 5.4 5.4 5.2 5.1 5.1 5.1 5.1 5.2 5.3 4.1 5.2 5.2 4.8 5 5 5 5 5 5 5 5 5 5 5 5 5 4.1 5 2.5 3.9 3.9 5 5.1 5.2 0 0 0 0 4.4 4.8 5.1 5.2 5.2 5.3 5.3 5.3 5.2 5.1 5.2 5.3 7.9 7.9 7.9 7.9 5.6 5 5 5 5 5 4.9 5 5 4.9 5.2 5.6 6 5.6 5.6 7.9 7.9 7.9 7.9 7.9 7.9 5.5 7.3 5.4 7.9 7.9 5.4 5.3 5.1	0.845 0.845 1.304 1.175 1.175 1.056 1.056 1.304 3.272 2.320 10.951 0.753 0.753 0.753 0.753 0.845 1.056 1.056 0.946 0.845 0.753 0.845 0.845 0.845 0.946 0.946 0.753 0.668 0.668 0.668 0.668 0.753 0.845 0.160 0.753 0.753 0.457 0.591 0.591 0.591 0.591 0.591 0.591 0.591 0.591 0.591 0.591 0.591 0.591 0.591 0.160 0.591 0.002 0.112 0.112 0.591 0.668 0.753 0.000 0.000 0.000 0.000 0.259 0.457 0.668 0.753 0.753 0.845 0.845 0.845 0.753 0.668 0.753 0.845 7.949 7.949 7.949 7.949 1.175 0.591 0.591 0.591 0.591 0.591 0.521 0.591 0.591 0.521 0.753 1.175 1.757 1.175 1.175 7.949 7.949 7.949 7.949 7.949 7.949 1.056 5.222 0.946 7.949 7.949 0.946 0.845 0.668

5. Detailed narrative information

Mount St. Helens, May 18, 1980

Observations

Eruption start: 08:32 AM local time (1532 UTC), determined to within seconds by seismic records and multiple visual observations [e.g., Christiansen and Peterson, 1981]. The first half hour of the eruption consisted mostly of a lateral blast and development of a large umbrella cloud, rising to >30 km elevation, above the elutriated blast. The vertical plinian column didn’t start until shortly after 09:00 local time (1600 UTC).

Eruption duration: Generally given as 9 hours, based on an observable decrease in intensity at 17:30 local time (0030 UTC, 19 May [Christiansen and Peterson, 1981]). Plume height measured by radar decreased between 0000 and 0100 UTC from about 18 km asl to 8 km asl [Harris et al., 1981]. Minor emissions continued until May 21. During Phase I, estimates of plume height and eruption rate for the time period of 15 April, 1200 UTC to 16 April, 0300 UTC are not included because few radar scans recorded a plume top, implying perhaps a pause in eruptive activity.

Plume height: Plume height was measured by a weather radar at Portland International Airport, 80km SW of the mountain [Harris et al., 1981]. Plume heights in the summary table from 1600 UTC onward on 18 and 19 May are digitized from Fig. 190 of Harris et al. [Harris et al., 1981], and then rounded to the nearest kilometer.

Erupted mass: Sarna-Wojcicki et al.,[1981] reported that a minimum bulk tephra volume of 1.1 km³ for the fall deposits. The dense-rock-equivalent (DRE) volume of the deposit is 0.20-0.25 km³, assuming a solid-rock density between 2000 and 2600 kg m^-3, implying an erupted mass of about 5×10¹¹ kg, or 500 Tg. Sarna-Wojcicki et al. [1981] did not extrapolate beyond the mapped area to obtain a total. Deposits were mapped and sampled within less than a week of the May 18 eruption to a distance of >600 km downwind [Sarna-Wojcicki et al., 1981]. The deposit fell east of the volcano on land, making essentially all of it accessible for sampling. Total number of sample locations, obtained by counting the number of map symbols in Fig. 336 of Sarna-Wojcicki et al., is approximately 131.

In order to arrive at the erupted mass in the summary table, we used the following procedure:

1) For each segment, we estimated the mass eruption rate using the empirical formula M=140H^0.414, rearranged from Mastin et al. [Mastin et al., 2009, eq. 1], where M is mass eruption rate in kg s^-1 and H is plume height above the 2.0-km-high vent. This relationship assumes a magma density of 2,500 kg m^-3.

2) We multiplied the mass eruption rate by the duration of each segment to yield a total erupted mass for each segment.

3) We summed the erupted masses for each segment to obtain a total erupted mass, and then compared the result with the mapped erupted mass. Using this procedure, the total erupted mass is 360 Tg, whereas the mapped eruptive mass is about 500 Tg as noted above.

4) We multiplied the erupted mass for each segment by 50/36, to ensure that the total erupted mass equals the mapped value.

Magma type: Rhyolitic melt with ~73 wt % SiO2 and about 40% crystals, dominantly plagioclase [Rutherford et al., 1985]. Whole-rock chemistry is dacite.

Particle shape & density: Carey & Sigurdsson [1982] analyzed the componentry of different particle sizes. Genareau et al. [e.g., 2012] have examined the bubble-size distribution. These data can be used to estimate clast density as a function of particle size.

Total grain-size distribution: Total grain-size distributions of the deposit were estimated by Carey and Sigurdsson [1982] and Durant et al. [2009]. Total grain-size data are posted as an online data supplement, file jgrb15763-sup-008-ts03.txt, to Durant et al. [2009], and on the data page of the IAVCEI Commission on Tephra Hazard Modeling’s web site. Please note: for simulations of ash clouds, grain sizes coarser than about 0.06mm may be omitted because they tend to deposit within a few hundred kilometers. And the mass of fine ash must be reduced to account for aggregation. The fraction of the total erupted mass that remains in ash clouds several hundred kilometers or more downwind, based on studies at Spurr [Wen and Rose, 1994] and Eyjafjallajökull [Bonadonna et al., 2011; Dacre et al., 2011 (in press); Devenish et al., 2012; Gudmundsson et al., 2012], ranges from about 1% to 10%.

References:

Bonadonna, C., R. Genco, M. Gouhier, M. Pistolesi, R. Cioni, F. Alfano, A. Hoskuldsson, and M. Ripepe (2011), Tephra sedimentation during the 2010 Eyjafjallajökull eruption (Iceland) from deposit, radar, and satellite observations, Journal of Geophysical Research: Solid Earth, 116(B12), B12202,doi 10.1029/2011jb008462.

Carey, S., and H. Sigurdsson (1982), Influence of particle aggregation on deposition of distal tephra from the May 18, 1980, eruption of Mount St. Helens volcano, J. Geophys. Res., 87(B8), 7061-7072.

Christiansen, R. L., and D. W. Peterson (1981), Chronology of the eruptive activity, in The 1980 Eruptions of Mount St. Helens, Washington, edited by P. W. Lipman and D. R. Mullineaux, pp. 3-30, U.S. Government Printing Office, Washington, D.C.

Dacre, H. F., A. L. M. Grant, R. J. Hogan, S. E. Belcher, D. J. Thomson, B. Devenish, F. Marenco, J. Haywood, A. Ansmann, and I. Mattis (2011 (in press)), The structure and magnitude of the ash plume during the initial phase of the Eyjafjallajökull eruption, evaluated using lidar observations and NAME simulations, J. Geophys. Res.

Devenish, B., P. N. Francis, B. T. Johnson, R. S. J. Sparks, and D. J. Thomson (2012), Sensitivity analysis of dispersion modeling of volcanic ash from Eyjafjallajökull in May 2010, J. Geophys. Res., 117(D00U21), doi:10.1029/2011JD016782,doi doi:10.1029/2011JD016782.

Durant, A. J., W. I. Rose, A. M. Sarna-Wojcicki, S. Carey, and A. C. Volentik (2009), Hydrometeor-enhanced tephra sedimentation: Constraints from the 18 May 1980 eruption of Mount St. Helens (USA), J. Geophys. Res., 114(B03204), doi:10.1029/2008JB005756.

Genareau, K., A. A. Proussevitch, A. J. Durant, G. Mulukutla, and D. L. Sahagian (2012), Sizing up the bubbles that produce very fine ash during explosive volcanic eruptions, Geophys. Res. Lett., 39(15), L15306,doi 10.1029/2012gl052471.

Gudmundsson, M. T., et al. (2012), Ash generation and distribution from the April-May 2010 eruption of Eyjafjallajökull, Iceland, Scientific Reports, 2(572), DOI: 10.1038/srep00572,doi 10.1038/srep00572.

Harris, D. M., W. I. Rose, R. Roe, and M. R. Thompson (1981), Radar observations of ash eruptions, in The 1980 Eruptions of Mount St. Helens, Washington, edited by P. W. Lipman and D. R. Mullineaux, pp. 323-333, U.S. Government Printing Office, Washington, D.C.

Mastin, L. G., et al. (2009), A multidisciplinary effort to assign realistic source parameters to models of volcanic ash-cloud transport and dispersion during eruptions, J. Volcanol. Geotherm. Res., 186, 10-21.

Rutherford, M. J., H. Sigurdsson, S. Carey, and A. Davis (1985), The May 18, 1980, eruption of Mount St. Helens: 1, Melt composition and experimental phase equilibria, J. Geophys. Res., 90(B4), 2929-2947.

Sarna-Wojcicki, A. M., S. Shipley, R. Waitt, D. Dzurisin, and S. H. Wood (1981), Areal distribution, thickness, mass, volume, and grain size of air-fall ash from the six major eruptions of 1980, in The 1980 Eruptions of Mount St. Helens, Washington; USGS Professional Paper 1250, edited by P. W. Lipman and R. L. Christiansen, pp. 577-601, U.S. Geological Survey.

Wen, S., and W. I. Rose (1994), Retrieval of sizes and total masses of particles in volcanic clouds using AVHRR bands 4 and 5, J. Geophys. Res., 99(D3), 5421-5431.

Chaitén, 2008

Description: The eruption occurred from approximately May 1-8, although the entry in the summary table includes only the beta phase which occurred on 6 May between 8:20 and 9:15 local time. During this phase, the eruption vigor increased, producing a wide and dark gray ash plume about 20 km high.

Observations

Eruption start: about 08:20 local time (1220 UTC) based on seismic detection [Alfano et al., 2011]

Eruption duration: About 55 minutes, from about 08:20 to 09:15 local time (1220-1315 UTC) based on the seismic record [Alfano et al., 2011].

Plume height: Ground-based reports of the 6 May event estimated plume heights to 30 km [Folch et al., 2008; Watt et al., 2009], however satellite-based estimates placed the top of the cloud around 20 km [Carn et al., 2009]. Satellite-based estimates are used in summary table.

Erupted mass: The 225 Tg erupted mass in the summary table is the midpoint between these estimates based on an exponential (1.8´10¹¹kg) and power-law (2.7´10¹¹) extrapolation of the mapped deposit [Bonadonna and Costa, 2012]. Watt et al. [2009] sampled the distal part of the deposit at 227 locations between 30 May and 11 June, 2008. They fit their data using an exponential with two line segments for the May 6 deposit, summing it up to an erupted mass of 0.17 km³. Alfano et al. [2011] sampled the proximal and medial sections of the deposit at 69 locations in January, 2009 (8 months after the eruption), and combined their points with the distal points of Watt et al. [2009], to estimate a bulk deposit volume for the beta phase of 0.14-0.21 km³. Bonadonna and Costa [2012] revised this to 0.21, 0.16, and 0.16 km³ bulk volume by extrapolating thicknesses using an exponential, power, and Weibull fit, respectively.

· number of points: 296

· measurement type: m (mass loading)

· extrapolation method: e (exponential)

Table 1: estimates of erupted volume and mass of the various Chaitén phases, from Alfano et al. [2011] and Bonadonna and Costa [2012]

Unit	alpha (May 1^st-2^nd)	A-M (May 3^rd-5^th)	beta (May 6^th)	Post May 6^th	Total deposit
Erupted Volume
Exponential¹(km³)	26.8 x 10^-4	2.8 x 10^-1	2.1 x 10^-1	--	4.9 x 10^-1
Power-law¹ (km³)	55.1 ± 0.2 x 10^-4	2.4 x 10^-1	1.4 x 10^-1	5.7 x 10^-1	9.6 x 10^-1
Weibull² (km³)	--	--	1.6 x 10^-1	--	--

Ht¹(km)	13	10	17 – 19	--	--

MER¹(kg/s)
Peak³	9.2 x 10⁶	3.2 x 10⁶	4.2 x 10⁷	--	--
Average⁴	1.2 x 10⁵	--	--	--	--

Erupted Mass¹(kg)
Exponential derived	2.7 x 10⁹	2.8 x 10¹¹	2.7 x 10¹¹	--	4.9 x 10¹¹
Power-law derived	54.9 ± 0.2 x 10⁸	2.4 x 10¹¹	1.8 x 10¹¹	5.4 x 10¹¹	9.6 x 10¹¹

Duration¹
Exponential derived	5 min	24 h	2 h	--	--
Power-law derived	10 min	20 h	1 h	--	--

Volcanic Explosivity Index (VEI)¹	2	4	4	--	4

1. Alfano et al (2011)

2. Bonadonna and Costa (2012)

Magma type: Nearly aphyric rhyolite with a glass composition of about 76 wt% SiO2 [Castro and Dingwell, 2009].

Particle shape & density: Particle density, measured using a helium picnometer on powdered pumices, is equal to 2,242±14 kg m^-3 [Alfano et al., 2012].

Total grain-size distribution: Alfano et al. [2016] obtained a total grain size distribution for the 6 May Chaitén deposit as given in Table 2, by integrating proximal and distal data. The deposit is characterized by a total grain size distribution with Md(phi) of 3.8 ± 1.9 with a main lithic fraction of about 77 ± 3 % and a juvenile fraction of 23 ± 3 %; the juvenile fraction is composed for a 52 ± 9 % of obsidian fragments and for a 48 ± 9 % of pumice fragments. Please note: for simulations of ash clouds, grain sizes coarser than about 0.06mm may be omitted because they tend to deposit within a few hundred kilometers. And the mass of fine ash must be reduced to account for aggregation. The Fraction of the total erupted mass that remain in ash clouds several hundred kilometers or more downwind, based on studies at Spurr [Wen and Rose, 1994] and Eyjafjallajökull [Bonadonna et al., 2011; Dacre et al., 2011; Devenish et al., 2012; Gudmundsson et al., 2012], ranges from about 1% to 10%.

Table 2: Grain-size distribution for the 6 May b layer of Chaitén, estimated by Alfano et al. [2016].

phi	mm	mass percent
-5	32	0.2
-4	16	0.7
-3	8	1.9
-2	4	3.1
-1	2	3.1
0	1	6.3
1	0.5	10
2	0.25	14.6
3	0.125	16.1
4	0.062	15
5	0.031	13
6	0.016	8.3
7	0.008	4
8	0.004	2
9	0.002	1.2
10	0.001	0.6
>10	<0.001	0.1

The deposit is characterized by a total grain size distribution with Md(phi) of 3.8 ± 1.9 with a main lithic fraction of about 77 ± 3 % and a juvenile fraction of 23 ± 3 %; the juvenile fraction is composed for a 52 ± 9 % of obsidian fragments and for a 48 ± 9 % of pumice fragments.

· number of points: 62

· interpolation method: Voronoi [Bonadonna and Houghton, 2005]

References:

Alfano, F., C. Bonadonna, and L. Gurioli (2012), Insights into eruption dynamics from textural analysis: the case of the May, 2008, Chaitén eruption, Bull. Volcanol., 74(9), 2095-2108,doi 10.1007/s00445-012-0648-3.

Alfano, F., C. Bonadonna, S. Watt, C. Connor, A. Volentik, and D. M. Pyle (2016), Reconstruction of total grain size distribution of the climactic phase of a long-lasting eruption: the example of the 2008–2013 Chaitén eruption, Bull. Volcanol., 78(7), doi:10.1007/s00445-016-1040-5.

Alfano, F., C. Bonadonna, A. M. Volentik, C. Connor, S. L. Watt, D. Pyle, and L. Connor (2011), Tephra stratigraphy and eruptive volume of the May, 2008, Chaitén eruption, Chile, Bull. Volcanol., 73(5), 613-630,doi 10.1007/s00445-010-0428-x.

Bonadonna, C., and B. F. Houghton (2005), Total grain-size distribution and volume of tephra-fall deposits, Bull. Volcanol., 67, 441-456.

Bonadonna, C., and A. Costa (2012), Estimating the volume of tephra deposits: A new simple strategy, Geology, 40(5), 415-418,doi 10.1130/g32769.1.

Carn, S., J. S. Pallister, L. Lara, J. W. Ewert, S. F. L. Watt, A. J. Prata, R. J. Thomas, and G. Villarosa (2009), The Unexpected Awakening of Chaitén Volcano, Chile, Eos, 90(24), 205-206.

Castro, J., and D. B. Dingwell (2009), Rapid ascent of rhyolitic magma at Chaitén volcano, Chile, Nature, 4681, 780-783,doi doi:10.1038/nature08458.

Dacre, H. F., et al. (2011), Evaluating the structure and magnitude of the ash plume during the initial phase of the 2010 Eyjafjallajökull eruption using lidar observations and NAME simulations, Journal of Geophysical Research: Atmospheres, 116(D20), n/a-n/a, doi:10.1029/2011JD015608.

Folch, A., O. Jorba, and J. Viramonte (2008), Volcanic ash forecast--application to the May 2008 Chaitén eruption, Natural Hazards and Earth System Sciences, 8, 927-940.

Watt, S. F. L., D. M. Pyle, T. A. Mather, R. S. Martin, and N. E. Matthews (2009), Fallout and distribution of volcanic ash over Argentina following the May 2008 explosive eruption of Chaitén, Chile, J. Geophys. Res., 114(B04207), doi:10.1029/2008JB006219.

Wen, S., and W. I. Rose (1994), Retrieval of sizes and total masses of particles in volcanic clouds using AVHRR bands 4 and 5, J. Geophys. Res., 99(D3), 5421-5431.

Eyjafjallajökull, 2010

Description: The Eyjafjallajökull eruption of April and May, 2010 has been documented by many papers, including special volumes of:

· the Journal of Geophysical Research (117, issue D20) http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)2169-8996/specialsection/ICEVOLCAN1

· Atmospheric Environment (v. 48, p. 1-240) http://www.sciencedirect.com/science/journal/13522310/

· Atmospheric Chemistry & Physics (v. 10, 11, 12) http://www.atmos-chem-phys.net/special_issue212.html

Gudmundsson et al. [2012] divide the eruption into three phases:

· Phase I: an explosive period from April 14-18, 2010

· Phase II: a low-discharge effusive period from April 18-May 4

· Phase III: a second explosive period from May 5-17.

During the weeks-long eruption, plume heights varied from about 5 to 10 km and were recorded at regular time intervals by both a C-band Doppler radar system at Keflavik (155 km distant) and by multiple web cameras. Both datasets are described in Arason et al. [2011]. Deposits for the ash-producing phases were mapped by Gudmundsson et al. [2012] and, for May 4-8, in a topical study by Bonadonna et al. [2011].

Observations

Eruption start: Determined seismically on 14 April 2010, at about 0100 UTC, although the first several hours of the eruption consisted of a steam-dominated plume as the eruption melted its way through the ice cap [Gudmundsson et al., 2012].

Eruption duration: In the summary table, we break the eruption into 3-hour segments, each with its own plume height, using radar data published by Arason et al. [2011]. The radar data (http://doi.pangaea.de/10.1594/PANGAEA.760690) summarizes statistics on plume height over time periods ranging from one to 24 hours. Modelers may choose other time periods as they deem appropriate.

Plume height: The summary table gives the 75^th percentile of plume height over each 3-hour period From data in Arason et al. [2011]. Because eruption rate scales with the fourth power of plume height [Morton et al., 1956], higher plumes contributed disproportionately to the erupted volume; hence our choice of the 75% percentile. Modelers may choose other values from the data as appropriate.

The Eyjafjallajökull plume vigor fluctuated over periods of seconds to minutes [Ripepe et al., 2013], producing a somewhat higher plume than would have been predicted using 1-D plume models that assume steady behavior. But wind also sometimes reduced plume height relative to that predicted by 1-D windless models [Bursik et al., 2012; Woodhouse, M. J. et al., 2013]

Concerning the vertical distribution of mass in the plume, inverse modeling [Kristiansen et al., 2012] suggests that tephra emission was concentrated within 1-2 km of the plume top.

Erupted mass: From mapping the deposit and integrating using a 3-segment piecewise exponential integration, Gudmundsson et al. [2012] estimated a total erupted mass of 170 Tg for phase I and 190 Tg for phase III (Table 1 of their paper). To estimate the erupted mass for each 3-hour time period listed in the summary table, we used the same procedure described for Mount St. Helens. The mass calculated from the empirical plume height-eruption rate relationship is 34 Tg (phase I) and 73 Tg (phase III), requiring us to use the correction factors 170/33 (phase I) and 190/72 (phase III). About 48-56% was transported offshore [Gudmundsson et al., 2012], while about 1-11% remained in the cloud as it passed over Europe [Bonadonna et al., 2011; Devenish et al., 2012].

The mass eruption rate during each phase and time period of this eruption has been heavily scrutinized, with some authors finding that more accurate eruption rates could be obtained through 1-D models or formulas that consider wind [Bursik et al., 2012; Degruyter and Bonadonna, 2012; Woodhouse, M.J. et al., 2013] or Bayesian inversion [Kristiansen et al., 2012; Stohl et al., 2011]. Thus the values in the summary table should be regarded as approximations that can be improved through modeling efforts.

· number of points: 400 by Gudmundsson et al. [2012], 17 by Bonadonna et al. [2011]

· measurement type: t (thickness) for Gudmundsson et al. [2012], m (mass) by Bonadonna et al. [2011]

· extrapolation method: e (exponential)

Magma type: Fallout from April 14-19 contains three glass types of basaltic, intermediate, and silicic compositions recording rapid magma mingling without homogenization [Sigmarsson et al., 2011]. Glass compositions from about April 17 through May ranged from benmoreite to trachyte.

Particle shape: Particle morphological parameters, as characterized based on the sphericity of Riley et al. [Riley et al., 2003] and Aschenbrenner [1956] and the shape factor of Wilson and Huang [1979], all show a similar trend with no significant variation with particle size and distance from the vent (samples between 2-56km from vent; Bonadonna et al. 2011). The sphericity of Aschenbrenner [1956] (i.e., 0.91 ± 0.02, average and standard deviation of the medians of each sample) is characterized by larger and less variable values than the sphericity of Riley et al. [2003] (i.e., 0.83 ± 0.04) and the shape factor of Wilson and Huang [1979] (i.e., 0.79 ± 0.01).

Deposit and particle density: Deposit density was calculated by gently pouring ash samples in a graduated cylinder, and measuring volume and weight for 5 times (i.e., 1226±88 kg m−3 for 10 samples collected between 2 and 56 km from vent and between 4-8 May 2010). The density of 50 clasts (sizes between about 13 and 30 mm) that fell at location EJ14 (2 km from the vent on May 5) was measured by determining weights in air and in water (Archimedes’ principle) (i.e., 986 ± 0.2 kg m−3). The density of glass (i.e., 2738 ± 0.7 kg m−3) was measured with a helium pycnometer (sample EJ14 collected 2 km from the vent on May 5) [Bonadonna et al., 2011].

Aggregation: Particles mostly fell as both particle clusters and accretionary pellets. Collections carried out sequentially on 4, 5, and 6 May showed that aggregate typologies changed spatially. Dedicated SEM grain‐size analyses have shown that they mainly consist of particles <0.063 mm (>5 phi), with liquid pellets showing also particles between 0.125 and 0.63 mm (4 phi). Associated Md(phi) and sorting vary between 4.0 and 6.2 f and 0.5 and 1.2, respectively [Bonadonna et al., 2011].

Total grain-size distribution: Grain-size distributions at selected sites have been analyzed by Gudmundsson et al. [2012]. Bonadonna et al. [2011]report a total grain-size distribution erupted during 30 minutes of activity between 4-8 May 2010 by combining deposit measurements with satellite retrievals. The resulting grain‐size distribution is posted at the IAVCEI Commission on Tephra Hazard Modeling database site. It is comprehensive of the mass that fell up to the coastline (i.e., corresponding to the 0.05 kg m⁻² isomass line; 9.7 × 10⁷ kg) and the mass that remained in the cloud up to 1000 km from the vent (i.e., 10⁷ kg). Associated Md(phi) and sorting are of 2.1f and 3.6, respectively, and a secondary mode around 7 phi is evident. The content of fine ash (<0.063 mm) is 26 wt % and 33 wt % for the ground‐based and the ground combined with MSG‐SEVIRI data, respectively [Bonadonna et al., 2011].

· number of points: 12 (between 2 and 56 km from vent) + MSG‐SEVIRI data

· interpolation method: Voronoi [Bonadonna and Houghton, 2005].

References:

Arason, Þ., G. N. Peterson, and H. Bjornsson (2011), Observations of the altitude of the volcanic plume during the eruption of Eyjafjallajökull, April–May 2010, Earth System Science Data, 4, 1-25,doi doi:10.5194/essdd-4-1-2011.

Aschenbrenner, B. C. (1956), A new method of expressing particle sphericity, Journal of Sedimentary Petrology, 26(1), 15-31.

Bonadonna, C., and B. F. Houghton (2005), Total grain-size distribution and volume of tephra-fall deposits, Bull. Volcanol., 67, 441-456.

Bursik, M., et al. (2012), Estimation and propagation of volcanic source parameter uncertainty in an ash transport and dispersal model: application to the Eyjafjallajokull plume of 14–16 April 2010, Bull. Volcanol., 74(10), 2321-2338,doi 10.1007/s00445-012-0665-2.

Degruyter, W., and C. Bonadonna (2012), Improving on mass flow rate estimates of volcanic eruptions, Geophys. Res. Lett., 39(16), L16308,doi 10.1029/2012gl052566.

Devenish, B., P. N. Francis, B. T. Johnson, R. S. J. Sparks, and D. J. Thomson (2012), Sensitivity analysis of dispersion modeling of volcanic ash from Eyjafjallajökull in May 2010, J. Geophys. Res., 117(D00U21), doi:10.1029/2011JD016782,doi doi:10.1029/2011JD016782.

Kristiansen, N. I., et al. (2012), Performance assessment of a volcanic ash transport model mini-ensemble used for inverse modeling of the 2010 Eyjafjallajökull eruption, J. Geophys. Res., 117, D00U11,doi 10.1029/2011jd016844.

Morton, B. R., G. I. Taylor, and J. S. Turner (1956), Turbulent gravitational convection from maintained and instantaneous sources, Proceedings of the Royal Society of London, ser. A, 234, 1–23.

Riley, C., W. I. Rose, and G. J. S. Bluth (2003), Quantitative shape measurements of distal volcanic ash, J. Geophys. Res., 108(B10),doi 10.1029/2001JB000818.

Ripepe, M., C. Bonadonna, A. Folch, D. Delle Donne, G. Lacanna, E. Marchetti, and A. Höskuldsson (2013), Ash-plume dynamics and eruption source parameters by infrasound and thermal imagery: The 2010 Eyjafjallajökull eruption, Earth Planet. Sci. Lett., 366(0), 112-121,doi http://dx.doi.org/10.1016/j.epsl.2013.02.005.

Sigmarsson, O., I. Vlastelic, R. Andreasen, I. Bindeman, J. L. Devidal, S. Moune, J. K. Keiding, G. Larsen, A. Höskuldsson, and T. Thordarson (2011), Dynamic magma mixing revealed by the 2010 Eyjafjallajökull eruption, Solid Earth Discuss., 3(2), 591-613,doi 10.5194/sed-3-591-2011.

Stohl, A., et al. (2011), Determination of time- and height-resolved volcanic ash emissions and their use for quantitative ash dispersion modeling: the 2010 Eyjafjallajökull eruption, Atmospheric Chemistry and Physics, 11(9), 4333-4351.

Wilson, L., and T. C. Huang (1979), The influence of shape on the atmospheric settling velocity of volcanic ash particles, Earth Planet. Sci. Lett., 44, 311-324.

Woodhouse, M. J., A. J. Hogg, J. C. Phillips, and R. S. J. Sparks (2013), Interaction between volcanic plumes and wind during the 2010 Eyjafjallajökull eruption, Iceland, Journal of Geophysical Research: Solid Earth, 118(1), 92-109,doi 10.1029/2012JB009592.

Woodhouse, M. J., A. J. Hogg, J. C. Phillips, and R. S. J. Sparks (2013), Interaction between volcanic plumes and wind during the 2010 Eyjafjallajkull eruption, Iceland, J. Geophys. Res.,doi 10.1029/2012JB009592.

Appendix: Ash Products Description for Kasatochi Eruption August 2008

This appendix gives instructions for downloading processed satellite data for the Kasatochi eruption from NOAA/NESDIS.

Dataset Contact: Mike Pavolonis (NOAA) (Mike.Pavolonis@noaa.gov)

Format: netCDF3 (“Classic” netCDF)

Obtaining the netCDFs:

The files may be downloaded via http here: ftp://ftp.ssec.wisc.edu/pub/geocat/noaa_ash_retv/kasatochi

If using FTP in a terminal, use the following commands:

ftp ftp.ssec.wisc.edu

When asked for your ‘Name:’, type ‘anonymous’.

For your ‘Password:’, type in an email address.

cd pub/geocat/noaa_ash_retv/kasatochi

prompt

mget *

bye

Filename format:

“Kasatochi_YYYYJJJ-HHMMSS_YYYYJJJ-HHMMSS.netcdf”

The two times in the filename represent the start of the first and last MODIS granules used to create the variables in the netCDF. The YYYY is the four-digit year (e.g., 2008), JJJ is the Julian Day (e.g., 221), and HHMMSS is the hour, minute, and seconds in UTC. If the dates are identical, then only that one granule was used in the netCDF.

Compression:

bzip2 (http://www.bzip.org/)

‘bunzip2 $FILENAME’ will decompress the data on LINUX machines.

Projection:

Polar stereographic. The first reference latitude is 90.0 N, the second reference latitude is 60.0 N, and the reference longitude is 215.0 E (145.0 W). The map origin latitude, longitude is (60.0 N, 124.99 E). The equatorial radius of the map is 6,378.137 km.

Dimensions: ny= 1450 ; nx = 1600 ; single = 1

Variables:

LAT dimensions = (ny, nx) type = FLOAT

The center latitude of each pixel, in units of “degrees_north”. Positive values indicate northern hemisphere latitudes. Missing value = -999.0

LON dimensions = (ny, nx) type = FLOAT

The center longitude of each pixel, in units of “degrees_east”. Positive values indicate eastern hemisphere longitudes and negative values indicate western hemisphere longitudes. Missing value = -999.0

BTD1415 dimensions = (ny, nx)

The brightness temperature difference between 11-µm (MODIS band 31) and 12-µm (MODIS band 32) channels (i.e., 11-µm minus 12-µm). Units of Kelvin. Missing value = -999.0

BTD714 dimensions = (ny, nx) type = FLOAT

The brightness temperature difference between 3.9-µm (MODIS band 21) and 11-µm (MODIS band 31) channels (i.e., 3.9-µm minus 11-µm). Units of Kelvin. Missing value = -999.0

BTD1114 dimensions = (ny, nx) type = FLOAT

The brightness temperature difference between 8.5-µm (MODIS band 29) and 11-µm (MODIS band 31) channels (i.e., 8.5-µm minus 11-µm). Units of Kelvin. Missing value = -999.0

BT14 dimensions = (ny, nx) type = FLOAT

The brightness temperature of the 11-µm channel (MODIS band 31). Units of Kelvin. Missing value = -999.0

REF2 dimensions = (ny, nx) type = FLOAT

The 0.65-µm reflectance (MODIS band 1), in dimensionless units. Missing value = -999.0

PIXEL_TIME dimensions = (ny, nx) type = LONG

The number of seconds since January 1, 1970 00:00:00 UTC for each pixel. Missing value = 0

ASH_PROBABILITY dimensions = (ny, nx) type = FLOAT

The computed probability of ash at a given pixel, in dimensionless units (between 0.0 and 1.0). Missing value = -999.0

ASH_HEIGHT dimensions = (ny, nx) type = FLOAT

The retrieved height of the highest layer of ash for each pixel identified as ash, in units of km above sea-level (ASL). Missing value = -999.0

ASH_MASS_LOADING dimensions = (ny, nx) type = FLOAT

The retrieved ash mass per unit area of for each pixel identified as ash, in units of g m-2. Missing value = -999.0

ASH_EFFECTIVE_RADIUS dimensions = (ny, nx)

The retrieved effective radius for each pixel identified as ash, in units of µm. Missing value = -999.0

TO dimensions = (single) type = LONG

The approximate start time of the eruptive event of interest, in units of seconds since January 1, 1970 00:00:00 UTC.

T dimensions = (single) type = LONG

The start time of the MODIS overpass of interest, in units of seconds since January 1, 1970 00:00:00 UTC.

TDIFF_HRS dimensions = (single) type = FLOAT

The number of hours elapsed since the start of the eruptive event of interest at 04:45 UTC on August 8, 2008.

DAY dimensions = (single) type = LONG

The day of the month of the MODIS overpass of interest (August 2008).

TOTAL_AREA dimensions = (single) type = FLOAT

The total accumulated area of the ash cloud in the composite netCDF, in units of km2.

TOTAL_MASS dimensions = (single) type = FLOAT

The total accumulated mass of the ash cloud in the composite netCDF, in units of Tg (1 Tg = 1012 g).

LOADING25 dimensions = (single) type = FLOAT

The 25th percentile mass loading of the ash cloud, in units of g m-2.

LOADING50 dimensions = (single) type = FLOAT

The 50th percentile mass loading of the ash cloud, in units of g m-2.

LOADING75 dimensions = (single) type = FLOAT

The 75th percentile mass loading of the ash cloud, in units of g m-2.

REFF25 dimensions = (single) type = FLOAT

The 25th percentile effective radius for the ash cloud, in units of µm.

REFF50 dimensions = (single) type = FLOAT

The 50th percentile effective radius for the ash cloud, in units of µm.

REFF75 dimensions = (single) type = FLOAT

The 75th percentile effective radius for the ash cloud, in units of µm.

HEIGHT25 dimensions = (single) type = FLOAT

The 25th percentile height of the ash cloud, in units of km ASL.

HEIGHT50 dimensions = (single) type = FLOAT

The 50th percentile height of the ash cloud, in units of km ASL.

HEIGHT75 dimensions = (single) type = FLOAT

The 75th percentile height of the ash cloud, in units of km ASL.

Global Attributes:

Projection: A string, “polar stereographic”

Composite_members: A comma-separated string of GEOCAT (NOAA/CIMSS satellite processing software) level-2 hdf4 files used to create the composite variables in the netCDF file. Each file has a format of “geocatL2.SENSOR.YYYYJJJ.HHMMSS.hdf”. SENSOR will be “Terra” or “Aqua”, representing which satellite the sensor is on. The year is represented by YYYY (e.g., 2008), the Julian Day is represented by JJJ (e.g., 224), and the hour, minute, and seconds in UTC are represented by HHMMSS.

First_time: A string of the time of the start of the first MODIS granule used in this composite netCDF, in the format YYYYJJJ-HHMMSS.

Last_time: A string of the time of the start of the last MODIS granule used in this composite netCDF, in the format YYYYJJJ-HHMMSS.

Comments:

The remapping of ash products from MODIS granule swaths (pixel areas ~1-10 km2), to the polar stereographic projection (pixel areas ~13-29 km2) results in some error in total ash area and the associated ash products calculated on the projected grid, compared to those calculated from the MODIS swaths. The total and percentile ash areas, mass loadings, effective radii, and heights in the netCDFs are computed from the MODIS granules themselves.