Difference between revisions of "Volcanic SO2 emissions from Aerocom"
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== Original Aerocom documentation ==
== Original Aerocom documentation ==
Volcanic SO2 emissions<br>
Volcanic SO2 emissions<br>
Revision as of 21:53, 17 February 2015
On this page we describe the Aerocom volcanic emissions inventory that is used by GEOS-Chem.
- 1 Files for GEOS-Chem
- 2 Description of original data
- 3 Original Aerocom documentation
- 4 Update to AEROCOM volcanic emissions
- 5 Validation
- 6 Known issues
- 7 References
Files for GEOS-Chem
The files containing the Aerocom volcanic emissions of SO2 are available for download from the following FTP sites:
Data for GEOS-Chem v10-01 and newer versions
In GEOS-Chem v10-01 and newer versions, the Aerocom volcanic emissions of SO2 are read with the HEMCO emissions component. We have created new Aerocom data files (in COARDS-compliant netCDF format) for use with HEMCO. These new data files are contained in the HEMCO data directory tree. For detailed instructions on how to download these data files to your disk server, please see our Downloading the HEMCO data directories wiki post.
--Bob Y. 12:29, 13 February 2015 (EST)
Data for v9-01-01 through v9-02
ftp ftp.as.harvard.edu cd pub/geos-chem/data/GEOS_1x1/volcano_SO2_200910/YYYY/ YYYY = Subdirectories containing volcanic SO2 emissions on the GENERIC 1x1 grid in bpch format for years 1979-2009. Filenames : SO2_volc.erup.YYYYMM.generic.1x1 SO2_volc.nonerup.YYYYMM.generic.1x1 Units of data : kg/event/day
These newer files (in the volcano_SO2_201010 directory structure) contain minor updates from Thomas Diehl.
Data for versions prior to v9-01-01
For GEOS-Chem versions prior to v9-01-01, download these files:
ftp ftp.as.harvard.edu cd pub/geos-chem/data/GEOS_1x1/volcano_SO2_200909/YYYY/ YYYY = Subdirectories containing volcanic SO2 emissions on the GENERIC 1x1 grid in bpch format for years 1985-2007. Filenames : SO2_volc.erup.YYYYMM.generic.1x1 SO2_volc.nonerup.YYYYMM.generic.1x1 Units of data : kg/event/day
Description of original data
Volcanic emission data files were put together by Jenny Fisher. Source data are from the AeroCom hindcast emissions of SO2 put together by Thomas Diehl, accessible at http://www-lscedods.cea.fr/aerocom/AEROCOM_HC/volc/. The README for these data is copied at the end of this file.
The data files are monthly but provide daily emissions of SO2. Emissions are all on a generic 1° x 1° x 0.5 km grid and are regridded to the correct model resolution by GEOS-Chem.
The data are separated for eruptive and non-eruptive volcanic emissions. Non-eruptive emissions are injected at the altitude of the volcanic crater, while eruptive emissions are distributed evenly in the top third of the volcanic plume, as described in Chin et al. 2000.
The original data were stored as netCDF files. The bpch files were created in IDL using the routine volc_preprocess.pro
Original Aerocom documentation
NOTE: This data (dated 06 Mar 2009) was used in versions of GEOS-Chem used in versions of GEOS-Chem prior to v10-01.
Volcanic SO2 emissions
Contact: Thomas Diehl
Date: 06 Mar 2009
Description of the emission file
The file volc_so2.nc contains volcanic SO2 emissions and other variables for all days from January 1st 1979 to December 31st 2007 for all volcanoes with historic eruptions listed in the Global Volcanism Program's database provided by the Smithsonian Institution. Subglacial and submarine volcanoes are excluded. Each element of a variable is dubbed an "event", where an event corresponds to the emission of SO2 by a specific volcano on a specific day. The order of events is as follows:
ED1Vm ... ED1Vn ED2Vp ... ED2Vq ...... EDkVr ... EDkVs
(with E indicating events, V volcanoes, and D days). The dimension nevents contains the total number of events. Currently, nevents=12,403,236. The following variables are provided:
- the standardized 8-character volcano number, which can be used in data processing for identification purposes.
- the volcano name as provided by the GVP database; this variable is for informational purposes only and should not be used in data processing, since it contains non-ASCII characters.
- jdn (integer)
- the Julian Day Number
- so2 (float)
- the amount of SO2 emitted by the given volcano on the given day in kt
- cloud_column_height (integer)
- the height of the volcanic plume in m above sea level
- elevation (integer)
- the elevation of the volcano in m above sea level
- lon (float)
- the longitude of the volcano
- the latitude of the volcano
The following four variables contain the grid indices of the volcanoes; they are specific to the grid of the GOCART model. Other models will typically have to compute their own indices from the provided longitude and latitude.
- the longitudinal grid index for a resolution of 2.5° x2.0°
- the latitudinal grid index for a resolution of 2.5° x2.0°
- the longitudinal grid index for a resolution of 1.25° x1.0°
- the latitudinal grid index for a resolution of 1.25° x1.0°
Since the inventory is constructed such that cloud_column_height = elevation for non-eruptive degassing, the SO2 emission should be placed only in the model level which contains the crater elevation for the case cloud_column_height = elevation. For all other cases, the emission should be injected into some fraction of the levels located within the plume. In the GOCART model, the SO2 emission is evenly distributed among the levels located within the top third of the plume.
Methodology used for compiling the inventory
Volcanoes are assigned posteruptive, extraeruptive, and pre-eruptive degassing rates depending on their eruptive state. In addition, we use the SO2 emission rates provided by Andres & Kasgnoc (1998) for 49 quasi-continuously erupting volcanoes. Additional results from observations (from the TOMS and OMI instruments and COSPEC measurements) were retrieved from the literature in a number of cases. For those days of eruptive periods without data from instruments, we compute an averaged daily emission rate from either the mass of the ejected magma (if available) and intraeruptive degassing, or from the VSI corresponding to the listed VEI and intraeruptive degassing. The plume height is derived from the VEI (for days with SO2 data from instruments) or from the mass weighted average of the VEI-based plume height and the emission height for intraeruptive degassing (assumed to be at the elevation of the crater). In some cases, the plume height is taken from measurements provided in the literature.
A more detailed description of the procedure, which assigns the SO2 emissions to each volcano for each day, is given below:
- Volcanoes with a timeframe code of D1 or D2 in the GVP database (i.e. those which had an eruption since 1900) are assigned a posteruptive degassing rate of 7.0x10-2 kt/d. All other volcanoes with historic eruptions are assigned an extraeruptive degassing rate of 6.2x10-4 kt/d.
- These values are overwritten with the SO2 emissions listed in Andres & Kasgnoc (1998) for 49 quasi-continuously erupting volcanoes.
- On days when the TOMS instrument provides SO2 data the entries from 1. and 2. are overwritten by the TOMS detected SO2 amount.
- Additional results from observations (from the OMI instrument or COSPEC measurements) were retrieved from the literature for a number of cases. These values overwrite entries from 1.-3. on the available days.
- For each eruption listed in the GVP table, the 7 days preceding the start of an eruption are assigned a pre-eruptive degassing rate of 7.5x10-1 kt/d. This step is not applied if a value was assigned for this volcano on this day in step 2, 3, or 4.
- For the days of each eruption listed in the GVP table, an SO2 value is assigned as follows:
- No value is assigned if an SO2 value was already assigned in steps 2-4 for a specific day and volcano.
- If none of the days within the eruption period was assigned an SO2 value in 2-4, the SO2 emitted during this period is derived from the mass of the ejected magma if this quantity is available. Otherwise, the SO2 amount is derived from the VSI corresponding to the VEI listed in the GVP table for this eruption. Also, an intraeruptive degassing rate is applied to ndays-1 days in both cases (where ndays is the length of the eruption period in days), and an average daily emission rate for the whole period is calculated.
- If one or more day(s) within the eruption period were assigned SO2 values in steps 2-4, we approximate the SO2 emitted during the remainder of the eruption period by applying an intraeruptive degassing rate to ndays-odays days, where odays are the number of days within the eruptive period with assigned values from 2-4. If the mass of the ejected magma is available and if SO2magma > SO22-4, the residual SO2magma - SO22-4 is added and an average daily emission rate for the remaining days of the eruption period is calculated.
The plume height is derived from the VEI for days with SO2 data from instruments. For other days, it is derived from the mass weighted average of the VEI-based plume height and the emission height for intraeruptive degassing, which is assumed to be located at the elevation of the crater. In some cases, the plume height is taken from measurements provided in the literature.
Our rates for preeruptive and intraeruptive degassing are simply the average of the range given by Berresheim & Jaeschke (1983) for these classes of degassing: degaspre = 7.5x10-1 kt/d and degasintra = 7.5x10-1 kt/d. Preeruptive degassing is applied to the 7 days preceding the start of an eruption.
We modified the rates provided by Berresheim & Jaescke for posteruptive and extraeruptive degassing, given as 1.05x10-1 kt/d and 5x10-3 kt/d, respectively. These rates were inferred (like the rates for intraeruptive and preeruptive degassing) from a small sample of volcanoes. Applying this rate to all posteruptive days of all volcanoes would probably overestimate the amount of SO2, since not all volcanoes are exhibiting this type of posteruptive degassing (or at least not on all days of their posteruptive period). Since we generally do not know the individual volcanoes which display this type of degassing, we reduce the degassing rate by the factor actualpostv/totpostv (where actualpostv is the actual (estimated) number of volcanoes displaying posteruptive degassing and totpostv is the total number of volcanoes which erupted during the past 100 years) and apply this effective rate to the posteruptive days of all volcanoes which erupted during the past 100 years. The number of 365 volcanoes given by Berresheim & Jaeschke exhibiting posteruptive degassing is most likely an overestimate, while the number of 102 provided by Stoiber et al. (1987) is probably an underestimate since they did not account for degassing without plumes, i.e. they omitted the fumarolic part of the posteruptively degassing volcanoes (see the discussion in Graf et al., 1997). In the current (as of September 2008) GVP database, 365 volcanoes had a subaerial eruption after 1900. On average, 60 volcanoes have an eruption per year(number from volcano.si.edu). Not counting the erupting volcanoes to a first approximation, we get totpostv = 305 volcanoes with potentially posteruptive degassing. Approximating actualpostv with (305+102)/2 yields 0.105x0.667 = 7.0E-2 kt/d.
For the extraeruptive case, we do not have a lower boundary from observations (like the 102 volcanoes in the posteruptive case) to derive a scaling factor. Thus, we simply evenly distribute the global 0.5 kt/d from B&J onto all 807 volcanoes in the GVP database whose last eruption occurred before 1900 (excluding volcanoes for which it is uncertain whether the last eruption was in the Holocene). This yields 6.2x10-4 kt/d per volcano. Thus, the rate is only about 10% of the one in B&J (5.0x10-3 kt/d). Alternatively, this can also be interpreted as only 10% of the volcanoes, which had eruptions before 1900 in the GVP database to display extraeruptive degassing (with the unmodified rate from B&J) in our inventory.
Estimation of SO2 from ejected magma
In some cases, the GVP database provides volume estimates for the erupted lava and/or tephra. In these cases, we use the formula from Blake (2003) to estimate the SO2 mass released during the eruption: mSO2 [Mt] = 1.77 mmagma[Gt] 0.64
Since the provided lava and tephra volumes are bulk volumes, they must be converted to dense rock equivalent (DRE) volumes. Averaging a range of values found in the literature yields ftephra = 0.5 and flava = 0.85. For (DRE, we use 2.7 g/cm3.
Update to AEROCOM volcanic emissions
NOTE: This update (dated 01 Mar 2010) was used in versions of GEOS-Chem used in support of the SEAC4RS aircraft mission. It was also introduced into the standard GEOS-Chem via the HEMCO emissions component in GEOS-Chem v10-01.
Volcanic SO2 emissions
01 Mar 2010
The volcanic emission inventory (as described in the previous section) was modified as follows:
- Eruptions for 2008 and 2009 were added.
- OMI observations were used in a number of cases to estimate SO2 emissions. Examples: Kasatochi (2008), Nyamuragira (2006), Okmok (2008), Redoubt (2009), Sarychev Peak (2009)
- The VSI/VEI based SO2 emissions for non-arc volcanoes were unrealistically large in many cases. The distinction between arc and non-arc volcanoes for the purpose of determinig emissions from the VEI was therefore abandoned and the SO2 emission numbers for the arc volcanoes are (for now) used for all volcanoes.
- The plume height for Pinatubo and El Chichon was changed to 25 km.
- Plume heights from BVGN reports were added for several eruptions.
- A bug in the code which generates the inventory was fixed (this affected some plume heights).
--Bob Y. 16:51, 17 February 2015 (EST)
Text to be added
Typo in VOLCPRESS definition
This update was tested in the 1-month benchmark simulation v9-02l and approved on 26 Jun 2013.
Thibaud Thonat wrote:
- I've a found a little typing error in Code.v9-01-03/GeosCore/sulfate_mod.F. At line 4614, for the definition of VOLCPRESS:
REAL*8 :: VOLCPRESS(LVOLC+1) = (/ & 1013.25, 954.61, 898.74, 845.56, 747.95, 746.83, 701.08, & 657.64, 616.40, 577.28, 540.20, 505.07, 471.81, 440.35, & 410.61, 382.52, 356.00, 330.99, 307.42, 285.24, 264.36 /)
- I think 747.95 should be 794.95, I've checked using the US standard atmosphere, the other values are correct.
Jenny Fisher wrote:
- That looks like a bug. We can update this in the standard code.
--Bob Y. 14:46, 11 June 2013 (EDT)
- AeroCom hindcast emisions and READMEs: http://www-lscedods.cea.fr/aerocom/AEROCOM_HC/
- M. Chin, R.B. Rood, S.-J. Lin, J.-F. Muller, and A. M. Thompson, Atmospheric sulfur cycle simulated in the global model GOCART: Model description and global properties, J. Geophys. Res., 105, D20, 4671-24687, 2000.
- Andres, R. J.. and A. D. Kasgnoc, A time-averaged inventory of subaerial volcanic sulfur emissions, J. Geophys. Res., 103, 25251-25261, 1998.
- Berresheim, H., and W. Jaeschke, The Contribution of Volcanoes to the Global Atmospheric Sulfur Budget, J. Geophys. Res., 88, 3732-3740, 1983.
- Blake, S., Correlations between eruption magnitude, SO2 yield, and surface cooling, in Volcanic Degassing, Special Publication of the Geological Society of London No. 213, edited by C. Oppenheimer, D. M. Pyle, and J. Barclay, 177-202, Geological Society, London, UK, 2003.
- Carn, S. A., A. J. Krueger, G. J. S. Bluth, S. J. Schaefer, N. A. Krotkov, I. M. Watson, and S. Datta, Volcanic eruption detection by the Ozone Mapping Spectrometer (TOMS) instruments: a 22-year record of sulphur dioxide and ash emissions, in Volcanic Degassing, Special Publication of the Geological Society of London No. 213, edited by C. Oppenheimer, D. M. Pyle, and J. Barclay, 177-202, Geological Society, London, UK, 2003.
- Graf, H.-F., J. Feichter, and B. Langmann, Volcanic sulfur emissions: Estimates of source strength and its contribution to the global sulfate distribution, J. Geophys. Res., 102, 10727-10738, 1997.
- Newhall, C. G., and S. Self, The Volcanic Explosivity Index (VEI): An Estimate of Explosive Magnitude for Historical Volcanism, J. Geophys.Res., 87, 1231-1238, 1982.
- Schnetzler, C. C., G. J. S. Bluth, A. J. Krueger, and L. S. Walter, A proposed volcanic sulfur dioxide index (VSI), J. Geophys. Res., 102, 20087-20091, 1997.
- Simkin T, Siebert L (2002-). Global Volcanism FAQs. Smithsonian Institution, Global Volcanism Program Digital Information Series, GVP-5 (http://www.volcano.si.edu/faq/), 2008.
- Stoiber, R. E., S. N. Williams, and B. Huebert, Annual Contribution of Sulfur Dioxide to the Atmosphere by Volcanoes, J. Volcanol. Geotherm. Res., 33, 1-8, 1987.
--Bob Y. 10:13, 16 February 2010 (EST)