The project has been successful and in all important aspects achieved or surpassed its goals. Below are listed the most important achievements without any relative grading. Although some partners have been more active than others in some of these achievements the overall success is due to the extraordinary enthusiasm and engagement of the whole consortium.
Volcano monitoring puts high demands on the hardware to be used. Many volcanoes are located in remote areas, lacking infrastructure like grid power and telecommunication, the climate can be harsh with highly variable temperatures, heavy rain, hurricanes, thunderstorms and high humidity. In addition the surroundings of an active volcano may be strongly affected by aggressive gases, acid rain and fine ash depositing. In specific these conditions are further stressed in relation to a volcanic crisis, a situation when sustained measurements are of outmost importance. Thus the instruments must be simple and robust without severely compromising data quality. This is to some degree a contradiction, and a trade-off has to be done between simplicity and data quality. Thus we decided to build 2 different instruments; NOVAC Mark I built to be robust and simple enough to be able to provide monitoring of gas emissions with minimum maintenance over longer periods, while the more sophisticated NOVAC Mark II instrument has additional features that provides more flexibility in operation modes as well as improved data quality, at the cost of higher maintenance needs.
A specific improvement is a minor hardware modification that facilitate the use of a novel measurement strategy, conical scanning. This modification enables each instrument to cover about twice as large deviations in wind direction without compromising the data. The method has been patented in Europe (approved), USA (pending) and Canada (pending).
Until May 2011 a total of 59 NOVAC Mark I instruments has been installed for routine monitoring on 24 volcanoes, while 5 NOVAC Mark II instruments are in use at 4 observatories for more advanced gas emission studies. At the end of the project about 10% of the Mark I instrument has needed a serious repair with broken electronics or spectrometer, primarily caused by thunder, heat or corrosion.
A Rapid Deployment NOVAC System has been developed. The system consist of 3 NOVAC instruments and a satellite communication unit that can rapidly be deployed during a volcanic crisis or and acquire a continued real-time data set of SO2 emission measurements.
The software developed includes software to run the instruments and store data locally in the instruments, software located at the volcano observatories to download data from the instruments and perform a real-time SO2 flux evaluation, software for post-processing of the data and software for archiving the data.
Each instrument is controlled by an embedded computer running Linux software. The computer run the measurements, store raw data in compressed form on a 1 Gb SD-card (enough for 3 months autonomous operation) and has an ftp-server for the communication with the volcano observatory via LAN or serial modems.
To evaluate the data collected by the scanning instruments, a software package called the NovacProgram has been developed. The software is designed to supervise several connected instruments simultaneously and to download data from them, one at a time. The raw data from the instruments are then evaluated in real-time and the results are presented and stored at the observatory, as well as passed on via internet to a server located at Chalmers in Gothenburg. The NovacProgram also has a post-processing unit for more detailed inspection and re-evaluation of the data off-line. A routine has been implemented that automatically download and utilize wind fields from the ECMWF global model, interpolated to the respective locations of the measurements, in the evaluation.
Data from the observatories are processed using different versions of the NovacProgram, different ways to implement meteorology and different QA/QC routines. Thus, in order to better control the quality of the final product that are stored in the NOVAC archive, standardization of data evaluation is required. To do this, the NOVAC Post Processing Program has been developed. This program is designed for batch processing of spectra collected in the NOVAC project. For example all the data from a given instrument and time-period can be processed in an effective way. In this way novel evaluation algorithms and schemes can be tested out effectively, and a careful analysis of data, and control of errors and uncertainties can be carried out, ensuring a consistent database in the archive. Work is underway to fully implement the spectroscopical achievements given below, in the processing of the data to be archived.
Spectroscopy and calibration routines
The measurements are based on UV-spectroscopy and state-of-the-art spectral evaluation algorithms are a key to obtain reliable data. Mayor achievements has been made in the project in relation to handling of atmospheric scattering, calibration schemes and optimization of spectral evaluation windows
While radiative transfer effects have been a known as a major error source in remote sensing measurements of volcanic plumes for 3 decades, a solution has been found that for the first time allows an accurate quantitative analysis of the effects and successfully ascribes previous observations to physical radiative transfer processes. Two radiative transfer effects were identified: the dilution effect and light path extension by multiple scattering in the plume. This concept for the first time allows the correction of radiative transfer effects in passive DOAS measurements, a major step forward considering the magnitude of radiative transfer related errors. Additionally, information on aerosol parameters inside the plume can be obtained. With the help of more sophisticated aerosol scattering models, such information could be used to constrain microphysical aerosol parameters in the near future.
Calibration of the spectrometers is usually made by recording of a low pressure mercury lamp emission spectrum and deriving the spectral dispersion and slit function from the known sharp emission lines. During the project, laboratory experiments have highlighted the sensitivity of the instruments to temperature changes, inducing shift and deformation of the instrumental slit functions, and impacting on the SO2 values retrieved. It was shown that these effects can to some degree be compensated by recording the instrument temperature and using a temperature correction coefficient. However a different approach using the Fraunhofer lines present in the individual measured spectra for the calibration could be successfully demonstrated. It was shown that the information about the slit function and its temperature dependence can be extracted from the data, so that it is not necessary anymore to measure the temperature in the field and store the slit functions of each spectrometer. As also the dispersion of the individual spectrometer can be deduced from the Fraunhofer lines in the measured sky-spectrum, each individual measured spectrum can in principle be internally calibrated, thus eliminating the need for externally derived calibration spectra using a mercury lamp.
An algorithm has been developed with the objective to find the optimal evaluation range of BrO. The method was developed to retrieve possible cross-correlations between different absorbers and uses the approach to systematically run the retrieval for a broad range of wavelength intervals. These methods have been applied to both artificial and measured spectra of volcanic plumes, satellite measurements, and comparisons between measured data and artificial spectra. The methods are not limited to BrO, but are rather applicable to any trace gas with differential absorption structures.
Until May 2011 more then 1.9 million emission measurements has been made (100 million individual spectra). To handle this large, and rapidly growing, dataflow in a safe, efficient and userfriendly way a database based on MySQL has been developed.
The data is stored in six different tables which are connected to ensure referential integrity. Storing and querying the data is done with PHP functions. The system runs both in Linux and Windows environments. A web interface with over 130 different search, display, and sorting options serves as the user interface and allows sophisticated data access. Each user has a separate account and can save his personal search configuration from session to session. Search results are displayed in table form and can be downloaded by the user. All in all, the NOVAC database represents a very powerful tool and is crucial for optimal access and exploitation of the immense dataset collected during the course of the project and its expected continuation.
The NOVAC network
During the course of the project a total of 64 instruments have been installed on 24 volcanoes. Considering the complicated logistics this is a remarkable echievement, only made possible by the strong commitment of all parties involved. This has made the NOVAC scanning mini-DOAS instrument a de-facto standard in automatic volcanic gas monitoring. This is also demonstrated by the fact that NOVAC partners have provided external funding for an additional 8 instruments to complement their existing networks. Finally external projects have funded 12 instruments that have been installed on non-NOVAC volcanoes, Vulcano in Italy, Villarrica and Llama in Chile, Conception in Nicaragua, Eyjafjallajokul on Iceland and Majon on Philippines.
The NOVAC consortium
To achieve the objectives of the project a multi-disciplinary team was formed involving scientists from Europe, Central America, South America, Africa and USA covering atmospheric spectroscopy, volcanology, atmospheric chemistry and satellite validation expertise. In addition 10 institutions responsible for the volcano risk assessment on 19 active volcanoes in 10 countries, besides their scientific contributions also added volcano monitoring and risk assessment experience to the project. This combination of different expertise and experience turned out to be very successfull and can be regarded as one of the most important achievements from the project.
This provides a unique platform not only for continued development and exploitation of the NOVAC instruments and data, but also for further research and development related to volcanic gas emissions and risk assessment as well as a broader cooperation related to volcano research and monitoring.
A study has been done on comparison of
degassing rates with changes in seismic activity of the Nicaraguan volcanoes
San Cristóbal and Masaya. Results from this study show that the volcanoes
The main new insight for INGV from the NOVAC SO2 network was related to high frequency, intraday variations. The NOVAC instruments have been integrated with the pre-existing FLAME network which provides real-time data updates to the 24 hour operations room of INGV Catania, and daily SMS messages to the volcanologist on duty.
Thanks to the mini-DOAS network installed at Popocatépetl volcano, it has been possible to identify the presence of different plumes, moving at different altitudes, originating from different vents of the volcano. Analyses of SO2 emissions and seismicity at Fuego de Colima volcano have revealed that the gas emissions of this volcano have shown increases at certain periods in a similar pattern as the seismicity has; however, the correlation between these two parameters has not been straight-forward.
The dataset produced by NOVAC instruments installed at Nyiragongo has shown a relatively large variability of the fluxes in a day-to-day and even in a, now achievable, minute-to-minute scale. The mean emission rate, however, showed a general pattern of steady state degassing over the study period. A comparison of the gas measurements with ground temperature measurements at the crater rim showed a coincident trend, which is compatible with long residence times of the lava lake at different altitudes, promoting gas emission and heat conduction.
performed a study of comparison between SO2 data obtained by the
NOVAC instruments at Tungurahua and a seismic energy parameter to derive a
probabilistic assessment of eruption scenarios. With the support of NOVAC, an
emergency team of IGEPN was able to conduct a measurement campaign at
Fernandina volcano in the
during the last period worked on the identification of cyclic degassing and
elaboration of conduit magma flow models, highlighting the value of high-time
resolution flux acquisition for open-vent volcanoes. An interpretation of
degassing and seismicity at Santiaguito and Fuego volcanoes (
Volcano risk assessment
All three INGEOMINAS Volcanological Observatories includes in their weekly and monthly reports for municipality majors, department governors, Red Cross office, civil defence organization, indigenous communities and general public, NOVAC gas flux data from Galeras, Nevado del Ruiz and Nevado del Huila volcanoes. During the high activity of Nevado del Huila and Galeras volcanoes in the last year, some comparisons between gas data obtained from OMI, SCIAMACHY and GOME-2 satellite sensors and from ground measurements were carried out by INGEOMINAS.
INSIVUMEH has incorporated into the daily monitoring routine of the institution, the NOVAC instruments as a new tool for measuring gas emissions in two of the four active volcanoes in Guatemala. The NOVAC stations have helped to view in almost real-time, the emission of gases from these volcanoes. The correlation between the emissions of gases with the seismicity has not proved easy. It is expected that in the not too distant future, data from the NOVAC instruments can join the volcanic risk management, which is the primary goal of this project for disaster prevention and the benefit of the population.
Molina Center for Energy and the Environment, in collaboration with UNAM and
Saint Louis University conducted a study of the impacts of SO2
emissions from Popocatépetl Volcano and Tula Industrial Complex on the air
quality of the México City Metropolitan Area (MCMA). Numerical simulations
including emissions from the
promising new technique for the validation of NOVAC ground-based SO2
flux observations with GOME-2 satellite data has been developed in
BIRA has also studied satellite data from OMI and GOME-2 instruments aiming to investigate the possibilities of those satellite datasets for monitoring volcanic gas emissions and to assess the quality of the data compared to the NOVAC ground-based data network. The consistency of the two data sets has been investigated and a study has been performed about the transformation of the SO2-columns into SO2 masses and fluxes with the aim of exploring how these can be compared with the NOVAC fluxes. Comparisons of the satellite’s masses with ground-based fluxes have been done at few stations showing a reasonable agreement for some of them, but also large differences during some time periods with much larger ground-based fluxes. Moreover, additional case studies have been computed in collaboration with Robin Campion from the Free University of Brussels (ULB) comparing the OMI data to an independent data set, coming from a very high resolution satellite (the ASTER instrument), in order to further explore the spatial gradients within an OMI pixel. A routine for the calculation of fluxes from these two instruments has also been developed and applied to several test cases. Comparisons of OMI columns with the ASTER instrument highlighted indeed the importance of the plume altitude estimation to get the best SO2 column, as well as the effect of averaging the spatial inhomogeneities within an OMI pixel. Calculation of fluxes from OMI has also been developed for the comparisons with ASTER, and the application to several case studies showed a relatively good correlation of the values obtained from the two instruments, with OMI fluxes around 20% smaller than those retrieved by ASTER.
BIRA also compared stratospheric NO2 columns evaluated from the NOVAC and BIRA instruments located at Harestua, Southern Norway with the objective to investigate if the NOVAC network of UV spectrometers could measure stratospheric trace gases such as NO2 with a sufficiently high accuracy when operating in zenith mode at twilight, so that NOVAC can be established as a NDACC associated network. Good agreement was found between NOVAC and BIRA UV and visible when the NO2 column is larger than 3.5-4 x 1015 molec/cm2 (this corresponds to the April-September period at 60°N).
also able to measure NO2 in the
NOVAC partners have presented results from the project on numerous international and national conferences. Most important are:
documentary of the NOVAC project was made by EuroNews - Futuris (http://www.euronews.net/sci-tech/futuris/)
entitled “High-tech tools help sniff out volcanic gas”, broadcasted from 16
December 2009. Details about the documentary are available online in http://www.euronews.net/2009/12/16/hi-tech-tools-help-sniff-out-volcanic-gas/.
This documentary was made in connection with installations of two NOVAC
stations at Nevado del Ruiz volcano,
Volcano observatories have progressively incorporated the information gathered by their NOVAC stations into the overall activity reports of the monitored volcanoes, which are distributed regularly to local authorities and general public, and are often accessible via internet. To mention some examples:
generated by the NOVAC stations operated by IGEPN are integrated with other
sources of information (seismicity, geodesy, thermal, infrasound, etc.) to
assess the current eruptive process of Tungurahua and
An interview in an Ecuadorian national TV news program was given by one member of IGEPN about the participation in the NOVAC project in February 2008.
All three INGEOMINAS Volcanological Observatories at Pasto, Popayan and Manizales, included in their weekly and monthly reports for municipality majors, department governors, Red Cross office, civil defense organization, indigenous communities and general public, NOVAC gas flux data from Galeras, Nevado del Ruiz and Nevado del Huila volcanoes (http://intranet.ingeominas.gov.co/popayan/MovilDOAS_VNH).
The NOVAC project in
OVSICORI-UNA included in their weekly and monthly reports for national and international users NOVAC gas flux data from Turrialba volcano. Data generated by the NOVAC stations operated by OVSICORI was integrated with other sources of information (seismicity, geodesy, geochemistry, etc.) to assess the current eruptive process of Turrialba, Poas and Arenal volcanoes. This information is reported regularly to authorities and general public and is freely accessible through our website. Several interviews (newspapers, radio and TV) were given by members of OVSICORI about the participation of this institution in the NOVAC project.
Traditionally, volcanic monitoring has been strongly focused on other parameters than gas flux emissions because of the difficulties involved in continuously acquiring data. The NOVAC project managed to fill this gap in the existing volcano monitoring networks of the project partners, bringing the scientific community one important step closer to the goal of an early volcanic crisis warning system. Considering that over 500 million peoplelive under direct threat of active volcanoes worldwide, the project is silently impacting the lives of all people living in close vicinity of observed volcanoes by supplying an additional data set to assess the state of the volcanoes. Additionally, the measured gases are used to study the impact of volcanic gas emissions on the atmosphere e.g. by the ongoing chemistry in volcanic plumes. Understanding the chemical pathways open possibilities to use additional constituents in volcanic emissions like bromine and chlorine species to gain further information on the volcanoes.
The impact described above can be assigned to a success of the NOVAC project in three fields: Strategic impact including infrastructure and standards, scienitific knowledge and networking between scientists of different fields of study and nationalities.
The great success of the NOVAC project in terms of infrastructure can be understood by the rapid deployment of novel instruments, which for the first time allowed the continuous measurements of gas fluxes at the majority of volcanoes in the project. Since the 1970s, correlation spectrometers (COSPEC) were used to determine gas fluxes of volcanoes by traversing underneath the volcanic plume. This approach is not only time consuming but at times simply impossible at remote volcanoes which plumes cannot be traversed by street. Also budget issues must be addressed, as a COSPEC instrument is relatively costly, with additional costs because every measurement needs at least a driver or a pilot if measurements need to be performed airborne due to insufficient road infrastructure. An alternative instrument has been developed in the previous EU project DORSIVA based on differential optical absorption spectroscopy (DOAS). Within the NOVAC project, this novel instrument was distributed at 24 volcanoes, most of them at observatories previously without or only limited access to remote sensing measurements of volcanic gases. Thus the network implemented the at times novel instrument to become a new quasi standard in ground based volcanic remote sensing. The mostly non-european partners of Latinamerican observatories profited from access and training in instrument and software as well as a novel dataset in volcanic monitoring which they use to improve real time early warning of volcanic activity and exploite scientifically . The European partners with and without a project volcano also profited in the same way but also by advancing in data evaluations and scientifically impacting the community, increasing their competiveness in volcanic remote sensing.
The fact that up to date 20 additional instruments have been funded outside the project and have been installed speaks for itself. New cooperations with Chile (SERNAGEOMIN), Philippines (PHIVOLCS) and Iceland (IMO) observatories make the NOVAC project a de-facto standard in Central- and Southamerica and with possible additional installations on Asian volcanoes on the brink of a global standard in ground based remote sensing of volcanic plumes.
The scientific impact of the project can be assessed by more than 70 contributions to conferences in the course of the project and 35 publications up to date. With the ongoing exploitation of data at the observatories these numbers will further increase due to pending and studies and long term measurements. On the global scale, the scientific impact of the project can be attributed to the creation of the first comprehensive database containing measured gas fluxes from ground based instruments. In order to assess volcanic emissions on the global scale, the scientific data gathered in project need to be homogenized to allow direct comparison. Findings in the course of the project lead to the development of a centralized data processing tool implementing e.g. advanced radiative transfer correction algorithms, mesoscale meteorological modelling and advanced data evaluations. Although re-evaluation of the data is not completed at the end the project, its outcome will allow to approximate global volcanic emissions at previously unknown accuracy. For other platforms, especially satellite measurements, data gathered in the NOVAC project is used for validation purposes.
Next to the scientific goals achieved within this project, one of its impacts is the creation of a network on personal bases because it brought together many scientists from all over the world. Especially for observatories with a tighter travel budget and greater focus on monitoring than scientific research, the project opened possibilities for communication and exchange. Also, many follow up projects can be ascribed to this created network and the achievements in NOVAC, either institution to institution based on national funding or including consortia of several institutions. One example is the FIEL-Volcan project in the framework of a cooperation between the EU and Mexico, involving next to the Mexican partner 5 Europian institutions.
Other projects include the German project Volatiles and fluids in subduction zones: Climate Feedback and Trigger Mechanisms for Natural Disasters, conducted in Chile by IFM-GEOMAR and the pending EU Fp7 application AVERT (Assessment of Volcano Eruption Risk in real-Time) incorporating 17 partners, 8 European ones and 9 from Latinamerica, which includes 12 former NOVAC partners.
As stated above the NOVAC project has been sucessful in extablishing a network comprising 64 NOVAC instruments on 24 volcanoes worldwide, but also in forming a strong dedicated mult-dicsiplinary consortium related to volcanic geophysical research and risk assessment. This provides us with a unique platform not only for continued development and exploitation of the NOVAC instruments and data, but also for further research and development related to volcanic gas emissions and risk assessment as well as a broader cooperation related to volcano research and monitoring. In Figure 3 a schematic picture of some ideas about the future of the NOVAC project is shown.
Figure 3. Schematic outline of the future of NOVAC
In the EU FP5 project DORSIVA (Development of Optical Remote Sensing Instruments for Volcanological Applications, 2002 - 2005), coordinated by Chalmers and with 3 partners in common with the NOVAC project, the instruments and measurement strategies that formed the ground for NOVAC was developed. In the following NOVAC project the focus was to implement these new techniques and demonstrate their usefulness in geophysical research and volcano risk assessment, and thus the consortium was expanded to make it more multi-disciplinary and in specific 10 volcano observatories were included. A very natural next step is now to focus on data exploitation. At the same time we need to consolidate the achievements made so far and take action to sustain and further develop and expand the network. We should also make use of the unique platform of the network for further research and developments related to volcano gas monitoring and risk assessment.
The project has been very successful in establishing the NOVAC instruments as a new standard instrument for volcanic gas monitoring and the NOVAC network as an important platform for research and risk assessment related to volcanic gas emissions. With 64 instruments in operation at 24 volcanoes and several additional partners/volcanoes wishing to join, an important question for the near future is to find a way to secure this achievement with funding to support the most basic network activities. These involves assembling and calibrating new instruments, giving support on hard- and software issues, maintaining the archive and linking it to global data initiatives (GAIA, WOVO, GEO...) and further develop the hard- and software to stay in the frontline of this field of research.These activities are fully in line with several ongoing global initiatives including:
A substantial effort is presently being devoted to the task of finding support for sustaining the network activities.
Volcanic gas emission and composition carry important information about the geophysical and geochemical status of the volcanoes. As have already been shown in this project the access to time-resolved SO2-emission from NOVAC instruments, in combination with other parameters, constitutes a considerable improvement in the toolbox for volcanological research. As the time-record of gas emission is evolving, including periods of baseline monitoring as well as volcanological crisis, it can be expected that the importance of this new parameter in volcanological research will further increase. In 2010 a proposal was submitted to EU for a FP7 project AVERT (Assessment of Volcanic Eruption Risk in real Time). This project aimed at exploiting the use of 4 real-time parameters, seismics, gas emission, displacement and heat, to assess the risk status of a given volcano in real time. This project incorporates 17 partners, 8 European ones and 9 from Latinamerica, which includes 12 former NOVAC partners. The proposal is still pending in July 2011.
Volcanoes constitute an important source of several gases to the atmosphere. Several of these are important in global and local atmospheric chemistry, both because of the magnitude of the emissions and because the volcanoes has a capability to inject these compounds in the free troposphere as well as the stratosphere. Of special importance are the sulphur compounds and the halogens. Thus further work to quantify the contribution of these compounds from volcanoes, as well as the atmospheric chemistry related to these emissions is of importance. It can also be noted that volcanic plumes in many cases constitute extreme conditions (concentrations, temperature, humidity, particles) which can be utilized for critical tests of existing atmospheric chemistry models.
In many cases, as have been shown also in this project, volcanic gas emissions have a severe environmental impact on local and regional as well as global scale. The NOVAC instruments can provide the source strength of SO2 emission from a volcano. In combination with other techniques yielding ratio measurements, (i.e. Solar FTIR spectroscopy that can provide HCl/SO2 and HF/SO2 ratios) and utilizing meteorological dispersion models and atmospheric chemistry models, the impact of several volcanic gases on the environment may be assessed. Also important here is the possibility to use the SO2-emission as a relatively inert tracer gas to validate the meteorological dispersion models used, by downwind transects and tomographic scanning of the plume using mobile and semi-mobile DOAS instruments. An example of such an effort is an ongoing project that Chalmers and OVG are conducting on Nyiragongo volcano, with support from Swedish International Development Agency.
The NOVAC network, constituting 24 volcanoes, 13 volcano observatories and a well collaborating multi-disciplinary team of scientists, is ideally suited for development of new techniques for volcano research and monitoring. With the strong development in opto-electronics, spectrometers and cameras the potential for further remote sensing development related to volcanic gases is large. Among recent such on-going developments can be mentioned SO2-cameras, Imaging DOAS systems and several instruments based on short- and mid-wavelength IR spectroscopy. Volcanic ash show spectroscopic features and work is on-going aiming at qualitative and possibly also quantitative estimates also of ash emissions from volcanoes using optical remote sensing techniques.
Volcano risk assessment
As mentioned above volcanic gas emission and composition is strongly related to the volcanic processes and thus has a large value in volcanic risk assessment. All the NOVAC observatories are already, as shown in this report, to various degrees using the NOVAC data in their risk assessment. With the ongoing implementation of meteorological forcasts in the evaluation algorithms, the accuracy in the real-time SO2 gas emission from the NOVAC instruments will be considerably improved. This, in combination with the experience gained from both baseline and crisis measurements as the time-series evolve, is expected to further increase the value of the NOVAC data for volcano risk assessment.
Climate change modelling
Sulphur dioxide is oxidized to suphate particles which have an impact on the global climate. It is estimated that 5-20 % of the global SO2 emissions has volcanic origin [Halmer et al 2002]. Of these volcanic emissions it is estimated that 95-99 % occurs through passive (quiescent) volcanic degassing [Andres and Kasgnoc, 1998]. The NOVAC data archive contains today more than 1.9 million individual flux measurements from 24 volcanoes, most of them with strong passive degassing. After the ongoing harmonization of the database with respect to the use of meteorological data in the evaluation preocedures, this dataset will be a truly unique source of information on volcanic SO2 emission, which can be expected to improve the confidence in the estimate of sulphate from volcanoes in climate change models.
Satellite monitoring is for several reasons an attractive means of studying volcanic gas emissions. These measurements are however associated with large uncertainties and thus need ground truth validation. In this project already a large step has been taken towards using the NOVAC network for satellite validation of volcanic gas emissions. Neverthless more work is needed, in specific related to the difference in space and time resolution of the methods, radiative transfer issues and plume height considerations. With the on-going improvement of the NOVAC data with respect to radiative transfer modelling and meteorological information, as well as launching of future satellites with improved spatial resolution, the use of the NOVAC data for validation of volcanic gas emission from satellites is expected to be even more important in the future.
Volcanic ash advisory
During 2010 and 2011, with the eruptions of the Icelandic volcanoes Eyjafjallajokul and Grimsvatn, the impact of volcanic ash on aviation in Europe has become evident. Although volcanic ash shows some spectroscopic features, the present software has very limited capacity to derive quantitative ash emission data. Nevertheless the instruments can give important information about plume height as well as determine, from the SO2 emission rate, the status of an ongoing or recently stopped eruption.