Mt. Etna aerosol optical thickness from MIVIS images

This work focuses on the evaluation of Aerosol Optical Thickness (AOT) in Mt. Etna volcano area starting from the analysis of MIVIS VIS images. MIVIS images and ancillary data (atmospheric profiles, photometric measurements, atmospheric infrared radiances, surface temperatures, ground reflectances, SO2 abundances) were collected during the Sicily '97 campaign. Data elaboration was performed with extensive use of 6S radiative transfer model, determining optical thickness with an inversion algorithm that uses atmospheric vertical profile, ground reflectance data and radiance measured by the first MIVIS spectrometer (channels 1-20; range 0.44-0.82 mu). Ground reflectance is the most problematic parameter for the algorithm. In order to have a low and 'uniform' surface reflectance, only pixels located at an altitude between 2000-3000 in a.s.l. were analysed. At this altitude, AOT is very low during non-eruptive periods: at Torre del Filosofo (2920 in a.s.l.) on June 16th 1997, during one MIVIS flight, AOT at 0.55 mu was 0.19. The uncertainty about ground reflectance produces significant errors on volcanic background AOT, and in some cases the error is up to 100%. The developed algorithm worked well on volcanic plume, allowing us to determine the plume related pixels' AOT. High plume AOT values minimize the problems deriving from reflectance uncertainty. Plume optical thickness shows values included in a range from 0.5 to 1.0. The plume AOT map of Mt. Etna volcano, derived from a MIVIS image of June 16th 1997, is presented

ANALYSIS OF THE SOIL MOISTURE BEHAVIOUR DURING WETTING AND DRYING EPISODES FROM TDR DATA COLLECTED AT PALLANZENO (TOCE VALLEY)

http://www.map.meteoswiss.ch/map-doc/NL15/menziani.pd

Mt. Etna aerosol optical thickness from MIVIS images

This work focuses on the evaluation of Aerosol Optical Thickness (AOT) in Mt. Etna volcano area starting from the analysis of MIVIS VIS images. MIVIS images and ancillary data (atmospheric profiles, photometric measurements, atmospheric infrared radiances, surface temperatures, ground reflectances, SO2 abundances) were collected during the «Sicily '97» campaign. Data elaboration was performed with extensive use of 6S radiative transfer model, determining optical thickness with an inversion algorithm that uses atmospheric vertical profile, ground reflectance data and radiance measured by the first MIVIS spectrometer (channels 1-20; range 0.44-0.82 n). Ground reflectance is the most problematic parameter for the algorithm. In order to have a low and 'uniform' surface reflectance, only pixels located at an altitude between 2000-3000 m a.s.l. were analysed. At this altitude,AOT is very low during non-eruptive periods: at Torre del Filosofo (2920 m a.s.l.) on June 16th 1997, during one MIVIS flight, AOT at 0.55 n was 0.19. The uncertainty about ground reflectance produces significant errors on volcanic background AOT, and in some cases the error is up to 100%. The developed algorithm worked well on volcanic plume, allowing us to determine the plume related pixels'AOT. High plume AOT values minimize the problems deriving from reflectance uncertainty. Plume optical thickness shows values included in a range from 0.5 to 1.0. The plume AOT map of Mt. Etna volcano, derived from a MIVIS image of June 16th 1997, is presented

A new simplified approach for simultaneous retrieval of SO2 and ash content of tropospheric volcanic clouds: an application to the Mt Etna volcano

A new procedure is presented for simultaneous estimation of SO2 and ash abundance in a volcanic plume, using thermal infrared (TIR) MODIS data. Plume altitude and temperature are the only two input parameters required to run the procedure, while surface emissivity, temperature, atmospheric profiles, ash optical properties, and radiative transfer models are not necessary to perform the atmospheric corrections. The procedure gives the most reliable results when the surface under the plume is uniform, for example above the ocean, but still produces fairly good estimates in more challenging and not easily modelled conditions, such as above land or meteorological cloud layers. The developed approach was tested on the Etna volcano. By linearly interpolating the radiances surrounding a detected volcanic plume, the volcanic plume removal (VPR) procedure described here computes the radiances that would have been measured by the sensor in the absence of a plume, and reconstructs a new image without plume. The new image and the original data allow computation of plume transmittance in the TIR-MODIS bands 29, 31, and 32 (8.6, 11.0 and 12.0 \u3bcm) by applying a simplified model consisting of a uniform plume at a fixed altitude and temperature. The transmittances are then refined with a polynomial relationship obtained by means of MODTRAN simulations adapted for the geographical region, ash type, and atmospheric profiles. Bands 31 and 32 are SO2 transparent and, from their transmittances, the effective ash particle radius (Re), and aerosol optical depth at 550 nm (AOD550) are computed. A simple relation between the ash transmittances of bands 31 and 29 is demonstrated and used for SO2 columnar content (cs) estimation. Comparing the results of the VPR procedure with MODTRAN simulations for more than 200 000 different cases, the frequency distribution of the differences shows the following: the Re error is less than \ub10.5 \u3bcm in more than 60% of cases; the AOD550 error is less than \ub10.125 in 80% of cases; the cs error is less than \ub10.5 gm 122 in more than 60% of considered cases. The VPR procedure was applied in two case studies of recent eruptions occurring at the Mt Etna volcano, Italy, and successfully compared with the results obtained from the established SO2 and ash assessments based on look-up tables (LUTs). Assessment of the sensitivity to the plume altitude uncertainty is also made. The VPR procedure is simple, extremely fast, and can be adapted to other ash types and different volcanoes

GPS Zenith Total Delays and precipitable water in comparison with special meteorological observations in Verona (Italy) during MAP-SOP

Continuous meteorological examination of the Pre-Alpine zones in Northern Italy (Po Valley) is important for determination of atmospheric water cycles connected kith floods and rainfalls. During a special meteorological observing period (MAP-SOP). radiosounding and other measurements were made in the site of Verona (Italy), This paper deals with Zenith Total Delay (ZTD) and Precipitable Water (PW) comparisons obtained by GPS, radiosounding and other meteorological measurements. PW and ZTD from ground-based GPS data in comparison with classical techniques (e.g.. WVR, radiosounding,) from recent literature present an accurate tool for use in meteorology applications (e.g., assimilation in Numerical Weather Prediction (NWP) models oil short-range precipitation forecasts). Comparison of such ZTD for MAP-SOP showed a standard deviation of 16.1 mm and PW comparison showed a standard deviation of 2.7 mm, confirming the accuracy of GPS measurements for meteorology applications. In addition, PW data and its time variation are also matched with time series of meteorological situations. Those results indicate that changes in PW values could be connected to changes in air masses, i.e. to passages of both cold and warm fronts. There is also a correlation between precipitation. forthcoming increase and the following decrease of PW. A good agreement between oscillation of PW and precipitation and strong cyclonic activities is found

Detection of meteorological inconsistencies by GPS

GPS observations, distances from satellites to receivers and meteorological conditions in neutral atmosphere are known to obey a constraint, which provides a residual or in other words a quality index. A method is discussed which provides a residual epoch by epoch in near real time. In general, distribution of residuals during several consecutive epochs belonging to the same satellites, allows estimates of a mean and a standard deviation of mean. Under normal meteorological conditions distribution of residuals appears to be consistent with zero mean as expected. However, consecutive residuals sometimes appear to have a mean different from zero by more than three standard deviations of mean. Such signifi cant consecutive epochs provide a warning of existing inconsistencies among GPS observations, distances from satellites to receivers as obtained by orbital information, meteorological conditions above receivers (as obtained by ground measurements or by extrapolation of meteorological analysis). A procedure has been set up which warns about these inconsistencies in near real time

A multi-sensor approach for volcanic ash cloud retrieval and eruption characterization: the 23 November 2013 Etna lava fountain

Volcanic activity is observed worldwide with a variety of ground and space-based remote sensing instruments, each with advantages and drawbacks. No single system can give a comprehensive description of eruptive activity, and so, a multi-sensor approach is required. This work integrates infrared and microwave volcanic ash retrievals obtained from the geostationary Meteosat Second Generation (MSG)-Spinning Enhanced Visible and Infrared Imager (SEVIRI), the polar-orbiting Aqua-MODIS and ground-based weather radar. The expected outcomes are improvements in satellite volcanic ash cloud retrieval (altitude, mass, aerosol optical depth and effective radius), the generation of new satellite products (ash concentration and particle number density in the thermal infrared) and better characterization of volcanic eruptions (plume altitude, total ash mass erupted and particle number density from thermal infrared to microwave). This approach is the core of the multi-platform volcanic ash cloud estimation procedure being developed within the European FP7-APhoRISM project. The Mt. Etna (Sicily, Italy) volcano lava fountaining event of 23 November 2013 was considered as a test case. The results of the integration show the presence of two volcanic cloud layers at different altitudes. The improvement of the volcanic ash cloud altitude leads to a mean difference between the SEVIRI ash mass estimations, before and after the integration, of about the 30%. Moreover, the percentage of the airborne “fine” ash retrieved from the satellite is estimated to be about 1%–2% of the total ash emitted during the eruption. Finally, all of the estimated parameters (volcanic ash cloud altitude, thickness and total mass) were also validated with ground-based visible camera measurements, HYSPLIT forward trajectories, Infrared Atmospheric Sounding Interferometer (IASI) satellite data and tephra deposits

Analisi spettrale di dati MIVIS: un caso di studio sull'isola di Vulcano

Si descrive un caso di studio mirato alla valutazione delle potenzialità del MIVIS in applicazioni di caratterizzazione della superficie. I1 data-set è costituito dai canali del Visibile e Infrarosso riflesso di un'immagine del cono vulcanico della Fossa (isola di Vulcano), trasformata in riflettanze superficiali. Lo studio comprende: una valutazione della qualità dei dati, l'applicazione di tecniche di classificazione spettrale, il confronto degli spettri MIVIS di alcune unità classificate con spettri misurati in laboratorio. I risultati mostrano come sia stato possibile individuare diversi tipi di depositi e alterazioni ed estrarre informazioni chimico-mineralogiche basandosi sull'identificazione delle bande di assorbimento, seppure con alcune limitazioni

CORREZIONI ATMOSFERICHE DEI DATI MIVIS

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TECNICHE DI INVERSIONE PER LA STIMA DELL"EMISSIONE DI ANIDRIDE SOLFOROSA DELL"ETNA DALLE IMMAGINI TELERILEVATE DAL MIVIS NELL"INFRAROSSO TERMICO

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