Remote sensing of volcanic ash plumes using groundbased. weather radars

Transcription

1 Remote sensing of volcanic ash plumes using groundbased microwave weather radars Frank S. Marzano 1, E. Picciotti, G. Vulpiani and M. Montopoli 1 ept. Information Eng., Sapienza University of Rome, Italy CETEMPS Center of Excellence, Univ. of L Aquila, Italy 3 Italian Civil Protection ept. (PC), Rome, Italy

2 MOTIVATION AN OUTLINE Monitoring of volcanic ash plumes Inference of Strombolian and sub-plinian eruption processes Air trafic control safety and civil protection alarming Remote sensing techinques of volcanic eruptions Sub-glacial eruption on Nov. 4 Radar data from Iceland Microwave radar reflectivity model Microphysical model Radar backscattering Quantitative radar retrieval of valcanic ash clouds Methodology Application to Grímsvötn volcanic eruption Open issues Conclusions

3 REMOTE SENSING OF VOLCANIC ERUPTIONS Geostationary and Low-Earth-Orbit satellites Eruption of Grimsvötn volcano (Iceland) on Nov., 4 from LEO MOIS radiometer Other ground-based remote sensing tools GPS receivers at L band Wind profiler system at L band Lidar Anything else??????????... F.S. Marzano Ash cloud radar retrieval 3

4 GRIMSVOTN ERUPTION ON NOV., 4 Eruption observed by the Keflavik C-band weather radar at about km far from Reykjavik at about 6 km from the volcano vent. F.S. Marzano Ash cloud radar retrieval 4

5 RAAR BACKSCATTERING MOEL P RH ( r) ln() 3 G 3 P t Z H r ( r) K L H ( r) constants Radar system Volcanic target Under Mie scattering regime, the radar reflectivty factor Z H is: Z H P t 5 4 K 1 bh ( ) N a ( ) d The expression of Z H, in db (log (Z H )), is usually visualized on radar system screens. P RH dbz Log Z H 5

6 range (km) CONICAL SCAN (PPI) OF RAAR REFLECTIVITY PPI image at: h. 4: GMT. Some PPI Radar image products: of the Grimsvotn volcano eruption: ore 3: 3:5 :5 1:5 3: 1: 3:3 :35 :5 4: 5:5 6:5 PPI (Plan Position Indicator): z y 8 dbz x range (Km) F.S. Marzano Ash cloud radar retrieval 6 85

7 altezza (km) SECTOR SCAN (RHI) OF RAAR REFLECTIVITY Another RHI image useful of Radar the Grimsvotn product eruption: ore 3: 3:5 :5 1:5 3: 1: 3:3 :35 :5 4: 5:5 6:5 RHI image at 4: GMT. RHI (Range Height Indicator) z Φ r θ.9.5 y Grimsvotn Volcano x range (Km) dbz F.S. Marzano Ash cloud radar retrieval 7

8 range (km) VOLCANIC CLOU RAAR REMOTE SENSING dbz range (Km) RAAR volume measurement Ash concentration and ash fallout 8

9 range (km) PHYSICAL RAAR REMOTE SENSING Forward physicalelectromagnetic model dbz range (Km) Volcaninc eruptive cloud Synthetic Reflectivity Inverse problem methodology 9

10 MOTIVATION AN OUTLINE Monitoring of volcanic ash plumes Inference of Plinian and sub-plinian eruption processes Air trafic control safety and civil protection alarming Remote sensing techinques of volcanic eruptions Sub-glacial eruption on Nov. 4 Radar data from Iceland Microwave radar reflectivity model Microphysical model Radar backscattering Quantitative radar retrieval of valcanic ash clouds Methodology Application to Grímsvötn volcanic eruption Open issues Conclusions

11 ASH PARTICLE SIZES THEPRA: Materials of all types and sizes, erupting from a crater or volcanic vent as a result of an intensive magma and rock fragmentation. This term describes volcanic ash and coarser detritus that are projected through the air. Tephra is chiefly characterized by clast size, shape, vesicularity, and composition. TEPRHA Particle type Particle size Ash Fine ash (FA) Coarse ash (CA) Less than 7 mm From 7 mm to mm istance from the volcano vent Hundred to thousand kilometers Few to hundred kilometers Residence time in the atmosphere ay to month ay Lapilli Small lapilli (SL) Large lapilli (LL) From mm to 3 mm From 3 mm to 64 mm Few to ten kilometers Few to ten kilometers Few seconds Seconds to minutes Block Blocks and bombs (BB) Greater than 64 mm Few kilometers Seconds to minutes F.S. Marzano Ash cloud radar retrieval 11

12 F.S. Marzano Ash cloud radar retrieval diametro Na() (m -3 mm -1 ) m n L n Sphere-particle size distribution (Gamma or Weibull): Ash mass concentration: Rayleigh radar reflectivity (Mie at X band and above): ASH PARTICLE MICROPHYSICS m L n n n n a e N N ) ( 3 6 ) ( ) ( 1 m d N m C a a a a ) ( ) ( ) ( m d N d N K Z a a bh H

13 NUMERICAL MOEL ATHAM (UCambridge) ATHAM (Active Tracer High Resolution Atmospheric Model) : Plume model designed to simulate the dispersal of an eruption column resulting from an explosive volcanic event Authors: H.F. Graf, M. Herzog, C. Textor et al. (1998-) Microphysical formulation based on the microphysical concept for usual atmospheric clouds Used to investigate processes leading to particle aggregation Used to study impact of aggregates on radar reflectivity Ash q ax 4 CLASSES: Hydrometeors q x Aggregates q px =q ax +q x Large cold T<T Large warm T>T Small cold T<T Small warm T>T 13

14 Altitude (km) Altitude (km) ATHAM SIMULATION OF RAAR REFLECTIVITY EXP NO AGG - initialization with particle modes at mm and mm minutes range (km) dbz minutes range (km) dbz minutes range (km) dbz minutes range (km) dbz EXP1(- mm) minutes range (km) dbz minutes range (km) dbz minutes range (km) dbz minutes range (km) dbz Marzano F.S., S. Marchiotto, C. Textor and. Schneider, Model-based Weather Radar Remote Sensing of Explosive Volcanic Ash Eruption, IEEE Trans. Geosci. Rem. Sensing, ISSN: , vol. 48, pp ,. 14

15 MOTIVATION AN OUTLINE Monitoring of volcanic ash plumes Inference of Plinian and sub-plinian eruption processes Air trafic control safety and civil protection alarming Remote sensing techinques of volcanic eruptions Sub-glacial eruption on Nov. 4 Radar data from Iceland Microwave radar reflectivity model Microphysical model Radar backscattering Quantitative radar retrieval of valcanic ash clouds Methodology Application to Grímsvötn volcanic eruption Open issues Conclusions 15

16 CLOU ASH RETRIEVAL METHOOLOGY Z Hm Radar specs Cloud Ash etection/classification Cloud Ash Retrieval Ash Micro Physical Radar Model C a, R a Ash data F.S. Marzano Ash cloud radar retrieval 16

17 log(c p )=loga+blog(z h ) log(c p )=loga+blog(z h ) CLASSIFICATION AN RETRIEVAL Volcanic cloud retrieval 1. Maximum A Posteriori classification. Regression estimation: cˆ Power-law model Mode c Z Hm Z m Hc 6 Z Hc ln( Small warm class / Aggregates ) ln 6 Z Hc ln p( c) Small cold class / Aggregates ˆ ( c ) p C a Z Hm b Simulation C-Z Z h [dbz] - Simulation C-Z Z h [dbz] Marzano F.S., S. Barbieri, G. Vulpiani and W.I. Rose, Volcanic cloud retrieval by ground-based microwave weather radar, IEEE Trans. Geosci. Rem. Sens., ISSN: , vol. 44, n.11, pp ,

18 segnale (dbz) RAAR RETRIEVAL SENSITIVITY Ash plume range model Gaussian shapes Minimum etectable reflectivity (MZ) Peak at 6 km Weather Radar specifications C band:5.6 GHz TX peak power: 5 kw Range: - km Range resolution: 3 m Antenna max gain: 45 dbi Minimum detectable power (MS): -113 dbm MZ ( r) ln() 5 19 G segnale effettivamente rilevato (blu) ad 8 di Azimuth e.5 di elevazione range (Km) 3 3 K P t r MZ MS Effect of range and range averaging At distances > 5 km, only coarse ash particles (> 5 microns) can be detecetd by ground microwave C-X-band radars! F.S. Marzano Ash cloud radar retrieval 18

19 C-BAN RAAR: REFLECTIVITY ATA F.S. Marzano Ash cloud radar retrieval 19

20 C-BAN RAAR: ASH CLASSES F.S. Marzano Ash cloud radar retrieval

21 C-BAN RAAR: ASH CONCENTRATION F.S. Marzano Ash cloud radar retrieval 1

22 C-BAN RAAR: GROUN VALIATION on 4 Marzano F.S., M. Lamantea, M. Montopoli, B. Oddsson and M.T. Gudmundsson, Validating sub-glacial volcanic eruption using ground-based C-band radar imagery, IEEE Trans. Geosci. Rem. Sens., ISSN: , vol. 5, pp , 1. F.S. Marzano Ash cloud radar retrieval

23 MOTIVATION AN OUTLINE Monitoring of volcanic ash plumes Inference of Plinian and sub-plinian eruption processes Air trafic control safety and civil protection alarming Remote sensing techinques of volcanic eruptions Sub-glacial eruption on Nov. 4 Radar data from Iceland Microwave radar reflectivity model Microphysical model Radar backscattering Quantitative radar retrieval of valcanic ash clouds Methodology Application to Grímsvötn volcanic eruption Open issues Conclusions 3

24 ISSUE1: ASH-WATER PARTICLE AGGREGATION Mixture of ash and cloud water/ice particles Fine ash (.1 mm), Coarse ash (.1 mm), Lapilli (1 mm) Mixture with cloud droplets (.1 mm) and ice (.1 mm) For fine and coarse ashes within a fractional combination of 5%, the expected reflectivity reduction is generally less than 1 db for coexistence and less than 5 db for mixture with respect to the measured values. Note that the received power will also depend that the dielectric factor K =.18 for ice and K =.93 for water (causing a difference of about 7.1 db) 4

25 ISSUE: MICROWAVE RAAR FREQUENCY Ash backscattering and absorption X-band more sensitive than C- band S-band ( -4 ) Ka-band wave is more attenuated than X-band ( - ) Higher freq., as W band (9 GHz), to be avoided X-band system aspects With respect to C- and S- band systems AVANTAGES Compact system Portable RX/TX behind antenna irective antenna More sensitive to ash ISAVANTAGES Less TX power Possible attenuation Lower oppler winds Higher RX noise F.S. Marzano Ash cloud radar retrieval 5

26 ISSUE4: X-BAN RAAR POLARIMETRY ual-polarized detection of ash category Fine ash with prolate, oblate, tumbling orientation Multiple observations Co-polar reflectivity Zhh ifferential reflectivity Zdr ifferential phase Kdp Co-polar correlation hv epolarization ratio Ldr Advantages Classification ata quality Clutter removal Marzano F.S., E. Picciotti, G. Vulpiani and M. Montopoli, Synthetic Signatures of Volcanic Ash Cloud Particles from X- band ual-polarization Radar, IEEE Trans. Geosci. Rem. F.S. Marzano Ash cloud radar retrieval Sens., ISSN: , vol. 5, pp , 1 6

27 Height [km] [km] Height [km] Height [km] Height [km] Lat [deg] ISSUE4: X-BAN POL from GRIMSVOTN 11 ZHH May nd 11 7:1 UTC ZR KP HV Lon [deg] Lon [deg] Lon [deg] Lon [deg] Azim avg.: 1. [deg] ZHH [dbz] ; 7:1 UTC istance [km] istance [km] istance [km] 96 1 istance [km] Azim avg.: 1. [deg] 4 3 ZR [db] at 7:1 UTC istance [km] KP [deg/km] at 7:1 UTC Azim avg.: 1. [deg] istance [km] Azim avg.: 1. [deg] RHOHV [ ] at 7:1 UTC istance [km] ZHH ZR KP HV 7

28 CONCLUSIONS Ash cloud radar remote sensing: possible! Physically-based retrieval scheme Retrieval sensitivity Good sensitivity for coarse ash and lapilli at S and C band Fine ash detectable only if increased sensitivity: Analysis of volcanic plumes in Iceland, Italy, Alaska Final issues Application of the VARR scheme Operational weather radar close to active volcanoes Ground validation of ash radar retrievals Sensor ynergy and development Exploitation of oppler polarimetric capability Synergy with satellite and other ground sensors F.S. Marzano, E. Picciotti, M. Montopoli, G. Vulpiani, INSIE VOLCANIC CLOUS: Remote Sensing of Ash Plumes Using Microwave Weather Radars, Bull. American Met. Society (BAMS), p. 1567, October 13 (free access on line). F.S. Marzano Ash cloud radar retrieval 8