EUMETSAT Volcanic Ash Products - €¦ · SCOPE-NWC, Geneva, 19-22 November 2013 EUMETSAT Volcanic...

SCOPE-NWC, Geneva, 19-22 November 2013

EUMETSAT Volcanic Ash ProductsMarianne König

Slide 1

SCOPE-NWC, Geneva, 19-22 November 2013Slide: 2

SEVIRI Ash Detection: Why does it work?


IR10.8 IR10.8-IR12.0Meteosat-9, 201004015, 14:00 UTCSlide: 3

SEVIRI Ash Detection - Example


SEVIRI Ash Detection

Simple test on brightness temperature difference:

BTD := T10.8 – T12.0 < 0. K

Many false alarms• over clear land at night• over cloud edgesi.e. "simple" detection is faced with many false alarms- Additional channel tests were introduced

Slide: 4


IR10.8-IR12.0 Ash detection Prata v1Meteosat-9, 201004015, 14:00 UTCSlide: 5

SEVIRI Ash Detection: Simple BTD Test


SEVIRI Ash Detection: Less False Alarms

IR10.8-IR12.0 Ash detection v2010Meteosat-9, 201004015, 14:00 UTC


For Detected Ash: Retrieval of Quantitative Information

(following scientific collaboration with Dr. Fred Prata, NILU)

Slide: 7

Background:

Retrieval of effective particle size and optical depth as a function of the BTD difference IR10.8 – IR12.0 (and some other parameters) , from pre-defined lookup-tables (computed using a given spectroscopic dataset).

Combining the size and optical depth gives the total mass loading as the final product.

Note:

“Thick” ash clouds cannot be discriminated from opaque water/ice clouds!


SEVIRI Ash Retrieval - Example


Corresponds to mass loading of

~ 0.4 g/m2

SEVIRI Ash Retrieval - Validation


Corresponds to mass loading of

~ 0.2 g/m2



Additional information on ash cloud thickness was used to turn MSG total mass loadings into concentrations:

Very good agreement found in this case (assumption is that concentration is vertically homogeneous)



0.0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 3.0

Mass loading (g m-2)

0.20.2 0.2

0.2

0.2

0.2

2.0

2.0

Date:2010.05.17 16:15 UT

-3 -2 -1 0 1 2 3 4 5 6 7

52

53

54

55

56

London

Amsterdam

Glasgow

Manchester

Track 1

Track 2

Track 3

Track 4

Track 5

1.6 1.8 2.0 2.2 2.4Longitude (o)

0.0

0.2

0.4

0.6

0.8

Con

cent

ratio

n (m

g m

-3)

SEVIRI

Less good agreement found in this case – but note:

These are very low concentrations!



SEVIRI can derive total mass loading, and with additional information on ash cloud thickness (models, other measurements), this can be turned into mass concentrations.

SEVIRI can thus derive ash concentrations over the entire range of interest

Very thick ash is not detected

Ash below thick clouds is not detected

Reliable detection remains a problem



SEVIRI Volcanic Ash Product

The ash product is available in the following formats:

•netCDF format (with ash effective radius, mass loading, height (incl. quality) per pixel) – 96 times per dayand in case of an event (upon request from the London VAAC):•CAP (Common Alert Protocol) format •Text files•Image (PNG format)Access restricted to National Meteorological Services of the EUMETSAT Member States and the London and Toulouse VAAC

Slide: 14


Word of Caution

No full validation of the operational product done yet – satellite product should always be used in combination with other information!

Example: Combination with “visual” impression from the RGB composites, e.g. the RGB colour composites

IR12.0 – IR10.8IR10.8 - IR8.7 IR10.8

Slide: 15


Eyjafjalla RGB Example

Slide: 16


SEVIRI Ash DetectionFuture Plans

• Reliable ash detection still a problem

• Improvements and tests are ongoing

• Plans to investigate all volcanic eruptions in the Meteosat FOV: science study commissioned with the Met Office in Nov 2013

• Use of two Meteosats (or Meteosat and a LEO satellite) for stereo height assignment – science study to be commissioned end of 2013

• Explore potential of an optimal estimation approach (promising especially in case of ash above lower clouds) – science study commissioned with RAL in Nov 2013 (also baseline for MTG);OE approach: fitting radiances of all channels to find best solution for ash properties, notably also height


Volcanic Ash: OE Approach

One layer

Two layers

Slide: 18


International Collaboration

CGMS resolution at its 40th meeting (2012):

”EUMETSAT, JMA and NOAA are invited to report on their development toward common and consistent volcanic ash products from Meteosat and MTSAT-2 and GOES, respectively.“

JMA and KMA have received a copy of our prototype code (following the Prata algorithm) and will make the product operationally available for MTSAT and COMS, in order to have a globally consistent product

Slide: 19

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