# Presentation: 326912

## Assessing Volcanic Ash Hazard by Using the CALPUFF System 

- S.Barsotti*, A.Neri*, J.Scire**
- *Istituto Nazionale di Geofisica e Vulcanologia,
- Centro per la Modellistica Fisica e Pericolosità dei Processi Vulcanici, Pisa, Italy
- **Earth Tech, Inc., Concord, Massachusetts, USA

**The 2nd International Conference on Volcanic Ash and Aviation Safety**June 21-24, 2004Alexandria, Virginia (USA)

## Outline

- Motivation and objective
- The CALPUFF modeling system structure (geophysical pre-processors, meteo diagnostic code CALMET and the dispersion code CALPUFF)
- Results of a preliminary application of CALPUFF to the July 2001 Mt.Etna’s eruption
- Conclusive remarks

## Motivation
During the last eruptions of Mt.Etna (2001 and 2002) the relatively minor explosive activity renewed the interest in the volcanic risk due to the presence of ash in the atmosphere

**Motivation**
- During the last eruptions of Mt.Etna (2001 and 2002) the relatively minor explosive activity renewed the interest in the volcanic risk due to the presence of ash in the atmosphere

**Objective**

_***To develope a predictive modeling tool***_ - able to forecast the movement and properties of an ash cloud in the atmosphere - to be used during a volcanic crisis

## Fig1: Picture of the city of Catania taken from the seaport during the 2001 eruption 

- Fig1: Picture of the city of Catania taken from the seaport during the 2001 eruption

- Fig3: The main air routes  that connect the Fontanarossa and Sigonella airports with national and international destinations (figure provided by Cap.G.A.r.s. Geof. Franco Colombo)

- Fig2: Photo of the ash cloud as seen from the airport of Catania

- Photo by Franco Crisafi

## CALPUFF Modeling System (Scire et al. 2000)

- CALPUFF Modeling System (Scire et al. 2000)

- Developed in the 90’s by Sigma Research Corporation (now part of the Earth Tech, Inc.) as air quality modeling system
- Proposed by U.S. EPA as a *Guideline *model for regulatory applications

**Terrain elevation data**
- (TERREL)

**Landuse data**
- (CTGPROC)

**Meteo data**
- (MM5 or CALETA)

**CALMET**(diagnostic meteo processor)

**Emission** **data**

**CALPUFF** (Lagrangian dispersion code)

- System Flowchart

## CALMET (diagnostic meteo processor) 

**Input data**:  P, Elevation m.s.l, T, wind direction, wind speed, vertical velocity, relative humidity at different levels and every *three *hours
**Output data**: U, V, W wind components, T and all the micrometeorological variables on a specified grid and *every *hour

***HOW DOES IT WORK?***

**Initial guess field**

- Terrain effects

**Step 1 wind field**

- Objective analysis

**Step 2 wind field**

- Prognostic code output

- Refinement by interpolation
- Correction by orography
- Divergence minimization

- Weighted observed data
- Divergence minimization

## CALPUFF

- It is a _*Lagrangian dispersion model*_ that treats the emitted material as a sequence of packets, or *puffs,* containing discrete quantity of particles. Each puff is then described with a _*Gaussian distribution and subjected to advection, diffusion and gravity*_
- Selected a set of receptors, gridded or discrete, in the domain investigated, CALPUFF computes _*hourly the concentration and flux of particles*_ at these points
- Main features:

- Different granulometric classes
- Time dependent emission and meteo data
- Dry and wet deposition
- Buoyant area source
- Domain from tens of ms to hundreds of kms
- from the source

## The basic equation

- is the *material mass* in the puff and is a function of the sampling interval. Its variations are due to _removal_ and to chemical processes.

- is the *vertical term* of the Gaussian distribution. It takes account for the vertical diffusion due to the _mixing lid and plume buoyancy_ and is a function of the distance from the source.

- The sigmas are the horizontal Gaussian *dispersion coefficients* and are functions of the sampling interval. They include effects of _atmospheric turbulence, plume buoyancy and lateral (crosswind) scale of an area-source. _

## Turbulence and deposition modeling

- The _atmospheric turbulence_ coefficients can be calculated on different meteo data:
-  **measured values** of turbulence,
**micrometeorological variables** calculated by CALMET,
-  PG dispersion coefficients calculated on the values of the **stability classes** provided by CALMET.

- The _dry deposition_ model is based on an approach which expresses the deposition velocity as the inverse of a sum of “**resistances**” (opposing to the transport through the atmosphere) plus **gravitational settling** terms (using Stokes equation).

## Area Source Plume Rise

- One of the main features of CALPUFF is the capability of treating the case of **very hot area source**. Using a file containing all the information related to the source, the code solves the three fundamental equations of conservation of mass, momentum and energy.

- The equation system is (Weil 1988):

## A First Volcanological Application(Etna July 2001)

**Simulation parameters**
-  *Computational domain*
- Cell numbers 100X100
- Δgrid=2km
- Grid origin  xUTM(km) = 411.021
-                      yUTM(km) = 4095.136
-  *Period*
- 20-24 July 2001

*Geo and meteo input data*
- GTOPO Global data ~900m res.
- USGS Global land-use data set ~900m res.
- ECMWF meteo data 2.5*2.5 degree res.
- NOAA meteo data 2.5*2.5 degree res.

## Source data

- For the **rising plume**:
- Exit velocity             25-75 m/sec
- Exit temperature       100-300 °C
- Initial radius                25-75 m
- Ground elevation         2550 m
- Emission height  a.g.   100 m

- For the **puff description**:
- Particles diameter    3-64 μm
- Particles density      2500 kg/m^3
- Emission rate          10^2-10^3 kg/sec

- Photo by Boris Bencke

- Photo by Tom Pfeiffer

- Coltelli and Macedonio, GNV Ass. 2001

## General features of ash dispersal

- Ash concentration on air (Kg/m^3)

## Temporal Evolution of the Emission Point

- The code computes the *effective height* and the *downwind** **distance* from the vent where a *puff *description of the emission begins

## Ash Cloud Concentration (1)Vertical distribution of ash concentration along the dispersal axis

- Temporal evolution of the vertical concentration at _25 km from the vent_

- Vertical distribution of particle concentration at a _fixed time_ and different distances from the vent

## The sensitivity to meteo data

- Image acquired by SeaStar Satellite at 1100UTC on 20July 2001

- ECMWF

- NOAA

- Vertical distribution of _wind direction_

- Concentration (kg/m^3) on air summed on different vertical levels

## The sensitivity to meteo data

- ECMWF

- Vertical distribution of _wind direction_

- NOAA

- Concentration (kg/m^3) on air summed on different vertical levels

- Image acquired by SeaStar Satellite at 1129UTC on 22July 2001

## Conclusive Remarks

- CALPUFF is a _promising system_ for real-time forecast of volcanic ash dispersal produced by weak explosive activity
- High _resolution meteo data_ and accurate _description of plume rise_ are critical for a correct modeling of plume dispersal
- Definition of well-known _test cases_ is fundamental for the validation of the code with observed data
- _Real-time measurements_ of the eruption plume and dispersal are crucial in order to obtain reliable forecasts

## CALPUFF Loop Structure

- Begin **HOUR**** **Loop

- End **HOUR**** **Loop

- Begin **PUFF**** **Loop

- End **PUFF**** **Loop

- Begin **SAMPLING**** **Loop

- End **SAMPLING**** **Loop

- Puff initialization

- Wind initialization for
- the advection

- Computes concentration at
- the **receptors**

## Ash Cloud Concentration (2) Horizontal distribution of concentration along the dispersal axis

- Cumulative concentration on all vertical levels

- Ash concentration at 3500m above sea level

## The sensitivity to source data

- To investigate the effects of the variation of emission parameters on the rising plume and to take account of the error affects the measures, we have assumed exit velocity and temperature to be affected by an 50% error

- Variation on exit velocity

- Variation on exit temperature