Download ppt - UCD Forecasting Course June2006 The Irish Meteorological Service Meteorology Forecast Applications Aviation Meteorology Wave Forecasting Atmospheric

UCD Forecasting Course June2006

The Irish Meteorological Service www.met.ie

Meteorology Forecast Applications

• Aviation Meteorology• Wave Forecasting• Atmospheric Dispersion• Decision Support Systems



Aviation Meteorology

Weather Conditions Important Element in Safety

Take Off/landing and Enroute Weather

Cloud Type - Amount and Height of Ceiling

Wind Speed and Direction

Terminal Forecasts (Tafs), Metars

Wind Shear, Clear Air Turbulence (CAT), Thunderstorms, Visibility, Fog, Icing, Cumulonimbus (Cb), Mountain Waves



Turbulence

• Wind shear – usually in vicinity of jet stream• Horizontal > 30kt deg-1 latitude (60nm)

• Vertical > 09kt 300m -1

• Near thermal gradients of >2.5°C deg-1 latitude • In anticyclonic curvature with winds of >130kt• Upper air troughs where wind shift > 90 °• In cols where wind direction can reverse rapidly• Topography – CAT reported twice as often over land

than at sea



300hPa Aviation Route Wind Map



Icing

• Occurs in clouds when temperature <0 °C, supercooled droplets build up on an airplane and freeze.

• Supercooled Liquid Water (SLW) can exist in clouds at -15 °C, below this ice crystals grow rapidly

• Occurs in deep convection scenariios (e.g. Cb)• Occurs where there are strong thermal gradients i.e. near

upper air fronts



Mountain Waves

1. In very stable conditions with light winds, the air will tend to flow around a hill

2. In neutral conditions with strong winds, a turbulent wake develops behind the hill



Mountain Waves

In stable conditions perturbed parcels oscillate at a characteristic frequency

For certain windspeeds the air has a natural wavelength

When that wavelength matches the height of the hill, a natural resonance occurs



Mountain Waves

CHARACTERISTICWAVELENGTH



Mountain WavesWIND DIRECTION IS PERPENDICULAR TO THE RIDGETHE LEE WAVES ARE PARALLEL TO THE RIDGE

15 kts



Mountain Waves

Conditions:• Orography

• A stable layer aloft

• Wind speed of >15 knots

• Uniform wind direction to the top of the stable layer

Lee Wave Clouds



Example of Mountain Waves



Aviation Significant Weather map



Marine Meteorology – Waves• A wave starts when the wind interacts with the water

surface and created a disturbance.• As the wind continues forcing the wave grows and

begins to move. • Eventually the wave moves outside of the area of initial

wind forcing and propagates across the water. (Swell)



Waves – Limiting FactorsThere are three basic components to wave growth: • Wind speed • Fetch or fetch length • Duration Fetch is the distance over which the wind blows from a

constant direction and at a constant speed. Duration is how long the wind affects that distance.

The Wave Analysis and Forecasting Nomogram quantitatively illustrates the relationship between wind speed, wind duration, fetch length, and wave growth



The Wave Analysis and Forecasting Nomogram

• Wind speed is charted on the y-axis and fetch length on the x-axis. Contour lines represent wind duration, wave height and wave period



The Wave Model - WAM

• The nature of waves is chaotic, Numerical methods allow a better approach based on the energy spectrum

• The sea surface may be represented as a Fourier series of superimposed waves with different wave lengths and statistically random phases



WAM Model Output



Atmospheric Dispersion Modelling Applications

Factors Influencing Dispersion• Wind speed and direction • Stability (mechanical turbulence, buoyancy)• Boundary layer depth



Stability Effects

Stable conditions

Unstable conditions

Neutral conditions



Atmospheric Dispersion Models

NWP Models provide wind fields etc.

Lagrangian Particle Dispersion Models• Individual particles are tracked

(Wind and turbulence needed from NWP• Large quantity of release particles to get concentration

Gaussian Dispersion Models• Simple statistical based calculations of concentration• Release and sample times large compared to travel time (approximately steady

state)• Horizontal and vertical dispersion is Gaussian distributed• Wind speed and direction constant with height (layer approach



Instantaneous point source with isotropic diffusion (puff) and transport with wind speed u away from source

2222

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2/32

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exp()2(

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zytuxr

rQtzyxC

Gaussian Dispersion Models




The Irish Meteorological Service www.met.ieT. Mikkelson et al.: Airborne Spread: Modelling Accuracy and Predictive Value



Applications: Airborne Spread of Foot and Mouth Virus

Depends on:• Virus emission (pigs have highest 106 , sheep and cattle

lowest 103 TICP50 per min - bovine thyroid tissue culture infections units)

• Virus survival (RH>60% several hours)• Virus dispersion• Virus deposition (direct contact through inhalation:

cattle large intake, sheep and pigs small intake)



Foot and Mouth Dispersion uses NWP data:

• U10, RH and rain from the nearest grid point x~15km

• Direct predictions of surface heat flux, friction velocity, stability and boundary layer depth (turbulent flux profiles)



Output of FMD model


The Irish Meteorological Service www.met.ieG McGRath, RF Hammond, K Towey: GIS Integration and Utilisation of the of Foot and Mouth Dispersion Model



Applications: Dispersion from Nuclear Accidents



RPII (Radio Protection Institute of Ireland) run a dispersion model with input data from Met Éireann:

• Hourly NWP output of fields at 20 levels of • 3 D wind speed and direction, geopotential height

• 2 D boundary layer height, rainfall

• Surface description:lat/lon, roughness length, land fraction

Applications: Rimpuff Dispersion Model



• ARGOS (Accident Reporting Guidelines and Operational Systems interface)

• Developed by DEMA (Danish Emergency Management Agency)

• Used in Denmark, Norway, Canada, Ireland• Plume trajectory model (<200km) RIMPUFF

(RIso Mesoscale PUFF)• time integrated concentration of 63 radio nuclides





Decision Support Systems

• Need Conceptual Model to describe system which is dependent on weather parameters

• Input of relevant weather parameters• Interpretation of result• Examples Potato Blight, Soil Moisture Deficits,

Fire Weather Index, Road Ice Prediction



Potato Blight (May-September)

Warm Humid weather favours the spread of fungal diseases:

Conceptual Model

Irish Blight Rules require: T >10 ºC and RH >90 %

for 12 hours if wet and 16 hours if dry, for development of blight.

……but farmers must spray before the onsest of blight conditions

Warning are issued 2 days ahead of spell if possible



NWP Application of Blight rules



Road Ice Prediction

• Over 50 sites located around the country

• Weather data and NWP ouptut fed into Icebreak prediction model

• Graphs and maps produced of forecast road surface temperatures and road state.



Cooling at road surfaceNon Radiation Energy Balance

•Latent Heat• Evaporation(loss)• Condensation (gain)

• Convection (Sensible heat)•Loss by day, gain by night

• Traffic Flow• Conduction from groundThese last two parameters are measurable and will be different for each site.

Bridges are prone to low Temperatures

Constant Physical parameters for each roadside station are used in the model and are contained in Local Information Files (LIF)

Input into Icebreak ModelHirlam Model is run every 6 hours.

• Model grid size 15X15km.

• Direct output in 3 hour steps is used as a first guess.

• Data manipulated by forecaster

• No manual intervention if expected

Troad > 5° Celsius.

Icebreak Output•Site specific graphical forecasts

•Short and long range text forecasts

•Thermal Map Forecasts

