ucd forecasting course june2006 the irish meteorological service meteorology forecast applications...
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UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ie
Meteorology Forecast Applications
• Aviation Meteorology• Wave Forecasting• Atmospheric Dispersion• Decision Support Systems
UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ie
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
UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ie
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
UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ie
300hPa Aviation Route Wind Map
UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ie
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
UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ie
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
UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ie
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
UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ie
Mountain Waves
CHARACTERISTICWAVELENGTH
UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ie
Mountain WavesWIND DIRECTION IS PERPENDICULAR TO THE RIDGETHE LEE WAVES ARE PARALLEL TO THE RIDGE
15 kts
UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ie
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
UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ie
Example of Mountain Waves
UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ie
Aviation Significant Weather map
UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ie
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)
UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ie
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
UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ie
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
UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ie
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
UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ie
WAM Model Output
UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ie
Atmospheric Dispersion Modelling Applications
Factors Influencing Dispersion• Wind speed and direction • Stability (mechanical turbulence, buoyancy)• Boundary layer depth
UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ie
Stability Effects
Stable conditions
Unstable conditions
Neutral conditions
UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ie
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
UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ie
Instantaneous point source with isotropic diffusion (puff) and transport with wind speed u away from source
2222
2
2
2/32
)(
),2
exp()2(
),,,(
zytuxr
rQtzyxC
Gaussian Dispersion Models
UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ie
UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ieT. Mikkelson et al.: Airborne Spread: Modelling Accuracy and Predictive Value
UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ie
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)
UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ie
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)
UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ie
Output of FMD model
UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ieG McGRath, RF Hammond, K Towey: GIS Integration and Utilisation of the of Foot and Mouth Dispersion Model
UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ie
Applications: Dispersion from Nuclear Accidents
UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ie
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
UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ie
• 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
UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ie
UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ie
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
UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ie
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
UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ie
NWP Application of Blight rules
UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ie
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.
UCD Forecasting Course June2006
The Irish Meteorological Service www.met.ie
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
UCD Forecasting Course June2006
UCD Forecasting Course June2006