GI: a primer
31
GI: a primer Application of GI to weather forecasting 11 th February 2005
description
GI: a primer. Application of GI to weather forecasting. 11 th February 2005. TOPICS. Operational needs of weather forecasts Operational constraints Old technology and GI Remote sensing for weather Modelling The future. Operational Needs. Rapidly changing (dynamic) - PowerPoint PPT Presentation
Transcript of GI: a primer
GI: a primerApplication of GI to
weather forecasting11th February 2005
TOPICSOperational needs of weather forecastsOperational constraintsOld technology and GIRemote sensing for weatherModelling
The future
Operational NeedsRapidly changing (dynamic)Regular instrumental updates (global)Dense coverage of stationsPoint to surface conversion (interpolate)Rapid dissemination to publicGlobal, regional and local scales
ABOVE: moored buoyLEFT: drifting buoy
LEFT:radiosonde
LEFT: launchof radiosondeballoon
RIGHT:sounding rocket
Operational ConstraintsLocations of stations are often sparseNo regular updates from inhospitable places (data retrieved from tapes)Large gaps in data – both spatial and temporalCollection of meteorological data requires access to Global Telecommunication System (GTS)
Global Station Coverage
Old technology and GIHistorically, meteorological records have satisfied the basic requirements of geographical dataEach station has a specific latitude, longitude and height above mean sea-levelFor each station, the synoptic hourly observations are the attribute data
Old technology and GIAll climate records possess an x,y,z coordinate referenceThe problem has always been the estimation of gaps between existing station locationsSpatial analysis makes use of techniques such as interpolation and kriging to generate surfaces
Old Technology and GIX Y Z
1 1 301 4 272 3 223 1 194 4 4
Example:4 stations with temperature readings (left)
Typically, we have to generate a continuous surface from these isolated points.
1 2 3 4X
1
2
3
4Y
4 .00
6.00
8.00
10.00
12.00
14.00
16.00
18.00
20.00
22.00
24.00
26.00
28.00
30.00
Individual Points
4.00
6.00
8.00
10.00
12.00
14.00
16.00
18.00
20.00
22.00
24.00
26.00
28.00
30.00
InterpolatedNearest Neighbour
1 2 3 4X
1
2
3
4
Y
4.00
6.00
8.00
10.00
12.00
14.00
16.00
18.00
20.00
22.00
24.00
26.00
28.00
30.00
Kriging applied
1 2 3 4X
1
2
3
4
Y
Remote Sensing and Weather
Geostationary satellites such as Meteosat provide high frequency data updates for a target region (15-30mins)Spectral channels on board the satellites yield useful information about position, direction and velocity of weather systems
Infraredradiant energy
Visiblealbedo
Water vapourTropos. WaterCloud motion
AVHRR
29/11/01
13:39
< VIS
IR >
Meteosat: 29/11/2001 at 12:00z
TOPEX-POSEIDONFor much of our oceans, temperature is not measured directly – but by proxyWarmer water expands – if surrounded by cooler water it rises. Its height is therefore an indication of its temperature
TOPEX-POSEIDONTOPEX is an altimetric satelliteReturn time of pulses of energy sent by TOPEX to the ocean surface are measuredDistance between satellite and water surface can be accurately measuredTOPEX used to measure El Niño
ModellingBecause of serious gaps in station observations, satellite data supplements ground station, ship, buoy and ascent readingsALL data, once collected, is used to initialise climate prediction modelsSmooth gridded interpolated surfaces of observed data are called reanalysis
ModellingReanalysis fields are generated for different pressure levels…from surface to 31 or so levels up to the top of the atmosphere
ModellingAll spatially referenced meteorological data are processed at the Met. Office and fed into global climate models via the COSMOS systemThe current Unified Model (HadAM3) performs weather (short-range) and climate (long-range) forecasts
ModellingWeather and climate predictions generated by models are essentially thematic maps showing specific variables (rain, temperature, cloud etc.)All forecast field data are spatially referenced and can be easily fed into additional models (flood defence, agriculture, hydrology etc.)
The futureMeteosat Second Generation is a new European weather satellite capable of observing Europe and Africa every 15 minutesHas more channels than the older MeteosatCan help resolve cloud physics parameters
The futureJason-1 is a new altimetric satellite designed to follow on from the TOPEX POSEIDON mission
