1. EG2234 Earth Observation
Weather Forecasting

2. TOPICS Operational needs Operational constraints
Remote sensing and weather
Rainfall estimation
TOPEX-Poseidon
Modelling

3. Operational Needs Rapidly changing (dynamic)
Regular instrumental updates (global)
Dense coverage of stations
Point to surface conversion (interpolate)
Rapid dissemination to public
Global, regional and local scales

5. ABOVE: moored buoy
LEFT: drifting buoy

6. LEFT:
radiosonde
LEFT: launch
of radiosonde
balloon
RIGHT:
sounding rocket

7. Operational Constraints
Locations of stations are often sparse
No regular updates from inhospitable places (data retrieved from tapes)
Large gaps in data – both spatial and temporal
Collection of meteorological data requires access to Global Telecommunication System (GTS)

8. Global Station Coverage

9. 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

10. Infrared
radiant energy

11. Visible
albedo

12. Water vapour
Tropos. Water
Cloud motion

13. AVHRR
29/11/01
13:39
< VIS
IR >

14. Rainfall estimation
Cold Cloud Duration (CCD) using Meteosat
Tropical Rainfall Measuring Mission using radar (TRMM)
Special Sensor Microwave Imager (SSM/I) rainfall measurement using microwave instruments

15. Pioneered by work of Lethbridge, 1967
Rainfall estimation
Cold Cloud Duration (CCD):
Pioneered by work of Lethbridge, 1967
Became an operational system thanks to Milford and Dugdale at TAMSAT (University of Reading)
Based on relationship between period during which convective cloud tops are below a specific threshold and rainfall measured beneath them

16. Rainfall estimation Cold Cloud Duration (CCD):
Convective clouds have a deep vertical structure.
Cloud base height is usually uniform (flat bottomed clouds)
Adiabatic cooling means that cloud becomes cooler with increasing height
Colder cloud tops reveal a deeper structure = greater probability of rainfall

17. TRMM was launched in 1997 – with an initial mission life of 3 years
Rainfall estimation
Tropical Rainfall Measuring Mission (TRMM):
TRMM mission is a joint US/Japan effort coordinated by NASDA (National Space Development Agency of Japan)
TRMM was launched in 1997 – with an initial mission life of 3 years
TRMM data is relayed to NASA Goddard Space Flight Center (GSFC)

18. TOPEX-POSEIDON
For much of our oceans, temperature is not measured directly – but by proxy
Warmer water expands – if surrounded by cooler water it rises. Its height is therefore an indication of its temperature

19. TOPEX-POSEIDON TOPEX is an altimetric satellite
Return time of pulses of energy sent by TOPEX to the ocean surface are measured
Distance between satellite and water surface can be accurately measured
TOPEX used to measure El Niño

21. Modelling
Because of serious gaps in station observations, satellite data supplements ground station, ship, buoy and ascent readings
ALL data, once collected, is used to initialise climate prediction models
Smooth gridded interpolated surfaces of observed data are called reanalysis

22. Modelling
Reanalysis fields are generated for different pressure levels…from surface to 31 or so levels up to the top of the atmosphere

23. Modelling
All spatially referenced meteorological data are processed at the Met. Office and fed into global climate models via the COSMOS system
The current Unified Model (HadAM3) performs weather (short-range) and climate (long-range) forecasts

24. Modelling
Weather 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.)

25. The future
Meteosat Second Generation is a new European weather satellite capable of observing Europe and Africa every 15 minutes
Has more channels than the older Meteosat
Can help resolve cloud physics parameters

26. The future
Jason-1 is a new altimetric satellite designed to follow on from the T.POSEIDON mission