EG2234 Earth Observation

1
EG2234Earth 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

4
(No Transcript)
5
ABOVE moored buoy LEFT drifting buoy
6
LEFT radiosonde
LEFT launch of radiosonde balloon RIGHT soundin
g 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 1339 lt VIS IR gt
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
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
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

20
(No Transcript)
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 levelsfrom 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

27
(No Transcript)