Transcript Tracking an Atlantic Wave Storm with Jason-2 Altimeter

Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Sérgio Muacho - IPMA
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Altimetry applications for oceans and seas:
- Operational oceanography
(waves and wind)
- Mean Sea Level
- Tides
- Ocean large-scale circulation
- Ocean currents and eddies
- Bathymetry
- Tsunamis
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Altimetry applications for oceans and seas:
here we will focus on…
- Operational oceanography
(waves and wind)
- Mean Sea Level
- Tides
- Ocean large-scale circulation
- Ocean currents and eddies
- Bathymetry
- Tsunamis
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Do you know other applications of altimetry?
Yes
No
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Do you know other applications of altimetry?
- Ice (Ice sheets; Sea ice)
- Climate (ENSO; NAO; Decadal oscillations)
- Atmosphere (Cyclones; Rain)
- Hydrology & land (Lake level; River level)
Yes
No
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Chapter I: Introduction
Jason-2 radar
http://www.eumetsat.int/Home/Main/Satellites/Jason-2/MissionOverview/index.htm?l=en
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Some considerations about altimetry:
-Satellite does not measure individual
waves…
- Satellite beam is about 1-2 km
minimum in diameter;
- Measurements are averaged (over 1s,
~7km along the track) to remove noise.
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
The radar altimeter receives the reflected wave (echo), which varies in intensity over time.
If sea surface is flat (a), the reflected wave's amplitude increases sharply from the moment the
leading edge of the radar signal strikes the surface.
In rough seas (b), the wave strikes the crest of one wave and then a series of other crests which
cause the reflected wave's amplitude to increase more gradually. *
Satellite
Radar wave
Radar wave as seen from
above the surface
Shape of the power as
received back by the
onboard radar
We can derive ocean wave height from the information in this reflected wave: the slope of the
curve representing its amplitude over time is proportional to wave height.
* from http://www.altimetry.info/html/alti/principle/waveform/ocean_en.html
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
How do satellite altimeters measure ocean waves?
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
How do satellite altimeters measure ocean waves?
- Over ocean surface, the echo waveform has a characteristic shape that can be
described analytically (Brown model);
- The edge slope is related to the significant wave height (SWH)
power
time
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
This is an ascending or descending orbit?
Ascending
Descending
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Can we use altimetry data in an operation way?
Yes
No
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Can we use altimetry data in an operation way?
No, because the satellite goes over
the same point every cycle (10 days
at least, up to 35 days depending on
the satellite)
Yes
No
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Can we use altimetry data in an operation way?
In my opinion, yes…!
If a satellite goes over your region of
interest (ROI), you can have data 2
hours after the measurements.
This is relevant in oceans and sea
zones with a lack of observations
(buoys), such as West Iberian coast
and more off-shore areas.
Yes
No
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
The Atlantic wave storm (17 – 20 April 2012)
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Wave storm life cycle: The early stages (synoptic conditions)
Plot: surface wind >10 m/s
Azores
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Wave storm life cycle: The early stages (synoptic conditions)
Plot: surface wind >10 m/s
Azores
Steady southwesterly flow with several cyclogenesis,
some of them originate deep lows with very strong winds
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Wave storm life cycle: The early stages (synoptic conditions)
Omega Block between 14 and 20th april 2012 with some minor changes in position
Azores
B
B
A
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Wave storm generation and propagation
Adapted for http://www.co.fc.ul.pt/
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Wave storm propagation (03UTC 17 April-12):
model results (WAM/ECMWF) and Jason-2
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Wave storm propagation (17 and 18 Apr 2012):
model results (WAM/ECMWF)
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Approaching shore in Bay of Biscay and West Iberian
coast (19 and 20 Apr 2012): model results
(WAM/ECMWF)
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Let’s track the storm… with Jason-2!
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Jason-2 data and wave model forecast (03 UTC 17-Apr)
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Jason-2 data and wave model forecast (03 UTC 17-Apr)
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Jason-2 data and wave model forecast (03 UTC 18-Apr)
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Jason-2 data and wave model forecast (03 UTC 18-Apr)
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Jason-2 data and wave model forecast (18 UTC 18-Apr)
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Jason-2 data and wave model forecast (21 UTC 18-Apr)
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Jason-2 data and wave model forecast (06 UTC 19-Apr)
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Important ideas:
• We collect 5 passages during a three days period (17, 18 and 19 April
2012) in our ROI;
• Jason-2 data is in good agreement with wave model and buoys (~2400
points with a mean difference of 3,5cm);
• We can use altimetry information to supply the lack of buoys in off-shore
areas (we can monitor sea conditions!).
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Important ideas:
• We collect 5 passages during a three days period (17, 18 and 19 April
2012) in our ROI;
• Jason-2 data is in good agreement with wave model and buoys (~2400
points with a mean difference of 3,5cm);
• We can use altimetry information to supply the lack of buoys in off-shore
areas (we can monitor sea conditions!).
But…. It is difficult to track a storm only with the altimetry data:
• Altimetry doesn’t give you an idea of sea conditions in all your ROI;
• Miss important information for marine forecasters, such as wave
direction.
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Jason-2 data against buoys data in West Iberian coast
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Jason-2 data and wave model forecast (03 UTC 18-Apr)
º
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Jason-2 data against buoys data
~1,4m 02h45m, 18-Apr
º
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Jason-2 data and wave model forecast (18 UTC 18-Apr)
º
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Jason-2 data against buoys data
º
~7,8m 17h17m, 18-Apr
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Additional issues:
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Jason-2 near costal regions (e.g., NW Iberian coast)
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Jason-2 near islands (e.g., Azores)
North swell: Wave refraction is well represented by altimetry
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Update – Atlantic ePort !
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Atlantic ePort (http://eumetrain.org)
Archive:
10 April 2012
onwards
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
Acknowledges
Portuguese Hydrographical Institute (www.hidrografico.pt)
Spanish Hydrographical Institute (www.puertos.es)
Tracking an Atlantic Wave Storm with Jason-2 Altimeter
- Thank you! -