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Section 3 Remote sensing of global change. El niño Global Change Instructor: Dr. Cheng-Chien Liu Department of Earth Sciences National Cheng Kung University Office: Building of Earth Sciences, room 30206 Voice: +886-6-2757575 ext. 65422 E-mail: ccliu88@mail.ncku.edu.tw

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section 3 remote sensing of global change
Section 3 Remote sensing of global change

El niño

Global Change

Instructor: Dr. Cheng-Chien Liu

Department of Earth Sciences

National Cheng Kung University

Office: Building of Earth Sciences, room 30206

Voice: +886-6-2757575 ext. 65422

E-mail: ccliu88@mail.ncku.edu.tw

Office hours: Monday 14:00 – 17:00, Wednesday 9:00 – 12:00

URL: http://mail.ncku.edu.tw./~ccliu88/

Last updated: 25 April 2005

introduction
Introduction
  • El Niño
    • El Niño was named by people who fish off the western coast of Central America to refer to the warm current that invades their coastal waters around Christmas time
  • Significance
    • Air-sea interaction  climate change
    • El Niño  a typical example of air-sea interaction  short term climate change
    • El Niño  disrupt fisheries and bring severe weather events worldwide
mechanism of el ni o
Mechanism of El Niño
  • Conditions of atmosphere and ocean during the normal year and El Niño (Fig. 1, 2)
  • A short videohttp://svs.gsfc.nasa.gov/vis/a000000/a000200/a000287/a000287.mpg
fig 3 1 1
Fig. 3.1.1

Fig. 1 Conditions of atmosphere and ocean during the normal year and El Niño. Source: http://140.115.123.30/gis/globalc/fig/06-10.gif

fig 3 1 2
Fig. 3.1.2

Fig. 2 Conditions of atmosphere and ocean during the normal year and El Niño. Source: http://svs.gsfc.nasa.gov/stories/elnino_20030114/norm_3dm.jpgand http://svs.gsfc.nasa.gov/stories/elnino_20030114/el_nino_3dm.jpg

consequences
Consequences
  • An immense pacific bloom
    • Along the equatorial Pacific
      • During El Niño  nearly a complete lack of plankton
      • During La Niña  enormous plankton bloom
      • A short video 1 (12 Month Sequence)
        • http://svs.gsfc.nasa.gov/stories/biosphere/movies/Bio_Globe_Pacific_1.mov
      • A short video 2 (22 Month Sequence)
        • http://svs.gsfc.nasa.gov/stories/biosphere/movies/Bio_Pacific_1.mov
fig 3
Fig 3

Fig. 3 Along the equatorial Pacific during El Niño and La Niña. Source: http://svs.gsfc.nasa.gov/stories/elnino/index.html

consequences cont
Consequences (cont.)
  • The carbon connection - physical and biological processes
    • Plankton bloom  biologic change  CO2 change
    • El Niño cut the amount of CO2 released into the atmosphere by 700 million metric tons
    • A short video 1
      • http://svs.gsfc.nasa.gov/stories/elnino/COphy.mov
    • A short video 2
      • http://svs.gsfc.nasa.gov/stories/elnino/CObio.mov
remote sensing techniques for studying el ni o sst
Remote sensing techniques for studying El Niño – SST
  • Sensor
    • Advanced Very High Resolution Radiometer (AVHRR)
      • Channel 1: 0.58-0.68 mm
      • Channel 2: 0.725-1.0 mm
      • Channel 3: 3.55-3.93 mm
      • Channel 4: 10.3-11.3 mm
      • Channel 5: 11.4-12.4 mm
  • Mission
table 1
Table 1

Satellite #

Dates

Pass

# of bands

NOAA-6

6/79 - 11/86

am

4

NOAA-7

8/81 - 6/86

pm

5

NOAA-8

5/83 - 10/85

am

4

NOAA-9

2/85 - 11/88

pm

5

NOAA-10

11/86 - 9/91

am

4

NOAA-11

11/88 - 9/94

pm

5

NOAA-12

5/91 - 12/94

am

5

NOAA-13

failed

pm

n/a

NOAA-14

12/94 - present

pm

5

NOAA-15

5/98 - present

am

5

NOAA-16

9/00 - present

pm

6

Table 1 Continuous observation of SST by AVHRR on boarded NOAApolar-orbiting satellite seriesSource: http://edc.usgs.gov/products/satellite/avhrr.html

remote sensing techniques for studying el ni o sst cont
Remote sensing techniques for studying El Niño – SST (cont.)
  • Principle
    • Compute actual scene radiance from satellite counts
      • E=S*C + I
    • Find scene "temperature" (uncorrected) from radiance
      • T=temperature in degrees Kelvin
      • E=scene radiance as computed above
      • nu=central wave number of the channel (cm^-1, listed in the NOAA Polar Orbiter Data Users Guide)
      • C1=2*pi*Planck's Constant* c(speed of light)^2
      • C2=c * Planck's Constant / Boltzmann Constant
remote sensing techniques for studying el ni o sst cont1
Remote sensing techniques for studying El Niño – SST (cont.)
  • Principle (cont.)
    • Correct for atmospheric effects and sensor artifacts
      • SST = a + b*T4 + c*(T4-T5)*Tsurf + d*(sec([[theta]])-1)*(T4-T5) + e*lifetime
        • T4 and T5 are the temperature measurements for channels 4 and 5 respectively
        • a,b,c,d, and e predetermined by comparing AVHRR radiance values to in situ temperature measurements taken from buoys.
        • Tsurf is an a priori estimate of the actual SST made from a precompiled composite SST map of the same area.
        • theta is the satellite zenith angle
        • lifetime is the number of days since the launch of the satellite, used to calibrate drift of the sensor response over time.
remote sensing techniques for studying el ni o sst cont2
Remote sensing techniques for studying El Niño – SST (cont.)
  • Measurements (0.50C)
    • NEW Rotating Globe Animation showing El Niño and La Niña events (1996-1999) using TOPEX/POSEIDON and Pathfinder SST Data Sets
      • http://podaac.jpl.nasa.gov/sst/movies/rotating_globe.mov
    • Animation showing El Niño and La Niña events (1996-1999) using AVHRR Oceans Pathfinder and TOPEX/ Poseidon Data Sets
      • http://podaac.jpl.nasa.gov/sst/movies/epacific_75q.mov
remote sensing techniques for studying el ni o sst cont3
Remote sensing techniques for studying El Niño – SST (cont.)
  • Useful links
    • Pathfinder SST
      • http://podaac.jpl.nasa.gov/sst/
    • SST Measurement with the AVHRR
      • http://www.ae.utexas.edu/courses/ase389/midterm/duncan/duncan.html#channels
    • AVHRR: A Brief Reference Guide
      • http://www.ngdc.noaa.gov/seg/globsys/avhrr2.shtml
  • Data
    • AVHRR Stitched Orbits
      • http://edcdaacftp.cr.usgs.gov/html/avhrr_orbits.html
    • NASA-Earth Observing System Data Gateway
      • http://edcimswww.cr.usgs.gov/pub/imswelcome/
remote sensing techniques for studying el ni o ssh
Remote sensing techniques for studying El Niño – SSH
  • Sensor: Altimeter
    • An instrument that measures altimetry
      • Aneroid altimeters measure air pressure
      • Radar or laser altimeters time returning microwaves or light
remote sensing techniques for studying el ni o ssh cont
Remote sensing techniques for studying El Niño – SSH (cont.)
  • Mission:
    • TOPEX/Poseidon (August 10, 1992 – present)
    • Jason-1 (December 07, 2001 – present)
      • The Tandem Mission Flash animation
      • http://topex-www.jpl.nasa.gov/mission/gary-interview3.mov
    • GRACE (March 17, 2002)
      • Gravity Recovery and Climate Experiment, is flying two identical spacecraft about 220 kilometers apart in a 500-kilometer polar orbit, and over its 5-year lifetime will produce an accurate map of the geoid. The geoid, the manifestation of the Earth's gravity field, is the basic figure on which all altimetry data is based.
    • OSTM (Proposed Launch: 2005)
      • OSTM - Ocean Surface Topography Mission, is a follow-on to Jason-1. (operational mode)
remote sensing techniques for studying el ni o ssh cont1
Remote sensing techniques for studying El Niño – SSH (cont.)
  • Principle
    • TOPEX/Poseidon Instruments
      • http://topex-www.jpl.nasa.gov/gallery/tiffs/videos/topomeas.mov
  • Measurements
remote sensing techniques for studying el ni o ssh cont2
Remote sensing techniques for studying El Niño – SSH (cont.)
  • Useful links
    • TOPEX/Poseidon
      • http://topex-www.jpl.nasa.gov/mission/topex.html
    • Jason-1
      • http://topex-www.jpl.nasa.gov/mission/jason-1.html
    • GRACE
      • http://www.csr.utexas.edu/grace/
questions
Questions
  • What are the abnormal events of climate during 1982/83 El Niño around the world?