Section 3 Remote sensing of global change El niño Global Change Instructor: Dr. Cheng-Chien LiuCheng-Chien Liu Department of Earth Sciences National Cheng Kung University Office: Building of Earth Sciences, room Voice: ext Office hours: Monday 14:00 – 17:00, Wednesday 9:00 – 12:00 URL: Last updated: 25 April 2005

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 Niño  Conditions of atmosphere and ocean during the normal year and El Niño (Fig. 1, 2)  A short video /a000287/a mpg /a000287/a mpg /a000287/a mpg

Fig Fig. 1 Conditions of atmosphere and ocean during the normal year and El Niño. Source:

Fig Fig. 2 Conditions of atmosphere and ocean during the normal year and El Niño. Source: and

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)   A short video 2 (22 Month Sequence) 

Fig 3 Fig. 3 Along the equatorial Pacific during El Niño and La Niña. Source:

Consequences (cont.)  The carbon connection - physical and biological processes Plankton bloom  biologic change  CO 2 change El Niño cut the amount of CO 2 released into the atmosphere by 700 million metric tons A short video 1  A short video 2 

Remote sensing techniques for studying El Niño – SST  Sensor Advanced Very High Resolution Radiometer (AVHRR)  Channel 1:  m  Channel 2:  m  Channel 3:  m  Channel 4:  m  Channel 5:  m  Mission

Table 1 Continuous observation of SST by AVHRR on boarded NOAA polar-orbiting satellite series Source: Table 1 Satellite #DatesPass# of bands NOAA-66/ /86am4 NOAA-78/81 - 6/86pm5 NOAA-85/ /85am4 NOAA-92/ /88pm5 NOAA-1011/86 - 9/91am4 NOAA-1111/88 - 9/94pm5 NOAA-125/ /94am5 NOAA-13failedpmn/a NOAA-1412/94 - presentpm5 NOAA-155/98 - presentam5 NOAA-169/00 - presentpm6

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 Niño – SST (cont.)  Principle (cont.) Correct for atmospheric effects and sensor artifacts  SST = a + b*T 4 + c*(T 4 -T 5 )*T surf + d*(sec([[theta]])-1)*(T 4 - T 5 ) + e*lifetime  T 4 and T 5 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.  T surf 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 Niño – SST (cont.)  Measurements (  C) NEW Rotating Globe Animation showing El Niño and La Niña events ( ) using TOPEX/POSEIDON and Pathfinder SST Data Sets  Animation showing El Niño and La Niña events ( ) using AVHRR Oceans Pathfinder and TOPEX/ Poseidon Data Sets 

Remote sensing techniques for studying El Niño – SST (cont.)  Useful links Pathfinder SST  SST Measurement with the AVHRR  #channels #channels AVHRR: A Brief Reference Guide   Data AVHRR Stitched Orbits  NASA-Earth Observing System Data Gateway 

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 Niño – SSH (cont.)  Mission: TOPEX/Poseidon (August 10, 1992 – present) Jason-1 (December 07, 2001 – present)  The Tandem Mission Flash animation  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 Niño – SSH (cont.)  Principle TOPEX/Poseidon Instruments   Measurements

Remote sensing techniques for studying El Niño – SSH (cont.)  Useful links TOPEX/Poseidon  Jason-1  GRACE 

Questions  What are the abnormal events of climate during 1982/83 El Niño around the world?