WPCk  
      2       B   V   o          Z      #| H          0pt (HP Roman 8) (Port) (FW) } 2 ] : , ,    ] 	[ 
    P fQ  
P21/01/96 05:49            Practical Lessons Using Marine and Coastal Image Data                                          1    XX  XX             X `  TTTTT|LxXxXxXxX@0@0@0@0`````````LT\``L `h`TTT|L|L|L|L\xXxXxXxXTTTTTT``@ @ @0@   L \p0p0p0p0p0``````  DDD`D`D`D`Dt8t8t8``````xL|L|L|L  \p0`D`Dt8LL\``  dh XX8TXXXX X@HX    h^                                  8d                                                        HP LaserJet Series II (Additional)   HLSEIIDU.PRS ] 	[ 
    P fQ     0Z
P 2       9     9     I  	       #| H          21/01/96 05:49            Practical Lessons Using Marine and Coastal Image Data                                          1     2 .                   Z      "  m^4HHl̰4TTl4H4<llllllllll<<lԤP`̤xԨH<Hl4lt`xlHhx<<p<xtxxTTHxd```llll ll  ll             l t  lllll䨘`llllP<P<P<P<xttttxxxx`lxtt` xxlll````xllllhhhhhhxxP P P<P   ` p<<<<<xxxxtt  TTTxTxTxTxTHHHxxxxxxԔ````  x<xTxTH``xtx    llHlllll lPXl    ^                                  Hx                                                         "  m^,8<X,DDX,8,0XXXXXXXXXX00Tx|xl@Lph`t|808X,T\L\X8T`00\0```\DD8`PxLLLXXXX XX  XX             X `  TTTTT|LxXxXxXxX@0@0@0@0`````````LT\``L `h`TTT|L|L|L|L\xXxXxXxXTTTTTT``@ @ @0@   L \p0p0p0p0p0``````  DDD`D`D`D`Dt8t8t8``````xL|L|L|L  \p0`D`Dt8LL\``  dh XX8TXXXX X@HX    h^                                  8d                                                        HP LaserJet Series II (Additional)   HLSEIIDU.PRS ] 	[ 
    P fQ     0Z
P 2 
      `    f  
  
          chapter                                                                      SI  e    #  ] 	[ 
    P fQ   
P# 
    
  t              J  g H    #  H 	`>	    xi fQ  ԩX# Marine and Coastal Image Data Module 5:t  k              (  } S    `(#7 #  H 	`>	    xi fQ  ԩX# Practical Lessons: 7k #  ] 	[ 
    P fQ   
P#  "  m^,4<X|,DDX(8,0XXXXXXXXXX00Pxt|xh@@xtht`ptthxL4HX,\XL\L4L\,,X,\\XX8D0`PtHHDXXXX XX  XX             X `  x\x\x\x\x\|LxLxLxLxL@,@,@,@,\\\\\````hHx\\\\hH \hXx\x\x\|L|L|L|L\xLxLxLxLLLLLLL\\@ @ @,@   @ xXt,t,t,t,t,\\\\\\  t8t8t8`D`D`D`Dp0p0p0``````thHxDxDxD  \t,\t8`Dp0hHhH\\`  dh XX4PHHXX XDDX    h^                                  8d                                                         "  m^ ((`@th 00@h (  @@@@@@@@@@$$hhh<|`TXdXLdh,8\Pt`dLd`DPh`|``X( (|@ <D8H<(<D$$@$dDDHH00(D8T488@@@h@ @@  @@             @ H  `<`<`<`<`<`X8X<X<X<X<,$,$,$,$`DdDdDdDdDhDhDhDhD`8`<dHdDdD`8 DLH`<`<`<X8X8X8X8dHX<X<X<X<d<d<d<d<d<d<hDhD, , ,$,   8 \@P$P$P$P$P$`D`D`D`DdDdD  `0`0`0D0D0D0D0P(P(P(hDhDhDhDhDhD|T`8X8X8X8  dHP$`D`0D0P(`8`8dHdDhD   H @@(<@@@@ @,4dd@    Ld^hh                                  (D                                                        \ 2           ,         "  m^ $(`@tX 00@h(  @@@@@@@@@@$ hhh8|TPX\TLd`,0TTp\`H`PDL\PpTLT8(4|@@@8D8$4@  < d@@@@(0$D8T400@@@h@ @@  @@             @ @  T@T@T@T@T@x\X8T8T8T8T8, , , , \@`@`@`@`@\D\D\D\DL0T@\D`@`@L0 DH@T@T@T@X8X8X8X8\DT8T8T8T8d4d4d4d4d4d4`@`@, , , ,   0 T<T T T T T \@\@\@\@`@`@  P(P(P(D0D0D0D0L$L$L$\D\D\D\D\D\DpTL0T0T0T0  \DT \@P(D0L$L0L0\D`@\D   H @@$844@@ @00dd@    Ld^hh                                  (D                                                        \ "  m^ (,`@`` 00@h (  @@@@@@@@@@$$hhh<|PTX\PL``,<`Pt\`L`XHP\PtXPP4$4|@ @D8D8$<H $@ hH@DD44,H8P<88@@@h@ @@  @@             @ D  P@P@P@P@P@tXX8P8P8P8P8, , , , \H`@`@`@`@\H\H\H\HP8P@\D`@`@P8 @LDP@P@P@X8X8X8X8\DP8P8P8P8`<`<`<`<`<`<`H`H, , , ,   < `@P P P P P \H\H\H\H`@`@  X4X4X4H4H4H4H4P,P,P,\H\H\H\H\H\HtPP8P8P8P8  \DP \HX4H4P,P8P8\D`@\H   H @@(<@@@@ @00dd@    Ld^hh                                  (H                                                        \ "  m^$,0lHt$88Ht$0$$HHHHHHHHHH((tttDl`dpdXtt0<h\ltTtlL\tllld0$0H$DL<LD,DL$$H$tLLLL840L@`<@<HHHtH HH  HH    H    H   H L  lDlDlDlDlDld<dDdDdDdD0$0$0$0$lLtLtLtLtLtLtLtLtLl@lDpLtLtLl@HLTLlDlDlDd<d<d<d<pLdDdDdDdDtDtDtDtDtDtDtLtL0 0 0$0   < hH\$\$\$HH\$lLlLlLlLtLtL  l8l8l8L4L4L4L4\0\0\0tLtLtLtLtLtL`l@d<d<d<  pL\$lLl8L4\0l@l@pLtLtLNH HT HH,DHHHHHH48ppHH HHTpH          H       H H             H                HmttHH    HH  HHHHH  HHHHHHHHHHHH     0P H         H                                            h              H "  m^,8<X,DDX,8,0XXXXXXXXXX00TptxthDXpl|dlt|ltL,LX,X\L\P8Td08\0dX\\LL<dPtTPLXXXX XX  XX             X `  pXpXpXpXpX|xLtPtPtPtPD0D0D0D0dXXXXddddlPpX\XXlP Xl\pXpXpXxLxLxLxL\tPtPtPtPTTTTTTddD D D0D   X \p0p0p0p0p0ddddXX  |L|L|LdLdLdLdLl<l<l<ddddddtlPtLtLtL  \p0d|LdLl<lPlP\Xd  dh XX8T\\XX XD@X    h^                                  8d                                                         2     ,  )  ,  U       	  r   "  m^$,0lHpp$88Ht$0$$HHHHHHHHHH((tttD\\dh\Tll4HlXhpXpdPXh\d\\<(<H$HL<L@,DT,,L,|THLH<<0P@\D@<HHHtH HH  HH    H    H   H L  \H\H\H\H\Hdd<\@\@\@\@4,4,4,4,hTpHpHpHpHhPhPhPhP\@\HhLpHpH\@HHXL\H\H\Hd<d<d<d<hL\@\@\@\@lDlDlDlDlDlDlTlT4 4 4,4   H lLX,X,X,HHX,hThThThTpHpH  d<d<d<P<P<P<P<X0X0X0hPhPhPhPhPhP\\@\<\<\<  hLX,hTd<P<X0\@\@hLpHhPNH HT HH,DLLHHHH84ppHH HHTpH          H       H H             H                HmttHH    HH  HHHHH  HHHHHHHHHHHH     0T H         H                                            h              H "  m^$(0lHd$88Ht 0$(HHHHHHHHHH($ttt@d\dh`Xpl48`\|hlTl\LXh\|`T`<(<H$HH@L<(<L$$H$tLLHH04(L@`<88HHHtH HH  HH    H    H   H L  dHdHdHdHdHhd@`<`<`<`<4$4$4$4$hLlLlLlLlLhLhLhLhLT8dHhLlLlLT8HLTHdHdHdHd@d@d@d@hL`<`<`<`<p<p<p<p<p<p<lLlL4 4 4$4   8 `H\$\$\$HH\$hLhLhLhLlLlL  \0\0\0L4L4L4L4X(X(X(hLhLhLhLhLhL|`T8`8`8`8  hL\$hL\0L4X(T8T8hLlLhLNH HT HH(@<<HHHH88ppHH HHTpH          H       H H             H                HmttHH    HH  HHHHH  HHHHHHHHHHHH     0P H         H                                            h              HDutch Roman 10.50pt (HP Roman 8) (Port) (FW) Courier 10cpi Dutch Roman 7.50pt (HP Roman 8) (Port) (FW) Dutch Italic 7.50pt (HP Roman 8) (Port) (FW) Dutch Bold 7.50pt (HP Roman 8) (Port) (FW) Dutch Roman 8.50pt (HP Roman 8) (Port) (FW) Dutch Bold 10.50pt (HP Roman 8) (Port) (FW) Dutch Bold 8.50pt (HP Roman 8) (Port) (FW) Dutch Italic 8.50pt (HP Roman 8) (Port) (FW) Dutch Roman 16pt (HP Roman 8) (Port) (FW) Dutch Italic 10.50pt (HP Roman 8) (Port) (FW) Dutch Roman 13pt (HP Roman 8) (Port) (FW) "  ^ D X X     D d d   @ X @ H           H H             ` t                X H X  D   t   T   H H  H      d d X  |  t x t                                                               t         ` H ` H ` H ` H                    x          x             t  t  t  t                           `   `   ` H `       t      H  H  H  H  H                  d  d  d  d  d  d  d  X  X  X               x  t  t  t        H    d  d  X  x  x                   X         d l              ^                                                                       X                                                                                                                    2      ^  R      R   c  J      $  } 2 ] : , ,    ] 	[ 
    P fQ  
P
 ? x x x , -  x 6X   @ 8; X@Z # C *   , ;  /%iC 	[ 
    P fQ  wP[ " @ *   , g  i@ 	`>	    xi fQ  wXZ # A *   ,   cA ~>	    p fQ  wf ( K / $ ,   WK 	[ 
    P fQ  Pd~ 1 \ : , ,   N,\ ~>	    p fQ  
f ( K / $ ,  1K ~>	    p fQ  Tg ' H / $ , B ԙH 	`>	    xi fQ  XL K  Y D , o  	[ 
    P fQ   P\ 0 Y : , ,  Y 	`>	    xi fQ  
X = s H 4 ,  qs 	[ 
    P fQ  P$'!!!""!!,!55! l$  "   0#    U$9 K K 3 ?1 ?  ?"?"?"?#??##?#?#߀#?π?$
$
$
$
Ͽ$
󟿀$
翿$
$
%	 %	3%	%	%	  % %	&?L&?&~&&?&&&Ͽ&翀(s&3&?&̿&?(?&&&?&?&xq(0p&&0&0q&;&??&:'π8&߀&߀&߀&߿&߿&&?& & &&%{%%?$$$π$߀##?#?"""""?!!??!!!?À   ?    	 		߀?	?
|9O
80
 
 ۃ?
L'ۃ
 ۃxۃߟ

?π
~8? ?
߿ ~}q8c|`8a~`0<~`0x
}ogِLɀ
0`
?8q
 






?

π

?
?

ߟπ߀ ???߀

w9

2	2	>w2	?y2	ϟ	?	?q $,,?,π,߀$?a????q7π	?	7g???8gÄǀɼ1_Ⴠh<n0?l;&g<fǀ7r:f 
p0g`L
v_}	gpi?πϿ??
?1?πg
?


?π
g
Ͽ?o
Oπ㏀?	? ?ǀÀ?߀?ϟ
??À??	 /??}????		7?	77	?77	7'	Ç	=~| π߀??>|?ǀ?πߟ>?x
߀

s
߀

?ɓ
>̞3
??w̞3

?ππ߀߀߀߀
?߀
߀
߀
߀
xp
9
;
xp
x9
π<
߀?	?x?	?|	?߀	߀ 	߀
߀
߀	߀	߀	߀	π߀	߀	?߀	߀	߀	߀	ǀ߀	߀߀	߀	߀	? ߀ ߀ ߀π ߀?π ߀ǿ ߀?? ߀	߀	߇|߀
qǹ>߀		|6À߀d߀d߀d߀?&d߀?f߀} ߀}!߀?!߀߿!߀?!߀π!߀!߀!߀!߀{!߀"߀!߀!߀!߀!߀"߀{"߀?"߀"߀"߀"߀π"߀߀"߀"߀?"߀?"߀?"߀"߀"߀#߀#߀#߀ ߀	߀	w߀ À߀?y߀s`ǀ߀s@À߀@߀߀$߀$߀?$߀$߀$߀$߀$߀ $߀ $߀$߀$߀ $߀$߀$߀$߀$߀?￀#߀#߀ π!߀	~{߀	~s;߀;߀
;߀
;6߀~;6߀s;6߀;v߀Ǐy9߀"߀"߀"߀"߀ "߀"߀"߀"߀"߀"<8??"0"""="}"}~?"<??"?"߀"߀"߀"߀"߀"߀"߀~"߀??π"߀	߀ǀ߀
=߀
`À߀
lɜπ߀
lɼÀ߀
lɼ߀
wlɼ߀
ݾÀ߀"߀!߀y!߀y!߀}?!߀ 	}!߀	~!߀	~!߀	!߀	?!߀	!߀	!߀	ߟ!߀	߀!߀ 	π!߀	π!߀ 	π!߀	π!߀ 	π!߀	!߀	!߀ 	!߀ 	!߀	!߀	!߀	!߀	!߀ 	!߀	π!߀	π!߀	ϟπ!߀	߿߀!߀	?!߀	!߀	!߀	?!߀	~?!߀~!߀!߀ "߀ "߀"߀"߀ "߀ "߀"߀"߀π"߀π"߀߀"߀ ϟ"߀Ͽ"߀ ?"߀ ߟ?"߀߿"߀?"߀"߀"߀"߀ >"߀~"߀"߀#߀#߀#߀#߀#߀#߀#߀#߀#߀ > ǀ
 ߀  5                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    i      5N H H ꏪo8߂`?gggg`?߃ggggυ ߄߅߆<999ϟ<???? <we߂߃߂_}{߄߿{{~߅ۿӂw߆	g
<9O?π ?o?<>y
g<9߄߂݂|߆/yj{k{nnkn?;-{߆/y߆r/|w߆?A?݂߆ﯮ}?	{~_w[
o޿
ﾯ	·	
G	/Y
߭W}	/v}	M<	7osoϷ\uO߂O߄߅
_`@p
<}o?o~oxonvo
paa߃
wivo߃
w~w;oo7<o{o==?߆߷_`씛ￆ _@ 
  x>a 	#<o{ 	D~go; 	6no 7r)o z~los<o;o
`x>Â?ϟϟυ	;D    ? o߂@ 	_{}ϯ{}{}χ{<>߃{}={}{}{߄߅߆翆?ʟOϪϪ???<<9τ9τυ?τ9υυ?υ9ϟO?<<?8υ>yυ?χυϟ<υ?̅χϟ9υ?τχ?8ɜǔ99yy   Ichapter    #  ] 	[ 
    P fQ   
P# 
    
  t                g H    #  H 	`>	    xi fQ  ԩX# Marine and Coastal Image Data Module 5:t  k              ){  } S    `(#i #  H 	`>	    xi fQ  ԩX# Practical Lessons: 7k #  ] 	[ 
    P fQ   
P#    
  O   
  3'                                          3'Standard                                  6&                                          6& Standard zar estilo t)cnico            ܰ                                          
a* Practical Lessons Using Marine and Coastal Image Data

#  qs 	[ 
    P fQ  P# 
   *  7: MONITORING THE COASTAL UPWELLING NW OF AFRICA WITH
 <  AVHRR-APT IMAGES
 D a # ] 	[ 
    P fQ   
P# 
 D a 
 D a 
  ~ R   =    Aim of Lesson
 ) `      

To use APT images from the AVHRR sensor for the characterization of upwelling events on the
northwest coast of Africa.


  ~ S  a? Objectivesă

On completion of this lesson you should be able to:

1) recognize the thermal characteristics of upwelling using APT images

2)  characterize upwelling using sea surface temperature (SST)

3) obtain sea surface temperature from the digital values recorded by the AVHRR sensor.



                Figure 1                                           1                                          !      a              0#  n d @   JAVIER.TIF                                           )   TK^ 
      Figure 1 : Map of the study zone with its bottom
   topography  $  ""o88  ! 8$  0  o         o.?+?+HH 80  !  0    ~ S      88  ""   a9 Background Informationă


  ~ R q Upwelling in the NW coast of Africa

The basic theory of upwelling events and how they are produced off the west coast of Africa, were
   S  explained in a concise and clear way in lesson 6 (Gonzlez-Mu9oz et al., 1994) of this module.


  ~ R S The AVHRR sensor and the APT transmission

The Advanced Very High Resolution Radiometer (AVHRR) sensor orbits on board satellites of the
NOAA series. It is equipped with a rotating mirror which picks up electromagnetic radiation, which
is divided into five spectral bands: a visible band and four infrared bands.

The sensor registers radiance every 1.3 milli-radians which, given the height at which it flies, provides
a spatial resolution of 1.1 km ' 1.1 km. In addition, it is provided with a black body of known
temperature, which is used to calibrate this radiance.

In the Automatic Picture Transmission mode (APT), an average of four out of every five records in
each of two channels, 1 (0.55 m ! 0.9 m) and 4 (10.5  m ! 11.7 m), of the images is transmitted
immediately to land by a radio signal at 137.62 MHz, in which the wave amplitude is proportional to
the radiance value registered by the sensor.

The signals are pre-processed on board for approximate correction of panoramic distortion, to give
a constant resolution over the whole 4.4 km ' 4.4 km image. Telemetry records, necessary for image
calibration, are transmitted to land at the same time as the image data.

The radiometric resolution of these images is 8 bits, and they can be captured by low-cost secondary
stations.




  ~ R  Images Used in this Lesson

For this lesson two APT images are provided. These were recorded at the secondary station (BAE
Dartcom [R]) of the Instituto Canario of Marine Sciences, and correspond to a pass of the NOAA-11
satellite during a transmission period of 6.71 minutes. The elevation of the pass was 57$. The
characteristics of the files used are summarized on Table 1.

Y  
    d d x                             !         S!   ]<        @@@@  Y  	 		 	 	 	S!               
  T File  #      5  
 0 [
 Date; Hour  #      Q  
 J  Sensor/Channel  #      n 
 
 j x Bandwidth 	 		 	 	 	S!               
   APTIR  $      5  
 .  09/02/93; 17:00  $      Q  
 M 0 AVHRR / 4  $      n 
 
 f v 10.5 m 11.7 m 	 						#               
   APTVS  s&      5  
 .  09/02/93; 17:00  s&      Q  
 M 0 AVHRR / 2  s&      n 
 
 f v 0.55 m0.90  m 			 $     
  ~ S C' 
a1 Table 1. Characteristics of the imagesă


   )        o.?+?+HH  Ԍ  ~ R    Lesson Outline

  ~ S  Activity 1: Display of the area.

  ~ S A Load the APTIR image using Load Image of the Main Menu. Given that the image size is 800' 800
pixels, it is necessary to select values that define the part of the scene to be displayed.

  ~ S  To see the full image, introduce the following parameters: First Line = 300, Last Line = 800. First
  ~ S  pixelĠ= 1, Last pixel = 800, and 2 as the application factor in the vertical and horizontal sampling.

The width of the scene corresponds in these latitudes to 2,750 km and the spatial resolution is, as a
function of the sampling factor used, 16 km x 16 km/pixel. On the image shown, the NW coast of
Africa is on the right and next to it, the Canary Archipelago may be seen to the north.

At the left margin of the image, telemetric data are shown, while on the right are shown the digital
values registered by the sensor in outer space (which is assigned a temperature of 0 K and a radiance
in the infrared band of 0 units).

  ~ S  Observe the histogram of the image. Apply a Linear Stretch, from the Modify LUT option.
Investigate with the left cursor the interval of values corresponding to land.

1.1. Display the enhanced image. What is the effect produced?

1.2. What is the interval of digital values corresponding to the cloudfree sea near to the coast?

1.3. What is the percentage of land in the image?

  ~ S  1.4. The APTIR Look up Table has been created for use with this base. Load it using the Load LUT
option. With this LUT, there is an enhancement of the differences in sea surface temperature;
keeping in mind that the clearest values correspond to the lowest temperatures, what can you say
about the distribution of surface temperature?


  ~ S  Activity 2: Classification

2.1. This exercise requires sub-scenes with the maximum possible resolution. To obtain them, again
  ~ S G load the APTIR.DAT image, but use the following display parameters: First Line = 400, Last Line
  ~ S  = 655. First pixel = 269, Last pixel = 780, using 1 as vertical and horizontal sampling factor. What
is the new spatial resolution?

  ~ S   Save the sub-scene (using Save Image option from the Main Menu) with the name SNIR. Repeat the
  ~ S Z! whole process with the image APTVS.DAT and save it as SNVS.

   S " 2.2. To perform a supervised classification of the spectral characteristics of the image, use the
  ~ S # Scattergram option from the Multi Image function. Introduce the visible image as the x axis and the
infrared as the y axis.

The two cursors that appear on the screen allow you to define the training polygons. Choose in
succession: rectangles on land, in the core of the upwelling, in the edge of clouds and in the cloud
core. Make a sketch of the position of the four classes in the dispersion diagram.

Are the classes easily separated by visual observation of the cloud of points?
   N*         o.?+?+HH  Ԍ  ~ S    ԙActivity 3: Estimation of Sea Surface Temperature

3.1. As noted earlier, the sensor has a black body of controlled temperature and radiance. The digital
value for the radiance of this black body gives us a reference point on the digital value-radiance line.
Another point is obtained from the registered values in outer space (right margin of the first image
- see activity 1). Since radiances are known, temperatures are obtained using the Planck equation. The
complete process has been described by Summers (1989).

Carrying out this process with the parameters corresponding to the NOAA-11 satellite, band 4, we
obtain the relation:

   S     )  Tasm($C) = 14 + 0.4 * (77  dv)    (dv: digital value)
 * a      

With this we obtain the apparent temperature of the sea surface in this scene. Why do we call it
apparent?

  ~ S 
 Use the Cursor function to select a few digital values and the given equation to obtain from them
the sea surface temperature.

3.2. One of the proposed indexes for the detection and quantification of upwelling is the so-called
   S  surface thermal anomaly which is defined as the difference in SSTs between shallow waters and
oceanic waters. Obtain the value of this index for several latitudes.

 - What is the value of this index in the Canary Islands?

 - What is the value near Dakhla?

Another factor playing an important role in the extension and displacement of cold waters is the
bottom topography. A line has been prepared representing the 200 m isobath, assumed to be the limit
  ~ S f of the continental platform. Use the option Radiometric Masking in the function Multi-Image to
display it.

  ~ S  Introduce ISO200 as answer to the question: Name of file defining the mask?, and SNIR.DAT as
  ~ S  answer to the question: Name of the file to be masked? Use the right cursor to mask the values up
to 253.


  ~ S  Activity 4: Visual enhancenment

Given that the APT antennas are not excessively selective, the recorded images usually show "noise".
This "noise" is random and can be attenuated using low-pass filters.

  ~ S " Load the SNIR image and use Smooth, from the submenu Filters. Annotate the modifications
  ~ S # suffered by the filtered image. Then apply another low-pass filter: the 3x3, (located in the submenu
  ~ S $ Filters). Use the following coefficients:

   =&         o.?+?+HH    Y    !         S!   ]<        @@@@   A              *      """  Y  		 	$           "   >  
 >  1      "   F  
 F  2      "   M  
 M  1 	 		 	             "   >  
 >  2   `   "   F  
 F  4   `   "   M  
 M  2 	 				           "   >  
 >  1       "   F  
 F  2       "   M  
 M  1 			 `     

  ~ S  Save the filtered image with the name 3x3.DAT. Display this image, annotate the modifications
produced in it, and compare it with the original. What differences do you see in the images produced
by the two filters?


  ~ S 
 a> BIBLIOGRAPHYă

 X  Jensen, J.R., 1986. Introductory digital image processing. Prentice Hall. pp. 125129."

 X  Summers, R.J., 1989. Educator's Guide for Building and Operating Environmental Satellite Receiving
Stations. NOAA Technical Report NESDIS N$ 44."

Other bibliographic references of interest:

 X       Chedin, A., Scott N.A., Berroir, A., 1982. A single channel double viewing angle method for sea
surface temperature determination from coincident METEOSAT and TIROSN radiometric
measurements. Jour. Appl. Meteor. 21: 613618.+"

 X       Mittelstaedt, E., 1983. The upwelling area off Northwest Africa. A description of phenomena related
to coastal upwelling. Prog. Oceanogr. 12: 307331."

 X  Mittelstaedt, E., 1991. The ocean boundary along the Northwest African Coast: Circulation and
oceanographic properties at the sea surface. Prog. Oceanogr. 26: 307335."

 X  Van Camp, L., Nykjaer, L., Mittelstaedt, E., Schlittenhardt, P., 1991. Upwelling and boundary
circulation off Northwest Africa as depicted by infrared and visible satellite observations.
Prog. Oceanogr., 26:357402."

 X  McClain, E.P., Pichel, W.G., Walton, C.C., 1985. Comparative performance of AVHRR based
multichannel sea surface temperature. J. Geophys. Res. 90 (C6): 1158711601."

      y    b :&                    d       d d                                                                         y 

This lesson was prepared by J.P)rezMarrero, A. GonzlezMu9oz y O. Llins.


   Q B# Suggestions and comments regarding this lesson should be sent to:

J. P)rezMarrero
Instituto Canario de Ciencias Marinas
Dto. de Oceanograf1a
Apdo. 56, 35200 Telde
Gran Canaria  ESPA8A

   Q ) Fax: 3428/693908   )        o.?+?+HH  Ԍ  ~ R       ; L ÙAnswers to Lesson 7
 * a      
  ~ R  Activity 1.

1.1.  A pattern appears in the image; clearer pixels (lower temperatures) are observed near the
coast that become progressively darker as we go towards the sea. The cloud boundary west of the
Canary Archipelago becomes brighter.

1.2. From 60 to 75. The marine pixels correspond to the defined peak observed in the histogram.

  ~ S   1.3. If with the Linear Stretch option the 0 colour (black) is assigned to the land and the 15
(white) to clouds, the percentage of pixels not masked (not counting the margins) corresponds to the
ocean. In this case this represents  about 50% of the pixels.

1.4. Low temperature waters lie mainly close to the coast and are stratified parallel to the
coastline. This indictes upwelling. Farther from the shore the temperatures increase and the
stratification disappears.

  ~ S  Activity 2.
 y A M;	                   5  n n                                                       M)        y  	  r	 

2.1. 1.1 km ' 1.1 km.

2.2. The characteristics of the cloud boundaries are similar to those of the upwelling core: the
classes are not easily separated by simple observation.
   D a 
  ~ S #  D a      Activity 3.

3.1. Because the atmospheric effects have not been corrected. Water vapour and other gases
absorb part of the infrared radiation emitted by the surface. For this corrections multi-band and
multi-view algorithms are used. Of the latter ones, can be applied using exclusively the APT images
   S ' (See, for example, Chedin et al., 1982).

3.2. - Canary: 3 $C
 - Dakhla: 3 $C   h*         o.?+?+HH  Ԍ   S    ԙNOTE:`	`	! The appraisal is better observed using Smooth, from the Filters menu.

  ~ S  Activity 4.

  ~ S C Using the Smooth filter, the field of surface temperature appears very homogeneous, that is, there
  ~ S  are no sharp changes in the brightness values. When using the 3x3 filter, even though the
temperature field is also homogeneous, the transition between colder waters (clear pixels) and
warmer waters is more evident. This is specially evident in the zone of Cape Bojador and south of
Tenerife island. (Suggestion: load the filtered image with Smooth and compared it with the image 3x3,
  ~ S U using the Toggle function, in the Multi-Image menu).   U        o.?+?+HH                          