OPERATOR(S) NAME: Ramon Ahumada and Laura Farias.

see the READ document for definitions of files and abbreviations

DATE:  May 2, 2001

Eastern South Pacific Region (ESPR)

DATABASE INFORMATION

Geographic Zones Selected (leave blank if done by range):

Geographic Range Selected (leave blank if done by zones):

0 – 55° S / 70 –80° W

Cell types selected from database (Terrestrial, Coastal, Oceanic I, Oceanic II, Oceanic III):

Terrestial, Coastal, Oceanic I.

Variables and ranges selected from database (if filtered – if not filtered, no entry is needed):

The variables were filtered depending on known ranges for the ESPR. See  Table 1

What do you expect to get out of clustering these variables or what are you trying to achieve?

OBJETIVES.

We expect:

1.- To identify  main climatological/hydrographical   and biogeographical  regions along  the coast of Eastern South Pacific

2.- How the main  climatological variables may modify the oceanographic variables.

2.- To  identify oceanographic processes in relation to  temporal variability  (i.e  coastal upwelling  and  ENSO phenomenon).

RESULT.

The exercises allow us  to separate the climatic and hydrographic  region along Peru and  Chile coast.  Under different set of selected variables (Experiments ESPR1, ESPR2 and ESPR3), LOICZ typology methodology can basically separate the same regions.  If we consider temporal variability in the SST, we can clearly distinguish ENSO phenomenon associated with equatorial dynamic in the Peru and North of Chile coast  (Experiment ESPR-T).  The social economical indexes were used to separate socio-economical regions. They were mainly associated with climatic regions  (Experiment ESPR-SE)

Table 1.  Cluster summary from several experiments that was done in the Eastern South Pacific Region (ESPR)

Experiment

ESPR-1

ESPR-2

ESPR-3

ESPR-T

ESPR-SE

Selected Criterion

Climatological/

Hydrographical

Climatological/

Hydrographical

Climatological/

Hydrographical

Temporal Oceanographic procesess

Socio-economical

Cluster run N

          

number of cluster

5

5

5

3

5

Distance methods

A

A

A

A

A

Variables

          

Temp LW ann avg

X

X

X

  

X

Temp CRU ann avg

X

X

X

    

Precip LW total

X

X

X

  

X

Precip  CRU ann avg

X

X

X

    

Windspeed ann avg

          

SST mean month

X

X

X

    

STTmin-max range

X

    

X

  

STT max month

X

        

STT min month

X

        

STT inter ann STdev

      

X

  

Salinity ann avg

X

X

      

Salinity max month

X

  

X

    

Salinity min month

X

  

X

    

Salinity gradient

          

Runoff  total ann

X

  

X

    

Runoff avg ann

X

X

      

Runnof int ann range

X

      

X

Cell% evgrn need for

        

X

Cell% evgrn  broad for

        

X

Cell% closed shrub

        

X

Cell% open

        

X

Cell% cropland

        

X

Dens pop

        

X

A= average

COMMENTS:

1.- The experiments were performed from 0-55° S and 70-80 W. This region comprises a wide latitudinal gradient in which climatic variables such temperature and precipitation were dominated. The clusters can separate region according to  main climatic and hydrographic features in the region.   Part of hydrographic variables (SST ann avg and  Salinity min month) were strongly modulated  by climatic variables.  

2.-The scale of the coastal upwelling process, only a few km upward the ocean (ca., 20 Km), do not permit to distinguish clearly coastal upwelling regions.  There is a diffuse signal of the upwelling process in the north of Chile and Peru coast.  In addition, the inter-annual variability associated with the ENSO phenomenon is possible to identify between 0-25° S, as expected.  In  next future,  we will  try to work with data obtained from ESPR at other resolution scale.

The ESPR  region correspond to well described   biogeographic region called: Peruvian Province, Chilean Province and  Patagonian Province and between on those there are transitional zones.The region was mainly characterized as:

i.- a dessert with some valley from the Andes to the coast on the north until 30° S. In all of these valley,  rivers do not reach the sea. The area is warm and dry;

ii.- a thorny bush (shrub) with farming land in the central and south area. This region extends from 30 to 40 degree. After that beginning a  wet forest are present. The precipitation regime ranges from 500 ml/y to 1500 ml/y, and temperature from 22 to 12o C

 iii.- a wet native forest . Fjord and channel systems are present in this region  from 42 to 56o S. 

Under hydrographic point of view, in the ESPR, Sub-Antarctic Water mass  (SAAW) was dominant on the surface water until 22° S, down that, the Subtropical Waters (STW) and the SAAW fall donw the surface. An under current subsurface water run from the equator to the pole and it is associated with the Equatorial Subsurface water (ESSW).

The principal oceanographic processes in the SRPR are:

a)     Upwelling Process along the coast from 10 -42 ° S. The water mass involved in this process is the  ESSW that  is characterized by waters cold,  poor in dissolved O2, and rich in nutrient. The upwelling process occurs during austral spring –summer time.

b)     An inter-annual signal of the “El Nino” (ENSO).