What can be found on this site?

This site presents the diurnal cycle of clouds over the Pacific Ocean west of Peru using GOES8 Satellite Imagery. The goal of this website is to provide the VOCALS project an additional tool that describes the climatology of the stratocumulus clouds that form west of subtropical South America. Please feel free to access the product webpages through the table in top of this page.

For now, the climatologies have been prepared using an entire year of 30-minutes visible and IR4 satellite images from the PERU sector. The period starts in May 2002 and ends in April 2003. The climatologies have been stratifies per product and per period of time.

The periods of time range from 6-month averages: December through May, which corresponds to the warm season and June through November, which corresponds to the cool season. 3-month climatologies have also been included. They are stratified in December-January-February (1), which corresponds to first half of the warm season; March-April-May (2), which corresponds to the end of the warm season; June-July-August (3), which correspond to the first half of the cold season, and September-October-November (4), which correspond to the end of the cold season. Finally the data is also presented monthly.

Six different products offered

  • An average over the visible channel (1). This product is great to see the stratus. The only limitation is daylight so the product is the most useful during late morning and early afternoon.
  • An Average over the IR4 Channel (2). This is the least useful product for viewing the stratus.
  • Frequency of clouds colder than 10°C (3). The frequency analyses are plotted in colors and are useful to see the stratus/stratocumulus with cloud tops colder than 10°C. Works well for the region south of 15°S.
  • Frequency of clouds colder than 12.5°C (4). Works well for the region south of 10°S.
  • Frequency of clouds colder than 15°C (5). Works well for the region north of 15°S, since during the winter most of the clouds south of this region reach temperatures colder than this threshold persistently. Also, cold SSTs near the coast of Chile and Peru could create some noise.
  • Frequency of clouds colder than a sloping threshold from 10°C at 20°S to 17.5°C at the equator (6). The explanation for this tecnhique can be found at the bottom of the current page.

    Technique #6: Sloping threshold.

    This technique is experimental and was applied because the temperature of the stratus/stratocumulus tops varies with latitude. In the southern portion of the domain (15-20°C) it is quite common to observe temperatures below than 10°C. Near the equator, though, (just south of the Galapagos), the cloud-top temperatures rarely descend from 12.5°C. A sloping threshold from 10°C at 20°S and 17.5°C at the equator was utilized in an intent of achieving a better analysis of the stratus/stratocumulus field.





  • Last Update: May 06, 2005.
    For questions or suggestions please contact Jose M. Galvez at jose.galvez@noaa.gov.