Saturday, November 12, 2011

Tehuantepecers or Tehuanos are accelerated winds (i.e., gap winds or gap jets) that develop downstream of the Chivela Pass in Central America, extending several hundred kilometers into the Gulf of Tehuantepec. Tehuanos reach 10-20 m/s, with gusts of 60 m/s in extreme events. Such strong winds have been shown to have a significant impact on the physical and biological characteristics of the local ocean.

Chlorophyll-a (chl-a), sea surface temperature (SST), and SST anomaly data on Nov. 12 show high chl-a concentrations and SST cooling (~3-4°C) in association with Tehuantepecers that induce vertical mixing and upwelling and bring cooler and nutrient-rich waters from depth to the surface. The high chl-a concentrations could also be attributed to advection of high concentrations from the coast.

Additionally, the winds generate anti-cyclonic eddies which can be observed to the west of the cool SSTs on Nov. 12, 2011.
Image 1: MODIS chlorophyll-a concentrations overlaid with ASCAT wind vectors on Nov. 12, 2011. Image 2: MODIS sea surface temperature overlaid with ASCAT wind vectors on Nov. 12, 2011.  Image 3: MODIS Sea surface temperature anomaly overlaid with ASCAT wind vectors on Nov. 12, 2011. Image Credit:
Images created using PO.DAAC's State of the Ocean tool (SOTO) on Nov. 12, 2011.