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NASA NTRS1993

Properties of the Central American cold surge

The Central American cold surge (CACS) is a frontal incursion from the United States into Central America and resembles the East Asian cold surge. They occur more frequently than analyzed by NMC or by published results, based on our observations between 1979 and 1990. Climatology and structure are quantified, based on surface and upper air stations throughout Central America and satellite products from GOES visible and infrared sensors and SSM/I precipitable water and rain rate sensors.

Mcguirk, James P.↗

NASA NTRS1993

Global barotropic response to a tropical forcing

Zonally varying flow has been used to initialize numerical models and has been shown to play an important role in strong localized responses both in extratropics and the tropics. In this study, a climatological 200 mb January mean is used as a steady basic state of a barotropical model which consists of shallow water equations and a mass source centered at 4 deg S/120 deg E to simulate convective heating over Indonesia region. In the experiment, tropical responses appear not only over the western Pacific, where the forcing is located, but also over the eastern Pacific where the response is related to the zonally varying basic state. The westward propagating equatorial Rossby waves excited by the forcing interact with waves out of and into the tropics and the positive and negative phase of the Rossby waves result in blocking circulation over North America and tropical plumes over equatorial eastern Pacific, respectively.

Zhang, Yuxia↗