What the grounding doesn't know.

PositionYOUR LIFE

Forget about the groundhog and his shadow. Scientists have discovered that the interplay between two layers of the atmosphere plays a major role in the arrival of spring--a finding that could lead to improved weather and climate forecasting.

"Our research indicates that the onset of spring is more rapid than suggested by the annual cycle of long-term daily averages and is linked to an event known as the stratospheric final warming," reports Robert Black, an associate professor at the Georgia Institute of Technology's School of Earth and Atmospheric Sciences, Atlanta.

For many years, scientists believed that the troposphere (the lowest region of atmosphere where weather occurs) drove changes in the stratosphere (the layer directly above the troposphere) without any feedback. Yet, in the late 1990s, new studies found that the stratosphere can affect the tropospheric circulation. These studies, however, focused on individual seasons.

"Because the arrival of spring has a pronounced influence on the hydrologic cycle, vegetative growing season, and ecosystem productivity, we wanted to study the transition between seasons," Black relates. To that end, his team gathered observational data derived from a variety of sources and constructed a composite picture of spring's arrival over a 40-year period.

As winter draws to a close, the westerly jet stream in the troposphere begins to weaken. At the same time, the westerly jet stream in the stratosphere not only weakens, but eventually reverses direction to become easterly. Black and his colleagues...

To continue reading

Request your trial

VLEX uses login cookies to provide you with a better browsing experience. If you click on 'Accept' or continue browsing this site we consider that you accept our cookie policy. ACCEPT