Stratosphere-Troposphere Coupling Studies

Northwest Research Associates, Incorporated, Seattle WA

Investigators

Abstract

The objective this research is to explore stratospheric variability and stratosphere-troposphere coupling, with an emphasis on how the stratosphere influences the troposphere. The stratosphere appears to be providing early evidence of global (surface) warming, which is observed as stratospheric cooling. Such trends are obfuscated in the stratosphere by interannual variability resulting from influences such as the quasi-biennial oscillation (QBO), solar cycle, volcanic eruptions and internal dynamics. One such mode of variability, the Arctic Oscillation (AO) has climate impacts very similar to the North Atlantic Oscillation (NAO) and shows strong coupling to the stratosphere. Modeling studies with increased greenhouse gases show that stratospheric trends, may through vertical coupling, amplify or induce tropospheric trends. The PIs will (i) use objective analysis techniques with reanalyzed NCEP and TOVS data to understand the process by which stratospheric circulation anomalies tend to propagate downward into the troposphere; (ii) examine the Southern Hemisphere, especially in late spring, to see if the same phenomenon can be seen; (iii) investigate and understand the relationship between observed poleward and downward propagation of zonal wind anomalies (within the stratosphere on a time scale of 2-3 mo) and downward propagation of the AO to the troposphere (~ 3 week time scale); (iv) investigate modes of variability in zonal wind to understand the relationship between tropical upper stratospheric zonal wind anomalies (~30-50 km) and high-latitude circulation anomalies in both hemispheres; (v) examine coupled patterns in the upper troposphere and lower stratosphere that explain the flux of wave activity from the troposphere to the stratosphere. The work is important because it will increase our understanding of stratosphere-troposphere coupling mechanisms. This could have implications for climate predictability.