and (2) an increase in the magnitude and
efficiency of the meridional eddy transport of latent heat,
which reduces the number of cyclones required to maintain
the meridional temperature gradient [Zhang and Wang,
1997]. Consistent with these studies, we find that the
meridional temperature gradient in the lower troposphere
between 30N and 55N over eastern North America weakens
in summer by about 1C. Over mid-latitudes at 600 –
800 hPa, the northward, zonally averaged eddy transport
of latent heat increases in summer by 5 – 10%