SIO 217B Atmospheric and Climate Sciences II
Winter 2012
Homework #2
Due February 2 at the beginning of class
1. Two dominant features of wintertime near-surface atmospheric circulation over the
midlatitude NH are large semi-permanent low pressure centers located over the North
Pacific and North Atlantic. They are commonly called the Aleutian Low and the
Icelandic Low as a result of where the lowest SLP is located. The continents are
contrastingly dominated by the semi-permanent Siberian High and North American
High. The wintertime pattern of low SLP over ocean and high SLP over land reverses
during summer, when near-surface circulation over the ocean is dominated by the
North Pacific High and the Bermuda/Azores High. The center of the former is located
over the North Pacific at the latitude of California, and the center of the latter is
located over the Azores and/or Bermuda. These large and SLP low and high centers
affect the meridional direction of the near-surface wind, but the zonal component is
generally always westerly at middle latitudes.
(a) Explain why NH midlatitude oceans have low SLP during winter but high SLP
during summer and NH midlatitude continents have high SLP during winter but low
SLP during summer. Hint: consider that the ocean has much greater thermal inertia
than land.
(b) Assuming surface friction is negligible, what will be the direction of the
meridional component of the near-surface wind on the eastern and western sides of
the ocean basins during winter and summer? Why?
(c) At the same latitude, the western coasts of continents are typically warmer than
the eastern coasts during winter but cooler during summer. Provide one reason for
this in terms of meridional temperature advection. Provide another reason for this in
terms of zonal temperature advection.
2. Midlatitude winds have a much stronger westerly component in the middle and upper
troposphere than is the case near the surface. There is also much less land/ocean
difference in the meridional wind component in the middle and upper troposphere
than is the case near the surface.
(a) Explain why the wind is strongly westerly in the middle and upper troposphere at
middle latitudes.
(b) Describe whether winds will turn cyclonically or anticyclonically with height on
the eastern and western sides of the NH midlatitude ocean basins during summer and
winter. Describe whether warm or cold advection occurs on the eastern and western
sides of ocean basins during summer and winter.