How does wind shear radar (used in airplanes to avoid dangerous
weather) detect lateral and vertical air movement?

I understand the physics of the doppler effect, but I don't see how a
bounced-back wave can carry information about lateral or vertical
movement of an object.

I'm looking for a basic explanation, nothing too technical, maybe
something you'd find in a basic physics textbook.

Hello Piledrivingbob,

There are actually several different types of systems used on aircraft
to help predict wind shear. A plane may use one or more of these as
well as getting help from ground based radar. A relatively short
summary (with illustrations) of these is at
  http://www.geo.mtu.edu/department/classes/ge406/jmedward/windsheer/solution.htm
This specific page was written in 1993, but the techniques described
are still relevant. Search using:
  wind shear aircraft radar
for several other pages, some from government / professional sites,
and others such as
  http://www.geocities.com/khlim777_my/fpwindshearx.htm
which describes the Boeing 777 aircraft radar and its operation during takeoff.

The following summarizes several types of systems and how they work:

Microwave Radar - detects the relative motion of raindrops. If you see
different densities in the rain, that indicates different conditions
in the area scanned. Large changes in signal strength may indicate
wind shear in an area. If combined with a doppler system, can also
detect the motion relative to the aircraft. Again, if the motion
changes abruptly, wind shear is predicted.

Doppler LIDAR - using laser technology, does similar processing to the
Radar, but is looking more at aerosols, not rain. May do poorly in
clouds / rain (less penetration distance) but has other advantages
(e.g., less interference from ground conditions).

Infrared - looking for "cool" pockets of air / rain in front of the
aircraft. A pretty simple system to implement, it assumes that
dangerous winds (e.g., downdraft) are cooler than the surrounding
conditions.

Ground Based Radars - more complex than can be effectively flown in
aircraft, a ground based radar can be directed to view the flight
paths of approaching / departing aircraft. In this case, the system
provides data to the flight controller and/or crew to provide the wind
shear warnings.

Several other good sites are also available. A longer explanation of
weather radar in general and wind shear detection is at:
 http://www.mnsu.edu/weather/wx_WALTER/Modules/Radar/radar_edu.html
As you scroll down, it describes a number of weather phenomena and how
they are detected / what they mean.

For more specific information, try searches such as:
  predict wind shear
  detect wind shear
  weather radar explanation "wind shear"
  LIDAR explanation "wind shear"
  infrared explanation "wind shear"
and similar searches.

If you need more specific information on a technique or if part of the
answer is unclear, please make a clarification request.

  --Maniac

Just what I was looking for, thanks!