Fog!                                                            3/4

     1.  Could you briefly explain (in basic terms) stability and instability?

              A stable atmosphere is one in which air parcels tend to remain fixed in height above the surface.  An unstable
                 atmosphere is just the opposite, one in which parcels tend to move up and down vertically, causing convection
                 to develop.  Because ascending parcels tend to cool with ensuing condensation and often precipitation or
                 precipitation enhancement, instability is generally associated with stormy, or unsettled conditions.  Stability is
                 associated with fair skies or, sometimes, skies with stratiform clouds and often, unfortunately, air stagnation and
                 pollution episodes.

                 Whether the atmosphere is stable or unstable depends upon the environmental lapse rate.  The greater the
                 temperature drop with increasing altitude, the more unstable is the atmosphere.

    2.  What is the difference between isobars and isotherms?

              On a weather map an isobar is a line drawn through points where the barometric pressure (adjusted for altitude)
                 is equal.  An isotherm is a line drawn through points where the temperature is equal.