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We went for a walk down to the beach with teas. It was quite cold. There was frost on the grass, which was kinda weird since it didn’t seem that warm today.

I wondered about the frost for a while, and then thought about dew for a bit. Came home and looked at the weather info for Toronto, and saw that the Dewpoint is 7 degrees celcius. This led me to wondering what the hell dewpoint means, exactly, so I looked that up (but not in the encyclopedia, because I don’t have one.) This is what I learned from this USA Today site:

Dewpoint: the temperature air would have to be cooled to in order for saturation to occur. The dewpoint temperature assumes there is no change in air pressure or moisture content of the air.

So I kind of half understand now. Maybe if I feel like really finding out I’ll ask Adam, he’s the one with the physics hobby.

Also, I am reading and looking at pictures on this site.

This rambly and meaningless lj entry brought to you by a walk on the beach.

6 Comments

  • spadoink

    March 19, 2004 at 7:03 am

    from britannica, perhaps a little clearer…

    The meaning of dew-point temperature can be illustrated by a sample of air with a vapour pressure of 17 mb. If an object at 15° C is brought into the air, dew will form on the object. Hence, 15° C is the dew-point temperature of the air—i.e., the temperature at which the vapour present in a sample of air would just cause saturation, or the temperature whose saturation vapour pressure equals the present vapour pressure in a sample of air, is the dew point. Below freezing, this index is called the frost point. There is a one-to-one correspondence between vapour pressure and dew point. The dew point has the virtue of being easily interpreted because it is the temperature at which a blade of grass or a pane of glass will become wet with dew from the air. Ideally, it is also the temperature of fog or cloud formation.

    • Jenny Lee Silver

      March 19, 2004 at 9:32 am

      That’s a bit more detailed and informative. 🙂 Thanks!

      • spadoink

        March 19, 2004 at 5:31 pm

        ya gots to love my reference power!

      • spadoink

        March 19, 2004 at 5:31 pm

        ya gots to love my reference power!

    • Jenny Lee Silver

      March 19, 2004 at 9:32 am

      That’s a bit more detailed and informative. 🙂 Thanks!

  • spadoink

    March 19, 2004 at 7:03 am

    from britannica, perhaps a little clearer…

    The meaning of dew-point temperature can be illustrated by a sample of air with a vapour pressure of 17 mb. If an object at 15° C is brought into the air, dew will form on the object. Hence, 15° C is the dew-point temperature of the air—i.e., the temperature at which the vapour present in a sample of air would just cause saturation, or the temperature whose saturation vapour pressure equals the present vapour pressure in a sample of air, is the dew point. Below freezing, this index is called the frost point. There is a one-to-one correspondence between vapour pressure and dew point. The dew point has the virtue of being easily interpreted because it is the temperature at which a blade of grass or a pane of glass will become wet with dew from the air. Ideally, it is also the temperature of fog or cloud formation.