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  • From: EarthNSky <erthnsky AT bellsouth.net>
  • To: Homestead List <homestead AT lists.ibiblio.org>
  • Subject: [Homestead] frosts and freeze information
  • Date: Thu, 08 Jan 2009 13:10:35 -0500

While looking at some weather data, I came across this page that talks
about frosts and freezes and has some good information and advice about
planting locations to avoid damage. I've pasted the guts of the article
here, but if you want to read more about frosts and freezes in GA, here
is the link
http://pubs.caes.uga.edu/caespubs/pubcd/MP117/MP117.htm

In many areas of Georgia, cold temperatures in late fall, winter and
spring can pose a threat to row crops, fruit trees and horticultural
plants. Exposure of sensitive crops to freezing temperatures (below
32o F) can result in significant damage and, in some cases, total
crop loss. For example, open peach and blueberry blooms are typically
damaged at 28-29 oF and below, although green fruit may be damaged at
higher temperatures. Susceptibility to frost depends on the health
and growth stage of the plants, and the intensity and duration of the
frost events.

The terms frost and freeze are often used synonymously, and frost
events fall into two categories, namely: radiation and advective.
Radiation frost is characterized by a clear sky, calm or very little
wind, temperature inversion, a low dew point temperature and an air
temperature that typically falls below 32° F during the night.
Cooling occurs due to energy loss through radiant exchange during
clear, calm nights (Snyder and Melo-Abreu, 2005). The temperature
falls faster near the radiating surface, causing a temperature
inversion, i.e., temperature increases with height above the ground.
Radiation frost is the most common type of frost in Georgia.
Advective frost occurs when a mass of cold air moves into an area and
displaces warmer air that was present prior to the weather change. It
is associated with cloudy conditions, moderate to strong winds, no
temperature inversion and low humidity.

The potential for frost damage depends on local conditions. Both
monitoring and local knowledge can prevent and/or minimize frost
damage. Most farmers and growers have a good idea about areas of cold
spots - where cold air settles - within their fields. As the air near
the ground cools, it becomes denser and flows back down the slope.
Generally, low spots where cold air settles are not suitable for
planting frost-sensitive crops such as blueberries and peaches unless
a frost protection system is installed. Also, areas where the natural
or modified topography prevents cold air drainage from the site
should be avoided. Because ground fog forms in low spots first, a
good rule of thumb is to avoid places where ground fog forms early.
Review local topographical maps before planting frost-sensitive crops
on high-risk sites.

Frost affects different aspects of agricultural and horticultural
production. There are more economic losses to frost damage than to
any other weather-related phenomenon (White and Haas, 1975).
Information about dates of the last frost events in the spring can
help farmers decide when to plant their crops. Similarly, information
on early frost dates in the fall can be useful for deciding when to
harvest.


--
"The world is my country, all mankind are my
brethren, and to do good is my religion."
Thomas Paine (1737 - 1809)



  • [Homestead] frosts and freeze information, EarthNSky, 01/08/2009

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