Sunday, August 06, 2017

Prescribed burns principles. Oh, yes. There are many principles and morality involved in all these decisions.

They gotta know their stuff. It is about water temperature of the oceans. Unless the corals are coming out of the laboratory more hearty then their predecessors, I remain concerned for the outcomes. 

...Weather conditions needed for the burn (click here)

Relative humidity and dew point are the most important factors, since they will have a controlling influence on fuel moisture. Even if the fuel was dry yesterday, a strong dewfall on the morning of the burn may delay things.

Weather conditions that are best for savanna burns are often different than for prairie burns. Whereas a wind speed of 5 mph and a relative humidity of 50% may be fine for a prairie burn, the conditions for a savanna burn should include a stronger wind speed and a lower relative humidity (for instance; 10-15 mph wind and 25-30% relative humidity). Oak leaves take longer to dry out than vertically standing grass, and flame heights are much lower, so the fire does not carry as well with lower wind speeds.

Wind direction is another important factor and the required direction will depend upon the location of the burn unit in relation to surrounding areas. Certain types of burn units can only be burned when the wind is from particular directions. Also, wind direction must be considered with different slopes and aspects of the site. A wind shift during a burn can have major effects, making it perhaps necessary to put out a burn that is already in progress (often difficult to accomplish). A north wind is generally associated with a cold front and a south wind with a warm front.

The ideal wind is one that is steady from the same direction throughout the duration of the burn. A very light wind, or none at all, may make the burn more difficult to accomplish. A steady 5 mph wind is preferable to no wind at all. For savanna burns, with their low flame heights and thin fuels, the wind should be at least 5 mph, preferably 8-10 mph, or on flat topography up to 15 mph. A steady wind of 10mph is better than a gusty wind of 5 mph.

Another consideration for wind direction is smoke management. If the burn is in an urban or suburban area, a wind direction must be selected that will blow the smoke away from the built-up area. Also, the wind cannot be allowed to blow smoke across a major highway.

Temperature is another important factor, because hot fuels ignite better than cold ones. Also, temperature affects relative humidity. A temperature of 75 degrees F may be too hot for a prairie burn but could be just right for a savanna burn. An ideal temperature for a spring savanna burn is 70 F, but successful burns can be accomplished at temperatures as low as 50 F when the R.H. is low and there is a good strong wind from the right direction....