4.4.2.CLIMATIC CONDITIONS In some regions the climatic conditions can change significantly over the course of a year. These changes will, in turn, change the characteristics of a sign, making it easier or harder to use it as evidence. Additionally, the climatic conditions present whilst MA staff are observing signs can also impact the results.
The following climatic conditions should be considered:
DIRECT SUNLIGHT
UV radiation will change how discardables look over time, making them more likely to appear to be an item not associated with IEDs. Conversely, it may cause expansion and bulging of IED main charges, making them easier to identify through signs. The level of sunlight at the time of observation is extremely important. For example, sunlight coming through a window in a building may increase the degree to which a disturbance in the dust on the floor can been seen.
STRONG WIND
Strong winds can completely remove signs such as discardables or enhance other signs, such as disturbances.
ׁ WARNING. Strong winds can also create ‘false signs and indicators’ by spreading objects like plastic bags that can be misinterpreted as markers or transference signs.
HEAVY RAIN
Heavy rain can cause localised flooding that submerges signs, significantly changing their appearance and making them very hard to identify. It may also cause IED components to rust, degrade or expand, potentially creating new signs even several years after the IED was emplaced.
Image 67. Flattening and regularity where an IED main charge has been submerged under water due to rainfall
IED signs
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