Unrelated, but let's discuss about the Cirno-type's ability to generate cold air year-round and the possibility of their usage as an energy storage device.
The generation of cold air is only an illusion caused by the human sensory system; the correct description of the event would be "to draw heat from the air and causing it to become cold". This can be proven by the following Gibbs free energy equation:
ΔG = ΔH - TΔS (1)
which can be converted into
ΔH = ΔG + TΔS (2)
As can be seen from (2), if normal air cools down to become cold air, then it would be a spontaneous process (ΔG < 0) with a negative entropy (ΔS < 0). Combined with a positive absolute temperature (T > 0), this would result in ΔH being always negative, or there would always be heat generated in this process. Normally, if we're talking about an air conditioner, then this heat would go out of the outdoor unit in the form of an infernally hot and dry wind. But this is a Cirno and not an AC or a refridgerator, so it'd only be natural to assume that this thermal energy is stored within the yukkuri's body, instead of being released somewhere - otherwise a Cirno would not be universally cold, having alternating regions of heat and chill instead.
Thusly, subsequent questions are raised: if a Cirno can store thermal energy within itself, then would it be plausible to use it as a medium for storing and transporting heat? What is its rate of energy absorption, and its maximum storage capacity? If a Cirno can constantly absorb thermal power from the ambient temperature, then what would be the method to control its charge/discharge status, and thus preserve it without causing it to melt prematurely from overly consuming energy beyond its capacity? And when heat is required, how would it be extracted from a storage Cirno? Last but not least, how would its efficiency compare to other methods of energy storage, namely electrical (electricity and a heating rod) and chemical energy (burning gasoline)?
Thusly, subsequent questions are raised: if a Cirno can store thermal energy within itself, then would it be plausible to use it as a medium for storing and transporting heat? What is its rate of energy absorption, and its maximum storage capacity? If a Cirno can constantly absorb thermal power from the ambient temperature, then what would be the method to control its charge/discharge status, and thus preserve it without causing it to melt prematurely from overly consuming energy beyond its capacity? And when heat is required, how would it be extracted from a storage Cirno? Last but not least, how would its efficiency compare to other methods of energy storage, namely electrical (electricity and a heating rod) and chemical energy (burning gasoline)?
-_- I doubt there would be an actual consensus about yu abilities but for the sake of lore creation (particularly mine) I would bite.
The regular adult cirno types would be about half the size of a regular adult marisa.
It can tolerate the heat of an average japanese spring. On the early summer months, it migrates as a flock to cooler areas.
The reason why it migrates as a flock is because if it flies on its own it will be stressed by the heat and may incur anti-yukkuritis.
Cirno types heal very fast if it is cool enough that its cool temperature allows the formation of ice crystals that coat its body.
Only when the core is damaged by force or anti-yukkuritis is when cirno types die and melt for good.