Today most of the persistent contrails in my area seem to be quite dense and "puffy" or "woolly", like altocumulus cloud texture. Other days they are thinner, more hazy and more cirrus like.

Does anyone know what factors affect this? I'm assuming it's something to do with altitude and temperature, as altocumulus clouds are generally lower than cirrus.

From what I have read, altocumulus cloud is made of supercooled water droplets whereas cirrus is made of ice crystals. Does that mean that these contrails are liquid water rather than ice? And if so how does that affect the persistence? Do we need to consider RHw rather than RHi?