Portfolio for the cold season. Distribution of the EOMs' weights as a function of the EOM numbers for March and December surveys. The weights for the surveys carried out in March (N = 10) are represented in black. The weights for surveys performed in December (N = 10) are given in red. The average values are superimposed. For the two instances where a December survey is followed by a March surveys three months later, the evolutions of the weights are represented by doted segments.