where C p,L : specific heat of liquid H 2 O, C p,L = 75.42 J mol -1 K -1 , ρ : density of liquid H 2 O, M 0 : molecular weight of H 2 O. As for dT L /dt, we consider that it is given by the wet lapse rate multiplied by the updraft velocity, since the droplet temperature, T L , should closely follow the air temperature. The wet lapse rate in the shaft experiment was reported to be -0.006 K m -1 by Tsuchiya et al. , while the updraft velocity was 0.7 m/s. Therefore, dT L /dt = -0.006 × 0.7 = -0.0042 K/s .