Cirrus Crystal Terminal Velocities

The fall speeds of sub‐100 µm ice crystals

“…Bullet-rosettes are often the dominant crystal habit in cirrus clouds (Heymsfield and Iaquinta, 2000) which are typically composed of between two and six bullet crystals in a radial formation. Small 'embryonic' bulletrosettes less than 100 µm in diameter have been observed (Figure 2 of Heymsfield and Iaquinta), and the fall speeds of these particles have been estimated using the HubbardDouglas and MHKC theories.…”

A concept for a satellite mission to measure cloud ice water path, ice particle size, and cloud altitude

“…Most important in this respect are assumptions on ice particle size, mass, and cross-sectional area, because these properties directly influence the particle fall velocities (Heymsfield and Iaquinta, 2000;Kristjansson et al, 2000).…”

“…These depend on the ratio of the particle mass to its area perpendicular to the fall direction. Heymsfield and Iaquinta (2000) have shown how this dependence can be parametrized as a function of the particle size. Thus, information on the effective particle size D me can be used to derive direct information on the effective ice particle fall speeds.…”

The influence of radiation on ice crystal spectrum in the upper troposphere

“…The expressions for the mass and terminal velocity of bullets come from Heymsfield and Iaquinta (2000); the expression for the dimensional relationship from Heymsfield (1972); and the expressions for the ventilation factors from Hall and Pruppacher (1976). Using those Figure 4.…”

“…The expressions for the mass and terminal velocity of columns come from Heymsfield and Iaquinta (2000), and that for the dimensional relationship from Auer and Veal (1970) and Heymsfield (1972). Figure 4 displays the time-scale for columnlike crystals against r * and shows that τ (1 − ε r η) is close to 3.6 days when r * is between 10 and 60 µm.…”