Bioprecipitation, the concept of rain-making bacteria, was proposed by David Sands from Montana State University. Such microbes – called ice nucleators – are found in rain, snow, HP Pavilion dm4-1008tu Battery and hail throughout the world. These bacteria may be part of a constant feedback between terrestrial ecosystems and clouds and may even have evolved the ability to promote rainstorms as a means of dispersal. They may rely on the rainfall to spread to new habitats, much as some plants rely on windblown pollen grainsHP Pavilion dm4-1008tx Battery.
Families A and B: All cirriform-category clouds are classified as high-range family A and thus constitute a single genus cirrus (Ci). Cumuliform and stratiform-category clouds in the high-altitude family carry the prefix cirro-,HP G62-144DX Battery yielding the respective genus names cirrocumulus (Cc) and cirrostratus (Cs). Similar genera in the middle-range family B are prefixed by alto-, yielding the genus names altocumulus (Ac) and altostratus (As).
Families C and D1: Any cumuliform or stratiform genus in these two families either has no prefix or carries one that refers to a characteristic other than altitude. HP G62-145NR BatteryThe two non-prefixed genera are non-convective low stratus (St: family C) that usually forms into a comparatively thin layer, and free-convective cumulus (Cu: family D1) that has moderate upward-growing vertical extent. One prefixed cloud in this group is stratocumulus (Sc: family C), HP G62-147NR Batterya low-range genus of limited convection that has some stratiform characteristics (as do the middle and high-based genera altocumulus and cirrocumulus, the genus names of which exclude strato- to avoid double-prefixing). The other prefixed cloud is nimbostratus (Ns: family D1), a non-convective genus that has moderate downward-growing vertical extent, HP G62-149WM Battery  and whose prefix refers to its ability to produce significant precipitation.
Family D2: This family comprises towering free-convective clouds that typically grow upward to occupy all altitude ranges. Their genus names also carry no height-related prefixes. They comprise the genus cumulonimbus (Cb) and the cumulus species cumulus congestus (Cu con). HP G62-150EE BatteryThe latter type is designated towering cumulus (Tcu) by the International Civil Aviation Organization. Under conditions of very low humidity, free-convective clouds may form above the low-altitude range and, therefore, be found only at middle- and high-tropospheric altitudes. In the modern system of cloud nomenclature, cumulonimbus is something of an anomaly. The cumuliform-category designation appears in the prefix rather than the root, HP G62-150EF Batterywhich refers instead to the cloud’s ability to produce storms and heavy precipitation. This apparent reversal of prefix and root is a carry-over from the 19th century, when nimbus was the root word for all precipitating clouds.