Cloud Types

1. Cloud Types Most common clouds are classified into ten categories using three criteria: Height of cloud base Cloud form, shape, appearance Whether or not cloud produces precipitation

2. Cloud Types (cont’d) • Categories based on height of cloud base • Low clouds (lower troposphere) • Middle clouds (middle troposphere) • cloud name usually includes “alto” • High clouds (upper troposphere) • Clouds of vertical development • base often low, but cloud might be very tall

3. Cloud Types (cont’d) • Categories based on form, shape, appearance • Cirroform(wispy) • cloud name includes “cirr(o)” prefix • cloud made of ice crystals • Stratiform(a layer: horizontally extensive, relatively shallow and flat; in pure form, featureless) • cloud name includes “strat” • Cumuliform (individual “cells”, or wavy) • cloud name includes “cumul” (Note: Some clouds are hybrids of two or three forms; e.g., horizontally extensive layers of individual cells or waves)

4. Cloud Types (cont’d) • Precipitation production • Clouds that produce precipitation • cloud name contains “nimbo” prefix • outside the tropics, part of cloud must contain mixture of water droplets and ice crystals • requires that upper parts of cloud be cold enough (but not too cold) • hence, cloud must be deep enough so upper parts will be high enough and hence cold enough • Clouds that don’t produce precipitation • most clouds are in this category