Fig. 6-CO, p. 138

Fig. 6-1, p. 140

Fig. 6-2, p. 141

Table 6-1, p. 141

Fig. 6-3, p. 142

Fig. 6-4, p. 142

Fig. 6-5, p. 143

Fig. 6-6, p. 143

Fig. 1, p. 144

Fig. 6-7, p. 145

Fig. 6-8, p. 146

Fig. 6-9, p. 146

Fig. 6-10, p. 147

Fig. 6-11, p. 147

Fig. 6-12, p. 147

Fig. 6-13, p. 148

Fig. 6-14, p. 148

Fig. 6-15a, p. 149

Fig. 6-15b, p. 149

Fig. 6-15c, p. 149

Fig. 6-15d, p. 149

Convection and Clouds• A thermal starts the convection current

rising as it reaches the LCL the cloud forms.

• Convection continues and the cooler air (because of Condensation) flows outside the cloud and back down to the surface.

• As clouds grow they cut off heating and convection. Without rising air, the cloud will begin to erode as droplets evaporate.

Fig. 6-16, p. 150

Fig. 6-17, p. 150

Convection and Clouds

• As the cloud dissipates the heating renews and new thermals are produced which generate another cumulus cloud.

• Cumulus come and go at the same spot. • However, if the air is hot and humid and the

sky is full of cumulus clouds then, if there is no mixing of air, one thermal produces a cumulus cloud when RH is

• 100% and rising air remains saturated...•

Convection and Clouds

• Let the lower region (A) of air below the LCL is conditionally unstable. Above the LCL (B) the air is absolutely stable and above that (C) there is a subsidence layer where the air is also absolutely stable.

• Region A ELR = 7.5oC/km

• Region B ELR = MALR = 6oC/km

• Region C ELR = +6 oC/km

Fig. 6-18, p. 151

Convection and Clouds

• If in Region B, the ELR becomes greater than the MALR, then the region becomes conditionally unstable and Cumulus Congestus clouds form.

• If Regions A&B are both conditionally unstable, then Cumulonimbus form.

• CN clouds are rarely in the stratosphere, they tend to spread out and form an anvil

• at the top. At mid-lat, winds flatten the top.

Fig. 6-19, p. 151

Fig. 6-20, p. 152

Fig. 6-21, p. 152

Fig. 2, p. 153

Fig. 6-22, p. 154

Mountain Wave Clouds

• Some clouds form on the lee sides of mountains.

• Stable air over a mountain may move in a wave shape.

• Dry and near the top --> rotor clouds

• Moist above top --> mountain wave clouds

• Moist very high above the top ---> Lee wave clouds.

Fig. 6-24, p. 155

Fig. 6-25, p. 155

Fig. 6-23, p. 155

Fig. 3, p. 156

Fig. 4, p. 156

Fig. 5, p. 156

Fig. 6, p. 157

Fig. 7, p. 157

Changing Cloud Forms

• With certain conditions

• altostratus --> altocumulus

• Conditions are: top of cloud -->cools

• bottom of cloud -->warms

• Similar effects for: stratocumulus and

• cirrocumulus

Changing Cloud Forms

• Uniform wind through cloud layer --> cloud streets. New cloud elements appear uniformly distributed.

• When wind reaches a critical value --> billow clouds form.(Tops have wave shape form)

• Altocumulus castellanus form when rising air causes conditionally unstable air above the cloud. The heat comes from condensation.

Fig. 6-26, p. 158

Fig. 6-27, p. 158

Fig. 6-28, p. 158

Mixing Moist Layers

• Vertical mixing of moist stable air by the wind, causes the lower warm air to warm more and the top to cool, causing saturation and stratocumulus clouds to form.

• If surface is very warm, thermals may move into the stable region and form congestus cumulus or cumulus clouds.

Fig. 6-29a, p. 159

Fig. 6-29b, p. 159