Clouds and storms

1
ATOC 4720 class20

• Clouds and storms
• 1. Cloud morphology
• 2. Types of clouds
• 3. The air-mass thunderstorm

2
From class-19
1

• Thermoelectric effect in ice
• T- degree C V--mV

2 Supercooled water in clouds
3
3. Lightning and thunder
Class-19
Dielectric breakdown Vgt3MV/m (dry) Vgt1MV/m
Moist with 1mm in radius
Lightning T--30,000K Thunder Shock waves
4
1. Cloud morphology
Clouds Mechanisms of formation 1 Convective
clouds local ascent of warm, conditionally
unstable air 0.1-10km in diameters
Vertical velocity w a few m/s Liquid
water or ice content
5
(No Transcript)
6
2 Layer clouds stratus Forced lifting of
stable air Examples fog is forced lifted
upwards cold fronts lift warm
air mass Hundres--thousands km Lifting rates a
few cm/s Water a few tens Tens of hours
7
stratus
8
3 Orographic clouds
Forced lifting of air by hills or
mountains Uplifting velocity depends on
windspeed and direction, And mountain height. Can
be a few m/s Water a few tens Can be
transitory, or can stay for long if winds are
Steady.
Lee waves can also produce orographic clouds
http//www.faa.gov/and/AC0057/AC0057.HTM
9
Orographic clouds
10
4 Advection fog Cooling of air below its dew
point due to warm air is Advected to a colder
surface.
11
Fog
12
5 Arctic sea-smoke (steam fog) Meeting of
two parcels of air with different temperatures
both close to be saturated.
13
Arctic sea-smoke
14
6 Funnel clouds
Adiabatic expansion and cooling due to a rapid
local Reduction in pressure.
Tornadoes or water spouts.
15
Funnel clouds
16
Funnel clouds
17
7 Instabilities (Kelvin-Helmholtz instabilities)
Strong wind-shear modify cloud shape
18
Billow clouds K-H instability
19
Types of clouds
Many types (International cloud Atlas) Cumulus
Stratus Cirrus Nimbus (combination) Cirrostratus
20
Cumulus
21
Cumulus tower
22
Cumulonimbus
23
Stratus
24
Cirrus clouds
25
Cirrostratus halos