What causes

Clouds?What are their Names?

CumulusStratus

Cumulonimbus

Cirrus

How does the temperature change in the troposphere?

Adiabatic lapse rate = ΔT / ∆Alt. Adiabatic means TE insulated air parcel (imaginary box of

air)

Air Parcel

P VolTE stays the sameT

DALR = Dry adiabatic lapse rate = cooling rate for air parcel <dew pt. Moist ALR = cooling rate for a.p. > dew pt. (latent heat release)

ELR = Environmental lapse rate = surrounding atm. lapse rate ΔDew pt. = change due to P change Lifting Condensation Level = (DALR-Δdew pt)-1x (TG-dew pt) If ELR<DALR, then air is stable If ELR>DALR, then air is unstable, rising air will gain buoyancy

Altitude

(km)

DALR ~ 100C/km

ELR ~ 6.50/km

ΔDew Pt. ~ 20/km

T(0C)

Problem: Cumulus clouds are observed on a sunny afternoon. The temperature is 250C and the dew point is 70C. How high are the flat bottoms of the cumulus clouds?

Answer: 2.25 km or 7380 ft.

Cloud Types Lift Mechanism

1. Cumulus: A. Convection

B. Cold fronts

2. Stratus: C. Warm fronts

D. Stationary fronts

3. Cumulonimbus: E. Convergence

F. Orographic lift

4. Cirrus:

Match the cloud type with the probable lift mechanism(s).

A

C D E F

A B

B C D E

Name 2 ways that the moisture in an air sample can begin to

condense?1. Lower its temperature!

2. Add moisture!

Let’s recall a few terms and add one or two…

Adiabatic

DALR

ELR

Dew Pt. LR

AH

RH

MALR = Moist ALR, the lower LR caused by latent heat release during condensation

Moisture

Evaporation

Condensation

Dew Point

Undersaturation

Saturation

Supersaturation

Lapse rate

What is relative humidity (RH)?

Relative humidity is a percentage measure of the amount of moisture in the air compared to the total amount present at saturation for a given air temperature.

RH = Dv / SDv x 100%

Or

RH = Partial Pv / SPv x 100%Partial Pv is P of only water molecules attaching to microdroplet

SPv is P of water molecules attaching at dew point

Solve these problems about air samples?

Saturation Vapor Pressure at Given Temperature

Temp Sat Vapor Prs (mb)

Temp Sat Vapor Prs (mb)(C) (F) (C) (F)

-18-15-12-09-07-04-01020407101316

00051015202530354045505560

1.51.92.43.03.74.65.66.98.4

10.212.314.817.7

18212427293235384143464952

65707580859095

100105110115120125

21.025.029.635.041.048.156.265.676.287.8

101.4116.8134.2

1. T = 800F, Pv = 35 mb, RH?

RH = 100%

2. T = 700F, Pv = 10.2 mb, RH?

RH = 41%

3. TD = 280C, Pv = 4.6 mb, RH?

RH = 12%

4. RH = 50%, Pv = 14.8 mb, T?

T = 750F

5. T = 900F, RH = 30%, TD?

TD = 540F

6. Air just above the ground has a saturated vapor pressure of 4.0 mb. What phase of water will occur if the ground cools the air to the dew point?

Frost

Consider 2 parcels of air…Parcel 1: T=310F, Td=280FParcel 2: T=890F, Td=480F

1. Which parcel has the absolute humidity?Parcel 2

2. Which one has the highest RH?Parcel 1

3. Which one will reach its dew point first at equal cooling rates?

Parcel 1

4. If both parcels reach saturation, which one has the highest potential precipitation?

Parcel 2

What happens to rising air?

Altitude

Temperature

ELR-60C/km

DALR-100/km SPv

MALR: Latent heat released-5 to -60C/km

Td

Td

Stable atm

Unstable atm

tropopause

W. Jetstream