Objectives • Clouds and the energy cycle • Electromagnetic radiation ...

3 downloads 7 Views 3MB Size Report
An Introduction to Atmospheric Radiation - K.N. Liou, Academic Press. • Atmospheric Science: An Introductory Survey –J.M. Wallce and P.V. Hobbs,. Academic ...

Lecture-2

Objectives • Clouds and the energy cycle • Electromagnetic radiation • Concepts of Scattering and absorption

Reference books • An Introduction to Atmospheric Radiation - K.N. Liou, Academic Press. • Atmospheric Science: An Introductory Survey –J.M. Wallce and P.V. Hobbs, Academic Press

Clouds and the energy cycle

High Clouds

Low Clouds

Deep Convective Clouds

5

6

7

Vertical profiles of cloud droplet size distribution observed in continental and maritime clouds

9

4000 June 15

Height above CB (m)

3500

June 16

3000

June 22

2500 2000 1500 1000 500 0

(d) 0

5

10 Reff (m)

15







A cloud with a greater number of small droplets has more reflective surface area than a cloud of the same volume with fewer large droplets. Therefore, aerosols increase the reflective surface area of the cloud by acting as condensation nuclei. This is the first indirect effect, or Twomey Effect.

Same volume, more surface area









Clouds precipitate when droplets collide and coalesce. If droplet size is smaller because of increased aerosols, then the clouds will not precipitate as much. If the cloud does not precipitate, then it retains its water, lasts longer, and becomes larger and more reflective. This is the second indirect effect.

11

Detecting and Quantifying AIE Cloud

Aerosol

(CDNC, LWC, re ff )

(number conc., CCN) At constant LWC

Changes in cloud parameters (CDNC, reff ) as a function of changes in CCN and its proxies

_ d ln re d ln Na

d ln Nc d ln Na CCN proxies

7000

Cloud droplet Reff, Size distribution, LWC

Height, m

6000

5000

H

4000

3000

HW(g/m3) CDP_LWC[g/m3]

2000 0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

-3

HW (gm )

Updraft

Aerosol, CCN Cycle below cloud base

3.5

3.0 8000

June 16, 2009

7000

Hyderabad

6000

2.0

5000

1.5

Altitude, m

-3

CDP LWC (g/m )

2.5

1.0

0.5

4000 3000 2000

CDP LWC=1.06*HW LWC+0.03 R=0.92, N=515, P