Clouds and Climate Through a Soda Straw

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Clouds and Climate Through a Soda Straw

• Mark Miller

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Earths Radiation 288 K
Suns Radiation 6000 K
Quantity of Radiation
Visible
Infrared
3
10
0.5
Wavelength (micrometers)
3

Visible Satellite Photo
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Infrared Satellite Image
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Source NASA/ Earth Radiation Budget Experiment
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• The study of climate and climate change is
  hindered by
• a lack of information on the effect of clouds on
  the
• radiation balance of earth.
• Ramanathan et al., 1989 Science, 243, 57-62.

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Figure 2.10

• IPCC Working Group I (2007)

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Representing Clouds in Climate Models
CLIMATE MODEL GRID CELL
60-N
Weather Forecast Model Grid Cell
Cloud Resolving Models Less Than Width Of Lines
55-N
172-W
157-W
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What Cloud Properties Change the Net Radiation
Received at the Surface?

• Amount of the sky that is covered
• Thickness
• Composition
• Contain ice crystals, liquid water, or both?
• Particle sizes?
• Particle concentrations?
• Height in the atmosphere

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How Does the Location of Cloud Impact the Surface
Temperature?
Space
High Clouds
10-km
Low Clouds
2-km
COOLING
WARMING
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What We Know About Solar Radiation and Clouds

• Solid theoretical foundation for interaction
  between a single, spherical liquid cloud droplet
  and sunlight

• Cloud Droplet

• Sun

• Scattered
• Light

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What We Know About Solar Radiation and Clouds

• Some theoretical foundation for interaction of
  sunlight and simple ice crystal shapes

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The Real World
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What We Wish We Knew About Solar Radiation and
Clouds

1. How do we compute the total impact of a huge
   collection of diverse individual cloud particles?
2. What are the regional differences in cloud
   composition, coverage, thickness, and location in
   the atmosphere?
3. If we knew (1) and (2), how do we summarize all
   of this information so that it can be
   incorporated into a climate model?

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What We Know About Outgoing Terrestrial Radiation
and Clouds

• Good theoretical foundation for interaction of
  terrestrial radiation and cloud water content
  (liquid clouds).
• Particle
• radius somewhat important in thin liquid clouds
• shape and size somewhat important in high level
  ice clouds (cirrus)
• Aerosols?

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CloudsThrough a SODASTRAW!
2-km
Meteorological Tower
Multiple Radars
Calibration Facility
Multiple Lidars
Surface Radiation
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The ARM Southern Great Plains Site
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SGP Central Facility SODA STRAW
Extended Measurement Facilities
Wichita
Oklahoma City
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What types of remote sensors do we use to make
cloud measurements?

• Visible and Infrared Sky Imagers
• Vertically-Pointing Lasers (LIDARs)
• Measure the height of the lowest cloud base
• Below cloud concentrations of aerosol and water
  vapor
• Beam quickly disperses inside cloud
• Cloud Radars
• Information about cloud location and composition
• Microwave Radiometers
• Measure the total amount of liquid water in
  atmosphere
• Cant determine location of liquid
• Presently not measuring total ice content

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Visual Images of the Sky

• cloud coverage (versus cloud fraction)
• simple! digitize images and
• daytime only
• integrated quantity

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A Time Series
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The Past Few Days in Oklahoma
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have been for the birds!
3/20/08
3/21/08
3/22/08
3/23/08
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Sky Imaging

• 500 nm
• RV Ron Brown
• Central Pacific
• AOT0.08

• AMF
• Niamey, Niger
• AOT2.5-3

• Sea of Japan
• AOT0.98

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Laser Data from Southern Great Plains
20-km
No Signal
10-km
Low Clouds
Ice Clouds
Surface
time
24 Hours
700 pm
700 am
700 pm
Negligible Return
Cloud and Aerosol Particles
Cloud droplets
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• V4500m

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• V700m, Mass Concentration1,700mg m-3

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Niamey, Niger, Africa

• 20

Cloud Droplets

• 15

Cloud and/or Aerosol
Height (km)

• 10

• LIQUID CLOUDS

• 5

• Biomass Burning
• Dust

Negligible Return

• 0

• 1200

• 0000

• 0000

Time (UTC)
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• Dust product (upper) and GERB OLR (lower) for
  1200UT on 8 March 2006

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At a Given Wavelength
A Cloud Particle At Different Wavelengths
Energy Returned to Radar
Energy Returned to Radar
radius6
wavelength-4
Size of Cloud Particle
Radar Wavelength
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94 GHz
35 GHz
Maximum Propagation Distance
Energy Absorbed by Atmosphere
10-15 km
20-30 km
3.2 mm
8 mm
Radar Wavelength
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The DOE Cloud Radars
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Cloud Radar Data from Southern Great Plains
20-km
Black Dots Laser Measurements Of Cloud Base
Height
10-km
Surface
time
700 pm
700 am
700 pm
Small Cloud Particles
Typical Cloud Particles
Very Light Precipitation
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Cloud Radar Data from Southern Great Plains
20-km
Black Dots Laser Measurements Of Cloud Base
Height
10-km
Thin Clouds
Insects
Surface
time
700 pm
700 am
700 pm
Small Cloud Particles
Typical Cloud Particles
Very Light Precipitation
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Top
Radar Echo
Low Radar Sensitivity
10-km
Base
Radar Echo
Top
Base
2-km
Emission
Radar Echo
Surface
Microwave Radiometer
Laser
Radar
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Evolution of Cloud Radar Science

• Cloud Structure and Processes
• Cloud Statistics
• Cloud Composition

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Applications of Surface-Based Cloud Observing
Systems
Example Marine Cloud Transitions
Solid Overcast
Broken Cloud
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Application of Surface-Based Remote Sensing to a
Cloud Problem

• Marine Stratocumulus Transition

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THEORY
Mid-latitudes
Tropics
2 km
0.5 km
Ocean Surface
OBSERVED
Mid-latitudes
Tropics
2 km
0.5 km
Ocean Surface
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Tropical Western Pacific
Jan 1999
June 1999
15-km
10-km
5-km
Cloud Top Height
3
1
3
10
1
10
Probability
Probability
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Retrieving Liquid Cloud Composition
Mode Radius??
Height
Width
Mode Radius


Number

Height
Particle Size
Height
Radar Echo Intensity
Number Concentration??
Number Concentration
Total Liquid Water (Microwave Radiometer)
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Liquid Cloud Particle Mode Radius
6
4
Height (km)
2
0
time
700 pm
700 am
700 pm
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17
1
4
10
Micrometers
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Active and Passive Cloud Remote Sensors (cont.)

• Wind Profiler
• 75-m, 6-min resolution
• 915 MHz 1270-1400 MHz COPS
• Minimum Height 120-m
• Maximum height 5.5-km
• Atmospheric Emitted Radiance Interferometer
  (AERI)
• 3-19.2 mm (1 cm-1 resolution)
• 6-min resolution (20-30 sec possible for COPS)
• 1.3 degree field-of-view

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AERI Spectra
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Analysis of the Impact of Clouds on Radiation
Remotely-Sensed Information about Cloud
Structure and Composition
Existing Theoretical Models of Radiation Transfer
Through Clouds
Compute the Energy Budgets at the Surface
and Top-of-Atmosphere
Compare with Coincident Measurements of the
Energy Budget
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Meteorological Models

• Global Climate Model (GCM)
• Forecast Period Decades to Centuries
• Resolution 300-km x 300-km
• Crude Representations of Many Processes
• Numerical Weather Prediction Model (NWP)
• Forecast Period Hours to a Few Days
• Resolution 29-km x 29-km
• Better Representations of Many Processes
• Cloud Resolving Model (CRM)
• Forecast Period Hours
• Resolution 1-km x 1-km
• Detailed Representations of Processes

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Super-Parameterizations The Grabowski, Randall,
and Arakawa Scheme
CLIMATE MODEL GRID CELL
60-N
5-10 years?
2-Dimensional Cloud Resoving Model
3-D Simulation
55-N
172-W
157-W
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Summary

• Collecting and analyzing large data sets to
  better understand cloud behavior
• Observations are more compatible with evaluation
  of cloud resolving models than current GCMs
• New super-parameterizations in GCMs appears to
  be the path forward 5-10 years
• Based on cloud resolving models