Clouds and Climate Through a Soda Straw Mark Miller

Visible Infrared Sun’s Radiation 6000 K Earth’s Radiation 288 K Wavelength (micrometers) Quantity of Radiation

Visible Satellite Photo

Infrared Satellite Image

Source: NASA/ Earth Radiation Budget Experiment

“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,

Figure 2.10 IPCC Working Group I (2007)

Representing Clouds in Climate Models 55-N 60-N 172-W157-W CLIMATE MODEL GRID CELL Weather Forecast Model Grid Cell Cloud Resolving Models: Less Than Width Of Lines

What Cloud Properties Change the Net Radiation Received at the Surface? 1.Amount of the sky that is covered 2.Thickness 3.Composition Contain ice crystals, liquid water, or both? Particle sizes? Particle concentrations? 4.Height in the atmosphere

How Does the Location of Cloud Impact the Surface Temperature? Low Clouds Space ~2-km High Clouds ~10-km COOLINGWARMING

What We Know About Solar Radiation and Clouds Solid theoretical foundation for interaction between a single, spherical liquid cloud droplet and sunlight Sun Cloud Droplet Scattered Light

What We Know About Solar Radiation and Clouds Some theoretical foundation for interaction of sunlight and simple ice crystal shapes

The Real World

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?

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?

Surface Radiation Calibration Facility Meteorological Tower Multiple Radars Multiple Lidars 2-km Clouds Through a SODA STRAW!

The ARM Southern Great Plains Site

SGP Central Facility SODA STRAW Extended Measurement Facilities Oklahoma City Wichita

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 –Can’t determine location of liquid –Presently not measuring total ice content

Visual Images of the Sky cloud coverage (versus cloud fraction) simple! digitize images and … daytime only integrated quantity

A Time Series

The Past Few Days in Oklahoma…

…have been for the birds! 3/20/083/21/08 3/22/083/23/08

500 nm RV Ron Brown Central Pacific AOT=0.08 Sea of Japan AOT=0.98 AMF Niamey, Niger AOT=2.5-3 Sky Imaging

Negligible Return Cloud and Aerosol ParticlesCloud droplets Surface 10-km 20-km 24 Hours Laser Data from Southern Great Plains Ice Clouds Low Clouds No Signal 7:00 pm7:00 am7:00 pm time

V=4500m

V=700m, Mass Concentration=1,700  g m -3

Niamey, Niger, Africa 0000 Negligible Return Cloud Droplets Cloud and/or Aerosol Time (UTC) Height (km) Biomass Burning Dust LIQUID CLOUDS

Dust product (upper) and GERB OLR (lower) for 1200UT on 8 March 2006 Cloud Lake Chad Dust

Energy Returned to Radar Size of Cloud Particle At a Given Wavelength Energy Returned to Radar Radar Wavelength A Cloud Particle At Different Wavelengths radius 6 wavelength -4

Energy Absorbed by Atmosphere Radar Wavelength 35 GHz 94 GHz Maximum Propagation Distance km km 8 mm 3.2 mm

The DOE Cloud Radars

Small Cloud ParticlesTypical Cloud ParticlesVery Light Precipitation Surface 10-km 20-km Cloud Radar Data from Southern Great Plains Black Dots: Laser Measurements Of Cloud Base Height 7:00 pm7:00 am7:00 pm time

Small Cloud ParticlesTypical Cloud ParticlesVery Light Precipitation Surface 10-km 20-km Cloud Radar Data from Southern Great Plains Black Dots: Laser Measurements Of Cloud Base Height Thin Clouds Insects 7:00 pm7:00 am7:00 pm time

Surface 2-km 10-km LaserRadar Base Radar Echo Top Base Top Low Radar Sensitivity Radar Echo Radar Echo Microwave Radiometer Emission

Evolution of Cloud Radar Science Cloud Structure and Processes Cloud Statistics Cloud Composition

Solid Overcast Cloud Transition Broken Cloud Azores Applications of Surface-Based Cloud Observing Systems Example: Marine Cloud Transitions

Application of Surface-Based Remote Sensing to a Cloud “Problem” Marine Stratocumulus Transition

Ocean Surface Mid-latitudesTropics 0.5 km 2 km Ocean Surface Mid-latitudesTropics 0.5 km 2 km THEORY OBSERVED

5-km 10-km 15-km Cloud Top Height Probability 1% 10% Tropical Western Pacific Jan 1999 June % 1% 10% 3% Probability

Retrieving Liquid Cloud Composition + Radar Echo Intensity Height Total Liquid Water (Microwave Radiometer) Particle Size Number Mode Radius?? + = Mode Radius Height Number Concentration?? Width Number Concentration Height

7:00 pm7:00 am7:00 pm Liquid Cloud Particle Mode Radius Micrometers Height (km) time

Active and Passive Cloud Remote Sensors (cont.) Wind Profiler –75-m, 6-min resolution –915 MHz [ MHz COPS] –Minimum Height: 120-m –Maximum height: 5.5-km Atmospheric Emitted Radiance Interferometer (AERI) –  m (1 cm -1 resolution) –6-min resolution (20-30 sec possible for COPS) –1.3 degree field-of-view

AERI Spectra

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

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

Super-Parameterizations: The Grabowski, Randall, and Arakawa Scheme 55-N 60-N 172-W157-W CLIMATE MODEL GRID CELL 2-Dimensional Cloud Resoving Model 3-D Simulation 5-10 years?

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