Clouds and Radiation “..there are substantial uncertainties in decadal trends in all data sets and at present there is no clear consensus on changes in total cloudiness over decadal time scales.” IPCC-The Scientific Basis-Chapter 3, p. 277 There has been an increase in clouds and precipitation, which reduce solar radiation available for actual and potential evapotranspiration but also increase soil moisture and make the actual evapotranspiration closer to the potential evapotranspiration. An increase in both clouds and precipitation has occurred over many parts of the land surface (Dai et al., 1999, 2004a, 2006), although not in the tropics and subtropics (which dominate the global land mean; Section ). IPCC-The Scientific Basis-Chapter 3, p. 279

IPCC WG1 AR4 Report Variability caused by model representations of clouds

How do Clouds Alter the State of the Atmospheric Column? Diabatic Heating Profiles –Latent Heating –Condensation (warming) –Evaporation (cooling) –Net column latent heating = Precipitation mass * L –where L = latent heat –Radiative Heating –Incoming solar –Outgoing IR –Net column radiative heating= net incoming minus net outgoing –Profiles of diabatic heating impact atmospheric dynamic and thermodynamic structure

TOA Surface Insolation OLR Reflected SW Upwelling and Downwelling SW and LW Incoming – Outgoing= net radiation into column Downwelling–Upwelling= net radiation into surface Radiative Flux Divergence = net radiation into column - net radiation into surface positive values imply heating negative values imply cooling Radiative Flux Divergence Primer

TOA Surface Insolation OLR Reflected SW Upwelling and Downwelling SW and LW positive values imply heating negative values imply cooling Radiative Heating Rate Profile negpos NET

What Cloud Properties Change the Radiative Heating Rate Profile? 1.Amount of the sky that contains cloud 2.Thickness of individual clouds and layers 3.Height in the atmosphere 4.Composition Contain ice crystals, liquid water, or both? Particle sizes? Particle concentrations?

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

Cirrus and Cumulus from the Space Shuttle Courtesy NASA CERES

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

Clouds and Radiation Through a Soda Straw

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

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 –cloud location and microphysical composition –In-cloud updrafts, downdrafts, and turbulence 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

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

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

VHF UHF 10 cm 8 mm 3.2 mm cloud radars

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

The DOE ARM 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

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

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

Height (km) Cloud Fraction (%) GFS cloud initialization data mandatory radiosonde data satellite retrievals of temperature satellite-derived cloud motion vector aircraft cloud fraction parameterization: Xu and Randall (1996) August GFS km cloud fraction larger than AMF AMF 0-10 km cloud fraction larger than GFS Kollias, P, M.A. Miller, K.Johnson, M. Jensen, D. Troyan, 2008

7:00 pm7:00 am7:00 pm Liquid Cloud Particle Mode Radius Micrometers Height (km) time Miller and Johnson, 2003

Tobin et al., 2007

Clouds and Radiation From Space

A-TRAIN CONSTELLATION The Afternoon or "A-Train" satellite constellation presently consists of 5 satellites Two additional satellites, OCO and Glory, were supposed to join the constellation OCO was lost during a launch failure on 2/24/2009. Glory is scheduled to launch (10/01/10) Approx equator crossing times

33 Afternoon Constellation Coincidental Observations (Source: M. Schoeberl) MODIS/ CERES IR Properties of Clouds AIRS Temperature and H 2 O Sounding Aqua CloudSat PARASOL CALIPSO- Aerosol and cloud heights Cloudsat - cloud droplets PARASOL - aerosol and cloud polarization OCO - CO 2 CALIPSO OCO Aura OMI - Cloud heights OMI & HIRLDS – Aerosols MLS& TES - H 2 O & temp profiles MLS & HIRDLS – Cirrus clouds Glory?

CloudSat (Hurricane Ike) 34

CloudSat 35

Radar/Lidar Combined Product Development Formation flying is a key design element in cloudsat CloudSat has demonstrated formation flying as a practical observing strategy for EO. Overlap of the CloudSat footprint and the CALIPSO footprint, within 15 seconds, is achieved >90% of the time.

lidar/radar combined ice microphysics - new A-Train ice cloud microphysics Preliminary example from Zhien

MLSECMWFCloudSat A-Train Cloud Ice

What We Know About Solar Radiation and Clouds Solid theoretical foundation for interaction between a single, spherical liquid cloud droplet and sunlight and populations of spherical droplets. 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?

Miller and Slingo, 2007