Geoscience Laser Altimeter System Aerosol and Cloud Observations by the GLAS Polar Orbiting Lidar Instrument NASA - Goddard Space Flight Center Launched – January 2003 Full Operations – September 2003 Ice, Cloud and Land Elevation Satellite

Surface Altimetry and Atmospheric Profiling Surface Altimetry – High Bandwidth, 10 cm, Strong Signals Atmospheric Profiling – Low Bandwidth, 30 m, Weak Signals >>>> Compatible System Requirements Surface Altimetry Requires Precise Cloud Clearing Atmospheric Retrieval Requires Surface Reflectance Measurement

GLAS Transmitter and Receiver Lasers: Three Diode Pumped Nd:YAG Units 40 Hz PRF 100 urad Beam Width 1064 nm - 65 mJ 532 nm - 36 mJ Receiver: One Meter Beryllium Mirror 1064 nm (main surface channel) Avalanche Photodiode Detector 1 gHz Surface Digitizer Channel 2 mHz Cloud Digitizer Channel 532 nm (high sensitivity atmospheric channel) 8 Geiger Mode Silicon APD Modules 2 mHz Photon Counting Channel

GLAS Measurement Components Solar Background Radiance at 1064 and 532 P = I   A S p = C b I Surface Return Pulse at 1064 nm E s =E o T e 2  A/r 2 = Cp  T e 2 (z o ) Surface Pulse Waveform Surface Pulse Reflectance Vertical Resolution – 15cm Signal Range to 300 m Atmospheric Profiles at 1064 and 532 nm S(z) = C E B(z) T e 2 (z) /r 2 Aerosol and Thin Cloud: 532 nm – GAPD Photon Counting Denser Cloud: 1064 nm – Analog APD Vertical Resolution – 75 m (20 m) Horizontal Resolution - ~ 175 m (500m) Signal Range --5 to 40 km

Ben Smith Univ. of Washington Crary Ice Rise Grounding line ROSS ICE SHELF SIPLE COAST ICE STREAMS SIPLE DOME West Antarctic - Siple Coast from ICESat

CLOUDS I’ve looked at clouds from both sides now…..

FROM GLAS QUICK LOOK WEB SITE: GLOBAL ORBIT LIDAR VIEWS OF CLOUD AND AEROSOL DISTRIBUTION

GLAS Data Visualization for October 3, 2003

GLAS Observed Backscatter Cross Section and Layer Heights Data Product Example (gla07,08, 09)

km Latent Heat Flux Sensible Heat Flux ECMWF PBLGLAS PBL Validation of Global Circulation Models (GCM’s) Detailed Comparison of GLAS And European Center Weather Forecast Model Boundary Layer Heights Cloud Fraction

Cloud Layer Count Distribution All clouds 01 Oct. – 15 Nov % 31% 17% Global cloudiness is 69% Single layers account for 64% of cloudy cases Attenuation causes layer numbers to be undercounted Shape of distribution is typical

Maximum cloud height km PSC Maximum cloud height in each cell over the observation period. Some features: warm pool; tropical central Africa; Carribbean; western coasts of the continents. Line plot shows the zonal maximum cloud height; note polar stratospheric clouds. 01 Oct. – 15 Nov. 2003

Zonal Cloud Top Frequency 01 Oct. – 15 Nov AM and PM PMAM 0.5 km vertical bins Top shows results from all observations Two lower images show the comparison between the AM and PM observations. Differences are the increase in the convective influence in the PM, with a lessening of the influence of the low clouds.

GLAS/MODIS Cloud Fraction Comparison October, 2003 GLAS, PM MODIS,AQUA Percent Cloud fraction, zonal GLAS MODIS Features in the expected locations. High cloud fraction the the ITCZ and north and south circumpolar regions. Low cloud fraction in deserts. GLAS finds significantly more cloudiness in the deserts regions. Zonal cloud fraction display shows excellent agreement between the two instruments except in the polar regions.

GLAS/MODIS Average Cloud Top Pressure Comparison October, 2003 GLAS, PMMODIS,AQUA Zonal cloud top pressure GLAS MODIS hPa GLAS results show higher clouds GLAS finds geometrical cloud top; MODIS finds thermal cloud top Other factors such as sampling differences are needed to explain large difference

Aerosols

Dust of the Sahara

GLAS Aerosol Optical Thickness GLAS MODIS October, 2003 GLAS, PMMODIS,AQUA OD Qualitative agreement in location of many persistent features GLAS misses transient features such as California fire because of sampling. GLAS retrieves generally lower OD because of a low bias in extinction to backscatter ratio.

Global Aerosol and Boundary Layer Height First Mapping of the Global Aerosol and Pollution Capping Inversion ‘Boundary Layer’ Height Model Output from European Center Forecast Model GLAS Measurement of the Height of the Planetary Boundary Layer – October 2003

Geoscience Laser Altimeter System Application to Aerosol Transport Models J. Spinhirne /GSFC January 2004 GLAS 532 nm Data Naval Aerosol Analysis and Prediction System

Observe backscatter cross sections below (1/m-sr) for aerosol transport Observe backscatter cross sections up to for dense aerosol events Observe backscatter cross sections over six orders of magnitude including clouds GLOBE GLOBE - Global Backscatter Experiment Definition of Space Lidar Requirements Menzies, Tratt, Spinhirne and Hlavka - JGR 2002.

South Africa Smoke Aerosol

Breon et al., GRL in press, 2005

Global lidar data are a fundamentally new measurement from space for global aerosol and cloud cover. GLAS data results have fully validated the science, technology and observation strategy and meet the objective of profiling all radiatively significant cloud and aerosol layers. GLAS Data products are in open release to the science community. Quick look and data visualization: Full Data Access: GLAS STATUS GLAS Observation Periods Observation Period Laser532 nm 1064 nm Feb 20 – Mar Sep 25 – Nov Feb 17 – Mar May 18 – Jun Oct 03 – Nov None Excellent Excellent - Good Excellent Excellent - Good Fair (Night Only) Poor (Night Only) Fair Excellent Laser Diode Failure Laser Contamination Severe Contamination Laser Doubler Failure 2005: Feb. 20 – Mar. 25 May 18 – June 22