Satellite Products Aerosols and Trace Gases Introduction to Remote Sensing for Air Quality Applications Richard Kleidman

Note: Significant parts of this presentation were taken from presentations originally produced for NASA.. They are freely available to the public in their original forms at or athttp://arset.gsfc.nasa.gov They have been modified by Richard Kleidman of AirPhoton LLC for this training.

AOD - Aerosol Optical Depth τ AOT - Aerosol Optical Thickness These optical measurements of light extinction are used to represent aerosol amount in the entire column of the atmosphere. Aerosol Optical Depth The optical depth expresses the quantity of light removed from a beam by scattering or absorption during its path through a medium.

Aerosol Optical Depth Surface I0I0 I Sun Atmosphere Whether we are measuring from space down through the atmosphere or from the ground up through the atmosphere this is a Total Column Measurement

Moderate AOD ~0.40 Near Mt. Abu, India Photo courtesy of Brent Holben Experience will provide a sense of what AOD values mean. Multiple conditions with very different vertical distributions may give the same AOD values.

AOD and PM2.5 One major goal of satellite remote sensing in the area of air quality is to use AOD measurements to determine PM 2.5 levels near the ground. This is a very difficult relationship to correlate with high accuracy. The most promising techniques make use of models and ground measurements in conjunction with satellite data

Challenges for inferring surface aerosol mass from column-integrated AOD: Even Distribution Challenges Slide courtesy of Andreas Beyersdorf NASA Langley

Boundary layer depth Stratospheric Burden Long-range Transport of Pollution Aloft Relative Humidity Surface Albedo Pixel Size Challenges Challenges for inferring surface aerosol mass from column-integrated AOD: Slide courtesy of Andreas Beyersdorf NASA Langley

1.Temporal Coverage 2.Vertical Resolution of Pollutants 3.Lack of Near Surface Sensitivity 4.Lack of specific identification of pollutant type

Modeling the Association of AOD With PM 2.5 The relationship between AOD and PM 2.5 depends on parameters hard to measure: Vertical profile Size distribution and composition Diurnal variability We can develop chemical process models with variables to represent these parameters Model simulated vertical profile Meteorological & other surrogates Average of multiple AOD measurements We can use statistical models to give us answers without understanding the processes No textbook solution!

Primary Sensors - AEROSOLS MODIS - MODerate resolution Imaging SpectroRadiometer Measures total column aerosol AOD - Aerosol Optical Depth MISR - Multi-angle Imaging SpectroRadiometer AOD Particle Type VIIRS - Visible Infrared Imaging Radiometer Suite AOD Particle Type OMI – Ozone Monitoring Instrument AOD Aerosol Index Aerosol Abroption Optical Depth

Level 1 Products - Raw data with and without applied calibration. – NO AEROSOL DATA Level 2 Products - Geophysical Products - AEROSOL DATA Level 3 Products - Globally gridded geophysical products - AEROSOL DATA Data Product Hierarchy

MODIS

Data Product Hierarchy and Description Product CategoryFile Name Examples Product Contains Level 1 Raw data MOD02 MYD02 Radiance values from all sensor channels Level 2Geophysical Product from a single overpass MOD04 MYD04 All parameters for a single product - Aerosol product Level 3Gridded product from multiple overpasses MOD08 MYD08 Selected parameters for all atmospheric products -Aerosol, Cloud, Water Vapor, Atmospheric Profile

Level 2 Aerosol Product (AOD) Level 3 Aerosol Product (AOD)

OMI

Instrument Characteristics -Nadir solar backscatter spectrometer -Spectral range nm (resolution~1nm ) -Spatial resolution: 13X24 km footprint -Swath width: 2600 km (global daily coverage) Ozone Monitoring Instrument (OMI) Retrieval Products Column Amounts -Ozone (O 3 ) -Nitrogen Dioxide (NO 2 ) -Sulfur Dioxide: (SO 2 ) -Others Aerosols One of four sensors on the EOS-Aura platform (OMI, MLS, TES, HIRDLS) An international project: Holland, USA, Finland Launched on

Applications of the Aerosol Index -Validation tool for transport models -Separation of carbonaceous from sulfate aerosols -Identification of aerosols above the Planetary Boundary Layer (i.e., PBL aerosols are not detectable by AI) -Tracking of aerosol plumes above clouds and over ice/snow Transport around the globe of a high altitude smoke layer generated by the Australian fires in December Numbers indicate the day of the month. Aerosol s over clouds: April 14, 2006

OMI data site OMI-Aura_L2-OMAERUV_2011m1024t0521-o38692_v m1024t he5 Product name YYYYmMMDDtHHMM

MISR

9 view angles at Earth surface 70.5º 60.0º 45.6º 26.1º 0.0º 60.0º 45.6º 26.1º 2800 km ← MISR instrument Four spectral bands at each angle: 446 nm ± 21 nm 558 nm ± 15 nm 672 nm ± 11 nm 866 nm ± 20 nm < 7 minutes to view each scene from all 9 angles

Angular observations (which are not available in MODIS) makes MISR capable of providing additional information on particle size, shape and aerosol height under specific cases

Smoke Signals from the Alaska and Yukon Fires - July 2004 Aerosol Heights from MISR

MISR Level 3 Tool

Level 2 & 3 aerosol 1 file = one orbit - about 98 min Data 17.6x17.6 km 2, 0.5x0.5, and 1x1deg, daily, monthly, seasonal _lcluc/misr_tutorial.pdf Data access and handling tutorial

VIIRS

VIIRS is a multiwavelength imager, like MODIS with similar wavelength bands in the aerosol range MODISVIIRS Orbit altitude 690 km824 km Equator crossing time 13:30 LT Granule size5 minutes86 seconds Swath2330 km3000 km Pixel nadir0.5 km0.75 km Pixel edge2 km1.5 km

VIIRS granule VIIRS 0.67 – 0.55 – 0.49 µm 2 Sep :24:27.8 UTC MODIS 0.66 – 0.55 – 0.47 µm 2 Sep :40 UTC NASA MODIS AtmospheresSSEC PEATE

VIIRS Nov 24, 2011 MODIS - AQUA Nov 24, 2011

Satellite Aerosol Products InInIMODISMISROMI VIIRS Strengths Coverage Resolution Calibration Accuracy Calibration Accuracy Particle shape Aerosol height for thick layer or plume Indication of absorbing or scattering particles Coverage Resolution Calibration Smaller bow-tie effect Weaknesses Bright Surfaces* Ocean glint Non-spherical particles CoverageResolution Cloud contamination Bright Surfaces* Ocean glint Main Products AOD Ocean – 5 wavelengths Land – 3 wavelengths Fine Fraction* *Ocean only AOD 4 wavelengths Spherical/ Non-spherical ratio Particle Size (3 Bins) AOD AAOD Aerosol Index AOD Aerosol Type Product Resolution (level 2 and at Nadir) 10 Km 3 Km 17.6 Km13 X 24 Km 0.75 km 6 km Product Levels Global Level 3 Aggregates Daily 8 Day 30 Day Monthly 3 Month Annual Daily Monthly Daily Monthly

AERONET Aerosol Robotic Network AERONET serve as validation tool for satellite aerosol product

A Brief Overview of Trace Gas Measurements and Products.

Absorption Unlike remote sensing of aerosols that use the signature of aerosol scattering, remote sensing of trace gases uses the signature of gas absorption. How Satellites Measure Trace Gases

Trace Gases Absorption Spectrum in UV and Visible Each trace gas has its own unique absorption spectra.

How Satellites Measure Trace Gases con’t Satellites detect backscattered solar radiation and/or emitted thermal radiation Trace gases absorb radiation at specific wavelengths. Knowing this … A model is then used to derive a trace gas column concentration or column amount. Trace Gas Absorption Scattered/emitted radiation detected by satellite

Limitations: - Sensors may or may not be sensitive to this variation. - Resolution - footprint - Spectral limits in interference - Clouds get in the way - Limited sensitivity in parts of the vertical column of the atmosphere. - Lack of data for validation Trace Gas Concentration and Absorption May Vary Throughout The Column

Also - Trace gas concentrations vary throughout the atmosphere - Meteorology/Transport - Chemistry (gas, heterogeneous) - Day vs Night - Polluted vs non-polluted regions

OMI – Ozone Monitoring Instrument - Tropospheric Column NO 2 [molecules/cm 3 ] - PBL, Volcanic SO 2 [Dobson Units - DU] TES – Tropospheric Emission Spectrometer - Vertical profiles of Ozone and CO AIRS – Atmospheric Infrared Sounder - Vertical profiles of CO [molecules/cm 3 ] Trace Gas Measurements from Space: What is available?

OMPS – Ozone Mapping and Profiler Suites Trace Gas Measurements from Space: What is available?

What You Need To Use Remote Sensing Products

Remote Sensing Product

Data Archives

LADSWeb - Webtool to download MODIS data

Tools Pre and Post Product Manipulation Stand Alone Tools Web Based Tools

Remote Sensing Science

Algorithms Cooking with Aerosols by Yoram Kaufman & Didier Tanre

Complementary Data Data for Validation Model Data Ground Data Synergistic use of data from multiple sensors

MODIS Aerosol and Cloud Complementary Data AERONET LADSWEB Lance GIOVANNI HDFLook, Matlab, IDL Tools Algorithms MODIS Ocean, Land, Deep Blue Archives Remote Sensing Products Remote Sensing Science Orbits, sensors, spectra, radiative transfer

Many Remote Sensing Products

For every sensor: Products Algorithms Raw data Data archives Web tools Stand alone tools

Underlying information: Product organization Data formats Remote sensing theory Sensor capabilities Underlying assumptions of web tools