Madhu GyawaliAdvisor - Dr. Pat Arnott

NASA-A Train

COORDINATED SATELLITE MEASUREMENTS OF THE EARTH’S

ATMOSPHERE

AN OVERVIEW

1

Outline Radiation transfer in the Earth’s atmosphere; effects of aerosols, clouds and CO2

Afternoon constellation “A-Train” overview

Importance of formation flying

Measurements techniques like active and passive remote sensing

Spectrum of Solar Radiation Flux

O3

H2O

H2O ,CO2

O2

From Cunningham & Cunningham, 2004,

.1 . 3 .5 1 1.5 2 2.5 3 )( m 3

Major Atmospheric Windows

Effects Of Aerosol Direct effect —Scattering and absorption of radiation Indirect effect —Roles in cloud micro physics

Clean cloud Polluted cloud Large cloud droplets Small Cloud droplets Low albedo High albedo Efficient precipitation Suppressed precipitation

5

How do Clouds Affect the Climate?

CirrusIce crystals

Cumulus Ice crystals/Water droplets

StratusWater droplets

Cooling effect

Warming effect

Dense clouds such ascumulus and low-altitude reflect sunlight

Thin, high-altitude cirrus clouds emits infrared radiation

Clouds Dominate the Energy Budget of the Earth

6

Since the beginning of the industrial age, the concentration of CO2 has increased by about 25%, from about 280 parts per million to over 370 parts per million.

Current research indicates that continuing increases in atmospheric CO2 may modify the environment in a variety of ways.

Source: Jet Propulsion Laboratory, California Institute of Technology, Pasadena

Why Study CO2 ?

7

Orbit Information

Orbit Sun synchronous, polar orbit Height -700 km Radius - 7000 km Inclination - 98.2o Time Period 98.8 minutes Make14.57 orbits in one day Repeat cycle 16days Speed 7.2 km/s All 7 members have equator crossing (ascending nodes) times 1:30 p.m.+/- 15 m Local Time

Source http://aura.gsfc.nasa.gov/instruments/index.html

Madhu GyawaliPat Arnott

Afternoon Constellation Evolution

May 4, 2002

Source http://aura.gsfc.nasa.gov/instruments/index.html

Afternoon Constellation Evolution

Aura(July-15) and PARASOL(Dec-18) joined in 2004

Source http://aura.gsfc.nasa.gov/instruments/index.html 10

CloudSat and CALIPSO joined in 2006,April-28

Afternoon Constellation Evolution

Source http://aura.gsfc.nasa.gov/instruments/index.html 11

Afternoon Constellation Evolution

Glory and OCO to be launched in 2008

Source http://aura.gsfc.nasa.gov/instruments/index.html12

13

The Afternoon ConstellationIs an International Undertaking

Source : AMSR-E Science Team MeetingAugust 14-16. 2007

Constellations opportunity Coincident, and nearly

simultaneous measurementsField of Views overlapData can be correlated

Why Fly Constellations?

The whole is greater than the sum of its parts

The new A-Train observations tell us much more about weather and climate-sensitive processes than can possibly be gleaned from any one instrument alone.

14

15

The Afternoon ConstellationIs an International Undertaking

16

13.5 km AIRS IR; AMSU & HSB wave

13.5 km AIRS IR; AMSU & HSB wave

6x7 km POLDER 6x7 km POLDER

5.3 x 8.5 km TES 5.3 x 8.5 km TES

CloudCloud

0.5 km MODIS Band 3-7

0.5 km MODIS Band 3-7

0.09 km CALIPSO0.09 km CALIPSO

1. 4 km Cloudsat1. 4 km Cloudsat

OCO1x1.5 km

The Afternoon Constellation “footprints”

Remote SensingTechniques for measuring or observing an object without touching. It involves the interpretation and inversion radiometric measurements of EM radiation . Example -Optical and radio telescope, camera, Atmospheric Infrared Sounder,LIDAR,RADAR

Active and Passive Remote sensing

17

Remote Sensing Tools

Long wavelengths are sensitive to large particles – cloud drops, raindrops, snowflakes, hailstones

Short wavelengths are sensitive to smallparticles –gas molecules, aerosols

....................................................................

LaserTransmitter

Receiver Telescope

Scattering of light

LIght Detection And RangingRAdio Detection And Ranging

Infrared sounding ,microwave sounding

LIDARRADAR

18

Remote sensing

19

Spaceborn

Airborn

Groundbased

Positions of Sensor

Ground Based Remote Sensing

20

To record detailed information from the surface for comparison withAircraft and/or satellite remote sensing

To observe the atmosphere from the ground (e.g. cloud base)

Advantages Low cost for transport and installation

Accessible for operatorsApplication of experimental sensorsHigh temporal coverage

Disadvantages

Low spatial coverage

Limitations in observational area

Airborne Remote Sensing

21

Aircrafts, balloons ,helicopters

Advantages

Used for detailed imaging of objects or areas

Accessible for operators

Satellite under flights for validation purposes

Flexibility in choosing the operation areaHigher spatial resolution than satellite resolution

Disadvantages

Higher costs for transportation and installation

Less temporal and spatial coverage

Spaceborn Remote Sensing

22

Artificial satellite ,space shuttle

High temporal and spatial coverage (global observations)

Repetitive coverage of the Earth’s surface on a continuing basis

Advantages

Can observe any portion of Earth

DisadvantagesHighest costs for transportation and installationNo accessible for operatorsVery long preparation phase

Ground Based and Airborne Coincident Remote Sensing

Source: A First course in Atmospheric Radiation, Grant W. Petty 23

Coincident measurements of the infrared emission spectrum of the cloud free atmosphere(a) 20km looking downward over the polar ice sheet and (b) at the surface looking upward

Aqua

Investigates the GLOBAL WATER CYCLE: evaporation from the oceans, water vapor , clouds, precipitation, soil moisture

Instruments: Six earth observing instruments

OVERVIEW

AIRS: Atmospheric InfRared Sounder – Obtains highly accurate temperature profiles within the atmosphere

AMSU: Advanced Microwave Sounding Unit – Obtains temperature profiles in the upper atmosphere

HSB: Humidity Sounder for Brazil – 4 Channel microwave sounder , measures humidity profiles throughout the atmosphere.

AMSR-E: Advanced Microwave Scanning Radiometer-Precipitation rate, cloud water, water vapor

MODIS: Moderate Resolution Imaging Spectroradiometer –Aerosol,cloud,temperature CERES: Clouds and the Earth's Radiant Energy System – Cloud properties, Aerosol

optical depth

Source http://www.nasa.gov/home/index.html24

MODIS

CERES

AIRS

HSB AMSR-E

AMSU-A1 AMSU-A2

Frequency750 THz 429 THz 300 GHz 0.375GHz

0.4 μm 0.7 μm

1 mm 0.8 mInfrared MicrowaveU-violet

Measurements

All measure electromagnetic radiation

All are passive instruments i.e. they simply recordradiation coming to them

Aqua Instruments

Hurricane Katrina approaching the Gulf Coast Aug. 28th 2005, MODIS

Aqua covers wide range of Earth scienceUV + VISIBLE + IR + Microwave

Source http://www.nasa.gov/home/index.html25

26

The Aura satellite provides us the first global view of the Earth's atmosphere.

HIRDLS: HIgh Resolution Dynamics Limb Sounder – global distribution of temperature and composition of the atmosphere

MLS: Microwave Limb Sounder –stratospheric temperature and upper tropospheric constituents

OMI : Ozone Monitoring Instrument – Distinguishes between aerosol types, tropospheric ozone.

TES: Tropospheric Emission Spectrometer – all radiatively active molecular species in the Earth's lower atmosphere.

Aura

Nadir view Limb View

TES

Instruments Source http://aura.gsfc.nasa.gov/instruments/index.html

Source http://aura.gsfc.nasa.gov/instruments/index.html

Measurements

HIRDLS in yellow, OMI(has a cross track swath of 2600km) in blue, MLS in green, and TES in red.

27

28

PARASOL

Measures radiative and microphysical properties of clouds and aerosols by measuring the directionality and polarization of light reflected by the earth-atmosphere-ocean system

(Polarization and Anisotropy of Reflectances for Atmospheric Science coupled with Observations from a LIDAR)

POLDER (POLarization and Directionality of the Earth’s Reflectance)

A rotating wheel scans 9 wavelength bands(443-1029 nm)

A target is viewed up to 16 times with various viewing angles

Three of the channels (490,670,865 nm) also measures linear polarization,Lidar 1064 nm 532 nm

Instrument

Source: CNES

Measurements Polarization distinguishes the liquid phase clouds and ice-phase clouds ,as the former has strong peak of polarization

The cloud level pressure (or altitude)is measured by using the differential absorption technique

PARASOL can discriminate large spherical marine aerosols from non-spherical desert aerosols

PARASOL first images over Europe(2005 January):natural(left) and polarized(right)

29

30

CALIPSO

Three instrumentsCALIOP : Cloud-Aerosol Lidar with Orthogonal

Polarization - Two wavelength polarization-sensitive Lidar (532 and 1064 nm) that provides high-resolution vertical profiles of aerosols and clouds

WFC: Wide Field Camera - Fixed, nadir-viewing imager with a spectral channel covering the 620-670 nm region

IIR: Imaging Infrared Radiometer - Nadir-viewing, non-scanning imager

Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations

30The orange and red colors signify regions of fine aerosols – that suspended above Earth’s surface.

CALIPSO’s polarization lidar instrument can detect aerosol Particles and can distinguish between aerosol and cloudparticles

0 A

ltitu

de

km

Measurement

31

CPR: Cloud Profiling Radar - A 94-GHz nadir-looking radar

Will advance our understanding of cloud abundance, distribution, structure, and radiative properties.

Able to detect the much smaller particles of liquid water and ice (ground-based weather radars use centimeter wavelengths)

CloudSat

Cloud Profiling Radar

Measures the power backscattered by clouds as a function of distance from the radar.

Instruments

Tight formation flying of CALIPSO and CloudSat- seperated by 15 s

32

A fraction of these pulses reflect back while others

continue downward, some being absorbed

Radar measures the time delay and magnitude of the reflected

signal

Measurements

CALIPSO and CloudSat will provide the first statistics on the vertical structure of clouds. For the first time ,we will see clouds from their tops to their bottoms-like getting CT scan of clouds from space

Provide the first validated estimate of how much clouds and aerosols contribute to the vertical distribution of atmospheric warming

CALIPSO +CLOUDSAT MISSION

34

Future MissionsSchedule date: Dec-15,2008

Instrument

Three grating spectrometers to measure at 2.06um and 1.61um,and 760nm for the Oxygen A-band .

OCO: Orbiting Carbon ObservatoryWill make first space based measurements of

column CO2 to quantify sources and sinks of CO2

Source: Jet Propulsion Laboratory, California Institute of Technology, Pasadena

Glory

OCO

35

Will make the measurements of the Earth's energy balance and the effect of black carbon soot and other aerosols in the atmosphere

Instrument

Aerosol Polarimetry Sensor -continuous scanning sensor that collect visible, near infrared, and short-wave infrared data scattered from aerosols and clouds.

Total Irradiance Monitor(TIM) will collect high accuracy, high precision measurements of total solar irradiance

Will measure the total solar irradiance to determine the Sun's direct and indirect effect on

the Earth's climate.

Glory Launch Date: December 2008 Launch Site: Vandenberg AFB, California

36

Sun synchronous satellites have many advantages than other satellites like geo stationary, as they offer higher resolution, carry many instruments and can observe at many more wavelengths.

The A-Train formation allows for coordinated and coincidence measurements. Also there are several complementary differences among the way the different instruments in the constellation observe the same object or process.

New data from NASA's A-Train constellation, coupled with recent advances in climate modeling, creates a rare opportunity to advance understanding of the interaction of atmospheric constituents and their climate consequence

Summary

37

THANK YOU

38

The “NASA-A Train“ constellation of seven Earth–orbiting satellites remotely sense Clouds , aerosols, water vapor, and trace gases such as CO2,NO2, and O3. The satellites orbit sun –synchronously at an altitude of 705 km with Aqua in the lead ,followed in order by CALIPSO,CloudSat,PARASOL,and Aura. With Aqua in the lead and Aura at the tail this formation has been termed the afternoon constellation or A-Train, and all satellites cross the equator within a few minutes around 1:30 pm local time. These satellites employ revolutionary measurement methods to probe the Earth’s atmosphere, and will improve our weather and climate forecasts. Data from these satellites can be used together to obtain comprehensive information about atmospheric processes. This talk will give an over view of the active and passive remote sensing.Measurement techniques used on satellite as well as description of the importance of the atmospheric properties being measured. A discussion will be presented on the importance of synergistic measurements of satellite suite.

ABSTRACT

39