Transcript Document

INTERPRETING SATELLITE OBSERVATIONS OF
ATMOSPHERIC COMPOSITION
Spring 2010
Class Objectives:
1. Familiarize ourselves with the basic techniques and measurements of
composition made from space (Lectures)
2. Learn to analyze and critically evaluate satellite data products (Labs)
Pre-requisites:
1. Atmospheric Radiation (ATS 622 or equivalent)
2. Programming experience (assistance from Colette will be limited to IDL)
Schedule:
Lectures (ACRC 212b): Mondays 2-2:50pm
Lab (ERC 210): Wednesday 2-4pm (lab booked until 5pm)
Extra Lab time (ERC 210): Fridays 1-3pm
OBSERVATION PLATFORMS FOR ATMOSPHERIC COMPOSITION
SURFACE
IN SITU
SONDES,
SURF.-BASED
REMOTE
AIRCRAFT
SATELLITES
Horizontal
coverage
-
-
+
+
Vertical range
-
+
~
~
(up to ~20 km)
(interferences)
Vertical
resolution
none
+
+
-
Temporal
coverage
+
+
-
~
Chemical detail
+
+
Cost
(polar = daily)
+
+
~
-
STRATOSPHERIC OZONE HAS BEEN MEASURED
FROM SPACE SINCE 1979
Last Monday’s ozone layer…
Notice the Antarctic ozone hole
Method: UV solar backscatter
(absorption spectroscopy*)
l1
l2
Ozone layer
Scattering by
Earth surface
and atmosphere
*Technique originally applied to ground-based
The satellite era for composition began with Nimbus 7 (launched Oct 1978) which
carried LIMS, SAMS, SAMII, SBUV/TOMS (and others)
ATMOSPHERIC COMPOSITION RESEARCH IS NOW MORE
DIRECTED TOWARD THE TROPOSPHERE
Air quality, climate change, ecosystem issues
Mesosphere
Stratopause
Ozone
layer
Stratosphere
Tropopause
Troposphere
…but tropospheric composition measurements from space are difficult:
optical interferences from water vapor, clouds, aerosols, surface, ozone layer
WHY OBSERVE TROPOSPHERIC COMPOSITION FROM SPACE?
Global/continuous measurement capability important for range of issues:
Monitoring and forecasting
of air quality: ozone, aerosols
Long-range transport of pollution
Monitoring of sources:
pollution and greenhouse
gases
Radiative
climate forcing
FOUR
OBSERVATION
METHODS:
• solar backscatter
• thermal emission
• solar occultation
• lidar
TROPOSPHERIC COMPOSITION FROM SPACE
multiple
Platform
ERS-2
Sensor
TOMS
AVHRR/ GOME
SeaWIFS
Launch
1979
1995
O3
ADEOS
IMG
1996
Terra
Envisat
MOPITT MODIS/ SCIAMA MIPAS AIRS
MISR
CHY
*
1999
1999
X
CO
X
Aqua
X
CO2
2002
2002 2002
X
X
X
X
X
Space
station
SAGE-3
SCISA
T-1
ACEFTS*
2003
2004
X
X
X
X
X
X
X
X
X
X
X
HNO3
X
HCHO
X
CHOCHO
OMI
MLS*
2004 2004
X
X
HIRDLS* CALIPSO IASI
2004
2004
X
2007
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
SO2
X
X
X
BrO
X
X
X
CH3CN
X
X
HCOOH
X
CH3OH
X
NH3
aerosol
MetOpA
X
X
X
CH4
TES
2004
NO
NO2
Aura
X
X
* Only in the UT
X
X
X
X
X
X
X
THERMAL EMISSION MEASUREMENTS (IR, mwave)
Examples: MLS, IMG, MOPITT, MIPAS, TES, HIRDLS, IASI
NADIR
VIEW
elIl(T1)
T1
LIMB VIEW
Absorbing gas
Pros:
• versatility (many species)
• small field of view (nadir)
• vertical profiling
Il(To)
To
EARTH SURFACE
Cons:
• low S/N in lower troposphere
• water vapor interferences
SOLAR BACKSCATTER MEASUREMENTS (UV to near-IR)
Examples: TOMS, GOME, SCIAMACHY, MODIS, MISR, OMI, OCO
absorption
l1
Scattering by
Earth surface
and by atmosphere
l2
l1 l2
z
wavelength
Retrieved column in scattering atmosphere
depends on vertical profile;
need chemical transport
and radiative transfer models
concentration
Pros:
• sensitivity to lower troposphere
• small field of view (nadir)
• Daytime only
Cons: • Column only
• Interference from stratosphere
OCCULTATION MEASUREMENTS (UV to near-IR)
Examples: SAGE, POAM, GOMOS
“satellite
sunrise”
Tangent point; retrieve vertical
profile of concentrations
EARTH
Pros:
• large signal/noise
• vertical profiling
• sparse data, limited coverage
Cons: • upper troposphere only
• low horizontal resolution
LIDAR MEASUREMENTS (UV to near-IR)
Examples: LITE, GLAS, CALIPSO
Pros:
Laser
pulse
Cons:
• High vertical resolution
• Aerosols only (so far)
• Limited coverage
Intensity of return vs. time lag
measures vertical profile
backscatter by
atmosphere
EARTH SURFACE
GETTING STARTED WITH IDL & ENS SERVERS
1. Get ENS userid
2. Log on to ENS servers (either from ERC classroom or remotely using ssh &
Xming or some other configuration)
Servers:
linux<1-12>.engr.colostate.edu
lcompute<1-7>.engr.colostate.edu
3. Set up .Xdefaults and .cshrc files in home directory to your preferences
(default option: copy those in ~heald/), including PATH information for IDL.
4. source .cshrc to refresh
5. Set up IDL  copy over ~heald/IDL into your home directory (GAMAP
routines, and idl_startup.pro information)
6. At the prompt anywhere type ‘idl’ to get started!
7. See examples of IDL code in ~heald/ATS681/idl_examples/