3. Research Capability
SMCD's Branches exploit a number of science and technology areas in
fulfilling its broad mission of transforming raw satellite observations
into the accurate, quantitative information that is needed to predict
weather, monitor climate, and detect environmental hazards. The science
and technology area of each of SMCD's branches are described here.
Sensor Physics Branch
The weighty responsibilities for ensuring that NOAA's satellite
observations are as accurate and stable as possible falls on the shoulders
of the Sensor Physics Branch. The first challenge is to transform the raw
satellite readings into accurate physical measurements of radiant energy -
the process of instrument calibration. The second challenge is to
transform these radiant energy measurements into atmospheric information
products - e.g., temperature, precipitation, ozone, air quality, carbon
dioxide - to predict weather, monitor climate, and detect environmental
hazards.
Calibration
Requirements for more accurate satellite information
products are steadily increasing. As numerical weather prediction models
become more reliable, their appetite for more accurate data input steadily
increases. As the requirements for monitoring global climate become
clearer - temperature changes as tiny as a few tenths of a degree per
decade, ozone trends as small as 1%/decade - the measurements become more
demanding. To create the stable long-term data sets needed for monitoring
climate change it becomes vital to inter- calibrate sensors on different
satellites. These are some of the challenges facing SMCD's calibration
scientists.
SMCD oversees the calibration of all of NOAA's Earth observing
satellite instruments, including the Polar-orbiting Operational Environmental
Satellites High-
Resolution Infrared Radiation Sounder (POES HIRS), Microwave Sounding Unit
(MSU), Advanced Microwave Sounding Unit (AMSU), Solar Backscatter
Ultraviolet Spectral Radiometer (SBUV), and AVHRR and the GOES Imager and
Sounder. The calibration process begins in the laboratory prior to
instrument launch. SMCD scientists specify the requirements for
instrumental accuracy, oversee the calibration, and analyze the laboratory
measurements to derive an operational calibration algorithm for the
instrument. Once the instruments are in orbit, SMCD scientists
continuously monitor their performance by comparing the measurements with
those of other satellites, simulations, and stable Earth targets.
Hyperspectral Infrared Soundings
Hyperspectral
infrared (IR) sounders are providing unprecedented high
spectral resolution capable of resolving individual absorption lines. This
new capability provides vastly improved accuracy and vertical resolution
of derived temperature and moisture profiles. In comparison with the HIRS
instrument, the precision of AIRS derived profiles are improved by 50% for
temperature (1 degree C vs. 2 degree C), and 50% for water vapor (15%
relative humidity vs. 30%). Vertical resolution is improved from 5 km
(HIRS) to 1 - 2 km. At NOAA/NESDIS, the NASA Atmospheric Infrared Sounder
(AIRS) is the first hyperspectral IR sounder to be provided to users for
operational applications. Hyperspectral IR sounders following AIRS, and
processed at NESDIS, include the Infrared Atmospheric Sounding
Interferometer on the EUMETSAT's METOP satellite in 2006, and the Cross-
track Infrared Sounder (CrIS) on NPP and NPOESS in 2008. In the next
decade, NOAA will have a hyperspectral IR sounder in geostationary orbit
(GOES-R) providing additional capability such as winds. In addition to
temperature and moisture profiles, hyperspectral IR measurements provide
information on ozone and other greenhouse gases such as carbon dioxide,
carbon monoxide and methane, clouds, aerosols, and surface characteristics
such as temperature and emissivity. Cloud corrected radiances are also
derived. The direct assimilation of AIRS radiances by operational
numerical weather prediction centers has resulted in significant
improvements in forecasting.
SMCD scientists are members of the
AIRS, Infrared Atmospheric Sounding Interferometer (IASI) and CrIS science
teams. SMCD developed many of the algorithms used for processing AIRS data
and developed the AIRS processing system used at NESDIS. SMCD scientists
are adapting the AIRS system to process IASI and CrIS observations.
Microwave Products
Satellite
microwave instruments are playing vital roles in improving
weather and climate prediction as measurements are less affected by clouds
than IR, visible, or UV observations and are directly related to
geophysical parameters. In the past decade, use of satellite microwave
measurements in numerical weather prediction models has resulted in major
positive impacts on weather forecasts, helping to extend forecast range by
an additional day. Temperature time series constructed from POES microwave
observations are the key source of information on global temperature
trends.
SMCD microwave scientists continue to improve operational
algorithms for microwave products and develop radiative transfer schemes
for cloudy skies and a model for surface radiative properties. Another
major challenge is developing the tools to exploit the enhanced microwave
observing capabilities of the Conical Microwave Imager and Sounder (CMIS)
on NPOESS.
Radiative Transfer Models
Satellite data now comprise over 90% of the observations
that feed the NWS forecast models. This remarkable fact is in no small
measure due to the development of accurate and fast radiative transfer
models by SMCD scientists. Largely due to these observations today's 3-day
weather forecasts are just as accurate as 2-day forecasts were just a
decade ago. These radiative transfer models facilitate the direct
assimilation of satellite observed radiances in the numerical prediction
initialization process. To date, the models have been for clear skies
only. This means that observations of cloudy areas - where much of the
weather occurs - are not assimilated. Developing a radiative transfer
model for cloudy skies is an outstanding challenge.
Ozone
As a result of the phase-out of CFCs, the
ozone layer is expected to make a gradual recovery to pre-CFC levels. The
rate of the expected recovery is based on theoretical calculations. NOAA's
ozone measurements are critical to checking whether the ozone layer is
indeed returning to normal values and how quickly. Another challenge
arises from phase-out of NASA's ozone observing program through NPP to
NPOESS. NPOESS will carry the nation's ozone monitoring instruments and
NOAA will be largely responsible for a reliable national ozone measurement
program.
SMCD scientists support calibration, algorithms and
validation of the existing SBUV/2 and Advanced TIROS Operational Vertical
Sounder (ATOVS) ozone products and prepare for future instruments in IJPS
and NPOESS (GOME-2 and the Ozone Mapping and Profiler Suite - OMPS,
respectively). The SMCD ozone program leverages capabilities at NASA in
ultraviolet sensor calibration and developing retrieval algorithms, and
NOAA/NWS/ Climate Prediction Center (CPC) experience in constructing and
analyzing ozone CDRs. Program scientists also participate in science teams
for research instruments, e.g., Stratospheric Aerosol and Gas Experiment
III (SAGE III) and OMI, development of validation sources, e.g., ground-
based Umkehr measurements, and are preparing for the advanced ozone
sensor, OMPS, on NPP and NPOESS. They have produced long-term ozone data
sets by stitching together the measurements of overlapping satellites.
These data sets captured the slow destruction of ozone in the 1980s and
1990s caused by industrial CFCs. SMCD also monitors the annual ebbing and
waning of the Antarctic ozone hole and issues timely reports on the
phenomena.
Air Quality
NOAA's
Air Quality Program, under its Weather and Water Goal, is a key
component of the Nation's effort to address and respond to air pollution.
The Program provides environmental policy makers and resource managers
with information on the causes of poor air quality and tools to support
effective decision-making. The Program also produces timely and accurate
air quality forecasts so the public can take appropriate action to limit
adverse effects of poor air quality.
NOAA plans to accelerate
nationwide implementation of ozone Air Quality forecasting capability from
FY 2009 to FY 2008 and to deliver an initial particulate matter
forecasting capability by FY 2011.
In support of these goals, SMCD has initiated a multi-year baseline
project to utilize GOES Aerosol and Smoke Product (GASP) in air quality
monitoring and forecasting. This project is closely tied to ongoing
activities at the EPA and the NWS to issue national air quality forecast
guidance. The project goals are to (1) evaluate the GOES aerosol and
smoke product, (2) to demonstrate its value
in air quality monitoring, (3) to use the product in the NWS air quality
forecast verification, and (4) direct assimilation of satellite-derived
aerosol products into NWS forecast models to improve forecasts by
improving model initial conditions.
Carbon Cycle Science
The amount of carbon
released into the atmosphere by industrial sources is reasonably well
known. So is the steadily increasing mean atmospheric CO2 concentration.
What is not known well is the rest of the carbon cycle - the magnitudes of
the natural sources and sinks of CO2 at the Earth's surface. Incomplete
knowledge of the carbon budget is an impediment to understanding and
predicting global climate change. Government agencies are exploring a
number of intensive observation campaigns and missions to better define
the carbon cycle, including dedicated space missions to measure
atmospheric carbon and its variations over the globe. The measurement of
atmospheric carbon in this content requires unprecedented precision.
SMCD scientists are exploring the possibilities of measuring carbon
dioxide and other greenhouse gases from infrared sounders. These sounders,
designed to measure global temperature and moisture for weather and
climate applications, have sensitivity to atmospheric carbon. The accuracy
of these measurements is a strong function of the vertical thermal
gradient and uncertainties in other components of the geophysical state,
such as moisture, ozone, and surface parameters. It may be possible to
derive estimates of carbon sources and sinks at the continental and
oceanic scale from AIRS atmospheric carbon products using atmospheric
transport models. Given that thermal sounders measure atmospheric carbon
in the mid-troposphere, where variability of these gases is very small,
deriving sources and sinks from AIRS will be a very difficult task.
Active Instruments: Doppler Wind Lidar and Global
Positioning System/Radio Occultation (GPS/RO)
According to the Strategic Plan for the U.S. Integrated Earth
Observation System high-resolution lower-atmosphere global wind
measurements from a spaceborne optical sensor would dramatically improve a
critical input for global prediction models, improving long-term weather
forecasting.
SMCD investigators face unprecedented challenges in
the long road to transition the completely new active measurements -
GPS/RO and Doppler Wind Lidar (DWL) - to operational use. Historically
operational atmospheric remote sensing from satellites has been based on
radiometric sounders and imagers. In the future, active remote sensors are
expected to complement these instruments, providing accurate observations
of unsurpassed vertical resolution. Prototype GPS/RO instruments are used
to measure atmospheric refractivity variations that result from the
temperature and humidity variations of the atmosphere, and the first
operational missions are expected in 2005/2006. DWLs have the potential to
sense the motion of atmospheric molecules or aerosols to measure the
horizontal wind. Surface and aircraft instruments DWLs are being used as
technology test-beds, and the first space-based demonstration is expected
in 2007.
GPS/RO.
Working with the JCSDA, SMCD is developing and testing the software tools needed
to assimilate upcoming GPS/RO observations in NWP models. SMCD is also
evaluating the accuracy of ground based DWL measurements as part of a program
to determine the feasibility of developing space-based instruments.
