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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.