George Ohring

Satellite Instrument Calibration for Measuring Global Climate Change: Report of a Workshop

Measuring the small changes associated with long-term global climate change from space is a daunting task. The satellite instruments must be capable of observing atmospheric and surface temperature trends as small as 0.1°C decade−1, ozone changes as little as 1% decade−1, and variations in the suns output as tiny as 0.1% decade−1. To address these problems and recommend directions for improvements in satellite instrument calibration, the National Institute of Standards and Technology (NIST), National Polar-orbiting Operational Environmental Satellite System–Integrated Program Office (NPOESS-IPO), National Oceanic and Atmospheric Administration (NOAA), and National Aeronautics and Space Administration (NASA) organized a workshop at the University of Maryland Inn and Conference Center, College Park, Maryland, 12–14 November 2002. Some 75 scientists participated including researchers who develop and analyze long-term datasets from satellites, experts in the field of satellite instrument calibration, and phy...

The Advanced Very High Resolution Radiometer (AVHRR) Pathfinder Atmosphere (PATMOS) Climate Dataset: Initial Analyses and Evaluations

Abstract As part of the joint National Oceanic and Atmospheric Administration–National Aeronautics and Space Administration (NOAA–NASA) Pathfinder program, the NOAA/National Environmental Satellite, Data and Information Service (NESDIS) has created a research-quality atmospheric, climate-scale dataset through the reprocessing of archived Advanced Very High Resolution Radiometer (AVHRR) observations from four afternoon satellites, in orbit since 1981. The raw observations were recalibrated using a vicarious calibration technique for the AVHRR reflectance channels and an improved treatment of the nonlinearity of the three infrared emittance channels. State-of-the-art algorithms are used in the Pathfinder Atmosphere (PATMOS) project to process global AVHRR datasets into statistics of channel radiances, total cloud amount, components of the earths radiation budget, and aerosol optical thickness over oceans. The radiances and earth radiation budget components are determined for clear-sky and all-sky condition...

Climate Signal Detection Times and Constraints on Climate Benchmark Accuracy Requirements

Long-term trends in the climate system are always partly obscured by naturally occurring interannual variability. All else being equal, the larger the natural variability, the less precisely one can estimate a trend in a time series of data. Measurement uncertainty, though, also obscures long-term trends. The way in which measurement uncertainty and natural interannual variability interact in inhibiting the detection of climate trends using simple linear regression is derived and the manner in which the interaction between the two can be used to formulate accuracy requirements for satellite climate benchmark missions is shown. It is found that measurement uncertainty increases detection times, but only when considered in direct proportion to natural variability. It is also found that detection times depend critically on the correlation time of natural variability and satellite lifetime. As a consequence, requirements on satellite climate benchmark accuracy and mission lifetime must be directly related to the natural variability of the climate system and its associated correlation times.

Satellite Determinations of the Relationship between Total Longwave Radiation Flux and Infrared Window Radiance

Abstract Nimbus-7 satellite observations are used to determine the relationship between the total longwave radiation flux and the radiance in the 10-12 μm infrared window. The total longwave fluxes are obtained from the earth radiation budget (ERB) narrow-field-of-view (NFOV) observations of total radiance; the IR window radiances are those measured by the Temperature Humidity Infrared Radiometer (THIR). Regression equations are obtained relating the total flux equivalent brightness temperatures to the radiance equivalent brightness temperature of the IR window. These empirical equations are compared to similar regression equations based on radiative transfer calculations for a large sample of atmospheric soundings. The latter theoretical equations are used by NOAA in the processing of IR window observations from operational polar orbiting satellites to obtain total longwave flux estimates. The observational results indicate that there is a very high correlation between the flux equivalent brightness temp...

The Advanced Very High Resolution Radiometer Pathfinder Atmosphere (PATMOS) Climate Dataset: A Resource for Climate Research

As part of the joint National Oceanic and Atmospheric Administration (NOAA) and National Aeronautics and Space Administration (NASA) Pathfinder program, the NOAA National Environmental Satellite, Data, and Information Service (NESDIS) has created a research-quality global atmospheric dataset through the reprocessing of Advanced Very High Resolution Radiometer (AVHRR) observations since 1981. The AVHRR is an imaging radiometer that flies on NOAA polar-orbiting operational environmental satellites (POES) measuring radiation reflected and emitted by the earth in five spectral channels. Raw AVHRR observations were recalibrated using a vicarious calibration technique for the reflectance channels and an appropriate treatment of the nonlinearity of the infrared channels. The observations are analyzed in the Pathfinder Atmosphere (PATMOS) project to obtain statistics of channel radiances, cloud amount, top of the atmosphere radiation budget, and aerosol optical thickness over ocean. The radiances and radiation bu...

Achieving satellite instrument calibration for climate change

For the most part, satellite observations of climate are not presently sufficiently accurate to establish a climate record that is indisputable and hence capable of determining whether and at what rate the climate is changing. Furthermore, they are insufficient for establishing a baseline for testing long-term trend predictions of climate models. Satellite observations do provide a clear picture of the relatively large signals associated with interannual climate variations such as El Nino-Southern Oscillation (ENSO), and they have also been used to diagnose gross inadequacies of climate models, such as their cloud generation schemes. However, satellite contributions to measuring long-term change have been limited and, at times, controversial, as in the case of differing atmospheric temperature trends derived from the U.S. National Oceanic and Atmospheric Administrations (NOAA) microwave radiometers.

Satellite Radiation Observations and Climate Theory

Publisher Summary This chapter illustrates some uses of satellite observations of the Earths radiation budget in studies of the Earths climate. Because of their importance to studies of the climate, radiation budget observations from satellites were initiated as early as 1962, only 2 years after the launching of the first weather satellite. The results of these observations are discussed and compared with the results of other satellite observations of the earths radiation budget. The longwave radiation and planetary albedo are components of the radiation budget that are measured from satellites. The application of satellite radiation observations to such sensitivity studies is discussed. Satellite observations of the radiation budget offer a means of validating model radiation calculations and of diagnosing possible causes of error in the simulations. The application of satellite radiation observations to the validation of a particular climate model of the statistical-dynamical type is described. The annual cycle of radiation budget components as observed from satellites for several climatic regions is explained. Finally, the time series of the global annual average, seasonal maps, and time-latitude sections of albedo, absorbed solar radiation, outgoing longwave radiation, and net radiation is presented.

Assimilating Satellite Observations of Clouds and Precipitation into NWP Models

what: Sixty-five experts in numerical weather prediction (NWP) and remote sensing were invited to document progress in cloud and precipitation data assimilation and to recommend pathways for future research and development. when: 15–17 June 2010 where: Reading, United Kingdom S atellite observations in the visible, infrared, and microwave spectrum provide a great deal of information on clouds and precipitation as well as the atmosphere in which the clouds are embedded. A major issue is how to use this information to initialize cloudy and precipitating atmospheric regions in NWP models. Most cloudand/or rain-affected observations are discarded in current data assimilation systems. The major problems are the discontinuous nature, in time and space, of clouds and precipitation, the complex nonlinear and not-well-modeled processes involved in their formation/prediction, and the need for current data assimilation systems to use linearized versions of these nonlinear processes. As a result, cloud/rain-affected radiances are much more difficult to assimilate than clear-sky radiances, which are sensitive to the smoother fields of temperature and water vapor that are controlled by more linear, wellmodeled processes. Since clouds and precipitation often occur in sensitive regions in terms of forecast impact, improvements in their assimilation are likely necessary for continuing significant gains in weather forecasting and, in particular, the prediction of two key weather elements affecting human activities: precipitation and cloudiness (which impacts another key weather factor, surface temperature). In 2005, the National Aeronautics and Space Administration (NASA)–National Oceanic and Atmospheric Administration (NOAA)–Department of Defense (DoD) Joint Center for Satellite Data Assimilation (JCSDA) sponsored an international workshop on assimilating observations in cloudy/ precipitating regions. Papers from that workshop were published in a special section of the November 2007 issue of the Journal of the Atmospheric Sciences AFFILIATIONS: bauer—European Center for Medium Range Weather Forecasting, Reading, United Kingdom; ohrinG—NOAA, Camp Springs, Maryland; Kummerow—Colorado State University, Fort Collins, Colorado; auliGne—University Corporation for Atmospheric Research, Boulder, Colorado CORRESPONDING AUTHOR: George Ohring, NOAA/NESDIS, 5200 Auth Rd., MD 20746 E-mail: george.ohring@noaa.gov

Climate and global change: Characteristics of NOAA satellite data

The principal finding of an International Council of Scientific Unions ICSU)/Committee on Space Research (COSPAR) ad hoc group on Remote Sensing for Global Change [Rasool, 1987] was that “The current international operational satellite system, augmented with the technology developed by research missions and supported by validation experiments and a comprehensive data system, could provide the basis for a global change observing system.” The National Oceanic and Atmospheric Administrations environmental satellites represent a significant part of the international system. NOAA manages a NOAA series of polar orbiters and a Geostationary Operational Environmental Satellite (GOES) series of geostationary satellites. A NOAA satellite can view each point on the Earths surface every 12 hours, at approximately the same local time each overpass. An attempt is made to maintain two NOAA satellites in orbit at all times, a so-called afternoon “bird” with nominal observing times of 2 P.M. and 2 A.M. and a morning bird with observations at 7 A.M. and 7 P.M. A GOES satellite hovering over the equator views continuously the surface of the Earth within 60° Earth central angle of the subsatellite point. NOAA operates a two-GOES system, one nominally stationed at 75°W and the other at 135°W.

NOAA–NASA–DoD Workshop on Satellite Data Assimilation

Abstract A workshop on the assimilation of satellite sounding information using global forecast and climate models was held at College Park, Maryland, 23–25 August 1999. Topics discussed included comparisons of assimilations of satellite retrievals versus satellite–observed radiances, planning for the use of advanced infrared sounders, the use of satellite sounding data affected by land surfaces, radiative transfer issues, and error characteristics of models and observations. The workshop concluded with a number of general and specific recommendations to advance the state of the art of assimilation of satellite sounding data.