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

Abstract

A recent reprocessing of AVHRR data results in a 20-yr global climate dataset providing information on the earth's radiation budget T he National Oceanic and Atmospheric Administration/National Environmental Satellite, Data, and Information Service (NOAA/NESDIS) has generated a consistent, calibrated, dataset of atmospheric products derived from nearly 20 yr of observations from Advanced Very High Resolution Radiometers (AVHRR) on board NOAA polar-orbiting satellites. This began as a partnership with the National Aeronautics and Space Administration (NASA), in a program called Pathfinder, to generate long-term datasets from archived satellite observations. NOAA has taken the lead in generating atmospheric products from AVHRR and making them easily accessible for climate research.The atmospheric products derived from AVHRR include such key climate variables as cloud amount, aerosol amount, and the top of the atmosphere net solar and long wave radiation. Clouds modulate the earth's radiation budget (ERB): they reflect solar radiation-a cooling effect-and recapture some infrared radiation otherwise lost to space-a warming effect. Uncertainties associated with how their radiative properties will evolve as the climate changes is a major cause for the large range in greenhouse warming predictions from climate models. Aerosols from very intense volcanic eruptions cause more sunlight to be reflected back to space leading to reductions of as much as 1°C or more in global temperatures that may persist for a year or more. Both man-made and natural aerosols reflect and absorb solar radiation. Current estimates indicate that the reflective component is larger and that aerosols could regionally cancel thewarming effects of increases in greenhouse gases. The ERB, representing the input and output of energy for the earth and its atmosphere, is a fundamental quantity and is the driver for climate variations.Constructing a dataset useful for climate studies from the archived AVHRR observations-representing data obtained from instruments on a series of operational satellites-is not a trivial task. Interannual climate variations, such as ENSOs and, particularly, decadal climate variations, such as global warming, are much smaller than typical weather changes. These smaller signals are more difficult to measure and require particular attention to instrument calibration and the long-term stability of the dataset: small, timedependent biases in the data cannot be tolerated. This paper illustrates the problems that arise from orbital drift. The PATMOS data sets are shown along with preliminary efforts to remove artificial trends and discontinuities due to the satellite orbit drift. This is demonstrated for a large tropical band. However, smaller regions require more sophisticated methods to account for the drift. Researchers should still find the Pathfinder Atmosphere (PATMOS) dataset of value in any number of studies. For example, one can obtain a climatological map showing the average global distribution of the earth's cloudiness (or...

Cloud retrievals from satellite data using optimal estimation: evaluation and application to ATSR

“…Various active and passive satellite cloud climatologies exist; for example, the active Cloud Profiling Radar (CPR) (Stephens et al, 2008) and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) sensors are able to provide height-resolved information on cloud properties (Winker et al, 2007), however, coverage is limited to the subsatellite track and the time-series are short. Of the passive satellite instruments the most widely known are the High resolution Infrared Sounder (HIRS, Wylie and Menzel, 1999), Moderate Resolution Imaging Spectroradiometer (MODIS, Platnick et al, 2003), Advanced Very High Resolution Radiometer (AVHRR, Jacobowitz et al, 2003;Heidinger and Pavolonis, 2009) and Multi-angle imaging SpectroRadiometer (MISR, Moroney et al, 2002) datasets. The passive sensors cannot represent the complex vertical structure, but have much better global coverage and longer time series than active instruments.…”

On the decadal increase in the tropical mean outgoing longwave radiation for the period 1984-2000

“…Observations from narrowband scanning radiometers (AVHRR and HIRS) have been used (Wielicki et al, 2002a, data supplement http://www.sciencemag.org/cgi/ content/full/295/5556/841/DC1) to derive broadband longwave radiative fluxes: AVHRR OLR fluxes showed a decrease of 2 Wm −2 /decade in the tropical region, for the period 1985-2000, while HIRS OLR data showed an increase of about 1 Wm −2 /decade for the same period. In the recent reprocessing of AVHRR data, which resulted in the PATMOS climate dataset, Jacobowitz et al (2003) examined the time-series of the OLR at TOA, in the tropics (20 • N-20 • S), for the period from September 1981 through to December 1999. They found that the OLR decreased by a little less than 2 Wm −2 for the period from 1985 to 2000.…”

Downscaling of METEOSAT SEVIRI 0.6 and 0.8 μm channel radiances utilizing the high-resolution visible channel

“…Passive meteorological satellite imagers provide important information for investigating cloud properties (Stephens and Kummerow, 2007), and for quantifying their influence on solar (Deneke et al, 2005) and thermal (Schmetz et al, 1990) radiation. Several projects generate data records of cloud properties, including the International Satellite Cloud Climatology Project (ISCCP, Rossow and Schiffer, 1991), the Pathfinder Atmospheres project (PAT-MOS, Jacobowitz et al, 2003), the MODIS project (Platnick et al, 2003), and the Satellite Application Facility on Climate Monitoring (CM-SAF, Schulz et al, 2009).…”

“…As demonstrated by Heidinger and Stephens (2001), unresolved spatial heterogeneity can cause errors in retrieved cloud properties large enough to render them useless. To partly overcome this problem, Klüser et al (2008) utilized the high-resolution broadband visible channel (HRV) with a sampling resolution of 1×1 km 2 at nadir to study the lifecycle of shallow convective clouds.…”