Daytime Global Cloud Typing from AVHRR and VIIRS: Algorithm Description, Validation, and Comparisons

Abstract

Three multispectral algorithms for determining the cloud type of previously identified cloudy pixels during the daytime, using satellite imager data, are presented. Two algorithms were developed for use with 0.65-, 1.6-/3.75-, 10.8-, and 12.0-μm data from the Advanced Very High Resolution Radiometer (AVHRR) on board the National Oceanic and Atmospheric Administration (NOAA) operational polar-orbiting satellites. The AVHRR algorithms are identical except for the near-infrared data that are used. One algorithm uses AVHRR channel 3a (1.6 μm) reflectances, and the other uses AVHRR channel 3b (3.75 μm) reflectance estimates. Both of these algorithms are necessary because the AVHRRs on NOAA-15 through NOAA-17 have the capability to transmit either channel 3a or 3b data during the day, whereas all of the other AVHRRs on NOAA-7 through NOAA-14 can only transmit channel 3b data. The two AVHRR cloud-typing schemes are used operationally in NOAA’s extended Clouds from AVHRR (CLAVR)-x processing system. The third algorithm utilizes additional spectral bands in the 1.38- and 8.5-μm regions of the spectrum that are available on the Moderate Resolution Imaging Spectroradiometer (MODIS) and will be available on the Visible–Infrared Imaging Radiometer Suite (VIIRS). The VIIRS will eventually replace the AVHRR on board the National Polar-Orbiting Operational Environmental Satellite System (NPOESS), which is currently scheduled to be launched in 2009. Five cloud-type categories are employed: warm liquid water, supercooled water–mixed phase, opaque ice, nonopaque high ice (cirrus), and cloud overlap (multiple cloud layers). Each algorithm was qualitatively evaluated through scene analysis and then validated against inferences of cloud type that were derived from ground-based observations of clouds at the three primary Atmospheric Radiation Measurement (ARM) Program sites to help to assess the potential continuity of a combined AVHRR channel 3a–AVHRR channel 3b–VIIRS cloud-type climatology. In this paper, “validation” is strictly defined as comparisons with ground-based estimates that are completely independent of the satellite retrievals. It was determined that the two AVHRR algorithms produce nearly identical results except for certain thin clouds and cloud edges. The AVHRR 3a algorithm tends to incorrectly classify the thin edges of some low- and midlevel clouds as cirrus and opaque ice more often than the AVHRR 3b algorithm. The additional techniques implemented in the VIIRS algorithm result in a significant improvement in the identification of cirrus clouds, cloud overlap, and overall phase identification of thin clouds, as compared with the capabilities of the AVHRR algorithms presented in this paper.

Recent Northern Hemisphere tropical expansion primarily driven by black carbon and tropospheric ozone

“…Observational data comes from several sources, including the Global Precipitation Climatology Project version 2.2 (GPCP) 31 the Integrated Global Radiosonde Archive (IGRA) 32 and five reanalyses [33][34][35][36][37] for MMC calculations. Cloud cover observations, which span July 1983 to June 2008 only, come from two recently homogenized satellite data sets 38 based on the International Satellite Cloud Climatology Project (ISCCP) 39,40 and the Advanced Very High Resolution Radiometer (AVHRR) Pathfinder Atmospheres Extended (PATMOS-x) 41,42 . Our P 2 E estimate is based on precipitation from GPCP and evaporation from the Woods Hole Oceanographic Institution (WHOI) Objectively Analyzed air-sea Flux (OAFlux) project 43 .…”

An Evaluation of Satellite Estimates of Solar Surface Irradiance Using Ground Observations in San Antonio, Texas, USA

“…The G s , cloud type, and cloud layer data used in this study come from the NOAA GOES Surface and Insolation Products (GSIP) based on the visible and infrared channels of GOES satellites (GOES East and GOES West), 45 min after the hour and on the hour during daytime [29]. The identification of cloud types and layers (Table 1) is based on the work of Pavolonis et al [30]. The resolution of the GSIP products in San Antonio is about 2.3 km in longitude × 4.9 km in latitude (i.e., about 11 km 2 ).…”

Model Calculations of Solar Spectral Irradiance in the 3.7-μm Band for Earth Remote Sensing Applications

“…The main objective in originally flying the channel was reported to be for cloud screening of sea surface temperature observations (Schwalb 1978). Measurements in this window are now routinely used for cloud detection and screening (Saunders and Kriebel 1988;Ackerman et al 1998;Heidinger et al 2002), fire detection (Kaufman et al 1990;Prins and Menzel 1992;Justice et al 2002), cloud phase and surface snow/ice discrimination (Pavolonis et al 2005), and quantitative cloud microphysical retrievals (Arking and Childs 1985;Platnick and Twomey 1994;Han et al 1994;Minnis et al 1995;Platnick et al 2003). The usefulness of the band for cloud observations essentially derives from the significant dependence of single scattering albedo on cloud thermodynamic phase and particle size (absorption increases for the ice phase and with particle size) and differences in single scattering albedo (and thereby cloud emissivity) when compared with window IR channels.…”