The Multi-angle Imaging SpectroRadiometer (MISR) currently provides three independently derived cloud mask products at 1.1 km spatial resolution. The Radiometric Camera-by-camera Cloud Mask (RCCM) is terrain-referenced and calculated for each of the nine MISR cameras, the Stereoscopically Derived Cloud Mask (SDCM) is feature-projected and uses radiances from one pair of the MISR cameras, and the Angular Signature Cloud Mask (ASCM) uses a band-differenced angular signature based on the two most oblique cameras viewing forward scattering radiation. While each mask has been extensively validated, each having its own strengths and weaknesses, there has been no effort to combine the strengths of all of the masks to create a single consensus product. We present an algorithm which addresses the problem and produces a so called "consensus cloud mask" of improved performance, and elaborate on further cloud climatology applications.
Trade wind cumulus clouds typically have horizontal sizes of tens of meters to tens of kilometers. Cloud products from MISR and MODIS instruments are available at spatial resolutions varying from 1 km to 5 km. Therefore some of these clouds have been poorly detected and studied. For the duration of the Rain in Cumulus over the Ocean (RICO) experiment, November 2004 - January 2005, data from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is available at 15 meters spatial resolution. We use this data along with a suite of aircraft data available as part of RICO to validate cloud macro-physical properties derived from meteorological satellites.
Recently developed, the Cloud Infrared Radiometer CIR-7, operates 7 infrared sensors, each with a 6-degree field of view, and spectral range 8-14 μm. The sensors are mounted on a semi-circular band at angles 0, 12, 24, 36, 48, 60 and 72°. A "hemispherical" mosaic of 181 brightness temperature measurements centered on the zenith is obtained by the rotation of the band around the vertical axis, performing 30 scans, every 12° from 0° (North) to 348 °.
We present an algorithm that utilizes the brightness temperatures from the CIR-7 given the precipitable water vapor amounts and vertical profiles of the thermodynamic state of the atmosphere from independent measurements. It estimates the total cloud amount, the amount of low, middle and high clouds, maps out the spatial distribution of the cloud field and determines the vertical distribution of the clouds by computing cloud base heights.
The algorithm is validated through comparisons with well studied ground-based and satellite retrieval techniques. Initial analyses show good cloud amount assessment and spatial mapping abilities. The estimated mean absolute cloud amount difference for day time is 12.3% when compared to the amount of opaque clouds derived with a total sky imager (TSI). For night time, this difference is 19.4% comparing to the effective cloud fraction derived with an atmospheric emitted radiance interferometer (AERI). The vertical distribution understanding is currently limited; however, the amounts of low, middle and high clouds could be determined and studied further.
A part of the results obtained during the winter experimental campaign 'LIRADEX'98' are presented. A vertically sounding aerosol lidar and a thermal infrared radiometer were used for joint investigation of low clouds. Both devices were placed at height of about 12 m above the ground and about 25 m apart. Data about the atmospheric parameters were obtained by parallel standard aerological observation. The experimental campaign extended two weeks during November and December, 1998. The data discussed in the presented paper are obtained on December 2, 1998.
The cloud field bottom was sounded in zenith direction by a single-channel IR radiometer which registers the downwelling thermal radiation in the spectral range 7.5 divided by 13 micrometers . The time dependence of the signal is related with the effective radiative temperature of the sounded cloud bottom. The registered records were statistically analyzed. The evaluated statistical characteristics of the signals were analyzed and compared with the information about the morphological structure of the corresponding clouds. It was proved that there exists relationship between the both types of cloud characteristics.
The preliminary results obtained during the experimental campaign `LIRADEX'98' are presented. A vertically sounding aerosol lidar and an infrared optical radiometer were used to investigate low clouds. Both devices were placed at height of about 12 m above the ground and about 25 m apart. Data about the atmospheric parameters were obtained by parallel standard aerological observation. The experimental campaign extended two weeks--from 06.05.1998 to 19.05.1998. The data presented in the paper are from 08.05.1998.
the time mutability method permits drift velocity estimation of statistically non-homogeneous and non-stationary objects. It is an alternative of cross-correlation techniques. Cloud fields are typical objects having the mentioned statistical features. Here we present and discuss results of cloud motion drift velocity estimation obtained by time mutability method based on handling of infrared METEOSAT images.