Removal of the Solar Component in AVHRR 3.7-µm Radiances for the Retrieval of Cirrus Cloud Parameters

1995 ◽  
Vol 34 (2) ◽  
pp. 482-499 ◽  
Author(s):  
N. X. Rao ◽  
S. C. Ou ◽  
K. N. Liou
Keyword(s):  
Lidar Data ◽  
Cirrus Cloud ◽  
Transfer Program ◽  
Ice Crystal ◽  
Threshold Values ◽  
Cloud Parameters ◽  
Look Up Table ◽  
Retrieval Scheme ◽  
The Look ◽  
Very High

Abstract A numerical scheme has been developed to remove the solar component in the Advanced Very High Resolution Radiometer (AVHRR) 3.7-µm channel for the retrieval of cirrus parameters during daytime. This method uses a number of prescribed threshold values for AVHRR channels 1 (0.63 µm), 2 (0.8 µm), 3 (3.7 µm), 4 (10.9 µm), and 5 (12 µm) to separate clear and cloudy pixels. A look-up table relating channels 1 and 3 solar reflectances is subsequently constructed based on the prescribed mean effective ice crystal sizes and satellite geometric parameters. An adding–doubling radiative transfer program has been used to generate numerical values in the construction of the look-up table. Removal of the channel 3 solar component is accomplished by using the look-up table and the measured channel 1 reflectance. The cloud retrieval scheme described in Ou et al. has been modified in connection with the removal program. The authors have applied the removal–retrieval scheme to the AVHRR global area coverage daytime data, collected during the First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment cirrus intensive field observation (FIRE IFO) at 2100 UTC 28 October 1986 over the Wisconsin area. Distributions of the retrieved cloud heights and optical depths are comparable to those determined from Geostationary Operational Environmental Satellite visible and IR channels data reported by Minnis et al. Morwver, verifications of the retrieved cirrus temperature and height against lidar data have been carried out using results reported from three FIRE IFO nations. The retrieved cloud heights are within 0.5 km of the measured lidar values.

scholarly journals A Fast Retrieval of Cloud Parameters Using a Triplet of Wavelengths of Oxygen Dimer Band around 477 nm

2021 ◽  
Vol 13 (1) ◽  
pp. 152
Author(s):  
Haklim Choi ◽  
Xiong Liu ◽  
Gonzalo Gonzalez Abad ◽  
Jongjin Seo ◽  
Kwang-Mog Lee ◽  
...  
Keyword(s):  
Scattered Light ◽  
Trace Gas ◽  
Retrieval Algorithm ◽  
The Novel ◽  
Cloud Parameters ◽  
Retrieval Scheme ◽  
The Difference ◽  
The Look ◽  
Time Required ◽  
Cloud Top Pressure

Clouds act as a major reflector that changes the amount of sunlight reflected to space. Change in radiance intensity due to the presence of clouds interrupts the retrieval of trace gas or aerosol properties from satellite data. In this paper, we developed a fast and robust algorithm, named the fast cloud retrieval algorithm, using a triplet of wavelengths (469, 477, and 485 nm) of the O2–O2 absorption band around 477 nm (CLDTO4) to derive the cloud information such as cloud top pressure (CTP) and cloud fraction (CF) for the Geostationary Environment Monitoring Spectrometer (GEMS). The novel algorithm is based on the fact that the difference in the optical path through which light passes with regard to the altitude of clouds causes a change in radiance due to the absorption of O2–O2 at the three selected wavelengths. To reduce the time required for algorithm calculations, the look-up table (LUT) method was applied. The LUT was pre-constructed for various conditions of geometry using Vectorized Linearized Discrete Ordinate Radiative Transfer (VLIDORT) to consider the polarization of the scattered light. The GEMS was launched in February 2020, but the observed data of GEMS have not yet been widely released. To evaluate the performance of the algorithm, the retrieved CTP and CF using observational data from the Global Ozone Monitoring Experiment-2 (GOME-2), which cover the spectral range of GEMS, were compared with the results of the Fast Retrieval Scheme for Clouds from the Oxygen A band (FRESCO) algorithm, which is based on the O2 A-band. There was good agreement between the results, despite small discrepancies for low clouds.

Remote sensing of cirrus cloud parameters using advanced very-high-resolution radiometer 37- and 109-μm channels

1993 ◽  
Vol 32 (12) ◽  
pp. 2171 ◽  
Author(s):  
S. C. Ou ◽  
K. N. Liou ◽  
W. M. Gooch ◽  
Y. Takano
Keyword(s):  
Remote Sensing ◽  
High Resolution ◽  
Cirrus Cloud ◽  
Cloud Parameters ◽  
Very High

scholarly journals Remote Sounding of Multilayer Cirrus Cloud Systems Using AVHRR Data Collected during FIRE-II-IFO

1998 ◽  
Vol 37 (3) ◽  
pp. 241-254 ◽  
Author(s):  
S. C. Ou ◽  
K. N. Liou ◽  
T. R. Caudill
Keyword(s):  
Cirrus Clouds ◽  
Lidar Data ◽  
Cirrus Cloud ◽  
Ice Crystal ◽  
Cloud Systems ◽  
Convective Clouds ◽  
Stratus Clouds ◽  
Remote Sounding ◽  
Avhrr Data ◽  
Surface Observations

Abstract Surface observations show that multilayer clouds frequently occur in frontal areas where cirrus clouds overlie boundary layer convective clouds or stratus clouds. In this paper, an algorithm is presented for the retrieval of cirrus cloud optical depths and ice crystal sizes in multilayer cloud systems based on the theory of radiative transfer and parameterizations. For the validation of the retrieval program, AVHRR data is analyzed for two dates during FIRE-II-IFO in which cirrus clouds overlie a layer of low stratus cloud. It is shown that the domain-averaged retrieved cloud temperatures are within the boundaries of cirrus clouds determined from the collocated replicator, radar, and lidar data. The retrieved ice crystal mean effective sizes and optical depths are also in general agreement with the values determined from the balloon-borne replicator and 2D probe data.

scholarly journals Remote Sensing of Cirrus Cloud Particle Size and Optical Depth Using Polarimetric Sensor Measurements

2005 ◽  
Vol 62 (12) ◽  
pp. 4371-4383 ◽  
Author(s):  
S. C. Ou ◽  
K. N. Liou ◽  
Y. Takano ◽  
R. L. Slonaker
Keyword(s):  
Remote Sensing ◽  
Particle Size ◽  
Optical Depth ◽  
Steepest Descent Method ◽  
Stokes Parameters ◽  
Retrieval Algorithm ◽  
Cirrus Cloud ◽  
Transfer Program ◽  
Ice Crystal ◽  
Cloud Particle

Abstract This paper presents a conceptual approach toward the remote sensing of cirrus cloud particle size and optical depth using the degree of polarization and polarized reflectance associated with the first three Stokes parameters, I, Q, and U, for the 0.865- and 2.25-μm wavelengths. A vector line-by-line equivalent radiative transfer program including the full Stokes parameters based on the adding method was developed. The retrieval algorithm employs the steepest-descent method in the form of a series of numerical iteration procedures to search for the simulated polarization parameters that best match the measured values. Sensitivity studies were performed to investigate the behavior of phase-matrix elements as functions of scattering angles for three ice crystal size–shape combinations. Overall, each phase-matrix element shows some sensitivity toward ice crystal shape, size, and surface roughness due to the various optical effects. Synthetic analysis reveals that the retrieval algorithm is highly accurate, while polarimetric and radiometric error sources cause very small retrieval errors. Finally, an illustrative example of applying the retrieval algorithm to airborne Polarization and Directionality of the Earth’s Reflectances (POLDER) data during the European Cloud and Radiation Experiment (EUCREX) is presented.

scholarly journals Impacts of cloud heterogeneities on cirrus optical properties retrieved from spatial thermal infrared radiometry

2014 ◽  
Vol 7 (8) ◽  
pp. 8777-8816 ◽  
Author(s):  
T. Fauchez ◽  
P. Dubuisson ◽  
C. Cornet ◽  
F. Szczap ◽  
A. Garnier ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Optical Thickness ◽  
Effective Diameter ◽  
Cirrus Cloud ◽  
Strong Impact ◽  
Ice Crystal ◽  
Cloud Parameters ◽  
Cloud Properties ◽  
Ice Crystal Size ◽  
The Impact

Abstract. This paper presents a study, based on simulations, of the impact of cirrus cloud heterogeneities on the retrieval of cloud parameters (optical thickness and effective diameter) for the Imaging Infrared Radiometer (IIR) on board CALIPSO. Cirrus clouds are generated by the stochastic model 3DCLOUD for two different cloud fields and for several averaged cloud parameters. One is obtained from a cirrus observed on the 25 May 2007 during the airborne campaign CIRCLE-2 and the other is a cirrus uncinus. The radiative transfer is simulated with the code 3DMCPOL. To assess the errors due to cloud heterogeneities, two related retrieval algorithms are used: (i) The split window technique to retrieve the ice crystal effective diameter and (ii) an algorithm similar to the IIR operational algorithm to retrieve the effective emissivity and the effective optical thickness. Differences between input parameters and retrieved parameters are compared as a function of different cloud properties such as the mean optical thickness, the heterogeneity parameter and the effective diameter. The optical thickness heterogeneity for each 1 km × 1 km observation pixel is represented by the optical thickness standard deviation computed using 100 m × 100 m subpixels. We show that optical thickness heterogeneity may have a strong impact on the retrieved parameters, mainly due to the Plane Parallel Approximation (PPA). In particular, for cirrus cloud with ice crystal size of approximately 10 μm, the averaged error on the retrieved effective diameter is about 2.5 μm (~ 25%) and on the effective optical thickness of about −0.20 (~ 12%). Then, these biases decrease with the increase of the ice effective size due to a decrease of the cloud absorption and thus of the PPA bias. Cloud heterogeneity effects are much more higher than other possible sources of error. They become larger than the retrieval incertitude of the IIR algorithm from a standard deviation of the optical thickness, inside the observation pixel, superior to 1.

Assessment of the look-up table using the tubular and bundle CHF data and modification of the bundle correction factor

Kerntechnik ◽  
2006 ◽  
Vol 71 (4) ◽  
pp. 192-202
Author(s):  
D. K. Chandraker ◽  
P. K. Vijayan ◽  
D. Saha ◽  
R. K. Sinha
Keyword(s):  
Correction Factor ◽  
Look Up Table ◽  
The Look

scholarly journals Development of Multilayer-Based Map Matching to Enhance Performance in Large Truck Fleet Dispatching

2021 ◽  
Vol 10 (2) ◽  
pp. 79
Author(s):  
Ching-Yun Mu ◽  
Tien-Yin Chou ◽  
Thanh Van Hoang ◽  
Pin Kung ◽  
Yao-Min Fang ◽  
...  
Keyword(s):  
Data Structures ◽  
Spatial Data ◽  
Spatial Information ◽  
Data Retrieval ◽  
Spatial Data Mining ◽  
Map Matching ◽  
Matching Algorithm ◽  
Table Method ◽  
Look Up Table ◽  
The Look

Spatial information technology has been widely used for vehicles in general and for fleet management. Many studies have focused on improving vehicle positioning accuracy, although few studies have focused on efficiency improvements for managing large truck fleets in the context of the current complex network of roads. Therefore, this paper proposes a multilayer-based map matching algorithm with different spatial data structures to deal rapidly with large amounts of coordinate data. Using the dimension reduction technique, the geodesic coordinates can be transformed into plane coordinates. This study provides multiple layer grouping combinations to deal with complex road networks. We integrated these techniques and employed a puncture method to process the geometric computation with spatial data-mining approaches. We constructed a spatial division index and combined this with the puncture method, which improves the efficiency of the system and can enhance data retrieval efficiency for large truck fleet dispatching. This paper also used a multilayer-based map matching algorithm with raster data structures. Comparing the results revealed that the look-up table method offers the best outcome. The proposed multilayer-based map matching algorithm using the look-up table method is suited to obtaining competitive performance in identifying efficiency improvements for large truck fleet dispatching.

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