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Author: Christopher Rogers Yost Publisher: ISBN: Category : Languages : en Pages :
Book Description
In this study, we use thermal infrared channels to retrieve the optical thickness and effective particle radius of ice clouds. A physical model is used in conjunction with Atmospheric Infrared Sounder (AIRS) temperature and water vapor profiles to simulate the top-of-atmosphere (TOA) brightness temperatures (BTs) observed by the Moderate Resolution Imaging Spectroradiometer (MODIS) for channels located at 8.5, 11.0, and 12.0 [mu] (1176, 909, and 833 cm−1). The model is initially validated by comparing simulated clear-sky BTs to MODIS-observed clear-sky BTs. We also investigate the effect of introducing a +3 [kappa] bias in the temperature profile, a +3 [kappa] bias in the surface temperature, and a +20% bias in the water vapor profile in order to test the sensitivity of the model to these inputs. For clear-sky cases, the simulated TOA BTs agree with MODIS to within 2-3 [kappa]. The model is then extended to simulate thermal infrared BTs for cloudy skies, and we infer the optical thickness and effective radius of ice clouds by matching MODIS-observed BTs to calculations. The optical thickness retrieval is reasonably consistent with the MODIS Collection 5 operational retrieval for optically thin clouds but tends to retrieve smaller particle sizes than MODIS.
Author: Christopher Rogers Yost Publisher: ISBN: Category : Languages : en Pages :
Book Description
In this study, we use thermal infrared channels to retrieve the optical thickness and effective particle radius of ice clouds. A physical model is used in conjunction with Atmospheric Infrared Sounder (AIRS) temperature and water vapor profiles to simulate the top-of-atmosphere (TOA) brightness temperatures (BTs) observed by the Moderate Resolution Imaging Spectroradiometer (MODIS) for channels located at 8.5, 11.0, and 12.0 [mu] (1176, 909, and 833 cm−1). The model is initially validated by comparing simulated clear-sky BTs to MODIS-observed clear-sky BTs. We also investigate the effect of introducing a +3 [kappa] bias in the temperature profile, a +3 [kappa] bias in the surface temperature, and a +20% bias in the water vapor profile in order to test the sensitivity of the model to these inputs. For clear-sky cases, the simulated TOA BTs agree with MODIS to within 2-3 [kappa]. The model is then extended to simulate thermal infrared BTs for cloudy skies, and we infer the optical thickness and effective radius of ice clouds by matching MODIS-observed BTs to calculations. The optical thickness retrieval is reasonably consistent with the MODIS Collection 5 operational retrieval for optically thin clouds but tends to retrieve smaller particle sizes than MODIS.
Author: Kevin James Garrett Publisher: ISBN: Category : Languages : en Pages :
Book Description
The research presented in this thesis involves the study of ice cloud microphysical and optical properties using both hyperspectral and narrowband infrared spectral data. First, ice cloud models are developed for the Infrared Atmospheric Sounding Interferometer (IASI) instrument onboard the METOP-A satellite, which provide the bulk-scattering properties of these clouds for the 8461 IASI channels between 645 and 2760 cm-1. We investigate the sensitivity of simulated brightness temperatures in this spectral region to the bulk-scattering properties of ice clouds containing individual ice crystal habits as well as for one habit distribution. The second part of this thesis describes an algorithm developed to analyze the sensitivity of simulated brightness temperatures at 8.5 and 11.0 ℗æm to changes in effective cloud temperature by adjusting cloud top height and geometric thickness in a standard tropical atmosphere. Applicability of using these channels in a bi-spectral approach to retrieve cirrus cloud effective particle size and optical thickness is assessed. Finally, the algorithm is applied to the retrieval of these ice cloud properties for a case of single-layered cirrus cloud over a tropical ocean surface using measurements from the Moderate Resolution Infrared Spectroradiometer (MODIS). Cloud top height and geometric thickness in the profile are adjusted to assess the influence of effective cloud temperature on the retrieval.
Author: Kuo-Nan Liou Publisher: Cambridge University Press ISBN: 0521889162 Category : Science Languages : en Pages : 461
Book Description
This volume outlines the fundamentals and applications of light scattering, absorption and polarization processes involving ice crystals.
Author: Yong-Keun Lee Publisher: ISBN: Category : Languages : en Pages :
Book Description
This dissertation reports on three different yet related topics in light scattering computation, radiative transfer simulation, and remote sensing implementation, regarding the cloud properties and the retrieval of cloud properties from satellite-based infrared radiometric measurements. First, the errors associated with the use of circular cylinders as surrogates for hexagonal columns in computing the optical properties of pristine ice crystals at infrared (8-12 [micron]) wavelengths are investigated. It is found that the differences between the results for circular cylinders and hexagonal columns are on the order of a few percent at infrared wavelengths. Second, investigated in this dissertation are the outgoing broadband longwave and window channel radiances at the top-of-atmosphere under clear-sky conditions on the basis of the data acquired by the Cloud and the Earth's Radiant Energy System (CERES) instrument onboard the NASA Terra satellite platform. Based on the comparison of the observed broadband radiances with those obtained from rigorous radiative transfer simulations, it is found that the theoretical results tend to be larger than their measured counterparts. Extensive sensitivity studies regarding the uncertainties of various parameters were carried out. Within the considered uncertainties of various factors, the computed radiances are still larger than the observed radiances if thin cirrus clouds are excluded. Thus, a potential cause for the differences could be associated with the presence of thin cirrus clouds whose visible optical thickness is smaller than approximately 0.3. Third, presented in this dissertation is an illustration of the application of hyperspectral infrared channel observations to the retrieval of the cloud properties. Specifically, the hyperspectral measurements acquired from the Atmospheric Infrared Sounder (AIRS) aboard the NASA Aqua platform are used to infer cloud top pressure, effective cloud amount, cloud thermodynamic phase, cloud optical thickness, and the effective size of cloud particles. The AIRS-based retrievals are compared with the counterparts of the operational cloud products derived from the Moderate Resolution Imaging Spectroradiometer (MODIS). The two retrievals agree reasonably well except for the retrieved cloud effective particle size. Furthermore, the diurnal and seasonal contrasts of cloud properties are also investigated on the basis of the cloud properties retrieved from the AIRS data.
Author: Kerry Glynne Meyer Publisher: ISBN: Category : Languages : en Pages :
Book Description
Ice clouds occur quite frequently, yet so much about these clouds is unknown. In recent years, numerous investigations and field campaigns have been focused on the study of ice clouds, all with the ultimate goal of gaining a better understanding of microphysical and optical properties, as well as determining the radiative impact. Perhaps one of the most recognized instruments used for such research is the Moderate-resolution Imaging Spectroradiometer (MODIS), carried aboard the NASA EOS satellites Terra and Aqua. The present research aims to support ongoing efforts in the field of ice cloud research by use of observations obtained from Terra and Aqua MODIS. First, a technique is developed to infer ice cloud optical depth from the MODIS cirrus reflectance parameter. This technique is based on a previous method developed by Meyer et al. (2004). The applicability of the algorithm is demonstrated with retrievals from level-2 and -3 MODIS data. The technique is also evaluated with the operational MODIS cloud retrieval product and a method based on airborne ice cloud observations. From this technique, an archive of daily optical depth retrievals is constructed. Using simple statistics, the global spatial and temporal distributions of ice clouds are determined. Research has found that Aqua MODIS observes more frequent ice clouds and larger optical depths and ice water paths than does Terra MODIS. Finally, an analysis of the time series of daily optical depth values revealed that ice clouds at high latitudes, which are most likely associated with synoptic scale weather sytems, persist long enough to move with the upper level winds. Tropical ice clouds, however, dissipate more rapidly, and are in all likelihood associated with deep convective cells.
Author: Yangang Liu Publisher: John Wiley & Sons ISBN: 1119528941 Category : Science Languages : en Pages : 483
Book Description
Improving weather and climate prediction with better representation of fast processes in atmospheric models Many atmospheric processes that influence Earth’s weather and climate occur at spatiotemporal scales that are too small to be resolved in large scale models. They must be parameterized, which means approximately representing them by variables that can be resolved by model grids. Fast Processes in Large-Scale Atmospheric Models: Progress, Challenges and Opportunities explores ways to better investigate and represent multiple parameterized processes in models and thus improve their ability to make accurate climate and weather predictions. Volume highlights include: Historical development of the parameterization of fast processes in numerical models Different types of major sub-grid processes and their parameterizations Efforts to unify the treatment of individual processes and their interactions Top-down versus bottom-up approaches across multiple scales Measurement techniques, observational studies, and frameworks for model evaluation Emerging challenges, new opportunities, and future research directions The American Geophysical Union promotes discovery in Earth and space science for the benefit of humanity. Its publications disseminate scientific knowledge and provide resources for researchers, students, and professionals.
Author: Volkan Huseyin Firat Publisher: ISBN: Category : Languages : en Pages :
Book Description
Clouds are still one of the largest uncertainties of the current climate models. While satellites provide suitable global datasets for comparing with cloud properties derived from models, satellite retrievals are inferences of cloud properties, rather than direct measurements, and therefore have errors. Therefore, it is important to evaluate satellite cloud products and gain advanced understanding of the products to accurately interpret the observations. This study investigates Aqua AIRS version 6 Level 2 cloud thermodynamic phase, ice cloud optical thickness, and ice cloud effective diameter, which released in April, 2013 and are available for all 13 years of the AIRS record. A filtering and gridding algorithm is used to create customized globally gridded datasets to evaluate the effects of satellite's viewing zenith angle, effective cloud fraction, cloud layers, cloud top temperature, time of the year, and geographic region. Viewing zenith angle does not strongly affect AIRS ice-phase, but higher viewing zenith angles lead to more water and fewer unknown pixels; the viewing zenith angle dependence is not strongly affected by the time of the year. Higher effective cloud fraction yields more ice- and water-phase, and less unknown-phase retrievals. Also, higher effective cloud fractions lead to greater values of ice cloud optical thickness. In addition, especially in high latitudes, ice-phase frequency is greater for two-layer clouds than single-layer clouds. On the other hand, water- and unknown-phase frequencies are greater for single layer clouds. Also, higher viewing zenith angles slightly decrease upper cloud top temperature. Approximately 90% of ice-phase cases have upper cloud top temperature values between 210 K and 235 K, ~80% of water-phase cases are found at 243-273 K upper cloud top temperature interval, and ~80% of the unknown cases have upper cloud top temperature values between 230 and 264 K. For ice cloud optical thickness and ice cloud effective diameter, no strong effects of satellite viewing zenith angle or cloud layering are observed. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/155521
Author: Christopher Rogers Yost
Author: Christopher Rogers Yost
Author: Kevin James Garrett
Author: Kuo-Nan Liou
Author: Yong-Keun Lee
Author: Bruce Anthony Wielicki
Author: Seiji Kato
Author: 
Author: Kerry Glynne Meyer
Author: Yangang Liu
Author: Volkan Huseyin Firat