Search Results
You are looking at 1 - 2 of 2 items for :
- Author or Editor: Robert A. Mack x
- Journal of Atmospheric and Oceanic Technology x
- Refine by Access: All Content x
Abstract
Aircraft passive microwave observations of deep atmospheric convection at frequencies between 18 and 183 GHz are presented in conjunction with visible and infrared satellite and aircraft observations and ground-based radar observations. Deep convective cores are indicated in the microwave data by negative brightness temperature (TB ) deviations from the land background (270 K) to extreme TB values below 100 K at 37, 92, and 183 GHz and below 200 K at 18 GHz. These TB minima, due to scattering by ice held aloft by the intense updrafts, are well correlated with areas of high radar reflectivity. For this land background case, TB is inversely correlated with rain rate at all frequencies due to TB -ice-rain correlations. Mean ΔT between vertically polarized and horizontally polarized radiance in precipitation areas is approximately 6 K at both 18 GHz and 37 GHz, indicating nonspherical precipitation size ice particles with a preferred horizontal orientation. Convective cores not observed in the visible and infrared data are clearly defined in the microwave observations and borders of convective rain areas are well defined using the high-frequency (90 GHz and greater) microwave observations.
Abstract
Aircraft passive microwave observations of deep atmospheric convection at frequencies between 18 and 183 GHz are presented in conjunction with visible and infrared satellite and aircraft observations and ground-based radar observations. Deep convective cores are indicated in the microwave data by negative brightness temperature (TB ) deviations from the land background (270 K) to extreme TB values below 100 K at 37, 92, and 183 GHz and below 200 K at 18 GHz. These TB minima, due to scattering by ice held aloft by the intense updrafts, are well correlated with areas of high radar reflectivity. For this land background case, TB is inversely correlated with rain rate at all frequencies due to TB -ice-rain correlations. Mean ΔT between vertically polarized and horizontally polarized radiance in precipitation areas is approximately 6 K at both 18 GHz and 37 GHz, indicating nonspherical precipitation size ice particles with a preferred horizontal orientation. Convective cores not observed in the visible and infrared data are clearly defined in the microwave observations and borders of convective rain areas are well defined using the high-frequency (90 GHz and greater) microwave observations.
Abstract
In Part II of the 29 June 1986 case study, a radiative transfer model is used to simulate the aircraft multichannel microwave brightness temperatures presented in Part I and to study the convective storm structure. Ground-based radar data are used to derive hydrometeor profiles of the storm, based on which the microwave upwelling brightness temperatures are calculated. Various vertical hydrometeor phase profiles and the Marshall and Palmer (M-P) and Sekhon and Srivastava (S-S) ice particle size distributions are experimented in the model. The results are compared with the aircraft radiometric data. The comparison reveals that 1) the M-P distribution well represents the ice particle size distribution, especially in the upper tropospheric portion of the cloud; 2) the S-S distribution appears to better simulate the ice particle size at the lower portion of the cloud, which has a greater effect on the low frequency microwave upwelling brightness temperatures; and 3) in deep convective regions, significant supercooled liquid water (∼0.5 g m−3) may be present up to the −30°C layer, while in less convective areas, frozen hydrometeors are predominant above −10°C level.
Abstract
In Part II of the 29 June 1986 case study, a radiative transfer model is used to simulate the aircraft multichannel microwave brightness temperatures presented in Part I and to study the convective storm structure. Ground-based radar data are used to derive hydrometeor profiles of the storm, based on which the microwave upwelling brightness temperatures are calculated. Various vertical hydrometeor phase profiles and the Marshall and Palmer (M-P) and Sekhon and Srivastava (S-S) ice particle size distributions are experimented in the model. The results are compared with the aircraft radiometric data. The comparison reveals that 1) the M-P distribution well represents the ice particle size distribution, especially in the upper tropospheric portion of the cloud; 2) the S-S distribution appears to better simulate the ice particle size at the lower portion of the cloud, which has a greater effect on the low frequency microwave upwelling brightness temperatures; and 3) in deep convective regions, significant supercooled liquid water (∼0.5 g m−3) may be present up to the −30°C layer, while in less convective areas, frozen hydrometeors are predominant above −10°C level.
