HR: 1340h
AN: A13C-1373    [Abstracts]
TI: In Situ and Remote Measurements of Ice Particles in TC4
AU: * Lawson, P
EM: plawson@specinc.com
AF: SPEC Incorporated, 3022 Sterling Circle, Boulder, CO 80301, United States
AU: Baker, B
EM: brad@specinc.com
AF: SPEC Incorporated, 3022 Sterling Circle, Boulder, CO 80301, United States
AU: Jensen, E
EM: eric.j.jensen@nasa.gov
AF: NASA Ames Research Center, Moffett Field, Moffett Field, CA 94035, United States
AU: Pilson, B
AF: SPEC Incorporated, 3022 Sterling Circle, Boulder, CO 80301, United States
AU: Mo, Q
EM: mo@specinc.com
AF: SPEC Incorporated, 3022 Sterling Circle, Boulder, CO 80301, United States
AU: Mitchell, D
EM: david.mitchell@dri.edu
AF: Desert Research Institute, Atmospheric Sciences, Reno, NV 89506, United States
AU: d'Entremont, R
EM: rdentrem@aer.com
AF: Atmospheric Environmental Research, 131 Hartwell Avenue, Lexington, MA 02421, United States
AB: In situ microphysical measurements using cloud particle imager (CPI) and 2D-S probes were collected on both the NASA DC-8 and WB-57F during the recent TC4 field campaign. Additional data were collected using a CAPS cloud particle probe and other devices that measured cloud particle mass, including a CVI. When appropriate, these measurements are combined or compared in maritime and continental cirrus as a result of outflows from tropical convection near Costa Rica. The results, in terms of particle size distribution, extinction coefficient, optical depth, ice water content, ice water path and particle habit are compared with similar measurements in outflows from continental convection and synoptic cirrus observed over various regions in the United States. Particle shapes observed in the (cirrus) outflows from convection are distinctly different than cirrus formed in situ, whether it is formed at mid-latitudes or in the tropics. Cirrus formed in situ is characterized by ice particles with rosette shapes, whereas the outflow from convection contains mostly irregular shapes, plates and columns. However, once the outflow has aged for several hours, if it encounters regions with high ambient relative humidity (e.g., > 120% with respect to ice), then rosette ice shapes may be generated. Ice particles generated over the ocean do not appear to form "chains" of small ice crystals, such has been observed in strong convection with high electric fields over land. From radiation and modeling perspectives, it appears that particle shapes in synoptic cirrus and convective outflows can be predicted to first order if the life history of the particles is known; i.e., where the ice particles were formed and the history of their exposure to temperature and relative humidity. The issue of small ice crystals is considered in conjunction with a new remote sensing technique for determining the contribution of small ice in cirrus clouds. The principle of photon tunneling in anomalous diffraction theory is applied to the brightness temperature difference (BTD) between 10.8 and 12 microns. Since anomalous diffraction theory predicts an abrupt change in absorption efficiency factor between 10.8 and 12 microns when small ice particles are present, this signal can be used to remotely assess the contribution of small ice. Comparisons between in situ measurements and new 10.8 – 12 micron BTD remote sensing retrieval technique are presented and discussed.
UR: http://www.specinc.com
DE: 0319 Cloud optics
DE: 0320 Cloud physics and chemistry
DE: 0335 Ion chemistry of the atmosphere (2419, 2427)
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting