Cirrus Microphysical Properties from Stellar Aureole Measurements, Phase I

DeVore, J. G. ; Kristl, J. A. ; Rappaport, S. A.

关键词: Aerosols;    Cirrus Ice Crystal Size Distributions;    Climate Change;    Stellar Aureole Measurement;    Solar Aureole Measurement;   

DOI  :  10.2172/1038676
RP-ID  :  DOE/SC0006325-1
PID  :  OSTI ID: 1038676

学科分类：环境科学（综合）

美国|英语

来源: SciTech Connect

【 摘 要 】

While knowledge of the impact of aerosols on climate change has improved significantly due to the routine, ground-based, sun photometer measurements of aerosols made at AERONET sites world-wide, the impact of cirrus clouds remains much less certain because they occur high in the atmosphere and are more difficult to measure. This report documents work performed on a Phase I SBIR project to retrieve microphysical properties of cirrus ice crystals from stellar aureole imagery. The Phase I work demonstrates that (1) we have clearly measured stellar aureole profiles; (2) we can follow the aureole profiles out to ~1/4 degree from stars (~1/2 degree from Jupiter); (3) the stellar aureoles from cirrus have very distinctive profiles, being flat out to a critical angle, followed by a steep power-law decline with a slope of ~-3; (4) the profiles are well modeled using exponential size distributions; and (5) the critical angle in the profiles is ~0.12 degrees, (6) indicating that the corresponding critical size ranges from ~150 to ~200 microns. The stage has been set for a Phase II project (1) to proceed to validating the use of stellar aureole measurements for retrieving cirrus particle size distributions using comparisons with optical property retrievals from other, ground-based instruments and (2) to develop an instrument for the routine, automatic measurement of thin cirrus microphysical properties.