Cloud geometry from oxygen-A-band observations through an aircraft side window

Autor(es)

Zinner, Tobias ^[1] ; Schwarz, Ulrich ^[1] ; Koelling, Tobias ^[1] ; Ewald, Florian ^{[1, 2]} ; Jaekel, Evelyn ^[3] ; Mayer, Bernhard ^[1] ; Wendisch, Manfred ^[3]

Afiliação do(s) autor(es)

^[1] Ludwig Maximilians Univ Munchen, Meteorol Inst, Munich - Germany

^[2] Deutsch Zentrum Luft & Raumfahrt, Inst Phys Atmosphare, Oberpfaffenhofen - Germany

^[3] Univ Leipzig, Leipziger Inst Meteorol, Leipzig - Germany

• Tipo de documento: Artigo Científico
• Fonte: Atmospheric Measurement Techniques; v. 12, n. 2, p. 1167-1181, FEB 25 2019.
• Citações Web of Science: 2

Resumo

During the ACRIDICON-CHUVA (Aerosol, Cloud, Precipitation, and Radiation Interactions and Dynamics of Convective Cloud Systems-Cloud Processes of the Main Precipitation Systems in Brazil: A Contribution to Cloud Resolving Modeling and to the GPM (Global Precipitation Measurement)) aircraft campaign in September 2014 over the Amazon, among other topics, aerosol effects on the development of cloud microphysical profiles during the burning season were studied. Hyperspectral remote sensing with the imaging spectrometer specMACS provided cloud microphysical information for sun-illuminated cloud sides. In order to derive profiles of phase or effective radius from cloud side observations, vertical location information is indispensable. For this purpose, spectral measurements of cloud-side-reflected radiation in the oxygen A absorption band collected by specMACS were used to determine absorption path length between cloud sides and the instrument aboard the aircraft. From these data, horizontal distance and eventually vertical height were derived. It is shown that, depending on aircraft altitude and sensor viewing direction, an unambiguous relationship of absorption and distance exists and can be used to retrieve cloud geometrical parameters. A comparison to distance and height information from stereo image analysis (using data of an independent camera) demonstrates the efficiency of the approach. Uncertainty estimates due to method, instrument and environmental factors are provided. The main sources of uncertainty are unknown in cloud absorption path contributions due to complex 3-D geometry or unknown microphysical properties, variable surface albedo and aerosol distribution. A systematic difference of 3.8 km between the stereo and spectral method is found which can be attributed to 3-D geometry effects not considered in the method's simplified cloud model. If this offset is considered, typical differences found are 1.6 km for distance and 230 m for vertical position at a typical distance around 20 km between sensor and convective cloud elements of typically 1-10 km horizontal and vertical extent. (AU)

• Processo FAPESP: 13/05014-0 - GoAmazon: interação da pluma urbana de Manaus com emissões biogênicas da Floresta Amazônica
• Beneficiário: Paulo Eduardo Artaxo Netto
• Modalidade de apoio: Auxílio à Pesquisa - Programa de Pesquisa sobre Mudanças Climáticas Globais - Temático
• Processo FAPESP: 09/15235-8 - Processos de nuvens associados aos principais sistemas precipitantes no Brasil: uma contribuição à modelagem da escala de nuvens e ao GPM (Medida Global de Precipitação)
• Beneficiário: Luiz Augusto Toledo Machado
• Modalidade de apoio: Auxílio à Pesquisa - Temático