Institut für Umweltphysik Universität Heidelberg High resolution spectroscopy of the Oxygen A-band in zenith-scattered light; Implications for cloudy sky photon path length T.Scholl, U.Nägele, U.Platt, and K.Pfeilsticker Institut für Umweltphysik, Universität Heidelberg, INF 229, D Heidelberg Overview: -Instrumentation -Method -Evaluation Example -Summary / Outlook

Institut für Umweltphysik Universität Heidelberg Setup / Geometry Ground v FOV = 1° RT Smoothing H H H: vertical cloud extension Short integration time required: Previous measurements: 900 sec BBC measurements: ~ 2 sec

Institut für Umweltphysik Universität Heidelberg Spectrograph CCD Detector Sopra UHRS 1500 Fastie-Ebert F = 1500 mm 110 x 220 mm 2, 316 g/mm Echelle f/13.5 Temp. const. +/- 1K ca. 500 kg pm (5ch, 1.93pm/ch) Spectral Range:ca. 4 nm 2048x512 pixel 27.6 x 6.9 mm 2 (13.5  m) QE ca. 770nm R/O noise 2e - /pixel FI, Marconi (EEV) TE cooling –90°C

Institut für Umweltphysik Universität Heidelberg Setup / Geometry Ground v FOV = 1° RT Smoothing H H H: vertical cloud extension Short integration time required: Previous measurements: 900 sec BBC measurements: ~ 2 sec

Institut für Umweltphysik Universität Heidelberg Radiative Smoothing Scales Savigny et al., 2002 Scale parameter r Time (UTC) Radiometer HDRAD (760nm)

Institut für Umweltphysik Universität Heidelberg Lévy Indices α: Lévy (transport) index; α = 1 direct transmission, 1< α < 2 anomalous diffusion, α = 2 classical diffusion  Observables are: (oxygen A band spectroscopy), H radar/Lidar, Inferred quantities: τ and α  ergo transport index α (describing a mean) can be inferred !

Institut für Umweltphysik Universität Heidelberg Inferred Lévy Indices (Pfeilsticker, JGR, 1999)

Institut für Umweltphysik Universität Heidelberg Measurement Sept.17, :30:32 UTC  =14 pm, integration time = 1.5 sec - Data available from Sept.6 – 25, ~ spectra were measured (~9GB) - Integration time ranging from sec (variable light intensity)

Institut für Umweltphysik Universität Heidelberg Data Analysis High Spectral Resolution Searched quantity p(l) ? Spectrum Measurement with given spectral resolution Measured Spectrum Nonlinear Least Square Fit (10min, 1GHz) Modeled Spectrum Spectroscopic Model Temp., Pressure Profile x T(p(a j ),  i ( ) Solar Fraunhofer p(l) Model Oxygen Absorption Spectrum Lines (VOD) Low Spectral Resolution Best estimate p(l) Convolution with instrument function

Institut für Umweltphysik Universität Heidelberg Evaluation Example Model Residual

Institut für Umweltphysik Universität Heidelberg Sensitivity Test

Institut für Umweltphysik Universität Heidelberg Summary Spectral retrieval software works, but needs some improvements (wavelength dependent convolution) Better time resolution (15 min few seconds) and better spectroscopical resolution ( 20pm 9.5 pm) Better understanding and sensitivity test for retrieval method necessary Determination of,,... Combination with , LWC, H, Outlook