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Cloud top pressure/altezza

Cloud top pressure/altezza. Temperatura Necessita il profilo, giorno/notte, emissivita’ Temperatura corretta Necessita il profilo, stima optical thickness, relazione optical thickness emissivita’ A partire dal tipo (soggettiva e storica)

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Cloud top pressure/altezza

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  1. Cloud top pressure/altezza Temperatura Necessita il profilo, giorno/notte, emissivita’ Temperatura corretta Necessita il profilo, stima optical thickness, relazione optical thickness emissivita’ A partire dal tipo (soggettiva e storica) Ombra (illuminazione, cloud detection, shadow detection, calcolo). Solo di giorno, sole allo zenith, solo bordi, no calibrazione, si risoluzione spaziale (OK per VIS), complessita’ nel riconoscimento di forme, solo su superfici riflettenti, nubi fine e senza contorni definiti (cirri) Stereoscopia. >1 osservazione contemporanee (vento) (geostazionari: perfettamente in fase, multiviewing: (A)ATSR (2), MISR (9), POLDER (14)), geometria (no calibrazione), cloud detection, navigazione, cloud recognition (difficile, limitato ai bordi), risoluzione spaziale, nubi fini e senza contorni Limb sounding + vede nubi fine, no calibrazione, problemi a scendere (<7 km), possibilie ambiguità con aerosols, numero di misure per orbita, risoluzione spaziale (cirri sono estesi) CO2 slicing MLEV (minimum local emissivity radiance) WV intercept method Molecolar scattering (Raman scattering) A-band assorbimento. Photon path length, solo giorno Lidar Cloud radar

  2. OMBRA http://www-research.ge.ucl.ac.uk/cloudmap/reports/firstreport.pdf

  3. Stereoscopia

  4. Stereoscopia

  5. Hasler, BAMS 1981

  6. Hasler, BAMS 1981

  7. Hasler, BAMS 1981

  8. IR-WV Curva precalcolata Misura clear sky Misura broken cloudy Stima Tb fully cloudy

  9. MLEV

  10. CO2Slicing • Input • Temperature and Water Vapor profiles (representative of the FOV under consideration) • Observations for, at least, two channels in the CO2 absorption band

  11. CO2Slicing: Theory Solving Equation: Iob(n1)-Iclear(n1) Icloud(n1,pc)-Iclear(n1) = Iob(n2)-Iclear(n2) Icloud(n2,pc)-Iclear(n2) The solution is given by the value of pc that minimizes the difference between the right and left side

  12. Pair Selection Broad Band Spectrometer: Interferometer:

  13. Example spectra

  14. CO2Slicing: weighting function space MODIS CO2 channels Interferometer CO2 channels

  15. IR Retrieval Scheme for Clouds Temperature and water vapor retrievals in clear sky FOVs Calibrated data Cloud mask Determination of cloud altitude, thickness and temperature Determination of cloud emissivity Retrieval of microphysical properties (optical thickness, ice water path, particle size and shape) Validation of Products

  16. Cloud Emissivity

  17. Minimum Local Emissivity Variance (MLEV) Observations between 750 and 900 cm-1

  18. Retrieved cloud at 9.5 km, lidar indicates single layer cloud between 7.5 and 9.8 km.

  19. lidar

  20. The fact that the depth of solar Fraunhofer lines in scattered light is less than those observed in direct sunlight, was discovered by Shefov [1959] [17] and Grainger and Ring [1962] [6] and is known as the ”Ring Effect” or ”Filling-in”. Several publications analysed this effect and its origins, showing that rotational Raman scattering provides the dominant contribution to the Ring Effect [1, 10, 4, 5, 8, 3, 18]. The majority of these studies however concentrated on cloud-free conditions.

  21. Cloud radar

  22. INIZIO VECCHIE: VERIFICARE

  23. Cloud top properties(P. Menzel, R. Frey, K. Strabala, L. Gumley, et al. – NOAA NESDIS, U. Wisc./CIMSS) • Cloud top pressure, temperature, effective emissivity • Retrieved for every 5x5 box of 1 km FOV’s, when at least 5 FOV’s are cloudy, day & night • CO2 Slicing technique (5 bands, 12.0-14.2 µm) – retrieve pc; Tc from temperature profile – ratio of cloud forcing in 2 nearby bands – most accurate for high and mid-level clouds • Previously applied to HIRS (NOAA POES, 20 km), GOES sounder (~ 30 km) • Accuracy of technique ~ 50 mb MODIS 1st satellite sensor capable of CO2 slicing at high spatial resolution S. Platnick, ISSAOS ‘02

  24. CO2 slicing: theory Solving Equation: Iob(n1)-Iclear(n1) Icloud(n1,pc)-Iclear(n1) = Iob(n2)-Iclear(n2) Icloud(n2,pc)-Iclear(n2) solution given by the value of pc that minimizes the difference between the right and left side

  25. MODIS CO2 band weighting functions Example spectra (~ 12.65-14 µm) CO2slicing: weighting functions Bands w/greater CO2 absorption have weighting functions more sensitive to high clouds S. Platnick, ISSAOS ‘02

  26. BT in and out of clouds for MODIS CO2 bands - demonstrate weighting functions and cloud top algorithm S. Platnick, ISSAOS ‘02

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