A dataset of ground, airborne and satellite data was measured during the comprehensive 2004 EAQUATE (European AQUA Thermodynamic Experiment) Italian campaign. We have used ground based and airborne data to evaluate the consistency of Raman lidar temperature and humidity profiles with NAST-I (The National Polar-orbiting Operational Environmental Satellite System Airborne Sounder Testbed-Interferometer) spectral radiance measurements in clear conditions, and the consistency of total cloud optical depth measured by the Raman lidar with the same quantity retrieved from NAST-I measurements. Lidar measurement of temperature and humidity profiles can resolve short time changes in mixing ratio due to its high time resolution. Brightness temperature simulations of clear sky, performed using lidar-derived profiles, are within 1 K difference with respect to data when averages over 25 cm−1 and emission from layers below 7 km are considered. High spectral resolution simulations agree with NAST-I measurements with a mean percentage difference less than 0.5% in the whole ν2 water vapour band. The simulations in cloudy conditions are based on crystal properties obtained assuming either an appropriate mixture of crystal habits (that for the first time is tested against high spectral resolution measurements) or pristine solid columns. Lidar-derived cloud base and top altitudes and lidar temperature and humidity profiles are exploited, for the first time, as inputs in a recently developed infrared cloud properties retrieval procedure. Total cloud optical depths, retrieved from 800 to 980 cm−1 NAST-I radiances, have values that, when converted to short-wave wavelengths, are in the range 0.05–2.2 and agree with lidar measurements to within experimental errors. A closer agreement is obtained with the mixture of habits. Simulated high resolution brightness temperatures based on retrieved cloud parameters (optical depths and effective dimensions) are compared with measured values in all the atmospheric windows covered by the NAST-I sensor. The agreement obtained in the 800–980 cm−1 interval is generally better for the mixture of habits, but solid columns produce smaller residuals in the 2000–2150 and 2400–2600 cm−1 spectral intervals. Uncertainties related to the surface properties (i.e. skin temperature) are recognized to be the main sources of error in the infrared retrieval of cloud properties and affect the comparison between forward simulations and NAST-I data in all the infrared window bands not used for the inverse problem.
Maestri T., Di Girolamo P., Summa D., Rizzi R. (2010). Clear and cloudy sky investigations using Raman lidar and airborne interferometric measures from the European AQUA Thermodynamic Experiment. ATMOSPHERIC RESEARCH, 97, 157-169 [10.1016/j.atmosres.2010.03.020].
Clear and cloudy sky investigations using Raman lidar and airborne interferometric measures from the European AQUA Thermodynamic Experiment
MAESTRI, TIZIANO;RIZZI, ROLANDO
2010
Abstract
A dataset of ground, airborne and satellite data was measured during the comprehensive 2004 EAQUATE (European AQUA Thermodynamic Experiment) Italian campaign. We have used ground based and airborne data to evaluate the consistency of Raman lidar temperature and humidity profiles with NAST-I (The National Polar-orbiting Operational Environmental Satellite System Airborne Sounder Testbed-Interferometer) spectral radiance measurements in clear conditions, and the consistency of total cloud optical depth measured by the Raman lidar with the same quantity retrieved from NAST-I measurements. Lidar measurement of temperature and humidity profiles can resolve short time changes in mixing ratio due to its high time resolution. Brightness temperature simulations of clear sky, performed using lidar-derived profiles, are within 1 K difference with respect to data when averages over 25 cm−1 and emission from layers below 7 km are considered. High spectral resolution simulations agree with NAST-I measurements with a mean percentage difference less than 0.5% in the whole ν2 water vapour band. The simulations in cloudy conditions are based on crystal properties obtained assuming either an appropriate mixture of crystal habits (that for the first time is tested against high spectral resolution measurements) or pristine solid columns. Lidar-derived cloud base and top altitudes and lidar temperature and humidity profiles are exploited, for the first time, as inputs in a recently developed infrared cloud properties retrieval procedure. Total cloud optical depths, retrieved from 800 to 980 cm−1 NAST-I radiances, have values that, when converted to short-wave wavelengths, are in the range 0.05–2.2 and agree with lidar measurements to within experimental errors. A closer agreement is obtained with the mixture of habits. Simulated high resolution brightness temperatures based on retrieved cloud parameters (optical depths and effective dimensions) are compared with measured values in all the atmospheric windows covered by the NAST-I sensor. The agreement obtained in the 800–980 cm−1 interval is generally better for the mixture of habits, but solid columns produce smaller residuals in the 2000–2150 and 2400–2600 cm−1 spectral intervals. Uncertainties related to the surface properties (i.e. skin temperature) are recognized to be the main sources of error in the infrared retrieval of cloud properties and affect the comparison between forward simulations and NAST-I data in all the infrared window bands not used for the inverse problem.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
