[1] The CALIOP depolarization measurements, combined with backscatter intensity measurements, are effective in discriminating between water clouds and ice clouds. The same depolarization measurements can also be used for estimating liquid water content information. Using cloud temperature information from the collocated infrared imaging radiometer measurements and cloud water paths from collocated MODIS measurements, this study compiles global statistics of the occurrence frequency, liquid water content, liquid water path, and their temperature dependence. For clouds with temperatures between −40°C and 0°C, the liquid phase fractions and liquid water paths are significantly higher than the ones from previous studies using passive remote sensing measurements. At midlatitudes, the occurrence of liquid phase clouds at temperatures between −40°C and 0°C depends jointly on both cloud height and cloud temperature. At high latitudes, more than 95% of low-level clouds with temperatures between −40°C and 0°C are water clouds. Supercooled water clouds are mostly observed over ocean near the storm-track regions and high-latitude regions. Supercooled water clouds over land are observed in the Northern Hemisphere over Europe, East Asia, and North America, and these are the supercooled water clouds with highest liquid water contents. The liquid water content of all supercooled water clouds is characterized by a Gamma (G) distribution. The mode values of liquid water content are around 0.06 g/m 3 and are independent of cloud temperature. For temperatures warmer than −15°C, mean value of the liquid water content is around 0.14 g/m 3 . As the temperature decreases, the mean cloud liquid water content also decreases. These results will benefit cloud models and cloud parameterizations used in climate models in improving their ice-phase microphysics parameterizations and the aviation hazard forecast.Citation: Hu, Y., S. Rodier, K. Xu, W. Sun, J. Huang, B. Lin, P. Zhai, and D. Josset (2010), Occurrence, liquid water content, and fraction of supercooled water clouds from combined CALIOP/IIR/MODIS measurements,

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Abstract.In this paper, we analyze the performance of the Infrared Atmospheric Sounding Interferometer (IASI), launched in October 2006 on board METOP-A, for the monitoring of carbon monoxide (CO) during extreme fire events, focusing on the record-breaking fires which devastated thousands of square kilometers of forest in Greece during the last week (23-30) of August 2007. After an assessment of the quality of the profiles retrieved using the Fast Optimal Retrievals on Layers for IASI (FORLI) algorithm, the information provided on fire emissions and subsequent pollution outflow is discussed. Large CO plumes were observed above the Mediterranean Basin and North Africa, with total CO columns exceeding 24×10 18 molecules/cm 2 and absolute volume mixing ratios up to 4 ppmv on the 25 August. Up to 30×10 18 molecules/cm 2 and 22 ppmv in the lower troposphere are retrieved close to the fires above the Peloponnese, but with larger uncertainty. The average root-mean-square (RMS) difference between simulated and observed spectra is close to the estimated radiometric noise level, slightly increasing (by ∼14%) in the fresh fire plumes. CO profiles are retrieved with a vertical resolution of about 8 km, with ∼1.7 pieces of independent information on the vertical in the region considered and a maximum sensitivity in the free troposphere (∼4-5 km). Using the integrated total amount, the increase in CO burden due to these fires is estimated to 0.321 Tg, ∼40% of the total annual anthropogenic emissions in Greece. The patterns of these CO enhanceCorrespondence to: S. Turquety (solene.turquety@lmd.polytechnique.fr) ments are in good agreement with the aerosol optical depth (AOD) retrieved from the MODIS measurements, highlighting a rapid transport of trace gases and aerosols across the Mediterranean Basin (less than one day). While the coarse vertical resolution will not allow the location of the exact plume height, the large CO enhancements observed in the lower troposphere are consistent with the maximum aerosol backscatter coefficient at ∼2 km detected by the CALIPSO lidar in space (CALIOP).