Comparison of CloudSat cloud liquid water paths in arctic summer using ground-based microwave radiometer
Arctic clouds strongly influence the regional radiation balance, temperature, melting of sea ice, and freezing of sea water. Despite their importance, there is a lack of systematic and reliable observations of Arctic clouds. The CloudSat satellite launched in 2006 with a 94 GHz Cloud Profiling Radar (CPR) may contribute to close this gap. Here we compare one of the key parameters, the cloud liquid water path (LWP) retrieved from CloudSat observations and from microwave radiometer (MWR) data taken during the ASCOS (Arctic Summer Cloud Ocean Study) cruise of the research vessel Oden from August to September 2008. Over the 45 days of the ASCOS cruise, collocations closer than 3 h and 100 km were found in only 9 d, and collocations closer than 1 h and 30 km in only 2 d. The poor correlations in the scatter plots of the two LWP retrievals can be explained by the patchiness of the cloud cover in these two days (August 5th and September 7th), as confirmed by coincident MODIS (Moderate-resolution Imaging Spectroradiometer) images. The averages of Oden-observed LWP values are systematically higher (40–70 g m−2) than the corresponding CloudSat observations (0–50 g m−2). These are cases of generally low LWP with presumably small droplets, and may be explained by the little sensitivity of the CPR to small droplets or by the surface clutter.
Key wordsCloudSat liquid water path Arctic microwave radiometer collocation Oden
Unable to display preview. Download preview PDF.
- Curry, J. A., Hobbs, P. V., King, M. D., Randall, D. A., Minnis, P., Isaac, G. A., et al., 2000. FIRE Arctic clouds experiments. Bull. Amer. Meteorol. Soc., 81(1): 29pp.Google Scholar
- Greenwald, T. J., L’Ecuyer, T. S., and Christopher, S. A., 2007. Evaluating specific error characteristics of microwave-derived cloud liquid water products. Geophys. Res. Lett., 34, doi: 10.1029/2007GL031180.Google Scholar
- Grenier, P., Blanchet, J. P., and Muñoz-Alpizar, R., 2009. Study of polar thin ice clouds and aerosols seen by CloudSat and CALIPSO during midwinter 2007. J. Geophys. Res., 114, doi:10.1029/2008JD010927.Google Scholar
- Li, L., Durden, S., and Tanelli, S., 2007. Level 1B CPR Process Description and Interface Control Document. Pasadena, California, version 5.3, 27 June 2007, 24pp.Google Scholar
- Miller, S. D., and Stephens, G. L., 2001. CloudSat instrument requirements as determined from ECMWF forecasts of global cloudiness, J. Geophys. Res., 106: 17 713–17 733. doi: 10.1029/2000JD900645.Google Scholar
- Rees, G., 2001. Physical Principles of Remote Sensing. Cambridge University Press, Cambridge, 360pp.Google Scholar
- Spreen, G., Kaleschke, L., and Heygster, G., 2008. Sea ice remote sensing using AMSR-E 89GHz channels. J. Geophys. Res., 113, doi: 10.1029/2005JC003384.Google Scholar
- Vicente, G. A., Smith, P., Kempler, Tewari, S., K., Kummerer, R., and Leptoukh, G. G., 2006. CloudSat and MODIS data merging: the first step toward the implementation of the NASA A-Train Data Depot. The 14th Conference on Satellite Meteorology and Oceanography at the 86th AMS Annual Meeting, January 28–February 3, Atlanta, GA, USA.Google Scholar
- Wood, N., 2008. Level 2B Radar-Visible Optical Depth Cloud Water Content (2B-CWC-RVOD) Process Description Document. Version: 5.1, 23 October 2008.Google Scholar