Comparison Of The Cloud Liquid Water Path In Arctic Using Satellite Date And Ground-based Microwave Radiometer Data

The cloud cover strongly influences the regional radiation balance and plays an important role on surface heat balance of sea ice in the Arctic Ocean. In contrast to their importance, there is a lack of systematic and reliable observations of Arctic cloud. The CloudSat satellite mission launched in 2006 with a 94 GHz Cloud Profiling Radar (CPR) has been aiming to close this gap. In this study, we investigate the cloud liquid water path (LWP), i.e. one of the key parameters retrieved from CloudSat. The ground-based microwave radiometer (MWR) data that have been taken during the ASCOS (Arctic Summer Cloud Ocean Study) cruise in August and September 2008 by Swedish Research/Vessel Oden are compared with the CloudSat data. During the total 45 days ASCOS cruise, (only on 9 days near than 3 h and 100 km collocations were found, and only 2 days with collocations nearer than 1 h and 30 km. The little correlations of the scatterplots of both LWP retrievals can be explained with the patchiness of the cloud cover of these two days (Aug.5th and Sep.7th), as confirmed by coincident MODIS (Moderate-resolution Imaging Spectroradiometer) images. The averages observation of LWP by Oden are systematically higher (40 gm-2-70 gm-2) than the corresponding CloudSat data (0 gm-2-50 gm-2). As these are cases of generally low LWP with presumably small droplets, this may be explained by the little sensitivity of the CPR to small droplets.We also compared and analyses the CloudSat observation and MWR data obtained at Alaska Barrow station (71°19'23.73"N,156°36'56.70"W). There are 135 days near then 2 h and 30 km collocations among the 300 days data. The LWP values of CloudSat are smaller than that in Barrow site in summer and winter 2008, 2009 and winter 2010. Derived LWP from MODIS data over open water in the comparison of Oden data shows good collocations. But not reasonable in the open water. Because it is not possible for the passive satellite to distinguish the high albedo of sea ice and clouds. Derived the cloud types from CloudSat, the LWP values are above 200 gm-2 in Cumulus. While LWP values are less than 100 gm-2 in Altocumulus.