Premium
Oceanic single‐layer warm clouds missed by the Cloud Profiling Radar as inferred from MODIS and CALIOP measurements
Author(s) -
Liu Dongyang,
Liu Qi,
Qi Lin,
Fu Yunfei
Publication year - 2016
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2016jd025485
Subject(s) - cloud top , environmental science , lidar , cloud computing , moderate resolution imaging spectroradiometer , cloud fraction , effective radius , cloud height , atmospheric sciences , aerosol , lapse rate , meteorology , radar , cloud cover , remote sensing , geology , geography , satellite , computer science , physics , quantum mechanics , astronomy , galaxy , telecommunications , operating system
Attributed to its unique advantage of cloud vertical resolving, Cloud Profiling Radar (CPR) measurements have been used as the primary component in synthetic cloud data for relevant studies. However, due to surface clutter and sensitivity limitation, considerable warm clouds over global oceans are missed by CPR, which causes severe sampling biases and problematic statistics of cloud properties. By using independent cloud mask data jointly from Moderate Resolution Imaging Spectroradiometer and Cloud‐Aerosol Lidar with Orthogonal Polarization measurements, this study gives an evaluation on these issues and focuses on single‐layer clouds. By excluding effects from CPR's spatial resolution, the CPR detection failures are found to be frequent over global oceans, with an overall miss rate at ~0.39. For each cloud type, altocumulus, stratus, stratocumulus, and cumulus, its miss rate decreases monotonically with height, and it is only at 2.5–3.0 km altitude that the miss rate is negligible for the ensemble of oceanic single‐layer warm clouds. The miss rates are different among cloud types, which are attributed to their distinct microphysical properties. Clouds with droplet effective radius below 12 µm or cloud optical depth below 4 are very likely to be missed by CPR, resulting the globally averaged overestimation of 10–24% and 24–36%, respectively. The miss rate has a strong negative correlation with cloud water path (CWP) and decreases below 0.1 only for CWP exceeding 200 g m −2 . The resulting overestimation on globally averaged CWP is 36.6 g m −2 (44.3%). Throughout the globe, the biases are mostly positive and have notable regional variations. Especially in the typical oceans that have abundant warm clouds, the CWP is overestimated by 20%–80%.