|Title||Using CALIOP to estimate cloud-field base height and its uncertainty: the Cloud Base Altitude Spatial Extrapolator (CBASE) algorithm and dataset|
|Publication Type||Journal Article|
|Year of Publication||2018|
|Authors||Mulmenstadt J, Sourdeval O., Henderson D.S, L'Ecuyer T.S, Unglaub C., Jungandreas L., Bohm C., Russell LM, Quaas J.|
|Journal||Earth System Science Data|
|Type of Article||Article|
|Keywords||assimilation; Geology; Meteorology & Atmospheric Sciences; misr; modis; orbit performance; products; radar; retrieval; surface|
A technique is presented that uses attenuated backscatter profiles from the CALIOP satellite lidar to estimate cloud base heights of lower-troposphere liquid clouds (cloud base height below approximately 3 km). Even when clouds are thick enough to attenuate the lidar beam (optical thickness tau greater than or similar to 5), the technique provides cloud base heights by treating the cloud base height of nearby thinner clouds as representative of the surrounding cloud field. Using ground-based ceilometer data, uncertainty estimates for the cloud base height product at retrieval resolution are derived as a function of various properties of the CALIOP lidar profiles. Evaluation of the predicted cloud base heights and their predicted uncertainty using a second statistically independent ceilometer dataset shows that cloud base heights and uncertainties are biased by less than 10 %. Geographic distributions of cloud base height and its uncertainty are presented. In some regions, the uncertainty is found to be substantially smaller than the 480 m uncertainty assumed in the A-Train surface downwelling longwave estimate, potentially permitting the most uncertain of the radiative fluxes in the climate system to be better constrained.