Retrieval of Ice Water Content in Convective Outflow Anvil Clouds Using Raman Lidar and Cloud Radar

Description

Anvil clouds refer to the detrained cloud ice from deep convective systems and cover a much larger area than the convective core. These clouds appear in the upper troposphere and have significant radiative effects and changes in anvil clouds may be an important cloud feedback. However, there are large uncertainties in the representation of anvil clouds in current climate models due to complex dynamics and microphysical processes that must be parameterized. Accurate ice water content (IWC) observations are vital to model parameterization evaluations. Here we aim to combine radar reflectivity from the Ka-band ARM zenith radar (KAZR) cloud radar and extinction coefficients from the Raman lidar (RL) at the ARM Tropical Western Pacific (TWP) and Southern Great Plain (SGP) sites to retrieve IWC in convective outflow anvil clouds. We consider three different scenarios: clouds detected by both instruments, clouds observed only by the radar, and clouds observed only by the Raman lidar. For the first scenario, an algorithm that relates the IWC with both Radar reflectivity and extinction from RL is used. For the other two scenarios, regressions (based on retrievals from the regions where both radar and lidar observations are present) are used to estimate IWCs based on the radar reflectivity or extinction, along with temperature. The Raman lidar can directly retrieve extinction coefficients without any assumptions of the extinction-to-backscatter ratio (i.e., lidar ratio) that is needed when the micropulse lidar (MPL) is used. Thus, the retrieved IWCs are expected to be more accurate. Furthermore, observed ice crystal size distributions based on in situ aircraft observations are employed to revisit the relationship between IWC and radar reflectivity and extinction coefficients.