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Abstract:
While a convective cloud grows and matures, its cloud top temperature decreases from above or close to 0°C to below homogeneous freezing conditions. This means that the entire mixed-phase temperature range is scanned in a relative short time span. In this study, we investigate in how far the concentration of ice nucleating particles (INP) leaves a measurable impact onto the liquid/ice distribution at the cloud top. Experiments are conducted using the ICOsahedral Nonhydrostatic model (ICON) at the convection-permitting resolution of about 1.2 km on a domain covering significant parts of central Europe, and are compared to two different retrieval products based on SEVIRI measurements. We select a day with several isolated deep convective clouds. The simulated cloud liquid pixel number fractions are found to decrease with increasing INP concentration both within clouds and at the cloud top. Cloud-top glaciation temperatures shift toward warmer temperatures with increasing INP concentration by as much as 8 °C. Moreover, the impact of INP concentration on cloud phase partitioning is more pronounced at the cloud top than within the cloud. Perturbing convective available potential energy (CAPE) is also found to affect the cloud phase distribution systematically. However, the simulated cloud-top liquid number fraction, diagnosed using radiative transfer simulations as input to a satellite forward operator and two different satellite remote sensing retrieval algorithms, deviates from one of the satellite products regardless of the examined parameter perturbations, while agreeing with the other retrieval scheme much better, in particular for the high INP and high CAPE scenarios.
