Project Details
Projekt
Stereo Observations of Clouds for LES Validation and Sub-scale Cloud Parameterizations (SOCLES)
Subject Area
Atmospheric Science
Term
from 2019 to 2023
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 430226822
We propose to combine high-frequency cloud observations by multiple stereo cameras with Large-Eddy Simulation (LES) at a mid-latitude continental meteorological supersite to better understand and quantify fine-scale spatial and temporal structures of shallow cumulus cloud populations. These cloud fields are highly heterogeneous and quickly evolving on a broad range of scales, a behavior which has complicated the representation of their impact on the larger-scale flow and energy budget in numerical models used for weather prediction and climate projection. The project will fill the information gap related to fine-scale cloud structures, that has hampered progress in cumulus parameterization. This problem became more urgent with ongoing developments in supercomputing, which allow simulations for increasingly finer resolutions that start to invalidate the conceptual basis of existing cumulus parameterizations. We approach this problem by exploiting the synergy between LES and stereo camera measurements. The high-resolution sampling capability of stereo reconstruction in four dimensions and its considerable spatial coverage will allow us to capture cumulus populations in unprecedented detail, which cannot be achieved with vertically pointing instrumentation or satellite sensors. These will be used to validate LES simulations and in parallel to test and develop cumulus parameterizations. The fine-scale model simulations thus supplement the observational data but also allow for the testing of measurement strategies with the stereo camera system. The use of open boundaries, multiple nesting and detailed topography is hypothesized to improve the realism of the simulated clouds beyond that of idealized routine LES at meteorological supersites. Testing this hypothesis is a major research objective, and involves determination of the resolution at which simulated cloud irregularity starts to match the stereo camera observations, as well as quantification of the impact of uncertainties in the large-scale forcings. A simple stereo camera simulator for LES is developed to ensure a fair comparison between modelled and measured data. Data stratification and clustering techniques will be applied to search and identify parametric relations between variables describing cloud size and irregularity and environmental conditions. The objective is to use this data to better constrain parameterizations of convection and cloud overlap for weather and climate models.
DFG Programme
Research Grants
