Aerosol and radiation observations and model forecasts

Atmospheric aerosols modify the incoming solar radiation by scattering and absorption and through their impact on the formation and dissolution of clouds and additionally change their optical properties. Currently, no NWP model can fully account for these very complex effects. Especially during weather conditions affected by high aerosol concentrations, as in the event of Saharan dust outbreaks or wildfires, this can lead to errors in the forecast. One important factor to overcome this shortfall of NWP models, aerosols need to be treated as a prognostic variable.

At Deutscher Wetterdienst (DWD) and Karlsruhe Institute of Technology (KIT) project "PermaStrom" aims to improve radiation forecasts during such events. Using the ICON-ART modeling system emission, transport, and deposition of mineral dust, black carbon from vegetation fires, and sea salt are explicitly simulated. To achieve the project goals and to examine the effect of Saharan dust on solar radiation, accurate and extensive measurements of the Saharan dust in the atmosphere and the ground reaching solar radiation are needed. Within the measurement network of the DWD, we currently have 35 Stations equipped with two secondary standard pyranometers. One to measure the global radiation and one shaded to measure the diffuse incoming solar radiation at the surface with a temporal resolution of 1 minute. At the Meteorological Observatory Lindenberg, we also develop a retrieval algorithm to estimate the AOD at 550 nm from those measurements. With the additional information on the vertical distribution of the dust cloud from Ceilometer measurements in Germany, we obtain a detailed picture of aerosols and radiation.

In our contribution, we will give an overview of how accurate measurements at the surface could help to identify deficiencies in the ICON-ART modeling system and how the development process could benefit. We will focus on the direct and indirect aerosol effects and the benefit of the information of two radiation components.