P5 – Field Campaigns

Project 5 is based on longer term observations in Lindenberg and Hannover in combination with a measurement campaign around the Meteorological Observatory Lindenberg. Thereby, we will combine methods and experiences from all project partners. At first, we will evaluate cloud fields from cloud resolving modelling and from ground- and satellite-based observations, using existing datasets. These studies will help to design, prepare and conduct the four-month measurement campaign in Lindenberg. The ground-based measurements performed at this campaign, will be combined with modelling output as well as satellite-based observations. Thereby, we will also include data from the new satellite sensors on Board MTG and EarthCARE that are uniquely suited to obtain cloud physical and radiative properties from space.

Overall, we want to provide the world’s most comprehensive co-located data set of cloud properties and high accuracy irradiance and radiance. This dataset will allow us to test the cloud-radiation dependencies developed in the partner projects of this Research Unit.

With help of the dataset we will pursue the concept of radiation closure. Thus, we aim to evaluate the input data sets of modelled, observed and reconstructed cloud properties by validating irradiance and radiance calculated with the 3D radiative transfer model MYSTIC for the ground and the top of atmosphere. Finally, we aim at investigating regime-dependent cloud-radiation relations based on long-term cloud and radiation data.

Principal Investigators:

Project Scientists:

Research Questions

The primary research questions of this project are:

  1. Do cloud fields and their temporal evolution as constructed from ground-based observation and satellite remote sensing match those from cloud resolving modelling?
  2. How well can we reproduce the observed spatiotemporal statistical properties of spectral irradiance and spectral radiance at the surface and at the top of the atmosphere from radiative transfer modelling based on observed and modelled cloud fields over the observed area?
  3. Can we quantify a cloud regime dependent bias-correction of cloud radiative effects and cloud remote sensing?

Work Programme

In order to address these research questions, the following work programme ist anticipated.

Evaluation of cloud fields from observed and modelled datasets of the HOPE-campaigns

HD(CP)2 (High definition of clouds and precipitation for advancing climate prediction) was a German-wide initiative for the investigation of cloud and precipitation processes and their influence on climate scenario calculations. In the frame of these activities, three field campaigns were conducted. The main campaign of this HD(CP)2 Observational Prototype Experiment (HOPE) was performed during four months in summer 2013 in the vicinity of Jülich. Two smaller field experiments were conducted, during which similar data sets were collected. The first was HOPE-Melpitz in 2014, which involved less ground-based remote sensing but included additional aircraft measurements. The second was HOPE-Lindenberg in 2015.

For these campaigns high-resolution modelling data, as well as satellite-based cloud and radiation products are available. The data sets are highly valuable for the synopsis of spatiotemporally resolved ground-based irradiance data and the overlying 3D cloud fields. However, the produced datasets of the HOPE campaigns are underexplored with respect to cloud-radiation relations. In particular, comprehensive radiation closure studies using 3D radiative transfer calculations in the cloudy atmosphere with input from high resolution cloud modelling or gridded observational data have neither been conducted using HOPE data so far.

Therefore, this project aims to exploit these data further. We will use the methods and algorithms from Cloudnet and further improved algorithms based on machine-learning techniques in order to retrieve profiles of microphysical cloud properties of the above mentioned measurements. Thus, we will compile profiles of liquid and ice water content as well as liquid and ice effective radius. These profiles, together with macrophysical cloud properties, such as cloud cover, will be used for a direct and statistical comparison to model output. On the one hand, highly resolved 3D cloud fields around the HOPE sites are already available from HD(CP)2. On the other hand, Project 1 of this Research Unit will contribute with new simulations, using the most recent model physics of ICON.

Illustration of the campaign setup at HOPE in summer 2013 in the vicinity of Jülich.
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The modelled and reconstructed 3D cloud fields will then serve as input to 3D radiative transfer model calculations to conduct high-resolved radiation closure studies at the ground and at the top of atmosphere. This will allow the modelled 3D cloud fields and the profiles of cloud properties from ground-based remote sensing to be evaluated in more detail. The 3D model calculations will be conducted using MYSTIC. Here, Project 2 will provide assistance for the model setup. Thus, the calculated spectral and broadband shortwave as well as the broadband longwave irradiance at the surface will be validated against the corresponding BSRN irradiance observations provided by Project 3. Additionally, the calculated short- and longwave broadband irradiance at the top of atmosphere will be compared to SEVIRI and CERES irradiance products, which will be provided by Project 4. The calculated longwave irradiance will be directly compared to the respective observations at the surface and the top of atmosphere. Furthermore, probability distributions of the 3D calculations and observations will be provided for comparison in the shortwave due to the higher variability of the shortwave irradiance.

These works will provide valuable input for the design of the C3SAR field campaign, which is described in the following section as well as here.

Field campaign at Lindenberg

Here, we present a brief description of the C3SAR field campaign. A more detailed description can be found here.

From 4 May to 30 August 2026 we will conduct a four-month measurement campaign at the Meteorological Observatory Lindenberg – Richard Aßmann-Observatory. Specific cloud scenes of various cloud regimes determined with the method developed in Project 2 will be observed extensively.

A wide range of ground-based instruments is operated at the Lindenberg observatory. Additionally, we will operate the novel AMUDIS system, which allows the spectral radiances to be measured at highest temporal resolution and accuracy. Together with hemispherical sky imagers (HSI) the 3D effect of clouds to be investigated more thoroughly. This setup will be complemented by a small-scale pyranometer network to better capture the spatial variability of the solar irradiance at the surface. Further scientific partners are welcome to take part at the campaign with their instruments.

By combining these ground-based observations with highly resolved modelled and reconstructed cloud fields, as well as data from the new generation of satellite sensors, a synergetic and holistic approach will be realized. Thus, we strive to compile an unprecedented dataset of validated cloud and radiation properties.

Case- and regime-based radiation closure studies

Datasets of cloud and radiation properties will be collected from the field campaign, as well as from modelling and observational work in the individual research projects. These datasets will be used for radiation closure studies based on specific cases and cloud regimes. The studies will focus on both hemispheric irradiance and spectrally resolved directional radiance, measured at the surface and at the top of the atmosphere. This allows to validate the calculated irradiance and radiance in a statistical sense. Furthermore, we will use the cloud properties retrieved from remote sensing as input parameters into the 3D radiative transfer model. Thus, these properties can be evaluated and refined. Additionally, we will study the 3D effect of clouds by comparing 3D radiative transfer calculations to the corresponding 1D approximations.

Thereby, the cloud regimes will be identified and provided by Project 2. Modelled and reconstructed cloud properties provided by Project 1 and Project 2, respectively, will serve as input for the 3D radiative transfer calculations. In contrast to the radiation closure study described in the first section of the work programme, reconstructed cloud fields from purely observational data provided by Project 2 will be available at this stage of the project.

Radiosonde system ISOLDE.

The 3D model calculations will be conducted with MYSTIC. Calculated spectral shortwave radiance at the surface will be compared to the AMUDIS measurements available for the field campaign. Calculated spectral and broadband shortwave and broadband longwave irradiance as well as the cloud radiative effect will be validated against the respective BSRN observations, which are provided by Project 3. In the atmosphere, calculated irradiance profiles, cloud radiative effect and heating rates will be compared to observed profiles of incoming and outgoing short- and longwave irradiance as well as the cloud radiative effect using the Irradiation SOunding LinDEnberg (ISOLDE). This sounding system is a radiosonde equipped with a four-component radiometer. ISOLDE will be launched for selected cases during the field campaign. Calculated short- and longwave radiance and irradiance as well as the cloud radiative effect at the top of atmosphere will be validated against the corresponding products from the Broad-Band long- and shortwave Radiometer for the top of atmosphere radiance (BBR) on EarthCARE provided by Project 4.

Apart from the use of novel observational technique in the shortwave, we will also put a focus on the longwave in the closure studies. This allows us to study the 3D effect of clouds on the greenhouse effect, which has been underexplored so far. As for the shortwave, this will be done by comparing 3D radiative transfer calculations with the corresponding 1D approximations for different cloud regimes.

Evaluation of the regime-based cloud relations

After all, we will study the relations between observed irradiance/radiance/cloud radiative properties and macro-/microphysical cloud properties for specific cloud regimes. We will first evaluate the relations for the cloud regimes of the dataset obtained during the field campaign with the satellite products from EarthCARE and MTG, which will be provided from Project 4. In a second step, we will extend the analysis to longer-term datasets from Lindenberg and include additional cloud regimes determined with the cloud classification method developed in Project 2. Thereby, observations at the surface will be provided by Project 3. Results from radiative transfer calculations with simplified cloud geometries will be used to investigate if it is possible to provide a regime-dependent bias-correction of cloud radiative effects and cloud remote sensing.