Tobias Wehr

The EarthCARE Satellite: The Next Step Forward in Global Measurements of Clouds, Aerosols, Precipitation, and Radiation

AbstractThe collective representation within global models of aerosol, cloud, precipitation, and their radiative properties remains unsatisfactory. They constitute the largest source of uncertainty in predictions of climatic change and hamper the ability of numerical weather prediction models to forecast high-impact weather events. The joint European Space Agency (ESA)–Japan Aerospace Exploration Agency (JAXA) Earth Clouds, Aerosol and Radiation Explorer (EarthCARE) satellite mission, scheduled for launch in 2018, will help to resolve these weaknesses by providing global profiles of cloud, aerosol, precipitation, and associated radiative properties inferred from a combination of measurements made by its collocated active and passive sensors. EarthCARE will improve our understanding of cloud and aerosol processes by extending the invaluable dataset acquired by the A-Train satellites CloudSat, Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), and Aqua. Specifically, EarthCARE’s c...

ECSIM: the simulator framework for EarthCARE

In 2013 an important ESA Core Explorer Mission, EarthCARE is scheduled to be launched. EarthCARE, (the Earth, Clouds, Aerosol and Radiation Explorer) will comprise two active (a cloud-profiling radar (CPR) and an high spectral resolution atmospheric lidar (ATLID)) and two passive (a Multi-spectral imager (MSI) and a Broad-Band Radiometer (BBR)) instruments. With these, EarthCARE will enable cloud and aerosol properties retrievals consistent with a Top-of-Atmospheric (TOA) flux accuracy of 10 Wm-2. This will be achieved by simultaneously probing the atmosphere vertically with the active instruments in synergy with the passive instruments. In order to facilitate and optimize algorithm development and to quantify the effect of different instrument configurations on the mission performance a simulator for EarthCARE (ECSIM) has been developed. ECSIM relies strongly upon a previous prototype developed by ESA/KNMI where a combination of forward and retrieval models (full End-to-End capabilities) have been included. In order to make this tool more useful within the scientific and engineering communities, the prototype simulator has been embedded into a completely reorganized architecture intended to improve a number of aspects: *Complex algorithms have been enclosed within logical entities: models. *Models are connected in a logical sequence with well-defined interfaces. *Users can customize almost every modes parameter values using configuration XML files. *Model outputs are well documented and stored in easy to access NetCDF files. *Complex simulations can be built up with a few mouse clicks. *Users can run lengthy simulations automatically iterating through different parameter values. *ECSIM can intercept and classify information and error messages from the simulations. *A database is maintained with all the information generated by the system. *It is possible to add third-party algorithms or tools to convert, analyze and visualize data extracted from generated products.

Use of Artificial Neural Networks to Retrieve TOA SW Radiative Fluxes for the EarthCARE Mission

The Earth Clouds, Aerosols, and Radiation Explorer (EarthCARE) mission responds to the need to improve the understanding of the interactions between cloud, aerosol, and radiation processes. The fundamental mission objective is to constrain retrievals of cloud and aerosol properties such that their impact on top-of-atmosphere (TOA) radiative fluxes can be determined with an accuracy of 10 W · m-2. However, TOA fluxes cannot be measured instantaneously from a satellite. For the EarthCARE mission, fluxes will be estimated from the observed solar and thermal radiances measured by the Broadband Radiometer (BBR). This paper describes an approach to obtain shortwave (SW) fluxes from BBR radiance measurements. The retrieval algorithms are developed relying on the angular distribution models (ADMs) employed by Clouds and the Earths Radiant Energy System (CERES) instrument. The solar radiance-to-flux conversion for the BBR is performed by simulating the Terra CERES ADMs us ing a backpropagation artificial neural network (ANN) technique. The ANN performance is optimized by testing different architectures, namely, feedforward, cascade forward, and a customized forward network. A large data set of CERES measurements used to resemble the forthcoming BBR acquisitions has been collected. The CERES BBR-like database is sorted by their surface type, sky conditions, and scene type and then stratified by four input variables (solar zenith angle and BBR SW radiances) to construct three different training data sets. Then, the neural networks are analyzed, and the adequate ADM classification scheme is selected. The results of the BBR ANN-based ADMs show SW flux retrievals compliant with the CERES flux estimates.

Development status of the EarthCARE Mission and its atmospheric Lidar

The European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) are co-operating to develop as part of ESA’s Living Planet Programme, the third Earth Explorer Core Mission, EarthCARE, with the fundamental objective of improving the understanding of the processes involving clouds, aerosols and radiation in the Earth’s atmosphere. EarthCARE payload consists of two active and two passive instruments: an ATmospheric LIDar (ATLID), a Cloud Profiling Radar (CPR), a Multi-Spectral Imager (MSI) and a Broad-Band Radiometer (BBR). The four instruments data are processed individually and in a synergetic manner to produce a large range of products, which include vertical profiles of aerosols, liquid water and ice, observations of cloud distribution and vertical motion within clouds, and will allow the retrieval of profiles of atmospheric radiative heating and cooling. Operating in the UV range at 355 nm, ATLID provides atmospheric echoes with a vertical resolution up to 100 m from ground to an altitude of 40 km. Thanks to a high spectral resolution filtering, the lidar is able to separate the relative contribution of aerosol (Mie) and molecular (Rayleigh) scattering, which gives access to aerosol optical depth. Co-polarised and cross-polarised components of the Mie scattering contribution are also separated and measured on dedicated channels. This paper gives an overview of the mission science objective, the satellite configuration with its four instruments and details more specifically the implementation and development status of the Atmospheric Lidar. Manufacturing status and first equipment qualification test results, in particular for what concerns the laser transmitter development are presented.

An overview of the EarthCARE mission and end-to-end simulator

The Earth Clouds, Aerosols and Radiation Explorer (EarthCARE) mission aims at improving the representation and understanding of the Earths radiative balance in climate and numerical weather forecast models by acquiring vertical profiles of clouds - including vertical motion within clouds - and aerosols, as well as measuring the broadband radiances at the top of the atmosphere for flux estimates in relation of the observed clouds and aerosols fields. The EarthCARE payload comprises an High Spectral Resolution (HSR) Lidar (ATLID) operating at 355 nm and equipped with a high-spectral resolution (HSR) receiver and the Cloud Profiling Radar (CPR), a highly sensitive 94GHz cloud radar with Doppler capability. A Multi-Spectral Imager (MSI) supporting the active instruments consists of a push-broom imager with 7 channels in the visible, near infrared, short-wave infrared and thermal infrared. Finally, a Broad-Band Radiometer (BBR) measures the outgoing top-of-atmosphere radiances in a short wave channel and a total wave channel, from which the long wave contribution can be deduced. The EarthCARE end-to-end Simulator (ECSIM) encompasses the full EarthCARE observation chain from scene definition to single-instrument and synergistically derived multi-instrument Level 2 products. Level 2 retrieval algorithms can be tested in the full chain (provision of input data, algorithm performance tests by comparison of outputs with known inputs) by using a single framework with well-defined interfaces helping to harmonise algorithm developments. The CPR is developed and procured by JAXA (Japanese Aerospace Exploration Agency) and NiCT (National Institute of Information and Communications Technology) and will be embarked as an integral part of the EarthCARE satellite in the context of the ESA/JAXA cooperation for EarthCARE.

Status of ESA's EarthCARE mission, passive instruments payload

EarthCARE is ESA’s third Earth Explorer Core Mission, with JAXA providing one instrument. The mission allows unique data product synergies to improve understanding of atmospheric cloud–aerosol interactions and Earth’s radiation balance. Retrieved data will be used to improve climate and numerical weather prediction models. EarthCARE accommodates two active instruments: an ATmospheric LIDar (ATLID) and a Cloud Profiling Radar (CPR), and two passive instruments: a Multi Spectral Imager (MSI) and a BroadBand Radiometer (BBR). The instruments will provide simultaneous, collocated imagery, allowing both individual and common data products. The active instruments provide data on microscopic levels, measured through the atmospheric depth. 3-D models of the atmospheric interactions are constructed from the data, which can be used to calculate radiation balance. The large footprint of the MSI provides contextual information for the smaller footprints of the active instruments. Data from the BBR allows the loop to be closed by providing a macroscopic measurement of the radiation balance. This paper will describe the passive instruments development status. MSI is a compact instrument with a 150 km swath providing 500 m pixel data in seven channels, whose retrieved data will give context to the active instrument measurements, as well as providing cloud and aerosol information. BBR measures reflected solar and emitted thermal radiation from the scene. To reduce uncertainty in the radiance to flux conversion, three independent view angles are observed for each scene. The combined data allows more accurate flux calculations, which can be further improved using MSI data.

Top of atmosphere thermal flux retrieval for the EarthCARE Mission: a preview

The forthcoming ESA/JAXA EarthCARE (Earth Clouds Aerosols and Radiation Explorer)Mission addresses the need to improve the understanding of the interactions between cloud, aerosol and radiation processes. These play a critical role in the Earths radiative balance in climate models. The broad-band radiometer (BBR) on-board the EarthCARE spacecraft provides measurements of broad-band reflected solar and emitted thermal radiances and fluxes at the top-of-atmosphere (TOA) over the along-track (AT) satellite path at three different viewing angles. This angular information together with the spectral information on the radiation from the EarthCAREs multi-spectral imager (MSI) is exploited to construct accurate radiance-to-flux conversion algorithms.