Why EarthCARE?

The Earth Cloud, Aerosol and Radiation Explorer (EarthCARE) is a satellite jointly developed by the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) that aims to tackle these questions. After a long history of development, by a large team of scientists and engineers, EarthCARE was launched at 22.20 UTC on 28 May 2024. It carries a unique payload of four instruments that are designed to work in synergy to obtain the best possible estimate of the vertical profile of the properties of clouds, aerosols and precipitation, and their interaction with solar and thermal-infrared radiation.

Flying at an altitude of 390 km, EarthCARE's four instruments have key new measurement capabilities. Its nadir viewing 94-GHz Cloud Profiling Radar (CPR) is the first radar in space to measure how fast cloud and precipitation particles are falling in the atmosphere or rising in the cores of thunderstorms. Its 355-nm Atmospheric Lidar (ATLID) has "high spectral resolution" capability enabling it to unambiguously infer how much clouds and aerosols block incoming sunlight. These are complemented by the Multi-Spectral Imager (MSI) providing the wider context, and the three-view Broadband Radiometer (BBR) that measures the fluxes of solar and thermal-infrared radiation emerging from the top of the atmosphere. Image from Wehr et al. (2023).

The estimates of cloud, aerosol and precipitation properties should be more accurate than any previously derived from space, and will be of used to learn about microphysical processes in clouds, and to evaluate the representation of these properties and processes in numerical models used for weather forecasting, air-quality forecasting and climate projections. Of particular interest are the velocity measurements by the radar: for the first time from space we can infer the strength and width of the updrafts in thunderstorms, providing a unique opportunity to evaluate high resolution models that can resolve these storms.

Another unique aspect of the mission is that the quality of the retrievals is be assessed routinely via a radiative closure assessment: the estimated cloud and aerosol properties are passed into a radiative transfer code that computes how much sunlight is reflected and thermal-infrared radiation is emitted at the top of the atmosphere. If these agree well with the values measured by the broadband radiometer then we can have much more confidence in the retrievals for downstream applications.

A further important application of EarthCARE is data assimilation: measurements are available for users within a few hours of being taken, enabling them to be assimilated into both weather forecasting and air-quality models. By enabling data assimilation systems to produce a better estimate of the initial state of the atmosphere, forecasts can be improved.