MULHACEN – Multi-instrumental Approach to Quantify Aerosol–Cloud Interactions and Their Impact on Climate
- Reference: PID2021-128008OB-I00
- Funding agency: Ministerio de Ciencia, Innovación y Universidades
- Principal Investigators: Francisco Navas Guzmán and Daniel Pérez Ramírez (University of Granada)
- Project period: 01/09/2022 – 31/08/2026
- Total budget: 194,810.00 €
Project description
The MULHACEN project aims to advance the understanding of aerosol–cloud interactions and their impact on climate, one of the largest sources of uncertainty in current climate projections. Aerosols influence cloud formation, microphysical properties, lifetime, and radiative effects, yet their indirect effects remain poorly constrained due to the lack of comprehensive vertically resolved observations.
MULHACEN adopts a unique multi-instrumental and multi-layer approach, combining in situ measurements with advanced ground-based and satellite remote sensing techniques. The project makes use of the facilities of the Andalusian Global ObseRvatory of the Atmosphere (AGORA), operating both an urban station in Granada (680 m a.s.l.) and a high-mountain site in Sierra Nevada (2550 m a.s.l.), providing an exceptional framework to investigate aerosol–cloud processes under contrasting atmospheric conditions.
A central component of the project is the optimization of the multi-wavelength Raman lidar ALHAMBRA, enabling high temporal resolution profiling of aerosols and water vapor during both daytime and nighttime. These improvements will allow, for the first time, the retrieval of vertically resolved aerosol microphysical properties both below and above cloud layers. Additional instrumentation, including microwave radiometers and HALO Doppler lidar, will provide complementary information on the thermodynamic state of the atmosphere in regions where aerosol–cloud interactions occur. In situ measurements at the Sierra Nevada station will further support the validation of remote sensing retrievals.
MULHACEN integrates these observations using the state-of-the-art SYRSOC retrieval framework, which provides a full microphysical characterization of liquid clouds and will be extended within the project to include ice cloud microphysics. The resulting aerosol and cloud products will be used to improve the parameterization of aerosol indirect effects and to assess their impact in the Weather Research and Forecasting (WRF) model, including simulations with interactive aerosol chemistry.
Expected impact
MULHACEN directly addresses the “Climate Action” challenge within the Spanish Strategy for Science, Technology, and Innovation. By combining observational techniques never jointly applied in Spain, the project will generate unique datasets for the study of aerosol–cloud interactions and significantly reduce uncertainties associated with aerosol indirect effects highlighted in recent IPCC reports.
The project will strengthen AGORA’s position as a reference observatory for aerosol and cloud research, advance methodologies for aerosol typing and cloud microphysical retrievals, and improve the understanding of aerosol activation as cloud condensation and ice-nucleating particles. These advances will contribute to more accurate climate modeling and to a better assessment of aerosol impacts on cloud formation, evolution, and lifetime.
The proposed research using WRF model will serve to evaluate the impact of aerosols in clouds modeling, and we believe that the results obtained in MULHACEN will serve as baseline for more extended and comprehensive studies that will focus on global evaluation of aerosol-clouds interactions. The new knowledge we plan to acquire will serve to the PIs and to the research team to compete in future European and International calls (e.g. ERC program).
The research tasks proposed in MULHACEN clearly adhere the research objectives of current and future space missions. Particularly, obtaining aerosol microphysical properties from the space and their impacts in clouds are the key aspects of the upcoming ACCP NASA mission and the EarthCARE ESA missions. These space missions plan to combine different remote sensing techniques, and MULHACEN clearly provide a first insight to such combinations. The advances proposed in retrieval of aerosol microphysical properties with lidar measurements will serve to validate satellite products from these missions. Actually, the PIs are leading an effort for coordinating ACTRIS-Spain activities in EarthCARE validation.
Figure 1: Experimental setting of remote and in-situ measurements at UGR station (660 m, asl) and SNS station (2510 m asl)