The Saudi Aerosol-Cloud-Precipitation Enhancement Campaign (SARPEC): Outlook and Research Roadmap

The limited success of statistical evaluation of many weather modification programs has shifted research efforts to physical process studies to detect cloud seeding effects. The representation of these processes in numerical models is difficult due to the complex interactions that occur on many different spatial and temporal scales encompassed through the chain of events leading to precipitation. Currently, the rain formation process is not fully understood to allow the development of sufficiently accurate numerical models to predict cloud seeding effects. This is particularly challenging in complex conditions with high background aerosol loadings from dust and pollution sources such as those found across the Middle East and North Africa (MENA) region. Without quantitative relationships, it is impossible to model the effects that weather modification methods have on precipitation amounts in an operational area.

In 2022, the Kingdom of Saudi Arabia launched a Regional Cloud Seeding Program under the National Center of Meteorology (NCM). A contemporaneous research program compatible with the operational cloud seeding program is planned with an overarching goal of conducting a techno-economic assessment of rainfall enhancement activities in the Kingdom. The availability of in situ aerosol and cloud microphysical observations from a research aircraft is an important prerequisite to develop a data-informed research and evaluation roadmap. The Saudi AeRosol-cloud-Precipitation Enhancement Campaign (SARPEC) is a series of intensive observation periods (IOPs) using the University of North Dakota Cessna Citation II research jet, equipped with state-of-the-art cloud physics instrumentation. Two IOPs are underway during the summer and fall 2023 seasons and a third IOP is planned for the spring 2024 season to sample both the southwest and central regions of the Kingdom during periods of frequent convective cloud development. The SARPEC measurements will provide the first contemporary cloud climatology of actively growing (natural and seeded) convective clouds from advanced instrumentation since the legacy measurements gathered during 2004-2010. We present the research questions and hypotheses driving the stepwise science objectives of SARPEC and the framework for the overarching techno-economic assessment of cloud seeding activities in the Kingdom. The outcomes of this research will contribute valuable insights to the current understanding and knowledge gaps in the weather modification community, particularly for rainfall enhancement strategies in arid regions.