Cloud Seeding Signature over Saudi Arabia - Insights from airborne observations and numerical model simulations

In arid and semi-arid subtropical regions like the Arabian Peninsula, rainfall enhancement through glaciogenic cloud seeding represents a critical strategy for water resource management. However, quantifying the efficacy of these interventions remains a challenge due to high natural meteorological variability. This study investigates the physical "seeding signature" of silver iodide (AgI) aerosols within mixed-phase convective clouds over Saudi Arabia, utilizing an integrated approach that combines in-situ aircraft measurements, polarimetric Doppler radar observations, and high-resolution Weather Research and Forecasting (WRF) simulations.

Airborne observations using high-frequency microphysical probes reveal a distinct modification of the cloud droplet size distribution (DSD) following AgI release in the seeded clouds compared to the non-seeded clouds. A significant depletion of supercooled liquid water content (SLWC) was recorded, concurrent with a three-to-fivefold increase in ice crystal number concentrations (N_ice) within the target volume. These in-situ findings are corroborated by ground-based Doppler radar products, which identify a characteristic "reflectivity plume" downwind of the seeding track. 

To isolate the seeding-induced perturbation from natural cloud evolution, high-resolution (3 km) WRF simulations were performed. By comparing "seeded" and "control" (non-seeded) model realizations, we establish a causal link between the introduction of artificial nuclei and the observed microphysical shifts. The model-derived baseline suggests that the observed SLWC depletion and subsequent reflectivity enhancement exceeded natural variability thresholds, providing a robust statistical signature of successful glaciation. This study underscores the necessity of a multi-platform framework linking microscopic particle-level changes to macroscopic radar signatures for the verification of weather modification efforts in subtropical climates.