Brief communication: First NISAR Interferometric snow water equivalent change retrieval evaluated against airborne lidar

Abstract. NISAR's global L-band repeat-pass interferometry should be sensitive to snow water equivalent change (ΔSWE). We compare ΔSWE from an operational NISAR interferogram to near-coincident airborne lidar snow-depth change over a February 2026 pair in southwest Idaho. Across the scene, ΔSWE correlates well with the lidar depth change (r = 0.82, rising to r = 0.93 above a coherence of 0.2). The agreement is dominated by variability at scales above ~1 km (r ≈ 0.94), while the correlation at sub-kilometer scales is weaker (r ≈ 0.42), improving over open terrain and at incidence angles below 50°. These results provide the first direct evidence that NISAR phase can measure dry-snow accumulation.