All‐sky radiation over a glacier surface in the Southern Alps of New Zealand: characterizing cloud effects on incoming shortwave, longwave and net radiation

ABSTRACT Clouds are important features of many high‐altitude and glaciated areas, yet detecting their presence and specifying their effects on incoming shortwave (SW↓), longwave (LW↓) and net all‐wave radiation (Rnet) remains challenging in these environments. These limitations hamper efforts to understand atmospheric controls on glacier surface mass balance (SMB) in the Southern Alps of New Zealand, as both cloud and airmass forcing accompanies key synoptic controls on SMB. Multi‐year datasets of four‐component broadband radiation from two sites at Brewster Glacier, Southern Alps of New Zealand, are used here to develop cloud metrics to account for the effects of clouds on SW↓, LW↓ and Rnet. On average 23% of top‐of‐atmosphere shortwave radiation (SWTOA) is attenuated by the clear‐sky atmosphere, while clouds attenuate a further 31%, resulting in