Consistency of reflected moonlight based nighttime cloud properties and precipitation product with its daytime equivalent

Several VIS/NIR based rain rate retrievals have been developed which relate cloud optical properties to precipitation at daytime. They usually assume that the probability of precipitation is a function of cloud liquid water path, which can in turn computed from cloud optical thickness (COD) and cloud effective radius (REF). More physically based rain rate algorithms from satellites use passive microwave radiometer observations, which penetrate clouds. Their principle is based on the physical relationship between observed microwave brightness temperatures and column water vapor and liquid water path and works equally well at day and night. The main disadvantages are the low spatial resolution (up to 2000 times coarser) and the higher uncertainty over land surfaces. The Suomi-NPP constellation with ATMS and VIIRS/Day-Night-Band (DNB) on the same satellite gives us ideal opportunity to make synergistic use of both precipitation retrieval techniques with merging the advantages of the high spatial resolution of VIS channels on S-NPP/VIIRS combined with quantitative adjustments of the more physically based rain rates from ATMS. The new and unique approach is the use of moon light reflectance measurements during night in DNB, which can be transformed to precipitation rate also when sunlight is not present. We will demonstrate the consistency and performance of precipitation retrieval and corresponding cloud properties at day and night. Special focus lies on the performance for Alaska region, where daytime observations are rarely available during winter, and thus will be particularly valuable for weather forecast and climate research.