Trends and variability of cloud liquid water path from satellite-based passive microwave observations

We present a climatology of cloud liquid water path (LWP) based on passive microwave observations, primarily from nearly two decades of Special Sensor Microwave Imager data. Because aliasing of any local diurnal cycle in LWP with drifts in satellite equator crossing time can lead to spurious trends, any trend analysis must properly account for the diurnal cycle. We present a methodology to estimate the diurnal cycle of LWP at all latitudes based purely on polar-orbiter data, and find this is consistent with previous estimates for the tropics. The resulting regional trends in LWP are discussed in terms of both robustness and possible relationships with anthropogenic climate change.