A 6 year comparison of surface and satellite Arctic cloud properties

A suite of cloud property retrieval techniques have been applied to a 6-year (1998-2003) data set of radar and radiometer measurements collected by the DOE/Atmospheric Radiation Measurement program in Barrow, Alaska. This multi-year, surface-based cloud data set provides information on cloud boundaries, optical depths, and vertical profiles of hydrometeor sizes (droplet and ice crystal), cloud water contents, and extinction. Cloud type classifications and retrievals have been applied to all cloud scenes including, ice, liquid, mixed-phase, multiple layer and for both night-time and day-time parts of the polar annual cycle (Figure 1).

This data set is a powerful tool for validation of satellite-based retrievals of Arctic cloud properties since it is long enough to provide statistically significant comparisons for a number of cloud type subsets including all-ice, all-liquid, night-time, day-time, multiple layer, and/or mixed phase. These satellite and surface and satellite data sets have become available for multi-year periods only recently as the result of a significant coordinated effort by NASA, DOE, NSF and NOAA to develop technologies, observing strategies, and ground-based/space-based retrieval techniques to observe the properties of Arctic clouds.

Results will be presented for comparison between surface measurements of cloud properties and satellites retrievals from the (1) AVHRR APP-X cloud data set, (2) CERES-team Arctic cloud retrievals that utilize measurements from the MODIS instrument, and (3) cloud retrievals from the standard MODIS MOD06 product. This preliminary inter-comparison study will assess the relative ability of different satellite sensors and cloud algorithms to determine the properties of different cloud types under different conditions of sun angle, underlying surface properties and multiple-layer situations.

Although the sensors on the NOAA satellites have less channels, are less stable, and not as calibrated as those on the TERRA and AQUA satellites, they now span two decades, they can provide a pan-Arctic, long-term perspective and may provide an important historical context within which to interpret the Arctic cloud record.