Arctic Stratus Cloud Properties and Radiaitve Forcing Derived From Ground-Based Data Collected at ARM NSA Site and SHEBA Ship
Dong, X. and Mace, G.G., University of Utah
Twelfth Atmospheric Radiation Measurement (ARM) Science Team Meeting
A record of single-layer and overcast low-level Arctic stratus cloud properties has been generated using data collected at the Atmospheric Radiation Measurement site near Barrow, Alaska from May to September 2000. The record includes liquid-phase and liquid dominant mixed-phase Arctic stratus macrophysical, microphysical, and radiative properties, as well as surface radiation budget and cloud radiative forcing. The macrophyiscal properties consist of cloud fractions, base/top heights and temperatures, and cloud thickness derieved from a ground-based radar and lidar pair, and rawinsonde sounding. The microphysical properties include cloud liquid water path and content, and cloud-droplet effective radius and number concentration obtained from microwave radiometer brightness temperature measurements, and a newly developed parameterization. The radiative properties contain cloud optical depth, solar tranmission, and surface/cloud/top-of-atmosphere albedos derived from a newly developed parameterization and standard Epply precision spectral pyranometers. The shortwave, longwave, and net cloud radiative forcings at the surface are inferred from the measurements of standard Epply precision spectral pyranometers and pyrgeometers. In order to establish the representativeness of the data sets collected at Barrow during summer 2000, the cloud properties are compared with similar properties derived from aircraft in situ measurements, surface observations, and satellite data during the FIRE ACE and SHEBA field experiments. Although these comparisons are based on data collected at different locations and different years (the same months), this allows us to pose the following scientific questions: 1) What are the seasonal variation of Arctic stratus cloud macrophysical, microphysical, and radiative properties at Barrow, Alaska from spring to autumn?, and how does this seasonal variation of cloud properties influence the surface radiation budget, cooling or warming, and when? 2) How do the summer 2000 results, generated at a single point over one summer, represent the Arctic summer climatology? For example, what are the differences between the cloud properties and associated radiative forcing found in data sets collected at Barrow and the SHEBA ship? Is the summer cloud cooling effect at Barrow longer and stronger than at the SHEBA ship?
Note: This is the poster abstract presented at the meeting; an extended version was not provided by the author(s).
