SURFOBS

Surface Observation in Support of in-situ Observations within the Arctic Boundary Layer

1 April 2008 - 31 May 2008

Lead Scientist: Ismail Gultepe

Observatory: NSA

The main objectives of the proposed project were 1) to investigate nucleation processes related to ice crystals and droplets, 2) to study ice microphysical processes during ice fog events, 3) to estimate the climatological effects of ice crystals in freezing fog, 4) to compare the underlined microphysics of observed fog (liquid or ice) with Convair-580 in-situ data from the ISDAC (Indirect and Semi-Direct Aerosol Campaign) project, and 5) to develop remote sensing methods for ice fog forecasting. Using detailed surface observations obtained from the surface instruments, studies included microphysical characteristics of ice particles and freezing droplets, nucleation processes, and their effect on extinction (and visibility) within the Arctic Boundary Layer (ABL). Measurements related to droplets in sizes ranging from 1 to 50 ƒÝm and to both ice crystals and droplets in sizes ranging from 15 to 1550 ƒÝm were collected using the optical instruments similar to airborne FSSP and CIP (or 2DC) optical probes. An ice particle counter from York University (YU IPC) was used to count ice crystals between 20 and 500 ƒÝm. The aerosols with size ranges between 0.3 and 10 ƒÝm were collected using the Climatronics Aerosol Profiles (CAP) instrument. In addition to optical probes, the VAISALA FD12P all weather instrument, ultrasonic wind anemometer, ClearView video processing unit, VAISALA DSC111 surface state instrument, and VAISALA DST111 surface temperature (T) instrument were used to measure precipitation rate (PR) and visibility (Vis), 3D wind components at 32 Hz sampling rate, visibility at 3 visible channels, surface snow amounts, and T, respectively. The ARM NSA site also provided a unique data set for the proposed research which was planned to be performed during the ISDAC project. The measurements were then used to study ice/freezing fog, ice nucleation, visible extinction, the fog/drizzle effect on surface heat budget, PR-T, and PR-reflectivity relationships. The results from the project will lead to a complete data set related to the ABL processes that have not been available previously, and will help for better understanding of the model simulations and remote sensing analysis of the condensation/precipitation processes.