BAECC: A Field Campaign to Elucidate the Impact of Biogenic Aerosols on Clouds and Climate

Abstract

During Biogenic Aerosols—Effects on Clouds and Climate (BAECC), the U.S. Department of Energy’s Atmospheric Radiation Measurement (ARM) Program deployed the Second ARM Mobile Facility (AMF2) to Hyytiälä, Finland, for an 8-month intensive measurement campaign from February to September 2014. The primary research goal is to understand the role of biogenic aerosols in cloud formation. Hyytiälä is host to the Station for Measuring Ecosystem–Atmosphere Relations II (SMEAR II), one of the world’s most comprehensive surface in situ observation sites in a boreal forest environment. The station has been measuring atmospheric aerosols, biogenic emissions, and an extensive suite of parameters relevant to atmosphere–biosphere interactions continuously since 1996. Combining vertical profiles from AMF2 with surface-based in situ SMEAR II observations allows the processes at the surface to be directly related to processes occurring throughout the entire tropospheric column. Together with the inclusion of extensive surface precipitation measurements and intensive observation periods involving aircraft flights and novel radiosonde launches, the complementary observations provide a unique opportunity for investigating aerosol–cloud interactions and cloud-to-precipitation processes in a boreal environment. The BAECC dataset provides opportunities for evaluating and improving models of aerosol sources and transport, cloud microphysical processes, and boundary layer structures. In addition, numerical models are being used to bridge the gap between surface-based and tropospheric observations.

Ensemble mean density and its connection to other microphysical properties of falling snow as observed in Southern Finland

“…The ensemble mean density is on average higher for snow events recorded during BAECC, which suggests more riming occurred during those events. Indication to this is that the ARM AMF2 dual-channel microwave radiometer located on the same measurement field detected the presence of liquid water more than 80 % of the BAECC SNEX campaign time (Petäjä et al, 2016) and the presence of supercooled liquid layers could also be observed in the backscatter coefficient and circular depolarization ratio measurements of the co-located ARM HSRL (High Spectral Resolution Lidar) in the majority of the BAECC cases (Goldsmith et al, 2014). In general the BAECC winter was milder than the next winter 2014-2015, and the case duration weighted average of maximum recorded temperatures was almost 1 • C higher for BAECC events compared to the value for winter 2014-2015 cases.…”

“…Measurements were made at the University of Helsinki Hyytiälä Forestry Field Station, Finland (61 • 50 37 N, 24 • 17 16 E), during the Biogenic Aerosols Effects on clouds and Climate (BAECC) field campaign (Petäjä et al, 2016) and during the consecutive winter of 2014/15. BAECC was a joint experiment between the University of Helsinki, the Finnish Meteorological Institute (FMI) and the United States Department of Energy Atmospheric Radiation Measurement (ARM) program.…”

“…To minimize effects of wind, a Double-Fence Intercomparison Reference (DFIR) wind protection (Rasmussen et al, 2012) was build on site as shown in Fig. 1 and discussed in more detail in Petäjä et al (2016). Inside of the DFIR, the 2-DVD, one of the OTT Pluvio 2 s and one of the Parsivel 2 disdrometers were placed.…”

Comparison of MODIS and VIIRS cloud properties with ARM ground-based observations over Finland

“…The deployment was part of a campaign called the Biogenic Aerosols Effects on Clouds and Climate (BAECC) (Petäjä, 2013;Petäjä et al, 2016), a collaboration between University of Helsinki, Finnish Meteorological Institute, University of Eastern Finland and ARM. AMF2 contains a comprehensive suite of ground-based in situ instrumentation together with active and passive remote sensing instruments to obtain numerous atmospheric properties with very high temporal and spatial resolution.…”

“…This study uses ARM data from the AMF deployment in Hyytiälä, Finland, from February 2014 to September 2014 during the Biogenic Aerosols -Effects on Clouds and Climate, (BAECC) campaign (Petäjä, 2013;Petäjä et al, 2016). The AMF data are used to evaluate the CTH from MODIS and VIIRS.…”