TRACER

During the TRacking Aerosol Convection interactions ExpeRiment (TRACER), scientists will use the first ARM Mobile Facility (AMF1), the second-generation C-Band Scanning ARM Precipitation Radar (CSAPR2), and a small satellite (ancillary) site with radiosonde and aerosol measurements to learn more about cloud and aerosol interactions in the deep convection over the Houston, Texas, area.

The Houston region offers a unique environment where isolated convective systems are common and experience a spectrum of polluted aerosol conditions from urban and industrial areas. In addition, surrounding areas also show significantly lower background aerosol concentrations.

The TRACER campaign has been postponed from its originally planned dates due to COVID-19 risks associated with the earlier dates. The revised dates for TRACER are October 1, 2021, to September 30, 2022.

TRACER also will include a four-month intensive operational period (IOP). A climatological analysis of radar observations from the Houston/Galveston-area NEXRAD (KHGX) shows that convective initiation occurs in this area on 40 to 55 percent of the days each month of the year. The total number of convective events is strongly peaked during the months of June through September. To capture these events, the TRACER IOP will run from June 1 to September 30, 2022.

With this single IOP during the convective season of 2022, this effectively postpones the original TRACER IOP by one year.

The TRACER campaign consists of three primary sites operated by ARM:

• the AMF1 main site (M1) in La Porte, Texas, an area that experiences significant polluted conditions
• the ancillary site (S3) to the southwest of downtown Houston in a rural region with less pollution
• the CSAPR2 site (S2) located approximately midway between the AMF1 and ancillary sites.

The main and CSAPR2 sites will operate during the entire TRACER campaign, while the ancillary site will only operate during the IOP. Operation dates for the three primary sites are as follows:

• Main (M1): October 1, 2021, to September 30, 2022
• CSAPR2 (S2): October 1, 2021, to September 30, 2022
• Ancillary (S3): June 1 to September 30, 2022.

During the IOP, ARM will host many guest experiments and interagency collaborations at the TRACER sites. All three primary sites will host guest experiments, but most will be at the main site.

Currently, ARM is not accepting new proposals for TRACER guest experiments. However, any previously approved experiments are welcome and encouraged to participate in the 2022 IOP.

In addition, during the 2022 IOP, ARM is planning tethered balloon system (TBS) flights at the ancillary site and a secondary site at Smith Point, Texas, on the eastern shore of Galveston Bay that will be strongly influenced by the bay breeze circulation. ARM is not currently considering new proposals for TBS experiments; however, any previously approved experiments are welcome for the 2022 IOP.