The university of houston (UH) and ST. Edward s university (SEU) have been working collaboratively since 2016 to develop a more capable balloon based sonde to measure SO2 in the atmosphere. The result…

The University of Houston System received a $201,393 grant award on August 9, 2018, for the "Big Island SO2 Survey" research project, with an ultimate completion date of January 31, 2025. This civilian research grant, funded through a federal agency's Shared Services Center, supports field testing of an improved sulfur dioxide (SO2) sonde developed collaboratively by the University of Houston and St. Edward's University since 2016. The sonde represents a significant advancement in atmospheric measurement capabilities, offering improved detection limits and the ability to measure SO2 at concentrations exceeding ozone levels—a limitation of previous methods. Laboratory testing demonstrated that the addition of a Nafion moisture exchanger with silica gel desiccant effectively stabilizes the sonde's performance across varying humidity conditions, reducing transmission efficiency variation to approximately 3% across a relative humidity range of 0–85%.

The project encompasses field validation of the improved SO2 sonde during active volcanic eruptions at Kilauea in Hawaii, which will provide critical data on plume vertical structure for evaluating satellite SO2 retrievals. In addition to sonde deployments, the research includes deployment of multiple Pandora instruments from both the University of Houston and NASA Goddard Space Flight Center to collect total column SO2 measurements, including replacement of a faulty Pandora unit at Mauna Loa Observatory, a key long-term measurement site in the Pandora network. Supporting remote sensing instruments will be collocated with one Pandora station to collect aerosol optical depth and boundary layer height measurements. The work is performed in Houston, Texas, with no set-aside designation applied to this competitive award.

The university of houston (UH) and ST. Edward s university (SEU) have been working collaboratively since 2016 to develop a more capable balloon based sonde to measure SO2 in the atmosphere. The result of this collaboration is a new sonde with improved upper and lower detection limits compared to previous dual-ozonesonde methods and the ability to measure SO2 at concentrations greater than O3, a limitation of the previous method. Initial field tests at kilauea in february 2018 showed significant variability in the sensitivity of the sonde in the ambient atmosphere, both from one sonde to the next and between zero-air calibration and ambient sensitivities. IT was hypothesized that differences in relative humidity (RH) were affecting the SO2 transmission efficiency (TE) of the O3 destruction filter was the cause of the observed variation in sensitivity. Subsequent lab tests have shown that SO2 TE is reduced as RH increases, buy as much as 50% at high RH. The addition of a nafion moisture exchanger encased in silica GEL desiccant dries the ambient sample to low RH levels such that the filter TE varies ~3% across a range of at least 0-85% RH. We propose to return to hawaii for additional field testing of this improvement in the SO2 sonde while kilauea is in a more active eruptive phase. These launches will also provide valuable information regarding the vertical structure of the plume which can be used in the evaluation of satellite retrievals of SO2. In addition to testing the improved SO2 sonde, we will also deploy multiple pandora instruments, two from UH and two from NASA goddard, to collect total column measurements of SO2. One of these instruments will replace the faulty pandora at the mauna LOA observatory, a key long-term measurement site in the pandora network. Additional remote sensing instruments will be collocated with one of the pandoras to collect supporting observations such as aerosol optical depths and boundary layer height measurements. These measurements will be used to better constrain and interpret the pandora measurements, which can then be compared to OMI and tropomi SO2 column retrievals.