Intercomparison of measurements of stratospheric hydrogen fluoride

Observations of the vertical profile of hydrogen fluoride (HF) vapor in the stratosphere and of the vertical column amounts of HF above certain altitudes were made using a variety of spectroscopic instruments in the 1982 and 1983 Balloon Intercomparison Campaigns. Both emission instruments working in the far infrared spectral region and absorption instruments using solar occultation in the 2.5m region were employed. No systematic differences were seen in results from the two spectral regions. A mean profile from 20–45 km is presented, with uncertainties ranging from 20% to 50%. Total columns measured from ground and from 12 km are consistent with the profile if the mixing ratio for HF is small in the tropophere and low stratosphere.     

Tunable diode laser measurements of trace gases during the 1988 Polarstern cruise and intercomparisons with other methods

Measurements of NO₂, HCHO, and H₂O₂ were made by the highly specific method of mid infra-red absorption spectroscopy using tunable diode lasers (TDLAS) during the 1988 Polarstern expedition. The TDLAS data are compared to those obtained during the cruise using less direct methods. Southern Hemisphere NO₂ levels suggest nett photochemical destruction of O₃ in the boundary layer. Northern Hemisphere HCHO averaged 0.47±0.2 ppbv; the HCHO measurements are used in a simple calculation to estimate OH noontime maxima of 3–6×10⁶ cm^-3.     

Stratospheric methane concentration profiles measured during the Balloon Intercomparison Campaigns

Following the Balloon Intercomparison Campaigns carried out from the NSBF, Palestine, Texas, in the fall of 1982 (BIC1) and spring of 1983 (BIC2), three instruments have reported infrared measurements (one in emission and two in absorption) from which results on the concentration of methane between 20 and 40 km altitude have been deduced. While the absorption-retrieved concentration profiles are in excellent agreement, the results from the emission measurements are significantly lower. Recent methane profiles obtained by satellite and from Spacelab 1 are in satisfactory agreement with the absorption data reported here.     

A recipe for why and how to set up and sustain an experimental catchment

Experimental catchments are fundamental elements in hydrological sciences as they provide key data for putting forward and testing hypotheses, developing theories, constraining models, and making predictions. Significant progress in catchment hydrology stemmed from field measurements but increasing costs and risks associated with field work and the availability of big data based on remote sensing, machine learning, and a plethora of models, as well as observations deriving from previous and current sites, raises questions on whether running an experimental catchment still provides individual and community benefits as in the past. In this commentary, I highlight the advantages of keeping experimental catchments alive and propose a personal 10-step “recipe” to set up a new experimental catchment and manage and sustain it in the long term. These suggestions can be useful both to young and less young researchers who are open to facing the challenge of measuring processes in the field and are willing to offer the scientific community new experimental evidence for advancing our current knowledge in catchment hydrology.     

Validation of GLI and other satellite-derived sea surface temperatures using data from the Rottnest Island ferry, Western Australia

An accurate platinum resistance thermometer (PRT) has been installed on a commercial ferry that operates between Hillarys Marina, some 15 km north of Fremantle, and Rottnest Island off the Western Australian coast. The PRT is located in the engine intake system and provides continuous under-way measurements of the bulk sea surface temperature (SST) at a depth of 1 m. The “SeaFlyte” ferry makes the trip to Rottnest Island between 3 and 5 times daily and so a wealth of data is available for comparison with the SST derived using data from the GLI instrument on ADEOS-II. Analyses of the ferry and satellite data confirm the excellent quality of SST estimates from the GLI as well as four other satellite instruments—AVHRR on NOAA-16, AATSR on ENVISAT, and the MODIS instruments on TERRA and AQUA. All satellite instruments showed a comparison standard deviation of better than 0.6°C with GLI being better than 0.4°C. The number of ferry-satellite data coincidences used in this study demonstrates one of the advantages of installing measurement systems on commercial ships that operate regular passenger or freight services rather than infrequent deployments on research vessels. The analyses also demonstrate that satellite-derived SST estimates obtained under low surface wind conditions must be treated with care.