Speaker
Description
Balloon-borne frost-point hygrometers have been used for process studies, trend analysis, and validation of satellite and radiosonde measurements for water vapor in the upper troposphere and lower stratosphere. They use a small mirror, which is cooled (or heated) appropriately, so that the condensate layer on the mirror surface is kept constant throughout the balloon sounding. The mirror temperature is measured as the frost (or dew) point temperature of the ambient air. The NOAA FPH and CFH instruments have been using a cryogen material which is trifluoromethane (R23) and electric heater to control the mirror temperature, while Meisei SKYDEW and some other instruments use a Peltier thermoelectric cooling device.
The cryogen R23 was covered by the 2016 Kigali Amendment to the Montreal Protocol because of its very large global warming potential, leading to a ban on its sale in several countries. Since then, versions with alternative coolants such as dry ice plus ethanol or liquid nitrogen have been developed for NOAA FPH and CFH.
The GRUAN stands for Global Climate Observing System (GCOS) Reference Upper Air Network (https://www.gruan.org/). It is an international ground-based reference observing network of sites measuring essential climate variables above Earth's surface, including stratospheric water vapour. For several radiosonde types, GRUAN has produced their GRUAN Data Products (GDPs), with fully quantified uncertainty budget for each data point. Currently, GRUAN is working on producing GDPs for NOAA FPH, CFH, and SKYDEW measurements.
In the presentation, we will discuss (i) brief technological introduction to balloon-borne frost-point hygrometers including the solutions for the R23 issue, (ii) some examples of past satellite validation activities using these hygrometers, and (iii) plans and issues toward the GDPs for NOAA FPH, CFH, and SKYDEW.
| You plan to attend | Online (MS Teams) |
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