NOAA frostpoint hygrometer (FPH) comparisons, uncertainty measurements, and recent instrument improvements

Emrys Hall1,2, Allen F Jordan3, Dale F Hurst3, Samuel J Oltmans4, Holger Voemel5 and Volker Ebert6, (1)CIRES, Boulder, CO, United States, (2)NOAA Global Monitoring Laboratory, Boulder, United States, (3)Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, United States, (4)Cooperative Institute for Research in Environmental Sciences, Boulder, CO, United States, (5)National Center for Atmospheric Research, Earth Observing Laboratory, Boulder, United States, (6)PTB Physikalisch-Technische Bundesanstalt, Braunschweig, Germany