What We Do
Since 1980, the water vapor group at NOAA/ESRL/GMD has made in situ measurements of atmospheric water vapor mixing ratios (mole fractions) from the lower free troposphere (~2 km) up to the middle stratosphere (~30 km) with small, lightweight, balloon-borne cryogenic frost point hygrometers (FPHs). These hygrometers, built and calibrated in our laboratory in Boulder, Colorado, are currently flown every 2 weeks from Boulder and Lauder, New Zealand. In addition, we have conducted several intensive water vapor measurement programs in Antarctica, the Arctic, and several tropical locations, often in support of aircraft-based scientific campaigns. Along with the FPH we normally include an electrochemical cell (ECC) ozonesonde and a commercial radiosonde on the balloon payloads. Our data sets therefore contain vertical profiles of water vapor and ozone mixing ratios, pressure, temperature and horizontal winds.
Why Is Atmospheric Water Vapor Important?
Our primary research focus is the long-term monitoring of stratospheric water vapor and the processes that control upper tropospheric and stratospheric water vapor. Water vapor is a natural and very important component of the Earth’s atmosphere. Its distribution influences many physical and chemical properties of the atmosphere, including weather, clouds, precipitation, lightning generation, convective uplift, and the Antarctic ozone hole. Most relevant to our study is water vapor’s effects on the Earth’s energy budget, influencing the budgets of both incoming solar radiation and outgoing heat (IR). Variations in the total amount of atmospheric water vapor are natural and normal, but changes in its vertical distribution, especially in the upper troposphere and lower stratosphere, may be indicative of changes in the Earth’s climate. For this reason there is great interest in our long-term (since 1980) record of water vapor vertical distributions over Boulder as it may reveal changes in atmospheric dynamics resulting from climate change.
The NOAA Cryogenic Frost Point Hygrometer (FPH) has evolved from an analog unit with strip chart recording of data to a digitally-controlled instrument with full downlink telemetry of data that is recorded on the ground. Read more on Basic descriptions of the hygrometer, frost point technique, data collection and launch procedures.
Click on the photos for site information, water vapor profile plots and access to water vapor data files.