As you may already know, at AWIPEV we launch daily a radio-sonde. Under perfect conditions the radio-sonde reaches an altitude of 35km and maybe more. On its way up, it measures the air temperature, atmospheric pressure and humidity as well as the wind direction and the wind speed. At the end we receive profiles of these parameter in dependence of the atmospheres altitude. The data is then used in the weather forecast for Germany and are part of the long term climate observations of the atmosphere.
In the stratosphere the humidity is extremely low and therefore it is difficult to measure it. To measure these low concentrations the sensor of our daily radio-sonde is too inaccurate: a special sensor is needed. Hence, every two month, a CHF-sonde is prepared. It is launched together with a radio-sonde and an ozone-sonde. With the CHF-sonde we receive much better and accurate data for the stratospheric humidity. At the same time we can validate the humidity sensor of the radio-sonde for the troposphere.
CFH stands for Cryogenic Frost Point Hygrometer. Within the sonde there is a small mirror. With the help of a cooling agent and a small heating unit the mirror is kept at a specific temperature so that a constant thin layer of ice is maintained on the mirror. This temperature is measured as accurately as possible and is called frost point. The frost point depends on the pressure and humidity. Therefore, if we know the temperature at which the thin ice layer is maintained then we also know the water content of the atmosphere.
But why are we interested in the water content of the atmosphere? In the troposphere we can observe the water cycle: evaporation, condensation(cloud formation), rain. Water in its gaseous form, thus as water vapor or humidity, plays an important role for the heat budget of Earth: water vapor is a greenhouse gas. Therefore it extremely important to know the water content in the atmosphere and what effects it has.
The stratosphere is extremely dry. Yet, the small amount of water present has important climate implications. Water in the stratosphere influences the radiation budget and affects the polar vortex. In the winter time so called Polar Stratospheric Clouds can form under very cold temperatures. These clouds can then dry out the stratosphere, thus changing its properties.
The CFH-sonde is usually prepared by someone from AWI Potsdam and/or the support of IMPRES. this time it was Marion’s and Ingo’s turn. The station personal is preparing at the same time a radio-sonde and an ozone-sonde. Finally it’s crafting time: all three sondes are combined and launched with our biggest available balloon. We have documented to preparations for such a balloon launch for you. Enjoy the pictures.