TY  - THES
AU  - Khordakova, Dina
TI  - Impact of severe convection on the water vapor mixing ratio in the extra-tropical stratosphere
VL  - 586
PB  - Wuppertal
VL  - Dissertation
CY  - Jülich
M1  - FZJ-2022-03686
SN  - 978-3-95806-648-9
T2  - Schriften des Forschungszentrums Jülich Reihe Energie & Umwelt / Energy & Environment
SP  - ii, 136
PY  - 2022
N1  - Dissertation, Wuppertal, 2022
AB  - The emission of anthropogenic greenhouse gases leads to a continuous increase in average global surface temperatures. The radiative effect of the anthropogenic sources is amplified by feedback processes, like the water vapor feedback. The rapid change in climatic conditions is evident not only in the mean of the relevant weather parameters, but also in the severity and frequency of extreme events. Extreme convective events in the troposphere not only have immediate impacts on the surface, they can also influence the dynamics and composition of the stratosphere. One major impact is the moistening of the stratosphere by the transport of tropospheric air masses by overshooting convection and pyro-convection. This effect plays a crucial role in climate feedback as small changes of water vapor mixing ratios in the upper troposphere and lower stratosphere (UTLS) have a large impact on the radiative budget of the atmosphere and hence have an additional positive feedback on the changing climate. In this thesis four cases are investigated in which water vapor was injected into the stratosphere. Two of them are cases of convective overshooting and two are cases of pyro-convection. In all of these cases, unusual values of water vapor were measured in the stratosphere and a persistent dynamical signature (potential vorticity anomaly) was produced. For the convective case, the measurements were made by the Cryogenic Frostpoint Hygrometer (CFH) which requires Triflouromethane (R-23) as a cooling agent. Since the year 2020, R-23 has not been acquirable in Europe. Hence, an alternative cooling method for the instrument was successfully explored and tested. The two cases of convective overshooting were investigated on two consecutive days in the European mid-latitudes in early summer of 2019. Using balloon-borne instruments, measurements of convectively injected water vapor in the stratosphere were performed. The magnitude of the affected stratospheric water vapor reached up to 12.1 ppmv with an estimated background value of 5 ppmv. The corresponding water vapor values measured by the Microwave Limb Sounder (MLS) satellite in the lower stratosphere (LS) are lower than the in-situ observations and the fifth generation of ECMWF atmospheric global reanalysis (ERA5) reanalysis overestimated water vapor mixing ratios.
LB  - PUB:(DE-HGF)3 ; PUB:(DE-HGF)11
UR  - https://juser.fz-juelich.de/record/910209
ER  -