Integrated water vapor above Ny Ålesund, Spitsbergen: a multisensor intercomparison
1Institute of Environmental Physics, Universität Bremen, Germany
2Alfred Wegener Institut, Bremerhaven, Germany
Abstract. Water vapor is an important constituent of the atmosphere. Because of its abundance it plays an important role for the radiation budget of the atmosphere and has major influence on weather and climate.
In this work the integrated water vapor (IWV) measurements derived from the measurements of two satellite sensors, SCIAMACHY and AMSU-B, and two ground-based sensors, a Fourier-transform spectrometer (FTIR) and an O3 microwave ozone sensor (RAM), are compared to radio-sonde measurements in Ny Ålesund, 79° N. All four remote sensors exploit different principles and work in different wavelength regions. Combined they deliver a comprehensive picture of the IWV above Ny Ålesund.
The ground-based FTIR reproduces the radio-sonde measurements very well and also shows a high correlation and very little scatter of about 10%. The other remote sensing instruments show a good correlation with the coincident radio-sonde measurements but show high scatter of about 20% (standard deviation). The ground-based RAM performs similar to the satellite instruments, which is somewhat surprising, because measuring IWV is only a by-product for this sensor.
The RAM sensor records a measurement every hour and is therefore suited to observe the diurnal variation. As measured by the RAM and FTIR the variance within 4 h is often in excess of 50% (minimum – maximum of the measured IWV). This large variance in the integrated water vapor renders the comparison of different sensors a difficult task. The derived variance of the instruments when compared to radio-sonde measurements can be explained by the high natural variability of IWV.