Vertical profiles of total reactive nitrogen (NOy = NO2 + HNO3 + ClONO2 + 2N2O5 + HO2NO2) along with the source gas N2O up to 38 km were retrieved from infrared limb emission spectra measured by the Michelson Interferometer for Passive Atmospheric Sounding, Balloonborne version (MIPAS-B) instrument from Aire sur l'Adour (France, 42¿N) on April 30, 1999. Three limb sequences of spectra were recorded 1 hour before, at and 3 hours after sunrise, respectively, allowing to investigate the NOy partitioning under night-time and - for the first time with the MIPAS-B instrument - also under day-time conditions and to study the temporal evolution of the short-lived species N2O5 and NO2 around sunrise. The MIPAS-B data are compared to calculations performed with the 3-D chemical transport model KASIMA (Karlsruhe Simulation model of the Middle Atmosphere). This comparison reveals a high degree of confidence in the model for the HNO3/NOy ratio in the whole altitude region and for the N2O5/NOy and NO2/NOy ratios above about 26 km. Below this altitude the N2O5/NOy ratio is significantly underestimated by the model. Also, the MIPAS-B measurement suggests a night-time built up of NO2 which is not reproduced by the model in an altitude region around 22 km.