Three‐dimensional simulation of stratospheric trace gas distributions measured by CRISTA

Abstract

Abstract. The Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere(CRISTA) experiment has been flown on two space shuttle missions (STS 66 and STS 85). During these missions, global trace gas distributions have been measured with high spatial resolution. The first flight was performed in early November 1994 during a period of disturbed dynamical conditions characterized by relatively large wave activity and associated exchange of tropical and extratropical air. As a result, numerous small-and medium-scale structures were present in the trace gas distributions measured by CRISTA.The detailed structure of the constituent distributions has been modeled with the National Center for Atmospheric Research Research on Ozone in the Stratosphere and Its Evolution (ROSE) model, which is driven by assimilated winds and temperatures provided by the U.K. Meteorological Office. The modeled trace gas distributions capture much of the measured structures. Very good agreement is found in the lower stratosphere of the northern hemisphere, with the exception of unrealisticly high variability of the modeled trace gas fields at equatorial and subtropical latitudes. In this paper, model results of two specific tracers, CFC-11 and N20 , are compared to respective CRISTA measurements. For quantitative comparisons of trace gas transport in the ROSE model and trace gas transport associated with the measurements, CRISTA version 1 (level 2) data have been assimilated into the model by using a simple sequential technique. The trace gas assimilation system interpolated the measured distributions of long-lived tracers onto the model grid and yields synoptic fields that are consistent with the CRISTA measurements, at each time step of the model (20 min). Horizontal eddy fluxes of CFC-11 (31.6 mbar) calculated from the assimilated trace gas concentrations are in reasonable agreement with respective fluxes calculated from modeled trace gas fields without data assimilation. Both data sets indicate a large degree of temporal cancellation of eddy transport during the time period of the CRISTA measurements. The assimilated trace gas distributions represent a value-added level 3 product, which has been used for transport and budget studies of CFC-11 (31.6 mbar) and CH 4 (4.6 mbar). The study indicates that irreversible transport processes are rather important at the 4.6 mbar pressure level during the time period of the CRISTA measurements. Most interesting is a pronounced mixing event from midlatitudes into the tropics, which is also evident in measured and calculated zonal mean CH 4 mixing ratio tendencies.

Satellite observations of cirrus clouds in the Northern Hemisphere lowermost stratosphere

“…The measurements demonstrate the potential of the IR limb viewing technique to provide information on several trace gas constituents (Riese et al, 1999a and clouds with high spatial resolution. The spectral information in the wavelength (λ) region 4-15 µm is scanned with a resolution of λ/ λ =∼ 500, which is equivalent to 1.6 cm −1 at 830 cm −1 .…”

“…The accuracy of the attitude system of the platform, which was also used for two astronomic missions, is excellent. The final pointing accuracy in the limb direction for the three viewing directions is of the order of 300 m (Riese et al, 1999a;Grossmann et al, 2002). The effect of refraction through the atmosphere in the limb direction is considered in the tangent height determination and can reduce the actual tangent height by up to ∼ 300 m at 12 km altitude.…”

“…The dense horizontal coverage of the measurement net over 24 h (here presented for 9 to 10 August 1997, noon to noon) allows us to track the horizontal transport patterns of trace gases for example streamers (e.g. Riese et al, 1999aRiese et al, , 2002 in conjunction with meteorological parameters such as the potential vorticity (PV). Figure 1 shows PV contours for the 350 K isentrope.…”

Climatological features of stratospheric streamers in the FUB-CMAM with increased horizontal resolution

“…High temporal and spatial resolution of the CRyogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA) instrument on board the space shuttle, has shed more light into the detection of both large-scale and smallerscale transport phenomena Riese et al, 1999). During the one week mission in November 1994, CRISTA measured broad, large-scale, tongue-like features of tropical and polar vortex air extrusions in the middle stratosphere.…”

“…Large-scale, tongue-like features or stratospheric streamers were successfully simulated with comprehensive models (Mahlmann and Umscheid, 1987;Boville et al, 1991;Rood et al, 1992;Orsolini et al, 1995;Riese et al, 1999;Kouker et al, 1999;Steil et al, 2003). A first climatology of streamers was derived with the mechanistic model KArlsruher SImulation of the Middle Atmosphere (KASIMA) using analyzed winds for the winters 1990 to 1998 (Langbein et al, 2001).…”