Balloon-borne measurements, stratosphere

Balloon-Borne Measurements. To illustrate the versatility possible with balloon-borne platforms, the in situ techniques that have recently made important contributions to our understanding of stratospheric reactive trace gases are highlighted. Each technique is based on a fundamentally different physical principle, providing measurements with unique and characteristic spatial and temporal scales. But first the advantages and disadvantages offered (and suffered) in balloon-borne experimentation are reviewed. Some unique facets of balloon behavior that are relevant to a specific experiment are discussed with that experiment. 

It is difficult to envision that balloon-borne techniques will be able to satisfy the demand for more complex and frequent measurements. Therefore it is critical for maximizing the scientific return of balloon-borne flights to include simultaneous measurements of the right mix of species and photolysis rates. In the absence of frequent balloon-borne measurements it is nonetheless very gratifying to have achieved the coalescence of results by independent techniques as a zero-order substitute for intercomparisons. A possible direction for future stratospheric research with a new platform, remotely piloted aircraft, that alleviates some disadvantages of balloon-borne platforms is discussed in the last section of this chapter. 

Aircraft measurements of CIO and BrO are discussed in some detail in the next section. Because the aircraft and balloon-borne techniques are essentially the same, further discussion about these two reactive trace gases is deferred to this later section. A discussion of some of the challenges of measuring atomic trace gases in the stratosphere follows. 

Thermal emission spectroscopy can be used in middle- and far-infrared spectral regions to make stratospheric measurements, and it has been applied to a number of important molecules with balloon-borne and satellite-based detection systems. In this approach, the molecules of interest are promoted to excited states through collisions with other molecules. The return to the ground state is accompanied by the release of a photon with energy equal to the difference between the quantum states of the molecule. Therefore, the emission spectrum is characteristic of a given molecule. Calculation of the concentration can be complicated because the emission may have originated from a number of stratospheric altitudes, and this situation may necessitate the use of computer-based inversion techniques (24-27) to retrieve a concentration profile. 

Waters, J.W., J.C. Hardy, R.F. Jamot, H.M. Pickett and P. Zimmermann (1984) A balloon borne microwave limb sounder for stratospheric measurements. Journal of Quantitative Spectroscopy and Radiative Transfer 32 407-433. 

Further extension of in situ ion composition measurements into the even denser stratospheric layer required greatly improved mass spectro-metric techniques and became feasible only in 1977 using balloon-borne mass spectrometers. The first negative ion composition measurements in... 

Measurements of the concentration of OH radicals in the stratosphere in the altitude range 34—37 km have been made by balloon-borne LIDAR. The first post-sunset concentration levels were reported and comparisons were made with current 1-dimensional models. The effects of reduced absorption cross-sections for O2 in the Herzberg continuum on the composition of the stratosphere have been examined by Brasseur et ai., " following the suggestion that laboratory values for the cross-sections might be overestimated by as much as 30—50%. A model for the circulation of atmospheric CO has been described by Pinto et and which includes photochemical production and... 

The earliest observations of the chemical composition of the middle atmosphere were performed primarily by balloon-borne (stratosphere) and rocket-borne (mesosphere) instrumentation. In recent decades, however, systematic observations have been made by space-borne sensors, and information on chemical processes in the upper troposphere and lower stratosphere has been provided through chemical measurements made from aircraft platforms (e.g., from high-altitude aircraft such as the ER-2, the WB-57 and the Geofysika). Measurements from ground stations, combined with satellite observations, have provided accurate estimates of long-term ozone trends in the different regions of the world. 

Stratospheric nitrogen species have been measured by balloon-borne instruments since about 1970, and more recently from satellites. Most measurements have been performed by chemiluminescence techniques... 

Anderson, J.G., H.J. Grassl, R E. Shetter, and J.J. Margitan, Stratospheric free chlorine measured by balloon-borne in situ resonance fluorescence. J Geophys Res 85, 2869, 1980. 

Heaps, W.S., and J.J. McGee, Balloon borne lidar measurements of stratospheric hydroxyl radical. J Geophys Res 86, 5281, 1983. 

May, R.D., and C.R. Webster, In situ stratospheric measurements of HNO3 and HC1 near 30 km using the balloon-borne laser in situ sensor tunable diode laser... 

Murcray, D.G., A. Goldman, W.J. Williams, F.H. Murcray, F.S. Bonono, G.M. Bradford, G.R. Cole, P.L. Hanst, and M.J. Mohna, Upper hmit for stratospheric CIONO2 from balloon-borne infrared measurements. Geophys Res Lett 4, 227, 1977. 

Oltmans, S.J., H. Vohnel, D.J. Hofmann, K. Rosenlof, and D. Kley, The increase in stratospheric water vapor from balloon-borne frost point hygrometer measurements at Washington, DC and Boulder, Colorado. Geophys Res Lett 27, 3453, 2000. 

Spreng, S., and F. Arnold, Balloon-borne mass spectrometer measurements of HNO3 and HCN in the winter Arctic stratosphere-Evidence for HN03-processing by aerosols. Geophys Res Lett 21, 1251, 1994. 

Fig. 3-12. Vertical distribution of CIO, HC1, and HF in the stratosphere. Left Filled circles give the averages of eight altitude profiles for CIO measured in 1976-1979 by in situ resonance fluorescence the envelope indicates the range of values (Weinstock etai, 1981) two additional high-mixing-ratio profiles are not included. The open circles are from balloon-borne infrared remote measurements by Waters et al. (1981) and Menzies (1983). Center The envelope encompasses observational data for HC1 obtained by balloon-borne infrared measurement techniques (Farmer et al, 1980 Buijs, 1980 Raper et al., 1977 Eyre and Roscoe, 1977 Williams et al., 1976 Zander, 1981) filled circles represent more recent preliminary data cited...

Figure Bl.4.1. Top schematic illustration of the observing geometry used for limb sounding of the Earth s atmosphere. Bottom illustrative stratospheric OH emission spectra acquired by the SAO FIRS-2 far-infiared balloon-borne FTS in autumn 1989. The spectra are from a range of tangent heights h = tangent height in the drawing), increasing toward the bottom, where the data are represented by solid curves nonlinear least-square fits to the measurements, based on a combination of laboratory data, the physical structure of the stratosphere and a detailed radiative transfer calculation, are included as dashed curves. The OH lines are Fj 7/2 ...

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