The purpose of the Balloon Ozone Intercomparison Campaign (BOIC) was to assess the accuracy and precision of various ozone measurement systems under development and those flown operationally. Ozone observations made by in situ UV absorption photometers from four groups, two solar UV absorption photometers, three varieties of electrochemical sondes, and a mass spectrometer were intercompared in three flight missions, each involving several balloon flights. Concurrent Umkehr and satellite observations were also intercompared. The National Bureau of Standards (NBS)provided a reference ozone source for intercomparing several of the in situ instruments at ground pressure. Harvard University and the University of Minnesota each developed a calibration facility after the BOIC flights which enabled a comparison of the flight in situ photometers under simulated stratospheric pressure and ozone concentrations. The following is a summary of results. The standard deviation of the sensitivities among 18 instruments tested about the NBS reference was 11%. These differences appear in flight at the lower altitudes, but they change at higher altitudes, indicating height dependent errors, particularly for the electrochemical sondes. Comparisons at the two laboratory facilities simulating stratospheric conditions indicated differences of about 2% at 3 mbar for two of the flight in situ photometers. Ozone values among four in situ UV photometers flown together had a standard deviation about the mean value of about ±3% from the tropopause to about 41 km. This is very close to the expected accuracy of these measurements and therefore is an excellent result. However, during float at 42 km the difference nearly doubled. Experiments performed during flight demonstrated that even near 40 km, wall losses in three UV photometers were less than 5%, which is consistent with the laboratory simulations. A comparison of a complement of electrochemical sondes yielded results that agreed with the mean of the in situ UV photometers to within 0–20%, depending on the sonde type and altitude. The electrochemical sondes gave systematically lower ozone values at pressures lower than 10 mbar (above 31 km). A comparison between an in situ UV and a solar absorption photometer indicated a 10% difference in the stratosphere, where the in situ measurement was lower. Comparisons of electrochemical sondes and Umkehr and Solar backscattered ultraviolet (SBUV) satellite observations showed agreement to within their error bars (stated to be about 5–10%). In two comparisons between in situ UV photometers and satellite measurements, a consistent difference occurred between 10 and 3 mbar (28–40 km), implying a possible bias between the measurement types. Intercomparisons among all the instruments in the troposphere showed 20–30% differences from the mean. A comparison of pressure measurements performed by several experimenters resulted in differences as high as ±15% from the average measurement.

During The European Correlative Experiment Program for SAGE II data validation, described by Lenoble (this issue), ozonesonde profiles from several stations were compared with SAGE II profiles. The agreement is always within 10% or better between 20 and 30 km, and it remains acceptable down to 12 km, especially when the two profile locations are close. For higher altitudes, microwave profiles were used, and they showed an agreement between 5 and 10% with SAGE II data between 35 and 60 km.

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For efficient application of optimum operating procedures to flood protection reservoirs it is essential to forecast on line, i.e., during a storm, the relevant inflow hydrographs. This can be achieved with the aid of a weather radar linked to a computer in which the optimum reservoir operating program is stored as well as a program of a hydrologic rainfall-runoff model producing the reservoir inflow hydrographs from radar-measured rainfall data. These inflow hydrographs may be evaluated on the computer during each storm event and can be updated every 5 min, if necessary. The accuracy of these computed hydrographs was tested against the recordings of two river gages installed in catchments close to a weather radar at Hohenpeissenberg in Upper Bavaria. By using a linearly distributed mathematical catchment model it was shown that for the two rivers the synthetic hydrographs computed from radar-measured rainfall were more accurate than those obtained from continuous measurements of the official point rain gage network of the German Weather Service (one recording gage in 500 km 2) and that they were of the same accuracy as those obtained from a special very dense rain gage network (one recording gage in 25 km 2) set up for research purposes in the same area. iNTRODUCTION The task of measuring rainfall distributions in time and space quantitatively by radar is usually carried out in accordance with meteorological standards of required accuracy. For hydrologic purposes, however, rainfall data represent only one input field. Other inputs include infiltration rates, evapotranspiration, base flow, and parameters describing the structure of a chosen hydrologic model. Thus the accuracy requirements are different.Besides the question of accuracy, which will be discussed in the ,section on results, radar has three major advantages compared to a conventional recording rain gage network' 1. The total information of rainfall distribution in time and space, i.e., over a catchment area, is collected and processed at one single point, where in addition, runoff hydrographs can be forecast on line. 2. it is much easier to operate a radar than a network of many recording rain gages connected to a central processing unit. [1973] indicate that costs for radar rainfall measurements are not higher than those for a dense network of conventional recording rain gages. Economic investigations carried out by the British Water Resources BoardThrough the use of radar rainfall measurements as input for a mathematical rainfall-runoff model it is possible to compute flood hydrographs during a storm. if these computations are carried out on a computer connected to the radar unit, an online forecast of reservoir inflow hydrographs becomes feasible. These hydrographs can be used to develop an optimum operating procedure for flood protection reservoirs if an appropriate computer program is stored in the machine in addition to the rainfall-runoff program. This rapid procedure of rainfall measurement and hydrograph computation, which may be Copyrigh...

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