Radar echo top height is one of the important factors to evaluate the activities of convective clouds. In order to fully understand the characteristics of the echo height, it is necessary previously to know the vertical intensity distribution of the target which is not distorted by the effect of the beamwidth, since the echo height is based on the measurement of the edge of the radar echo region.
   For this purpose, the vertical intensity distributions of various precipitative clouds were obtained by means of a vertically pointing X-band radar. And the characteristics of the echo top height are simulated taking the radar sensitivity, the beamwidth and the side lobe effect into account for 5-cm weather radar.
   It was found that the range dependence of the radar echo height can be divided into three regions for convective clouds having the vertical intensity distributions well developed as the thunder shower.
   The first region is within a radius of about 50 km, where the echo height corresponds to the cloud height and the reflected signal is caused by the weaker intensity area around the cloud top.
   In the radar range beyond about 50 km, the echo top increases with the radar distance based on the effect of the beamwidth which is emphasized by the intensive reflectivity area (cloud turret) below about 1 km of the cloud top. This is the second region.
   The echo top decreases rapidly as the radar distance increases further, because the cloud turret sinks below the radio horizon. This is the third region, which starts at 200∼300 km depending on the magnitude of the cloud severities.
   In some clouds of less severity, the second region cannot be clearly discriminated, and the third region starts at a range as short as 150 km.
   The range suitable for echo top measurement is limited in the lst and 2nd regions. Therefore, in the second region, it is necessary to make a correction of the effect of the beamwidth to reproduce the cloud height. It was found that the radar derived cloud height measurements had errors ranging from -0.3 to +0.7 km for rain shower and thunder shower, after the correction was made, and that without correction the maximum error reaches +3.4 km.
   Comparisons were made of echo top heights observed by two radars. It was found that the main factors contributing to the relative errors between the two radars are the time difference of observation, the difference of the minimum signal level and misreading of the elevation angle indicator. It was found that the error was kept within ±0.35° in taking care these factors.
   Comparisons were made of the cloud heights observed by radar and airplane. It was found that the measurement error of the radar derived cloud height is within 1.5 km by comparing it with the visible cloud height obtained by photogrammetry from airplane. The accuracy for distant echoes is further improved if we use the values of the modified refractive indexes suitable for the respective region and season.

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   In this note, we investigate analytically how the bifurcation diagram of Pedlosky (1981)'s barotropic model is modified by introducing meridional structure into the forced basic zonal flow. If the basic zonal flow deviates from a uniform one to some degree, then two Hopf bifurcation points emerge (i.e., periodic solutions are generated) on the steady solution curve corresponding to blocking flows and steady solutions between them lose their stability. Moreover, the diagram may be qualitatively altered as the basic zonal flow further deviates from a uniform one.

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