Tornadoes - Severe Convective Storms and Tornadoes: Observations and Dynamics - page 330

Figure 6.22. Vertical cross section of estimated azimuthal wind speeds (mph) in a tornado
from photogrammetric analysis debris and cloud tags in movies of the Dallas, TX tornado of
April 2, 1957 (from Hoecker, 1960).
tornadoes consisted mostly of serendipitous in situ measurements and photo-
graphs, studies with conventional radar, and photogrammetric analyses of debris
movies. Analysis of movies and photographs and, in the last 30 years or so, of
videos, showing tornadoes and tornadic debris, have been valuable ( Figure 6.22 ),
though debris cannot be seen inside the condensation funnel and only two-
dimensional analyses are possible without a second view from another viewing
angle. Fixed site Doppler radar networks in the 1970s and early 1980s afforded a
look at the wind field in storms with spatial resolution on the scale of 500m-
1 km and temporal resolution 2-5min. ''Storm-chasers'' began to document
storm features in a systematic way beginning in the 1970s and with in situ
instrumentation in the 1980s. In situ measurements are dicult to obtain while
measurements are valid only at a point or several points. Laboratory experiments
in vortex chambers were carried out in the 1970s and 1980s at Purdue University