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<br />be examined in the model architecture experiments. These three sensitivity ana- <br />lyses focus on the numerical procedures used in various models. In these sen- <br />sitivity analyses the model architecture will be studied to determine the most <br />efficient and effective analysis method. The cumulus congestus case recommended <br />in section 3.1.1.1.3.A. provides an excellent basis for experimentation. The <br />July 19, 1981 case was selected because it represents a relatively simple, well <br />documented cumulus congestus cloud system. The effects of different numerical <br />procedures should be readily identified using this case. <br /> <br />3.3 Applications of models to increase understanding <br /> <br />Two data sets were recommended for these modeling studies: a convective case <br />and a nimbostratus case. <br /> <br />3.3.1 Convective situation - CCOPE, August 1, 1981 <br /> <br />The well documented convective case from CCOPE on August 1, 1981 is recommended for <br />for study here because four to five clouds occurred within the multiple Doppler <br />network and were intensively studied by several penetrating aircraft. Complete <br />boundary layer information and radar data are available for this case. Three <br />soundings from Miles City are also available along with aircraft soundings. <br />Detailed information is provided in section 3.2.1.1.C. <br /> <br />3.3.2 Nimbostratus situation - PEP, May 20, 1981 <br /> <br />A very interesting, well documented case of nimbostratus occurred during PEP <br />(the WMO Precipitation Enhancement Project) on May 20, 1981. This case was <br />selected because it provides a basis of study of rain producing nimbostratus <br />clouds with cloud physics aircraft information and radar data. The PEP location <br />in the Duero Basin of Spain also provides different geographic influences that <br />were not present in the other cases. Hence this case provides a unique <br />challenge to modelers interested in simulations of nimbostratus and embedded <br />convective bands. <br /> <br />A strong low center to the northwest of the Iberian Peninsula produced strong <br />f1 ow from the southwest over the Duero Basi n with moi sture extendi ng to the 450 <br />mb 1 eve 1 . <br /> <br />A wide rain band (70 - 100 km width and at least 500 km long) and oriented along <br />the 020 - 2000 line lay to the west of the study area at 0700. The band passed <br />through the Duero Basin by approximately 1230 but by that time it had also <br />changed character considerably. Even early on the rain band exhibited a fair <br />amount of structure, and this had progressed to a breakup into more cellular <br />patterns and into an overall decrease in the width of the band (to approximately <br />50 km). Following the passage of the band there was noticeable mid-level <br />cooling and a strong drying at levels above 700 mb. <br /> <br />Total precipitation deposited by the band was an average of 2.5 mm. <br /> <br />The clouds extended to approximately 6 km altitude, near -25 oC. <br /> <br />22. <br />