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. . . The raw1nsonde observations used to initialize the model simulations were selected from days with either (1) mesoscale organized convection, which indicates the eKlstence of a mesoscale- triggering mechanism that may result 1n lifting. or (2) isolated or random convective clouds or clear skies. GOES-TAP (Corbel" 19761 satellite imagery was used to visually classify each day from May to August of 1916 400 1977 at the HIPLEX field site (see Matthews and Koshto, 19771. Then all model results were stratified accordfng to the existence of mesoscale trig- gering or random convection to determine if there were significant thermodynamic differences between these conditions. 2 hours of lifting; however, no clouds ~fre diagnosed tn the no-lifting and 10-cm s lifting simulations. The simulat10n with 20-00 S'l lifting showed that, although the strong subsidence inversion was sharply eroded by 4 hours of lifting (see figure 5.1). no s1gniffcant clouds could develop In this suppressed environment. On August 24, 1977, strong development In the fonn of a mesoscale line was observed in satellite imagery at 2030 G.m.t., 150 km west of GLO I figure 4.2). This 1 fne later moved through western Kansas producing heavy precipitation. In this case of observed mesoscale triggering, the model sl~ulatlons indicated that lifting would have s1gnlf- fcant effects on cloud growth. The total depth of seven clouds supported in this case was 76 km. and significant total precipita- tion (183 1MI1 was produced in the model simulation. Heavy rain was observed throughout western Kansas wfth 80 mm at GLD. Two examples of significant differences between the mesoscale-triggered cases and random con- vection were examined to illustrate important effects of lifting on the release of avaflable potential instability. 3. RESULTS The model was a useful objective tool for examining the effect of lifting on the release of available potential instability. However, the model could not detect many significant differences in the thenllodynamlcs of days having mesoscale triggering and those with random or fsolated convection. This result suggested that the three-dimensional atmos- pheric dynamics may be the controlling factor which deterMInes the ~pe of random or organized mesoscale convection. The soundfng on August 24 is significantly less stable than that on June 30. and the moisture content is much higher (see figure 5.3). In this case, seven large cumulonimbus (Cb) clo~ds were diagnosed by the model under conditions of 20-c. S.I lifting Isee figure 5.4). Careful examina- tion of figure 5.3 shows that lifting causes complicated changes in environmental telllper- ature and MOisture and that clOud-environment Interaction further complicates the resulting thermodynamic structure. Strong coo11ng In excess of 3. to 5 .C occurred in regions where very stable lapse rates existed. as shown in figure 5.1, between 70 and 50 kPa. Upward moisture advection due to lifting also produces large changes in environment relative humidity, which permits stronger cloud growth due to less entrainment erosion of cloud buoyancy. The shape and magnitude of the lifting profiles are discussed In 9reater detail in Lease and Matthews (1978). 3.1 Effect of lifting on Available Potential Instabilfty It was quite clear that latent instability very often exists on the High Plains at Goodland and Big Spring. On both mesoscale~ triggered days and isolated random convection days, the atmosphere was very sensitive to lfft1ng. As the lifting amplitude increased, considerably more clouds and deeper clouds were supported in the IIlOdel, as Shown in figures 2 and 3. In most cases, the MOdel was unable to initiate convection without lifting, as seen by the few clouds gel'lerated in the nO-11ft cases. In nearly all cases. the 20-em s' 11ft produced significant convective development. Differences between the sample of cases having observed mesoscale triggering and that with little or no observed mesoscale triggering are discussed later in section 3.2. MESOCU simulates the effect of mass contt- nulty on cloud-environment mass balance by producing local substdence. Subsidence wa~s the environment, thus compensating for the cooling effects of mesoscale lifting. These complex interactions require an objective numerical model to fully under- stand their net effect on convective cloud development. 3.2 Dlscrlmtnat10n Between Mesoscale- triggered and Isolated Convection Although MESOCU was able to determine the effect of 11 ftlng on the release of available potential instabf11ty, 1t was less successful at distinguishjng between thermodynamic Two cases ~ich clearly show differences in the effect of llftjng occurred on June 30. 1917. and August 24, 1917, at Goodland, Kansas (GlD). Clear skies in a ridge behind a cold front prevailed at GLD on June 30, as seen in figure 4.1. The IIOdel simulations were unable to produce any significant 2 ., convection on this day even, with O-cm s lifting. Two high-based cumulus congestus clouds only 3 km deep were produced after