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<br />Table 2. - Model-predicted cloud development vs. observed <br />convective clouds in 1976 samples at MlS, GlD, and BGS, and <br /> 1977 at GlD and BGS <br /> Model-predicted clouds <br />Observed Site MlS GlD BGS <br />convective clouds Yes No Yes No Yes No <br />1976 <br />Ail - Yes 61 0 64 1 62 0 <br />clouds* - No 3 0 10 0 4 0 <br />1977 <br />Ail - Yes 51 8 63 +7 66 +2 <br />clouds* - No 6 2 1 2 10 0 <br />1977 <br />-sne - Yes 36 7 47 +6 57 +2 <br />clouds** - No 21 3 18 2 19 0 <br /> <br />*All convective clouds within 250 km of the sounding site. <br />**All convective clouds within 75 km of the sounding site. <br />+Raob top below 200 mbar. <br /> <br />d. Cloud-base Height and Cloud-top Verification <br /> <br />Model sensitivity to errors in cloud-base height as small as 500 m has <br />been noted by Sax (1972). A difference between observed cloud-base height <br />and model-determined height as small as 500 m may produce large errors in <br />model-diagnosed cloud development. The effect of the cloud-base height <br /> <br />error on diagnosed cloud development depends on the size of this error and <br /> <br />the nature of the sounding. In order to minimize this error, the mixing <br /> <br />depth used to determine the CCl was set at 5 kPa, or approximately 500 m, <br /> <br />throughout this modeling experiment. <br /> <br />This mixing depth minimized the error in cloud-base height by averaging <br /> <br />local vertical variations in mixing ratio in the lowest 5 kPa. Soundings <br />with anomalously high surface mixing ratios (which would result in low <br /> <br />13 <br />