High Level (Cirriform) Frequency of Occurrence (%) April (1954 - 1997) Night, Ship Observations Only Global Average: 27.6 Zonal Averages 16 zones Lat.N Average 85 58.4 75 44.2 65 31.7 55 29.7 45 28.1 35 28.8 25 24.8 15 25.4 5 35.4 -5 33.9 -15 26.5 -25 24.3 -35 24.6 -45 23.0 -55 23.2 -65 19.5 Grid Box Averages 305 filled boxes Box # Lat.N Lon.E Average 1 85 60 58.4 2 85 180 62.0 3 85 300 53.0 4 75 20 27.7 5 75 60 25.7 7 75 140 48.8 8 75 180 54.2 9 75 220 74.0 12 75 340 23.2 13 65 10 30.4 14 65 30 28.0 15 65 50 34.0 21 65 170 26.3 22 65 190 32.6 29 65 330 34.4 30 65 350 30.7 31 55 10 34.3 32 55 30 38.2 38 55 150 20.6 39 55 170 24.4 40 55 190 30.7 41 55 210 27.7 42 55 230 28.9 46 55 310 33.3 47 55 330 32.0 48 55 350 35.9 49 45 5 38.6 50 45 15 37.8 51 45 25 27.1 52 45 35 18.5 62 45 135 22.2 63 45 145 22.9 64 45 155 24.8 65 45 165 25.7 66 45 175 30.0 67 45 185 33.1 68 45 195 36.0 69 45 205 31.5 70 45 215 28.6 71 45 225 23.4 72 45 235 28.2 77 45 285 31.8 78 45 295 31.2 79 45 305 27.9 80 45 315 30.4 81 45 325 26.0 82 45 335 24.4 83 45 345 26.0 84 45 355 30.4 85 35 5 33.6 86 35 15 32.8 87 35 25 21.6 88 35 35 21.1 97 35 125 27.3 98 35 135 34.1 99 35 145 28.9 100 35 155 25.8 101 35 165 28.5 102 35 175 34.5 103 35 185 38.1 104 35 195 39.1 105 35 205 34.4 106 35 215 25.6 107 35 225 24.1 108 35 235 20.8 109 35 245 21.9 112 35 275 33.5 113 35 285 34.1 114 35 295 24.6 115 35 305 25.6 116 35 315 31.4 117 35 325 27.7 118 35 335 25.1 119 35 345 22.1 120 35 355 29.4 124 25 35 18.7 125 25 45 24.1 126 25 55 26.5 127 25 65 20.8 129 25 85 28.6 132 25 115 22.9 133 25 125 22.7 134 25 135 23.4 135 25 145 24.9 136 25 155 23.4 137 25 165 23.8 138 25 175 25.8 139 25 185 28.2 140 25 195 27.7 141 25 205 25.6 142 25 215 24.2 143 25 225 27.2 144 25 235 22.8 145 25 245 27.7 146 25 255 30.0 147 25 265 40.1 148 25 275 34.3 149 25 285 31.4 150 25 295 21.8 151 25 305 20.8 152 25 315 20.9 153 25 325 22.2 154 25 335 17.3 155 25 345 17.3 160 15 35 15.0 161 15 45 21.1 162 15 55 14.9 163 15 65 13.1 164 15 75 18.8 165 15 85 32.5 166 15 95 35.7 167 15 105 34.3 168 15 115 18.9 169 15 125 21.4 170 15 135 21.2 171 15 145 23.8 172 15 155 22.5 173 15 165 23.9 174 15 175 24.2 175 15 185 33.4 176 15 195 32.8 177 15 205 33.4 178 15 215 31.4 179 15 225 32.1 180 15 235 27.3 181 15 245 23.7 182 15 255 28.6 183 15 265 36.5 184 15 275 38.8 185 15 285 28.0 186 15 295 20.2 187 15 305 18.8 188 15 315 21.4 189 15 325 21.8 190 15 335 19.8 191 15 345 20.9 193 5 5 48.5 197 5 45 26.8 198 5 55 17.3 199 5 65 17.2 200 5 75 32.6 201 5 85 47.4 202 5 95 60.4 203 5 105 42.5 204 5 115 38.5 205 5 125 35.0 206 5 135 38.2 207 5 145 43.6 208 5 155 42.0 209 5 165 35.1 210 5 175 38.6 211 5 185 53.5 212 5 195 34.1 213 5 205 34.7 214 5 215 31.7 215 5 225 26.8 216 5 235 27.8 217 5 245 23.1 218 5 255 29.3 219 5 265 37.5 220 5 275 49.3 221 5 285 46.5 223 5 305 29.6 224 5 315 33.4 225 5 325 30.4 226 5 335 25.2 227 5 345 31.0 228 5 355 41.3 229 -5 5 36.2 230 -5 15 34.0 233 -5 45 28.5 234 -5 55 21.3 235 -5 65 29.2 236 -5 75 37.1 237 -5 85 41.6 238 -5 95 48.8 239 -5 105 54.4 240 -5 115 44.5 241 -5 125 42.3 242 -5 135 45.5 243 -5 145 57.9 244 -5 155 45.7 245 -5 165 46.3 246 -5 175 42.9 247 -5 185 50.6 248 -5 195 33.5 249 -5 205 28.0 250 -5 215 29.9 251 -5 225 20.5 252 -5 235 18.3 253 -5 245 18.3 254 -5 255 17.8 255 -5 265 22.0 256 -5 275 34.3 260 -5 315 61.1 261 -5 325 35.6 262 -5 335 22.4 263 -5 345 25.5 264 -5 355 29.0 265 -15 5 16.6 266 -15 15 20.1 268 -15 35 15.0 269 -15 45 28.0 270 -15 55 25.1 271 -15 65 22.9 272 -15 75 24.9 273 -15 85 33.0 274 -15 95 40.2 275 -15 105 29.4 276 -15 115 23.5 277 -15 125 28.3 278 -15 135 38.2 279 -15 145 33.6 280 -15 155 32.2 281 -15 165 29.4 282 -15 175 40.7 283 -15 185 48.3 284 -15 195 39.9 285 -15 205 26.4 286 -15 215 24.6 287 -15 225 22.5 288 -15 235 17.0 289 -15 245 17.5 290 -15 255 16.9 291 -15 265 20.0 292 -15 275 26.5 293 -15 285 23.5 297 -15 325 29.5 298 -15 335 18.7 299 -15 345 14.0 300 -15 355 18.0 301 -25 5 17.3 302 -25 15 13.1 304 -25 35 18.6 305 -25 45 20.4 306 -25 55 29.8 307 -25 65 25.4 308 -25 75 20.4 309 -25 85 18.9 310 -25 95 23.3 311 -25 105 25.9 312 -25 115 23.2 316 -25 155 19.2 317 -25 165 26.4 318 -25 175 29.2 319 -25 185 32.3 320 -25 195 27.6 321 -25 205 40.1 322 -25 215 34.2 323 -25 225 31.2 324 -25 235 22.4 325 -25 245 19.7 326 -25 255 15.4 328 -25 275 18.0 329 -25 285 23.0 332 -25 315 32.2 333 -25 325 27.6 334 -25 335 22.4 335 -25 345 21.1 336 -25 355 18.6 337 -35 5 29.0 338 -35 15 21.0 339 -35 25 22.8 340 -35 35 19.7 341 -35 45 20.9 342 -35 55 24.2 343 -35 65 28.6 344 -35 75 20.2 345 -35 85 17.9 346 -35 95 27.9 347 -35 105 23.6 348 -35 115 23.1 349 -35 125 27.6 350 -35 135 27.8 351 -35 145 23.7 352 -35 155 22.4 353 -35 165 20.9 354 -35 175 22.9 355 -35 185 27.1 356 -35 195 26.8 357 -35 205 19.1 358 -35 215 31.2 359 -35 225 29.1 364 -35 275 18.1 365 -35 285 20.4 367 -35 305 24.2 368 -35 315 32.3 369 -35 325 25.5 370 -35 335 27.3 371 -35 345 27.3 372 -35 355 27.4 387 -45 145 30.2 388 -45 155 22.0 389 -45 165 16.7 390 -45 175 28.3 391 -45 185 19.8 400 -45 275 15.0 401 -45 285 13.5 402 -45 295 33.0 403 -45 305 29.6 417 -55 170 11.1 423 -55 290 26.4 424 -55 310 33.5 425 -55 330 22.6 442 -65 310 19.5