High Level (Cirriform) Frequency of Occurrence (%) May (1954 - 1997) Night, Ship Observations Only Global Average: 28.0 Zonal Averages 15 zones Lat.N Average 85 52.4 75 37.7 65 36.6 55 35.9 45 34.4 35 33.3 25 27.6 15 31.3 5 41.9 -5 30.5 -15 21.4 -25 20.9 -35 23.1 -45 18.1 -55 19.5 Grid Box Averages 305 filled boxes Box # Lat.N Lon.E Average 1 85 60 43.6 2 85 180 52.8 3 85 300 64.1 4 75 20 33.7 5 75 60 34.6 8 75 180 43.5 11 75 300 43.6 12 75 340 34.6 13 65 10 35.2 14 65 30 34.0 15 65 50 43.5 20 65 150 47.5 21 65 170 30.7 22 65 190 33.9 23 65 210 40.4 28 65 310 41.0 29 65 330 40.5 30 65 350 33.5 31 55 10 38.3 32 55 30 41.5 38 55 150 32.9 39 55 170 33.4 40 55 190 38.6 41 55 210 36.6 42 55 230 30.7 46 55 310 37.5 47 55 330 32.9 48 55 350 41.0 49 45 5 41.1 50 45 15 42.6 51 45 25 29.4 52 45 35 23.8 62 45 135 29.6 63 45 145 27.6 64 45 155 32.7 65 45 165 35.6 66 45 175 37.5 67 45 185 37.3 68 45 195 42.0 69 45 205 37.8 70 45 215 36.8 71 45 225 27.3 72 45 235 25.6 77 45 285 41.5 78 45 295 44.2 79 45 305 39.1 80 45 315 34.4 81 45 325 28.0 82 45 335 31.4 83 45 345 33.6 84 45 355 36.0 85 35 5 34.6 86 35 15 34.5 87 35 25 27.5 88 35 35 19.5 97 35 125 34.6 98 35 135 41.6 99 35 145 38.9 100 35 155 36.8 101 35 165 42.0 102 35 175 39.9 103 35 185 40.5 104 35 195 44.9 105 35 205 38.6 106 35 215 29.2 107 35 225 23.8 108 35 235 18.7 109 35 245 25.0 112 35 275 41.8 113 35 285 42.9 114 35 295 36.0 115 35 305 30.5 116 35 315 30.1 117 35 325 25.9 118 35 335 24.5 119 35 345 24.3 120 35 355 31.4 124 25 35 18.8 125 25 45 20.3 126 25 55 12.7 127 25 65 10.1 129 25 85 46.9 132 25 115 36.5 133 25 125 34.5 134 25 135 36.7 135 25 145 36.0 136 25 155 27.8 137 25 165 27.5 138 25 175 28.0 139 25 185 30.3 140 25 195 31.2 141 25 205 22.3 142 25 215 21.6 143 25 225 24.9 144 25 235 19.9 145 25 245 22.5 146 25 255 29.1 147 25 265 40.0 148 25 275 36.9 149 25 285 39.7 150 25 295 32.3 151 25 305 28.5 152 25 315 23.7 153 25 325 18.4 154 25 335 17.6 155 25 345 20.3 160 15 35 15.4 161 15 45 23.4 162 15 55 17.2 163 15 65 16.3 164 15 75 27.8 165 15 85 42.1 166 15 95 51.1 167 15 105 53.0 168 15 115 32.5 169 15 125 33.1 170 15 135 30.8 171 15 145 29.2 172 15 155 24.3 173 15 165 29.2 174 15 175 31.9 175 15 185 39.5 176 15 195 40.6 177 15 205 30.5 178 15 215 29.2 179 15 225 37.3 180 15 235 29.1 181 15 245 27.2 182 15 255 36.5 183 15 265 49.4 184 15 275 49.6 185 15 285 41.6 186 15 295 31.9 187 15 305 24.1 188 15 315 21.1 189 15 325 21.6 190 15 335 21.4 191 15 345 24.0 193 5 5 50.1 197 5 45 32.7 198 5 55 31.4 199 5 65 34.0 200 5 75 40.9 201 5 85 54.1 202 5 95 65.4 203 5 105 49.3 204 5 115 47.6 205 5 125 47.3 206 5 135 54.4 207 5 145 46.4 208 5 155 48.2 209 5 165 47.1 210 5 175 44.3 211 5 185 53.5 212 5 195 35.6 213 5 205 39.7 214 5 215 26.6 215 5 225 38.6 216 5 235 36.1 217 5 245 40.5 218 5 255 32.7 219 5 265 45.5 220 5 275 55.6 221 5 285 52.0 223 5 305 32.5 224 5 315 36.3 225 5 325 31.2 226 5 335 27.6 227 5 345 34.1 228 5 355 40.7 229 -5 5 31.4 230 -5 15 18.6 233 -5 45 22.7 234 -5 55 26.4 235 -5 65 35.9 236 -5 75 38.9 237 -5 85 51.7 238 -5 95 55.5 239 -5 105 43.3 240 -5 115 39.2 241 -5 125 35.8 242 -5 135 30.0 243 -5 145 48.1 244 -5 155 43.4 245 -5 165 40.8 246 -5 175 38.8 247 -5 185 48.1 248 -5 195 27.5 249 -5 205 28.9 250 -5 215 25.9 251 -5 225 13.6 252 -5 235 12.4 253 -5 245 12.9 254 -5 255 12.7 255 -5 265 17.8 256 -5 275 29.4 260 -5 315 45.2 261 -5 325 27.0 262 -5 335 18.7 263 -5 345 18.4 264 -5 355 25.3 265 -15 5 15.6 266 -15 15 8.4 268 -15 35 9.3 269 -15 45 13.2 270 -15 55 16.3 271 -15 65 16.5 272 -15 75 22.6 273 -15 85 24.1 274 -15 95 36.3 275 -15 105 25.9 276 -15 115 14.7 277 -15 125 16.2 278 -15 135 31.6 279 -15 145 26.7 280 -15 155 26.8 281 -15 165 29.9 282 -15 175 25.7 283 -15 185 40.2 284 -15 195 28.6 285 -15 205 30.7 286 -15 215 22.0 287 -15 225 14.9 288 -15 235 14.5 289 -15 245 8.2 290 -15 255 12.9 291 -15 265 16.7 292 -15 275 24.5 293 -15 285 20.8 297 -15 325 27.2 298 -15 335 16.1 299 -15 345 13.8 300 -15 355 17.7 301 -25 5 15.6 302 -25 15 14.2 304 -25 35 14.7 305 -25 45 15.6 306 -25 55 18.0 307 -25 65 14.5 308 -25 75 13.5 309 -25 85 10.5 310 -25 95 20.4 311 -25 105 18.9 312 -25 115 19.4 316 -25 155 19.5 317 -25 165 22.1 318 -25 175 30.2 319 -25 185 29.7 320 -25 195 24.7 321 -25 205 30.7 322 -25 215 30.5 323 -25 225 27.8 324 -25 235 22.3 325 -25 245 23.8 328 -25 275 18.5 329 -25 285 19.1 332 -25 315 32.4 333 -25 325 24.3 334 -25 335 23.4 335 -25 345 14.8 336 -25 355 13.3 337 -35 5 26.8 338 -35 15 22.6 339 -35 25 26.4 340 -35 35 19.4 341 -35 45 19.9 342 -35 55 19.1 343 -35 65 20.6 344 -35 75 27.2 345 -35 85 16.5 346 -35 95 20.8 347 -35 105 21.0 348 -35 115 22.1 349 -35 125 22.9 350 -35 135 24.0 351 -35 145 26.3 352 -35 155 24.4 353 -35 165 23.7 354 -35 175 19.8 355 -35 185 23.9 356 -35 195 23.4 357 -35 205 28.1 358 -35 215 19.8 364 -35 275 26.9 365 -35 285 26.9 367 -35 305 27.8 368 -35 315 27.4 369 -35 325 30.7 370 -35 335 17.5 371 -35 345 20.1 372 -35 355 22.6 387 -45 145 24.9 388 -45 155 17.3 389 -45 165 12.1 390 -45 175 21.1 391 -45 185 23.5 399 -45 265 4.9 400 -45 275 11.4 401 -45 285 12.8 402 -45 295 42.7 403 -45 305 19.8 417 -55 170 9.1 423 -55 290 27.6 424 -55 310 33.0 425 -55 330 10.0