High Level (Cirriform) Frequency of Occurrence (%) March, April, May (1954 - 1997) Night, Ship Observations Only Global Average: 28.2 Zonal Averages 17 zones Lat.N Average 85 58.3 75 43.4 65 32.5 55 30.9 45 29.5 35 29.7 25 24.8 15 25.6 5 36.3 -5 33.3 -15 26.2 -25 23.6 -35 23.6 -45 23.6 -55 23.1 -65 29.0 -75 31.8 Grid Box Averages 349 filled boxes Box # Lat.N Lon.E Average 1 85 60 56.9 2 85 180 60.0 3 85 300 57.6 4 75 20 30.0 5 75 60 28.5 6 75 100 28.4 7 75 140 48.3 8 75 180 53.1 9 75 220 73.5 11 75 300 38.7 12 75 340 24.3 13 65 10 31.7 14 65 30 31.7 15 65 50 38.6 21 65 170 26.7 22 65 190 29.4 23 65 210 37.9 29 65 330 38.1 30 65 350 30.4 31 55 10 34.6 32 55 30 39.0 38 55 150 25.5 39 55 170 26.0 40 55 190 31.5 41 55 210 30.2 42 55 230 28.8 46 55 310 33.0 47 55 330 31.8 48 55 350 36.4 49 45 5 37.8 50 45 15 37.9 51 45 25 27.5 52 45 35 20.4 53 45 45 22.7 54 45 55 16.6 62 45 135 20.1 63 45 145 23.2 64 45 155 26.7 65 45 165 28.4 66 45 175 30.1 67 45 185 32.6 68 45 195 36.5 69 45 205 33.3 70 45 215 31.3 71 45 225 24.9 72 45 235 27.5 77 45 285 35.3 78 45 295 36.5 79 45 305 31.8 80 45 315 29.9 81 45 325 26.2 82 45 335 27.8 83 45 345 28.2 84 45 355 31.1 85 35 5 32.8 86 35 15 32.3 87 35 25 24.1 88 35 35 20.2 90 35 55 18.6 96 35 115 22.2 97 35 125 27.8 98 35 135 32.5 99 35 145 29.7 100 35 155 29.0 101 35 165 32.1 102 35 175 33.9 103 35 185 37.9 104 35 195 39.4 105 35 205 34.9 106 35 215 27.3 107 35 225 23.9 108 35 235 21.2 109 35 245 24.5 112 35 275 36.7 113 35 285 37.7 114 35 295 30.3 115 35 305 27.0 116 35 315 29.3 117 35 325 27.5 118 35 335 24.3 119 35 345 22.6 120 35 355 28.7 124 25 35 18.5 125 25 45 19.9 126 25 55 20.6 127 25 65 15.9 128 25 75 16.5 129 25 85 29.9 130 25 95 57.5 132 25 115 27.9 133 25 125 25.5 134 25 135 25.7 135 25 145 25.5 136 25 155 21.5 137 25 165 23.1 138 25 175 24.0 139 25 185 26.7 140 25 195 27.6 141 25 205 23.4 142 25 215 24.1 143 25 225 26.5 144 25 235 23.9 145 25 245 25.8 146 25 255 29.6 147 25 265 38.5 148 25 275 34.4 149 25 285 33.8 150 25 295 23.9 151 25 305 22.1 152 25 315 21.4 153 25 325 20.5 154 25 335 17.1 155 25 345 18.8 160 15 35 15.1 161 15 45 19.0 162 15 55 13.6 163 15 65 12.2 164 15 75 19.7 165 15 85 32.1 166 15 95 36.7 167 15 105 38.6 168 15 115 22.8 169 15 125 24.5 170 15 135 24.2 171 15 145 26.0 172 15 155 21.2 173 15 165 25.1 174 15 175 24.6 175 15 185 30.6 176 15 195 30.3 177 15 205 27.9 178 15 215 28.9 179 15 225 32.4 180 15 235 28.6 181 15 245 24.9 182 15 255 30.7 183 15 265 36.9 184 15 275 38.4 185 15 285 30.7 186 15 295 21.4 187 15 305 18.6 188 15 315 20.1 189 15 325 21.6 190 15 335 19.6 191 15 345 21.3 193 5 5 46.7 197 5 45 22.8 198 5 55 20.4 199 5 65 20.6 200 5 75 31.1 201 5 85 46.4 202 5 95 59.6 203 5 105 43.8 204 5 115 40.8 205 5 125 39.9 206 5 135 46.5 207 5 145 44.4 208 5 155 43.3 209 5 165 40.9 210 5 175 43.4 211 5 185 47.7 212 5 195 35.1 213 5 205 35.5 214 5 215 27.4 215 5 225 32.4 216 5 235 31.7 217 5 245 27.6 218 5 255 26.6 219 5 265 37.0 220 5 275 46.9 221 5 285 44.3 223 5 305 28.4 224 5 315 33.3 225 5 325 29.1 226 5 335 24.3 227 5 345 30.9 228 5 355 39.1 229 -5 5 36.1 230 -5 15 33.3 232 -5 35 22.2 233 -5 45 25.8 234 -5 55 24.6 235 -5 65 31.2 236 -5 75 37.7 237 -5 85 45.1 238 -5 95 52.9 239 -5 105 51.8 240 -5 115 45.8 241 -5 125 42.2 242 -5 135 43.4 243 -5 145 53.0 244 -5 155 45.4 245 -5 165 44.7 246 -5 175 42.0 247 -5 185 51.2 248 -5 195 34.5 249 -5 205 29.9 250 -5 215 25.6 251 -5 225 20.5 252 -5 235 17.6 253 -5 245 17.0 254 -5 255 15.3 255 -5 265 21.2 256 -5 275 35.0 257 -5 285 38.0 260 -5 315 52.2 261 -5 325 33.7 262 -5 335 22.1 263 -5 345 20.5 264 -5 355 25.6 265 -15 5 17.2 266 -15 15 23.9 268 -15 35 17.7 269 -15 45 25.2 270 -15 55 25.1 271 -15 65 23.6 272 -15 75 25.1 273 -15 85 30.2 274 -15 95 39.2 275 -15 105 29.1 276 -15 115 23.1 277 -15 125 25.5 278 -15 135 38.8 279 -15 145 31.9 280 -15 155 30.4 281 -15 165 32.5 282 -15 175 36.7 283 -15 185 47.8 284 -15 195 39.8 285 -15 205 32.6 286 -15 215 26.2 287 -15 225 21.0 288 -15 235 19.1 289 -15 245 15.1 290 -15 255 14.7 291 -15 265 17.2 292 -15 275 25.5 293 -15 285 32.7 297 -15 325 29.6 298 -15 335 16.6 299 -15 345 13.0 300 -15 355 17.1 301 -25 5 15.5 302 -25 15 13.5 304 -25 35 17.4 305 -25 45 19.1 306 -25 55 25.3 307 -25 65 19.7 308 -25 75 18.0 309 -25 85 19.7 310 -25 95 23.8 311 -25 105 22.4 312 -25 115 20.3 315 -25 145 18.3 316 -25 155 19.8 317 -25 165 24.4 318 -25 175 31.0 319 -25 185 34.6 320 -25 195 33.3 321 -25 205 35.8 322 -25 215 34.0 323 -25 225 31.3 324 -25 235 23.7 325 -25 245 21.9 326 -25 255 22.2 327 -25 265 18.7 328 -25 275 16.6 329 -25 285 20.1 332 -25 315 32.9 333 -25 325 28.8 334 -25 335 21.8 335 -25 345 18.1 336 -25 355 15.6 337 -35 5 27.5 338 -35 15 19.3 339 -35 25 22.4 340 -35 35 18.8 341 -35 45 19.4 342 -35 55 21.2 343 -35 65 23.4 344 -35 75 23.7 345 -35 85 20.7 346 -35 95 25.6 347 -35 105 21.7 348 -35 115 20.9 349 -35 125 25.0 350 -35 135 23.8 351 -35 145 25.1 352 -35 155 21.8 353 -35 165 20.7 354 -35 175 23.0 355 -35 185 27.7 356 -35 195 28.3 357 -35 205 22.9 358 -35 215 25.8 359 -35 225 29.8 360 -35 235 28.0 363 -35 265 18.7 364 -35 275 20.7 365 -35 285 19.5 367 -35 305 24.7 368 -35 315 26.4 369 -35 325 26.6 370 -35 335 24.0 371 -35 345 25.6 372 -35 355 27.1 373 -45 5 24.6 374 -45 15 29.9 376 -45 35 32.6 377 -45 45 24.2 378 -45 55 27.6 379 -45 65 18.9 380 -45 75 16.9 382 -45 95 32.6 386 -45 135 26.9 387 -45 145 27.1 388 -45 155 21.8 389 -45 165 16.2 390 -45 175 25.4 391 -45 185 23.5 392 -45 195 32.8 393 -45 205 14.2 397 -45 245 32.3 398 -45 255 16.8 399 -45 265 8.6 400 -45 275 13.8 401 -45 285 19.6 402 -45 295 34.7 403 -45 305 23.8 404 -45 315 25.5 405 -45 325 22.4 409 -55 10 25.6 412 -55 70 18.1 413 -55 90 19.2 417 -55 170 14.8 422 -55 270 26.2 423 -55 290 31.3 424 -55 310 34.8 425 -55 330 16.8 427 -65 10 32.2 428 -65 30 31.8 429 -65 50 18.3 430 -65 70 21.9 431 -65 90 32.1 435 -65 170 25.6 441 -65 290 48.0 442 -65 310 21.3 449 -75 180 24.7 453 -75 340 43.1