High Level (Cirriform) Frequency of Occurrence (%) March (1954 - 1997) Night, Ship Observations Only Global Average: 27.4 Zonal Averages 17 zones Lat.N Average 85 61.4 75 43.4 65 25.6 55 23.8 45 23.7 35 25.6 25 21.5 15 19.9 5 32.1 -5 35.8 -15 30.0 -25 25.6 -35 23.1 -45 25.2 -55 25.8 -65 30.2 -75 31.6 Grid Box Averages 315 filled boxes Box # Lat.N Lon.E Average 1 85 60 63.1 2 85 180 62.0 3 85 300 58.0 4 75 20 24.7 5 75 60 20.0 8 75 180 58.8 9 75 220 81.0 12 75 340 15.7 13 65 10 26.0 14 65 30 33.0 21 65 170 16.1 22 65 190 19.1 29 65 330 37.3 30 65 350 20.6 31 55 10 28.5 32 55 30 28.0 38 55 150 20.7 39 55 170 18.9 40 55 190 24.9 41 55 210 18.9 42 55 230 25.2 46 55 310 23.8 47 55 330 28.4 48 55 350 27.6 49 45 5 33.4 50 45 15 30.7 51 45 25 23.2 52 45 35 15.6 62 45 135 13.8 63 45 145 19.1 64 45 155 18.6 65 45 165 21.4 66 45 175 23.8 67 45 185 28.5 68 45 195 28.3 69 45 205 25.6 70 45 215 26.1 71 45 225 24.4 72 45 235 30.2 77 45 285 27.2 78 45 295 21.2 79 45 305 23.3 80 45 315 24.8 81 45 325 23.2 82 45 335 24.3 83 45 345 21.0 84 45 355 23.7 85 35 5 29.9 86 35 15 27.2 87 35 25 19.9 88 35 35 19.9 97 35 125 22.6 98 35 135 23.1 99 35 145 21.4 100 35 155 20.5 101 35 165 23.8 102 35 175 26.9 103 35 185 36.0 104 35 195 30.8 105 35 205 30.5 106 35 215 27.1 107 35 225 23.7 108 35 235 23.7 109 35 245 26.4 112 35 275 35.0 113 35 285 32.5 114 35 295 22.6 115 35 305 24.7 116 35 315 26.7 117 35 325 28.8 118 35 335 23.3 119 35 345 20.0 120 35 355 23.8 124 25 35 18.0 125 25 45 16.6 126 25 55 22.8 127 25 65 16.6 129 25 85 18.4 132 25 115 20.3 133 25 125 16.7 134 25 135 16.9 135 25 145 17.8 136 25 155 15.2 137 25 165 16.4 138 25 175 19.2 139 25 185 22.6 140 25 195 22.1 141 25 205 22.6 142 25 215 26.1 143 25 225 27.0 144 25 235 27.8 145 25 245 26.7 146 25 255 30.3 147 25 265 34.7 148 25 275 31.9 149 25 285 26.9 150 25 295 17.6 151 25 305 17.8 152 25 315 20.0 153 25 325 20.7 154 25 335 16.6 155 25 345 17.6 160 15 35 15.1 161 15 45 13.1 162 15 55 9.0 163 15 65 7.5 164 15 75 13.2 165 15 85 21.2 166 15 95 28.7 167 15 105 25.0 168 15 115 17.1 169 15 125 17.5 170 15 135 20.3 171 15 145 25.1 172 15 155 17.5 173 15 165 19.5 174 15 175 16.9 175 15 185 20.0 176 15 195 15.8 177 15 205 21.1 178 15 215 26.5 179 15 225 29.6 180 15 235 29.2 181 15 245 24.3 182 15 255 22.2 183 15 265 23.5 184 15 275 27.5 185 15 285 19.4 186 15 295 13.8 187 15 305 13.4 188 15 315 18.1 189 15 325 21.6 190 15 335 17.9 191 15 345 18.9 193 5 5 41.6 197 5 45 11.6 198 5 55 12.2 199 5 65 12.2 200 5 75 19.6 201 5 85 37.8 202 5 95 54.5 203 5 105 40.3 204 5 115 37.1 205 5 125 37.6 206 5 135 47.0 207 5 145 43.3 208 5 155 40.4 209 5 165 39.5 210 5 175 47.9 211 5 185 37.7 212 5 195 35.4 213 5 205 32.3 214 5 215 23.3 215 5 225 31.6 216 5 235 31.1 217 5 245 24.1 218 5 255 17.9 219 5 265 29.6 220 5 275 38.8 221 5 285 36.8 223 5 305 23.7 224 5 315 30.6 225 5 325 25.5 226 5 335 20.9 227 5 345 27.9 228 5 355 34.7 229 -5 5 40.0 230 -5 15 45.6 233 -5 45 25.9 234 -5 55 26.6 235 -5 65 28.3 236 -5 75 37.3 237 -5 85 42.7 238 -5 95 54.8 239 -5 105 55.5 240 -5 115 55.2 241 -5 125 48.7 242 -5 135 55.2 243 -5 145 51.9 244 -5 155 47.3 245 -5 165 48.1 246 -5 175 44.5 247 -5 185 54.8 248 -5 195 42.0 249 -5 205 33.2 250 -5 215 21.8 251 -5 225 29.0 252 -5 235 22.2 253 -5 245 19.9 254 -5 255 15.4 255 -5 265 24.0 256 -5 275 40.0 257 -5 285 48.2 260 -5 315 50.9 261 -5 325 37.9 262 -5 335 25.7 263 -5 345 17.9 264 -5 355 22.3 265 -15 5 20.0 266 -15 15 32.5 268 -15 35 28.7 269 -15 45 35.0 270 -15 55 32.7 271 -15 65 29.5 272 -15 75 27.8 273 -15 85 31.5 274 -15 95 40.7 275 -15 105 30.9 276 -15 115 31.8 277 -15 125 36.7 278 -15 135 47.9 279 -15 145 35.4 280 -15 155 32.1 281 -15 165 38.4 282 -15 175 43.1 283 -15 185 54.5 284 -15 195 47.4 285 -15 205 40.6 286 -15 215 32.5 287 -15 225 24.9 288 -15 235 25.5 289 -15 245 19.2 290 -15 255 14.3 291 -15 265 14.8 292 -15 275 25.1 293 -15 285 41.0 297 -15 325 32.0 298 -15 335 14.5 299 -15 345 10.8 300 -15 355 15.6 301 -25 5 13.5 302 -25 15 13.4 304 -25 35 19.3 305 -25 45 21.7 306 -25 55 28.6 307 -25 65 19.7 308 -25 75 20.1 309 -25 85 25.8 310 -25 95 27.6 311 -25 105 22.4 312 -25 115 18.5 316 -25 155 20.7 317 -25 165 24.7 318 -25 175 32.7 319 -25 185 41.5 320 -25 195 43.3 321 -25 205 37.5 322 -25 215 37.2 323 -25 225 34.4 324 -25 235 26.3 325 -25 245 22.5 328 -25 275 13.4 329 -25 285 18.2 332 -25 315 34.2 333 -25 325 34.2 334 -25 335 19.8 335 -25 345 18.6 336 -25 355 14.5 337 -35 5 26.6 338 -35 15 15.7 339 -35 25 16.8 340 -35 35 17.2 341 -35 45 17.5 342 -35 55 20.4 343 -35 65 20.2 344 -35 75 24.0 345 -35 85 24.6 346 -35 95 27.6 347 -35 105 20.9 348 -35 115 17.9 349 -35 125 24.8 350 -35 135 19.5 351 -35 145 25.2 352 -35 155 18.7 353 -35 165 17.4 354 -35 175 24.5 355 -35 185 31.7 356 -35 195 32.5 357 -35 205 20.7 358 -35 215 25.6 359 -35 225 38.2 363 -35 265 15.8 364 -35 275 20.1 365 -35 285 17.1 367 -35 305 22.6 368 -35 315 20.0 369 -35 325 23.3 370 -35 335 29.4 371 -35 345 28.2 372 -35 355 29.1 387 -45 145 26.5 388 -45 155 25.1 389 -45 165 17.6 390 -45 175 25.7 391 -45 185 26.1 392 -45 195 39.3 400 -45 275 14.9 401 -45 285 24.3 402 -45 295 32.0 403 -45 305 22.9 412 -55 70 20.3 417 -55 170 17.5 423 -55 290 35.3 424 -55 310 36.7 425 -55 330 21.1 427 -65 10 34.2 428 -65 30 33.3 429 -65 50 18.7 430 -65 70 22.3 431 -65 90 35.1 435 -65 170 26.2 441 -65 290 49.7 442 -65 310 21.5 449 -75 180 24.4 453 -75 340 42.9