High Level (Cirriform) Amount-When-Present (%) March, April, May (1954 - 1997) Night, Ship Observations Only Global Average: 36.4 Zonal Averages 16 zones Lat.N Average 85 35.5 75 48.1 65 34.7 55 38.6 45 38.5 35 39.2 25 34.5 15 36.8 5 36.9 -5 34.9 -15 33.5 -25 34.8 -35 35.3 -45 37.6 -55 38.2 -65 35.5 Grid Box Averages 286 filled boxes Box # Lat.N Lon.E Average 1 85 60 33.1 2 85 180 42.1 3 85 300 28.7 4 75 20 34.8 5 75 60 35.9 7 75 140 43.4 8 75 180 53.6 9 75 220 59.2 12 75 340 28.7 13 65 10 31.4 14 65 30 32.6 15 65 50 31.5 21 65 170 35.6 22 65 190 35.9 23 65 210 33.2 29 65 330 35.2 30 65 350 36.5 31 55 10 34.9 32 55 30 35.6 38 55 150 35.5 39 55 170 38.0 40 55 190 38.9 41 55 210 36.7 42 55 230 35.2 46 55 310 44.4 47 55 330 43.9 48 55 350 33.4 49 45 5 36.8 50 45 15 39.2 51 45 25 41.3 52 45 35 38.0 62 45 135 40.4 63 45 145 38.3 64 45 155 37.2 65 45 165 36.7 66 45 175 39.4 67 45 185 41.4 68 45 195 40.4 69 45 205 38.3 70 45 215 35.2 71 45 225 41.0 72 45 235 35.6 77 45 285 41.5 78 45 295 38.0 79 45 305 38.5 80 45 315 42.9 81 45 325 38.9 82 45 335 38.5 83 45 345 35.5 84 45 355 34.0 85 35 5 35.7 86 35 15 36.3 87 35 25 38.1 88 35 35 38.5 97 35 125 46.9 98 35 135 46.9 99 35 145 41.4 100 35 155 42.0 101 35 165 46.0 102 35 175 36.6 103 35 185 37.1 104 35 195 35.5 105 35 205 37.9 106 35 215 38.5 107 35 225 42.3 108 35 235 37.8 109 35 245 40.2 112 35 275 38.0 113 35 285 39.4 114 35 295 37.8 115 35 305 38.8 116 35 315 42.8 117 35 325 37.9 118 35 335 35.3 119 35 345 34.8 120 35 355 33.4 124 25 35 37.2 125 25 45 45.6 126 25 55 40.9 127 25 65 36.3 132 25 115 38.9 133 25 125 37.0 134 25 135 30.9 135 25 145 30.0 136 25 155 30.8 137 25 165 32.4 138 25 175 32.2 139 25 185 32.6 140 25 195 34.8 141 25 205 39.3 142 25 215 38.5 143 25 225 41.7 144 25 235 38.2 145 25 245 37.5 146 25 255 35.5 147 25 265 33.6 148 25 275 30.1 149 25 285 32.4 150 25 295 31.9 151 25 305 32.9 152 25 315 33.3 153 25 325 32.7 154 25 335 38.2 155 25 345 36.0 160 15 35 37.3 161 15 45 35.6 162 15 55 33.4 163 15 65 32.7 164 15 75 36.5 165 15 85 32.5 166 15 95 36.3 167 15 105 42.5 168 15 115 30.7 169 15 125 29.8 170 15 135 27.3 171 15 145 29.6 172 15 155 32.5 173 15 165 51.2 174 15 175 38.9 175 15 185 36.2 176 15 195 39.3 177 15 205 38.2 178 15 215 31.8 179 15 225 50.5 180 15 235 39.6 181 15 245 37.4 182 15 255 35.7 183 15 265 38.9 184 15 275 33.2 185 15 285 35.0 186 15 295 31.3 187 15 305 32.9 188 15 315 36.2 189 15 325 39.0 190 15 335 47.6 191 15 345 46.5 193 5 5 43.8 197 5 45 32.2 198 5 55 32.7 199 5 65 37.5 200 5 75 37.2 201 5 85 34.2 202 5 95 39.2 203 5 105 36.0 204 5 115 36.2 205 5 125 30.4 206 5 135 38.7 207 5 145 36.7 208 5 155 39.6 209 5 165 34.4 210 5 175 31.8 211 5 185 32.0 212 5 195 36.9 213 5 205 34.2 215 5 225 39.6 218 5 255 31.3 219 5 265 33.4 220 5 275 35.5 221 5 285 42.0 223 5 305 36.5 224 5 315 40.6 225 5 325 42.0 226 5 335 47.9 227 5 345 46.8 228 5 355 40.0 229 -5 5 37.1 230 -5 15 32.5 233 -5 45 31.7 234 -5 55 31.1 235 -5 65 35.7 236 -5 75 35.7 237 -5 85 33.0 238 -5 95 36.5 239 -5 105 44.5 240 -5 115 39.7 241 -5 125 34.6 242 -5 135 41.5 243 -5 145 42.4 244 -5 155 40.8 245 -5 165 36.3 246 -5 175 34.3 247 -5 185 31.6 248 -5 195 37.2 249 -5 205 31.1 251 -5 225 30.5 252 -5 235 29.9 253 -5 245 20.6 254 -5 255 26.4 255 -5 265 28.1 256 -5 275 36.1 257 -5 285 37.6 260 -5 315 34.7 261 -5 325 32.5 262 -5 335 32.4 263 -5 345 33.4 264 -5 355 33.2 265 -15 5 30.4 266 -15 15 39.4 268 -15 35 31.9 269 -15 45 31.1 270 -15 55 34.0 271 -15 65 35.0 272 -15 75 39.1 273 -15 85 33.3 274 -15 95 33.2 275 -15 105 29.2 276 -15 115 33.9 277 -15 125 36.9 278 -15 135 40.3 279 -15 145 39.5 280 -15 155 37.6 281 -15 165 43.3 282 -15 175 30.6 283 -15 185 33.4 284 -15 195 37.1 285 -15 205 31.6 286 -15 215 26.3 287 -15 225 24.6 288 -15 235 31.7 289 -15 245 30.2 290 -15 255 30.4 292 -15 275 34.4 293 -15 285 38.4 297 -15 325 30.4 298 -15 335 29.5 299 -15 345 27.1 300 -15 355 30.3 301 -25 5 31.3 302 -25 15 30.8 304 -25 35 33.6 305 -25 45 32.3 306 -25 55 34.5 307 -25 65 35.3 309 -25 85 34.8 310 -25 95 33.9 311 -25 105 31.2 312 -25 115 34.3 316 -25 155 35.9 317 -25 165 32.3 318 -25 175 33.4 319 -25 185 33.1 320 -25 195 42.3 321 -25 205 45.0 322 -25 215 35.6 323 -25 225 35.4 324 -25 235 33.9 325 -25 245 29.2 329 -25 285 33.1 332 -25 315 34.3 333 -25 325 35.5 336 -25 355 28.6 337 -35 5 31.1 338 -35 15 35.8 339 -35 25 36.1 340 -35 35 34.8 341 -35 45 31.3 342 -35 55 27.6 346 -35 95 30.7 347 -35 105 35.4 348 -35 115 37.7 349 -35 125 40.5 350 -35 135 43.7 351 -35 145 42.0 352 -35 155 37.5 353 -35 165 41.9 354 -35 175 33.4 355 -35 185 37.0 356 -35 195 38.2 364 -35 275 27.5 365 -35 285 34.5 367 -35 305 35.3 368 -35 315 38.1 369 -35 325 40.7 372 -35 355 29.9 387 -45 145 44.9 389 -45 165 40.6 390 -45 175 32.4 391 -45 185 38.5 400 -45 275 30.8 402 -45 295 34.6 403 -45 305 38.2 417 -55 170 35.5 423 -55 290 43.5 424 -55 310 35.4 430 -65 70 31.3 441 -65 290 37.4