Table I
Solar radiation intensities at normal incidence. Composite average, January, 1928, through August, 1932 (g cal./sq. cm/minute).
| No. of observations | 10:00 a.m. | Noon | 2:00 p.m. | Absolute maximum |
---|
Jan. | 17 | 1.046 | 1.151 | 0.980 | 1.360 |
Feb. | 20 | 1.019 | 1.186 | 0.972 | 1.392 |
Mar. | 18 | 1.176 | 1.305 | 1.166 | 1.450 |
Apr. | 20 | 1.172 | 1.196 | 1.108 | 1.349 |
May | 28 | 1.158 | 1.201 | 1.048 | 1.344 |
June | 22 | 1.177 | 1.212 | 1.151 | 1.323 |
July | 19 | 1.070 | 1.122 | 1.018 | 1.305 |
Aug. | 17 | 1.096 | 1.104 | 1.086 | 1.276 |
Sept. | 17 | 1.122 | 1.192 | 1.089 | 1.291 |
Oct. | 28 | 1.106 | 1.273 | 1.110 | 1.407 |
Nov. | 25 | 1.039 | 1.075 | 0.983 | 1.334 |
Dec. | 17 | 1.155 | 1.273 | 0.986 | 1.313 |
Table II
Average amount of total radiation (sunshine and skyshine) received on a horizontal surface (g cal./sq. cm/min.).
Hour ending 1931 | 7 | 8 | 9 | 10 | 11 | 12 | 1 | 2 | 3 | 4 | 5 | 6 | Average daily total |
---|
Mar. | 0.062 | 0.155 | 0.337 | 0.541 | 0.625 | 0.723 | 0.676 | 0.636 | 0.508 | 0.424 | 0.154 | 0.048 | 293.3 |
Apr. | 0.063 | 0.207 | 0.418 | 0.632 | 0.745 | 0.783 | 0.747 | 0.698 | 0.601 | 0.462 | 0.242 | 0.075 | 340.4 |
May | 0.107 | 0.273 | 0.448 | 0.631 | 0.780 | 0.743 | 0.818 | 0.779 | 0.714 | 0.504 | 0.311 | 0.095 | 372.2 |
June | 0.148 | 0.256 | 0.497 | 0.591 | 0.731 | 0.731 | 0.692 | 0.641 | 0.569 | 0.468 | 0.315 | 0.103 | 344.5 |
July | 0.137 | 0.258 | 0.427 | 0.551 | 0.686 | 0.765 | 0.650 | 0.628 | 0.577 | 0.475 | 0.260 | 0.103 | 331.0 |
Aug. | 0.133 | 0.281 | 0.446 | 0.630 | 0.701 | 0.761 | 0.713 | 0.601 | 0.533 | 0.428 | 0.275 | 0.090 | 335.5 |
Sept. | 0.117 | 0.267 | 0.480 | 0.647 | 0.718 | 0.811 | 0.833 | 0.758 | 0.665 | 0.430 | 0.224 | 0.063 | 360.8 |
1932 | | | | | | | | | | | | | |
Jan. | | 0.053 | 0.156 | 0.302 | 0.422 | 0.515 | 0.486 | 0.423 | 0.329 | 0.212 | 0.089 | | 179.2 |
Feb. | 0.010 | 0.089 | 0.237 | 0.422 | 0.512 | 0.495 | 0.472 | 0.439 | 0.376 | 0.247 | 0.124 | 0.017 | 206.4 |
Mar. | 0.034 | 0.150 | 0.315 | 0.472 | 0.585 | 0.637 | 0.650 | 0.619 | 0.493 | 0.348 | 0.184 | 0.051 | 272.3 |
Apr. | 0.098 | 0.277 | 0.460 | 0.644 | 0.830 | 0.767 | 0.735 | 0.721 | 0.605 | 0.447 | 0.261 | 0.097 | 356.5 |
May | 0.110 | 0.215 | 0.447 | 0.588 | 0.656 | 0.734 | 0.698 | 0.564 | 0.493 | 0.358 | 0.249 | 0.115 | 313.6 |
June | 0.262 | 0.467 | 0.632 | 0.706 | 0.809 | 0.804 | 0.787 | 0.703 | 0.587 | 0.447 | 0.285 | 0.166 | 399.3 |
July | 0.155 | 0.387 | 0.589 | 0.683 | 0.762 | 0.738 | 0.626 | 0.546 | 0.491 | 0.400 | 0.300 | 0.207 | 353.0 |
Aug. | 0.123 | 0.293 | 0.479 | 0.558 | 0.621 | 0.587 | 0.562 | 0.499 | 0.381 | 0.285 | 0.201 | 0.104 | 281.6 |
Table III
Average amount of total radiation (sunshine and skyshine) received on a horizontal surface on clear days only (g cal./sq. cm/min.).
Hour ending 1931 | 7 | 8 | 9 | 10 | 11 | 12 | 1 | 2 | 3 | 4 | 5 | 6 | Average daily total |
---|
Mar. | 0.072 | 0.209 | 0.447 | 0.703 | 0.873 | 0.989 | 1.049 | 0.994 | 0.855 | 0.608 | 0.282 | 0.061 | 428.5 |
Apr. | 0.067 | 0.260 | 0.549 | 0.810 | 0.984 | 1.086 | 1.070 | 1.015 | 0.851 | 0.651 | 0.326 | 0.080 | 464.9 |
May | 0.134 | 0.324 | 0.587 | 0.790 | 0.976 | 1.057 | 1.133 | 1.063 | 0.914 | 0.654 | 0.384 | 0.105 | 487.3 |
June | 0.125 | 0.433 | 0.706 | 0.725 | 1.009 | 1.058 | 1.069 | 1.070 | 0.940 | 0.729 | 0.445 | 0.149 | 507.5 |
July | 0.188 | 0.345 | 0.543 | 0.771 | 0.900 | 1.054 | 1.034 | 1.045 | 0.875 | 0.653 | 0.343 | 0.109 | 471.6 |
Aug. | 0.163 | 0.342 | 0.536 | 0.789 | 0.929 | 1.071 | 1.066 | 0.959 | 0.815 | 0.646 | 0.343 | 0.121 | 468.8 |
Sept. | 0.122 | 0.293 | 0.537 | 0.720 | 0.882 | 1.011 | 1.092 | 0.959 | 0.831 | 0.550 | 0.282 | 0.085 | 441.8 |
1932 | | | | | | | | | | | | | |
Jan. | | 0.082 | 0.259 | 0.484 | 0.704 | 0.805 | 0.836 | 0.768 | 0.591 | 0.376 | 0.160 | | 303.9 |
Feb. | 0.018 | 0.155 | 0.374 | 0.606 | 0.746 | 0.834 | 0.803 | 0.720 | 0.595 | 0.415 | 0.217 | 0.029 | 330.7 |
Mar. | 0.044 | 0.208 | 0.452 | 0.687 | 0.863 | 0.930 | 0.905 | 0.862 | 0.700 | 0.480 | 0.264 | 0.051 | 386.8 |
Apr. | 0.114 | 0.325 | 0.574 | 0.779 | 0.932 | 1.002 | 0.947 | 0.881 | 0.716 | 0.502 | 0.292 | 0.102 | 430.0 |
May | 0.178 | 0.426 | 0.645 | 0.780 | 0.961 | 1.072 | 1.023 | 0.889 | 0.778 | 0.620 | 0.396 | 0.166 | 476.0 |
June | 0.269 | 0.484 | 0.682 | 0.790 | 0.978 | 1.057 | 1.052 | 0.935 | 0.804 | 0.594 | 0.377 | 0.186 | 492.5 |
July | 0.224 | 0.440 | 0.628 | 0.810 | 0.958 | 1.057 | 1.031 | 0.893 | 0.665 | 0.553 | 0.333 | 0.165 | 465.4 |
Aug. | 0.154 | 0.397 | 0.625 | 0.786 | 0.950 | 1.023 | 0.980 | 0.941 | 0.642 | 0.468 | 0.262 | 0.144 | 442.3 |
Table IV
Energy distribution at noon on clear days. Direct solar radiation at normal incidence. Composite average for 56 months.
| Total energy (g cal./cm2/min.) | <400mμ (g cal./cm2/min.) | Percent of total | 400–620mμ (g cal./cm2/min.) | Percent of total | 620mμ–1.4μ (g cal./cm2/min.) | Percent of total | >1.4μ (g cal./cm2/min.) | Percent of total |
---|
Jan. | 1.173 | 0.0143 | 1.2 | 0.414 | 35.4 | 0.499 | 42.5 | 0.246 | 20.9 |
Feb. | 1.148 | 0.0194 | 1.7 | 0.409 | 34.7 | 0.459 | 40.0 | 0.261 | 23.6 |
Mar. | 1.365 | 0.0510 | 3.7 | 0.512 | 37.5 | 0.468 | 34.2 | 0.335 | 24.6 |
Apr. | 1.203 | 0.0289 | 2.4 | 0.448 | 37.2 | 0.428 | 35.6 | 0.298 | 24.8 |
May | 1.126 | 0.0364 | 3.2 | 0.424 | 37.7 | 0.400 | 35.5 | 0.266 | 23.6 |
June | 1.185 | 0.0389 | 3.3 | 0.449 | 37.9 | 0.382 | 32.2 | 0.315 | 26.6 |
July | 1.145 | 0.0326 | 2.9 | 0.450 | 39.3 | 0.348 | 30.4 | 0.314 | 27.4 |
Aug. | 1.128 | 0.0363 | 3.2 | 0.464 | 41.2 | 0.334 | 29.6 | 0.294 | 26.0 |
Sept. | 1.189 | 0.0349 | 2.9 | 0.494 | 41.6 | 0.385 | 32.4 | 0.275 | 23.1 |
Oct. | 1.178 | 0.0370 | 3.1 | 0.463 | 39.3 | 0.400 | 34.0 | 0.278 | 23.6 |
Nov. | 1.091 | 0.0246 | 2.3 | 0.451 | 41.3 | 0.364 | 33.3 | 0.252 | 23.1 |
Dec. | 1.303 | 0.0186 | 1.4 | 0.556 | 42.6 | 0.462 | 35.6 | 0.266 | 20.4 |
Table V
Energy distribution on representative clear days.
Date | Time | Total energy (g cal./cm2/min.) | <400mμ (g cal./cm2/min.) | Percent of total | 400–620mμ (g cal./cm2/min.) | Percent of total | 620mμ–1.4mμ (g cal./cm2/min.) | Percent of total | >1.4μ (g cal./cm2/min.) | Percent of total |
---|
1930 | | | | | | | | | | |
Jan. 8 | 10:00 | 1.068 | 0.0098 | 0.92 | 0.346 | 32.4 | 0.407 | 38.1 | 0.305 | 28.6 |
| 12:00 | 1.152 | 0.0147 | 1.28 | 0.396 | 34.4 | 0.461 | 40.0 | 0.280 | 24.3 |
| 2:00 | 0.988 | 0.0099 | 1.00 | 0.357 | 36.1 | 0.321 | 32.5 | 0.300 | 30.4 |
Mar. 10 | 10:00 | 1.362 | 0.0163 | 1.20 | 0.456 | 33.5 | 0.492 | 36.1 | 0.398 | 29.2 |
| 12:00 | 1.391 | 0.0599 | 4.30 | 0.491 | 35.3 | 0.442 | 31.8 | 0.398 | 28.6 |
| 2:00 | 1.204 | 0.0355 | 2.95 | 0.397 | 33.0 | 0.393 | 32.7 | 0.378 | 31.4 |
July 6 | 10:00 | 1.247 | 0.0249 | 2.00 | 0.591 | 47.4 | 0.410 | 32.9 | 0.221 | 17.7 |
| 12:00 | 1.276 | 0.0276 | 2.16 | 0.606 | 47.5 | 0.355 | 27.8 | 0.287 | 22.5 |
| 2:00 | 1.290 | 0.0200 | 1.55 | 0.595 | 46.1 | 0.386 | 29.9 | 0.289 | 22.4 |
Oct. 8 | 10:00 | 1.014 | 0.0162 | 1.60 | 0.484 | 47.7 | 0.369 | 36.4 | 0.145 | 14.3 |
| 12:00 | 1.167 | 0.0286 | 2.45 | 0.526 | 45.1 | 0.396 | 33.9 | 0.216 | 18.5 |
| 2:00 | 1.038 | 0.0218 | 2.10 | 0.425 | 40.9 | 0.386 | 37.2 | 0.206 | 19.8 |
Table VI
Comparison of midday energy values of wave-lengths less than 313mμ.
| | Midsummer | Midwinter |
---|
Authors | Location | (g cal./cm2/min.) | μw/sq. cm | (g cal. cm2/min.) | μw/sq. cm |
---|
Greider and Downs | Springfield Lake, O. Alt. 1200 ft. (366M.) | 0.00043 | 30 | 0.00023 | 16 |
Greider and Downs | Cragmoor, Colo. Alt. 6500 ft. (1981M.) | 0.00098 | 69 | 0.00030 | 21 |
Pettit | Estimate for mid-latitude, sea level | 0.00129 | 90 | — | — |
Coblentz and Stair | Washington, D. C. Alt. 350 ft. (107M.) | 0.00129 | 90 | 0.00029 | 20 |
Luckiesh | Estimate from erythemal observations | 0.00047–0.00057 | 33–40 | — | — |
Clark | Baltimore, Md. | 0.00860 | 602 | 0.00072 | 50 |
Laurens and Mayerson | New Orleans, La. Alt. 100 ft. (26M.) | 0.00099 | 69 | 0.00040 | 28 |
Table VII
Limits of spectrum on clear days (1929 through August, 1932).
| 10:00 a.m. | 12:00 m. | 2:00 p.m. |
---|
Month | High | Low | High | Low | High | Low |
---|
Jan. | 313 | 303 | 311 | 300 | 312 | 306 |
Feb. | 309 | 304 | 308 | 300 | 313 | 308 |
Mar. | 313 | 303 | 308 | 300 | 311 | 304 |
Apr. | 309 | 302 | 308 | 300 | 311 | 304 |
May | 311 | 304 | 309 | 303 | 309 | 306 |
June | 308 | 299 | 310 | 303 | 308 | 305 |
July | 307 | 304 | 304 | 302 | 308 | 304 |
Aug. | 309 | 304 | 309 | 302 | 309 | 306 |
Sept. | 311 | 307 | 314 | 305 | 312 | 307 |
Oct. | 315 | 303 | 312 | 300 | 313 | 305 |
Nov. | 311 | 309 | 313 | 307 | 318 | 307 |
Dec. | 311 | 308 | 309 | 306 | 312 | 308 |
Table VIII
Percentage of total energy (sun and sky) contributed by sky. (Noon values in g cal./sq. cm/min.).
Date 1931 | Sky conditions | Sun and sky | Sky | Percent of total |
---|
Apr. 6 | clear | 0.868 | 0.134 | 15.4 |
“ 24 | cumulus, fleecy | 0.734 | 0.228 | 31.0 |
| clouds | | | |
June 1 | clear | 1.219 | 0.094 | 7.7 |
“ 18 | fleecy clouds | 0.649 | 0.174 | 26.8 |
July 2 | fleecy clouds | 0.898 | 0.201 | 22.3 |
“ 9 | clear | 1.040 | 0.107 | 10.3 |
Table IX
Distribution of solar energy as measured on a horizontal surface (g cal./sq. cm/per min.).
Date | Time | Total energy | <313mμ | <400mμ | 400–620mμ | >620mμ |
---|
Sun and sky |
1932 | | | | | | |
Jan. 19 | 10:30 | 0.665 | | 0.103 | 0.186 | 0.376 |
| 12:10 | 0.845 | 0.000456 | 0.090 | 0.234 | 0.521 |
| 3:00 | 0.540 | 0.000226 | 0.049 | 0.125 | 0.366 |
Apr. 13 | 10:00 | 1.000 | 0.001001 | 0.174 | 0.289 | 0.537 |
| 12:10 | 1.120 | 0.002060 | 0.168 | 0.266 | 0.686 |
| 2:30 | 0.890 | 0.000932 | 0.150 | 0.251 | 0.489 |
July 13 | 10:00 | 0.880 | | 0.102 | 0.223 | 0.555 |
| 12:20 | 1.080 | 0.002551 | 0.196 | 0.235 | 0.649 |
| 3:20 | 0.620 | 0.002410 | 0.043 | 0.136 | 0.441 |
1931 | | | | | | |
Oct. 12 | 11:00 | 0.840 | 0.000800 | 0.087 | 0.241 | 0.512 |
| 12:00 | 0.987 | 0.001070 | 0.144 | 0.260 | 0.583 |
| 1:30 | 0.824 | | 0.070 | 0.248 | 0.506 |
Sky only |
1932 | | | | | | |
Jan. 19 | 10:30 | 0.0715 | | 0.0325 | 0.0270 | 0.0120 |
| 12:10 | 0.0785 | 0.000238 | 0.0311 | 0.0289 | 0.0185 |
| 3:00 | 0.0635 | 0.000204 | 0.0326 | 0.0218 | 0.0091 |
Apr. 13 | 10:00 | 0.1080 | 0.000099 | 0.0503 | 0.0393 | 0.0184 |
| 12:10 | 0.1120 | 0.000620 | 0.0510 | 0.0367 | 0.0243 |
| 2:30 | 0.1010 | 0.000740 | 0.0519 | 0.0394 | 0.0097 |
July 13 | 10:00 | 0.1160 | 0.000136 | 0.0445 | 0.0432 | 0.0283 |
| 12:20 | 0.1350 | 0.000873 | 0.0489 | 0.0464 | 0.0397 |
| 3:20 | 0.0950 | 0.000646 | 0.0475 | 0.0402 | 0.0073 |
1931 | | | | | | |
Oct. 12 | 11:00 | 0.0907 | 0.000387 | 0.0305 | 0.0389 | 0.0213 |
| 12:00 | 0.1056 | 0.000475 | 0.0385 | 0.0401 | 0.0270 |
| 1:30 | 0.0824 | | 0.0340 | 0.0349 | 0.0135 |
Table X
Increase in total energy of skyshine with solar altitude. Measured on a horizontal surface in g cal./sq. cm/min.
Solar altitude | 40° | 50° | 60° | 70° | 80° | 90° |
---|
Total energy | 0.0730 | 0.0795 | 0.1013 | 0.1054 | 0.1108 | 0.1370 |
Table XI
Comparison of solar and sky ultraviolet (<400mμ) (g cal./sq. cm/min. on a horizontal surface).
Solar altitude | 40° | 50° | 60° | 70° | 80° | 90° |
---|
Sun | 0.0327 | 0.0420 | 0.0515 | 0.0576 | 0.0804 | 0.1166 |
Sky | 0.0336 | 0.0313 | 0.0420 | 0.0445 | 0.0613 | 0.0714 |
Sun and sky | 0.0663 | 0.0733 | 0.0935 | 0.1021 | 0.1417 | 0.1880 |
| 0.97 | 1.34 | 1.23 | 1.29 | 1.31 | 1.63 |
Table XII
Comparison of solar and sky antirachitic radiation (<313mμ) (g cal./sq. cm/min. on a horizontal surface).
Solar altitude | 50° | 60° | 70° | 80° | 90° |
---|
Sun | 0.000285 | 0.000447 | 0.000560 | 0.000800 | 0.001395 |
Sky | 0.000133 | 0.000217 | 0.000348 | 0.000418 | 0.000754 |
Sun and sky | 0.000418 | 0.000664 | 0.000908 | 0.001218 | 0.002149 |
| 2.14 | 2.06 | 1.61 | 1.91 | 1.85 |