> head(data.frame(lag = 32-0:(length(ta)-1), ta ta, tal=c(rep(NA, 3), ta[1:(length(ta)-3)]),t3=t3, t30 t30), 34)
lag ta tal t3 t30
1 32 23.635 NA NA NA
2 31 24.940 NA NA NA
3 30 26.160 NA 24.91167 NA
4 29 27.160 23.635 26.08667 NA
5 28 26.910 24.940 26.74333 NA
6 27 26.450 26.160 26.84000 NA
7 26 26.940 27.160 26.76667 NA
8 25 27.320 26.910 26.90333 NA
9 24 31.990 26.450 28.75000 NA
10 23 32.620 26.940 30.64333 NA
11 22 29.525 27.320 31.37833 NA
12 21 32.555 31.990 31.56667 NA
13 20 30.310 32.620 30.79667 NA
14 19 30.235 29.525 31.03333 NA
15 18 33.540 32.555 31.36167 NA
16 17 33.455 30.310 32.41000 NA
17 16 35.390 30.235 34.12833 NA
18 15 36.130 33.540 34.99167 NA
19 14 34.900 33.455 35.47333 NA
20 13 32.870 35.390 34.63333 NA
21 12 30.880 36.130 32.88333 NA
22 11 29.390 34.900 31.04667 NA
23 10 29.505 32.870 29.92500 NA
24 9 32.885 30.880 30.59333 NA
25 8 32.145 29.390 31.51167 NA
26 7 26.140 29.505 30.39000 NA
27 6 19.655 32.885 25.98000 NA
28 5 21.985 32.145 22.59333 NA
29 4 22.920 26.140 21.52000 NA
30 3 23.370 19.655 22.75833 NA
31 2 24.660 21.985 23.65000 NA
32 1 27.385 22.920 25.13833 NA
33 0 32.135 23.370 28.06000 29.06367
34 -1 33.550 24.660 31.02333 29.09783
> mean(ta[1:30])
[1] 29.06367
> mean(ta[31:33])
[1] 28.06
>
http://www.bom.gov.au/info/thermal_stress/#wbgt cited 19/9/2017
Values for the black globe temperature and natural wet-bulb temperature cannot be accurately determined from a standard meteorological site.
Instead the Bureau uses an approximation to the WBGT. This approximation uses standard meteorologically measured temperature and humidity to calculate an estimation of the WBGT under moderately sunny light wind conditions. Real variations of sunshine and wind are not taken into account. The formula is likely to overestimate the WBGT in cloudy or windy conditions, or when the sun is low or below the horizon. Under clear full sun and low humidity conditions the approximation underestimates the WBGT slightly. The formula for the approximation is shown at the end of this document.