This dataset contains solar zenith angles (in degrees, with the range of
0-90) every half hour from 04:00 to 12:00, true solar time. This set of
values is calculated on the first of every month for 4 different northern
hemisphere latitudes. For determination of afternoon values, the presented
tabulated values are symmetric about noon.

sza

A tibble with 816 rows and 4 variables:

- latitude
The latitude in decimal degrees for the observations

- month
The measurement month; all calculations where conducted
for the first day of each month

- tst
The true solar time at the given `latitude`

and date
(first of `month`

) for which the solar zenith angle is calculated

- sza
The solar zenith angle in degrees, where `NA`

s
indicate that sunrise hadn't yet occurred by the `tst`

value

## Source

Calculated Actinic Fluxes (290 - 700 nm) for Air Pollution
Photochemistry Applications (Peterson, 1976), available at:
https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=9100JA26.txt.

## Details

The solar zenith angle (SZA) is one measure that helps to describe the sun's
path across the sky. It's defined as the angle of the sun relative to a line
perpendicular to the earth's surface. It is useful to calculate the SZA in
relation to the true solar time. True solar time relates to the position of
the sun with respect to the observer, which is different depending on the
exact longitude. For example, two hours before the sun crosses the meridian
(the highest point it would reach that day) corresponds to a true solar time
of 10 a.m. The SZA has a strong dependence on the observer's latitude. For
example, at a latitude of 50 degrees N at the start of January, the noontime
SZA is 73.0 but a different observer at 20 degrees N would measure the
noontime SZA to be 43.0 degrees.

## Examples

#> Observations: 816
#> Variables: 4
#> $ latitude <dbl> 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, …
#> $ month <fct> jan, jan, jan, jan, jan, jan, jan, jan, jan, jan, jan, jan, …
#> $ tst <chr> "0400", "0430", "0500", "0530", "0600", "0630", "0700", "073…
#> $ sza <dbl> NA, NA, NA, NA, NA, NA, 84.9, 78.7, 72.7, 66.1, 61.5, 56.5, …