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

Format

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 NAs 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

# Here is a glimpse at the data # available in `sza` dplyr::glimpse(sza)
#> 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, …