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Macros | Functions
Solar Utilities

Macros

#define PI   3.141592653589793
 The value of PI.
#define TWO_PI   6.283185307179586
 The value of 2 * PI.
#define DEG_TO_RAD(a)   (a * 0.017453292519943)
 Convert degrees to radians.
#define RAD_TO_DEG(a)   (a * 57.29577951308232)
 Convert radians to degrees.
#define IS_LEAP_YEAR(y)   (((y%4) == 0 && (y%100) != 0) || (y%400) == 0)
 Determine if a 4 digit year is a leap year.
#define SECS1970_TO_J2000(s)   ((s - 946728000.0)/86400.0)
 Convert seconds since 1970 to days since 2000-01-01 12:00:00.
#define JD_TO_J2000(JD)   (JD - 2451545.0)
 Convert Julian Day to days since 2000-01-01 12:00:00.
#define SZA_TO_AIRMASS(sza)   (1.0 / (cos(DEG_TO_RAD(sza)) + 0.50572 * pow((96.07995 - sza), -1.6364)))
 Get the airmass corresponding to a solar zenith angle.

Functions

double get_julian_day (int year, int month, int day, int hour, int minute, int second)
 Get the Julian day from a calendar date (UT).
double get_solar_distance (double days_J2000)
 Get the distance from the Earth to the Sun.
double get_solar_distance_AA1990 (double days_J2000)
 Get the distance from the Earth to the Sun.

Detailed Description

Macro Definition Documentation

#define JD_TO_J2000 (   JD)    (JD - 2451545.0)

Convert Julian Day to days since 2000-01-01 12:00:00.

Definition at line 72 of file solar_utils.h.

#define SZA_TO_AIRMASS (   sza)    (1.0 / (cos(DEG_TO_RAD(sza)) + 0.50572 * pow((96.07995 - sza), -1.6364)))

Get the airmass corresponding to a solar zenith angle.

Where sza is the apparent solar zenith angle in degrees.

Kasten, F. and Young, A. 1989. Revised optical air mass tables and approximation formula. Applied Optics 28 (22), pp. 4735-4738

Definition at line 85 of file solar_utils.h.

Function Documentation

double get_julian_day ( int  year,
int  month,
int  day,
int  hour,
int  minute,
int  second 
)

Get the Julian day from a calendar date (UT).

This function is based the JavaScript routines provided by NOAA at: 

http://www.srrb.noaa.gov/highlights/sunrise/calcdetails.html

which were base on Jean Meeus's book "Astronomical Algorithms".

Parameters:
year4 digit year
month[1 - 12]
day[1 - 31]
hour[0 - 23]
minute[0 - 59]
second[0 - 59]
Returns:
The Julian day corresponding to the specified UT date.

Definition at line 53 of file solar_utils.c.

double get_solar_distance ( double  days_J2000)

Get the distance from the Earth to the Sun.

This function is based the JavaScript routines provided by NOAA at: 

http://www.srrb.noaa.gov/highlights/sunrise/calcdetails.html

which were base on Jean Meeus's book "Astronomical Algorithms".

This function can report values between the years -2000 and +3000.

Parameters:
days_J2000days since 2000-01-01 12:00:00
Returns:
The distance from the earth to the sun in AU's.

Definition at line 91 of file solar_utils.c.

double get_solar_distance_AA1990 ( double  days_J2000)

Get the distance from the Earth to the Sun.

Algorithm from the Astronomical Almanac 1990, C24.

This function can report values between the years 1950 and 2050.

Parameters:
days_J2000days since 2000-01-01 12:00:00
Returns:
The distance from the earth to the sun in AU's.

Definition at line 132 of file solar_utils.c.