DIURNAL 04 March 2003 R^2
The files in this directory can be used to produce
SST values for any hour of the day at any location on
earth ( over the oceans ) using the Clayson and Curry
formula from C. A. Clayson and J. A. Curry , J. Geophys.
Res. Vol. 101, No. C12, Pages 28515-28528, 15 Dec. 1996 .
This method requires as input values the daily averaged wind
speed, the daily averaged precipitation, and the peak
solar insolation for the day. Also one needs an estimate of
predawn sea surface temperature. The Clayson and Curry formula
calculates a maximum temperature excursion from the predawn
surface temperature. This can be used to produce a sinusoidal
varying temperature time series for the day with a minimum
corresponding to the predawn sst and a maximum corresponding
to the predawn temperature plus the amplitude calculated
from the Clayson and Curry formula. The temperatures are scaled
according to the solar zenith angle with maximum temperature
at local noon. Although they can easily be shifted in time to
better match measured sst values.
This directory contains seven subroutines and an example file
demonstrating the use of the subroutines to calculate an actual
sst time series. This is a listing of the subroutines and their
uses :
ydate.f This routine is used to calculate the day-of-year ( 1 thru
365 ) for an input integer containing the month and day ( mmdd ).
One needs to have a decimal day-of-year value as input to the
routines used to calculate solar declination angle and earth-
sun distances.
diurn.f This routine calculates the diurnal cycle factor for a
given time ( GMT day, hour, min. in decimal day-of-year ) at
a given location ( latitude and longitude in decimal degrees ).
It also incorporates a simple sea surface albedo factor which
can be changed or removed.
aten.f This routine calculates the cosine of the solar zenith angle
and downward solar radiation at top-of-atmosphere for a
specified time and location.
ratio.f This routine calculates the squared ratio of the mean earth-sun
distance to the actual distance for a given decimal day-of-year .
dec.f This routine calculates the declination angle of the sun for
a given decimal day-of-year .
dsst.f This is the Clayson and Curry regression formula evaluation
for the daily temperature amplitude.
zenith.f This routine returns the maximum solar radiation at TOA for the
day.
The program newsst.f is an example code using the above routines to
calculate the sst time series for the 1999 JASMINE experiment using
NCEP values to estimate predawn sst, average wind speed, precipitation,
and maximum solar insolation. The program first reads an NCEP data file
corresponding to Jasmine times and positions and finds daily averaged
wind speeds and precipitation. The lowest NCEP sst is found and assigned
to the predawn sst value. The maximum NCEP surface solar flux is also
found and a value of the TOA solar flux calculated from the subroutines
for that time and position. An attentation factor is than assigned to the
ratio of NCEP-max to TOA flux. This factor is assumed to be due to clouds
and normal atmospheric attenuation for that day. To obtain the maximum
solar insolation for the day needed in the regression formula, the
maximum TOA solar radition is found using zenith.f and that value
is multiplied by the attentation factor. The daily temperature amplitude
is then calculated using dsst.f . The diurnal factor for the time and
location of the Jasmine ship is then calculated using diurn.f . It is a
ratio of the cosine of the zenith angle to the cosine of the maximum
zenith angle for the day times an albedo factor. The final calculated
sst value is assigned to be the predawn sst plus an offset factor that
depends upon the daily averaged wind speed plus the product of the
diurnal factor and the daily temperature amplitude.
The program outputs three files : time.dat that contains the decimal
day-of-year data for the time series, insitu.dat that contains the
sst values from the original Jasmine data file jasm_hr_99.dat , and
model.dat that contains the sst values calculated by the procedure
described above using only the NCEP data ( ncep_jasm_99.dat file ).
Also included in the directory is a PostScript plot comparing the
calculated and in situ data called ncep_jasm.ps and the idl plotting
code plot.pro .
This directory now contains the file lodl.f . This program
calculates the length of daylight for any day of the year
( February 29 in not a valid input date ) at any latitude on
earth. It is set up as an interactive code but can be modified
to be a subroutine in some other program. Probably accurate to
+- 5 min for any latitude and date.
Any questions regarding these codes should be addressed to:
Randy Reeder
University of Colorado, Boulder
(303) 492-4266
rreeder@cloud.colorado.edu