s_phys_pkgs/text/cal.tex

\subsection{CAL: The calendar package
\label{sectioncal}}
\begin{rawhtml}
<!-- CMIREDIR:sectioncal: -->
\end{rawhtml}

Authors: Christian Eckert and Patrick Heimbach

This calendar tool was originally intended to enable the use of
absolute dates (Gregorian Calendar dates) in MITgcm. There is,
however, a fair number of routines that can be used independently of
the main MITgcm executable. After some minor modifications the whole
package can be used either as a stand-alone calendar or in connection
with any dynamical model that needs calendar dates. Some
straightforward extensions are still pending e.g. the availability of
the Julian Calendar, to be able to resolve fractions of a second, and
to have a time- step that is longer than one day.

\subsubsection{Basic assumptions for the calendar tool}

    It is assumed that the SMALLEST TIME INTERVAL to be resolved is
    ONE SECOND.

    Further assumptions are that there is an INTEGER NUMBER OF
    MODEL STEPS EACH DAY, and that AT LEAST ONE STEP EACH DAY is
    made.

    Not each individual routine depends on these assumptions; there
    are only a few places where they enter.

\subsubsection{Format of calendar dates}

    In this calendar tool a complete date specification is defined
    as the following integer array:

\begin{verbatim}
c           integer date(4)
c
c           ( yyyymmdd, hhmmss, leap_year, dayofweek )
c
c             date(1) = yyyymmdd    <-- Year-Month-Day
c             date(2) =   hhmmss    <-- Hours-Minutes-Seconds
c             date(3) = leap_year   <-- Leap Year/No Leap Year
c             date(4) = dayofweek   <-- Day of the Week
c
c             leap_year is either equal to 1 (normal year)
c                              or equal to 2 (leap year)
c
c             dayofweek has a range of 1 to 7.
\end{verbatim}

          In case the Gregorian Calendar is used, the first
          day of the week is Friday, since day of the Gregorian
          Calendar was Friday, 15 Oct. 1582. As a date array
          this date would be specified as

\begin{verbatim}
c               refdate(1) = 15821015
c               refdate(2) =        0
c               refdate(3) =        1
c               refdate(4) =        1
\end{verbatim}

\subsubsection{Calendar dates and time intervals}

    Subtracting calendar dates yields time intervals.
    Time intervals have the following format:

\begin{verbatim}
c         integer datediff(4)
c
c           datediff(1) = # Days
c           datediff(2) = hhmmss
c           datediff(3) =      0
c           datediff(4) =     -1
\end{verbatim}

    Such time intervals can be added to or can be subtracted from
    calendar dates. Time intervals can be added to and be
    subtracted from each other.

\subsubsection{Using the calendar together with MITgcm}

    Each routine has as an argument the thread number that it is
    belonging to, even if this number is not used in the routine
    itself.

    In order to include the calendar tool into the MITgcm
    setup the MITgcm subroutine "initialise.F" or the routine
    "initilise\_fixed.F", depending on the MITgcm release, has
    to be modified in the following way:

{\footnotesize
\begin{verbatim}
c         #ifdef ALLOW_CALENDAR
c         C--   Initialise the calendar package.
c         #ifdef USE_CAL_NENDITER
c               CALL cal_Init(
c              I               startTime,
c              I               endTime,
c              I               deltaTclock,
c              I               nIter0,
c              I               nEndIter,
c              I               nTimeSteps,
c              I               myThid
c              &             )
c         #else
c               CALL cal_Init(
c              I               startTime,
c              I               endTime,
c              I               deltaTclock,
c              I               nIter0,
c              I               nTimeSteps,
c              I               myThid
c              &             )
c         #endif
c               _BARRIER
c         #endif
\end{verbatim}
}

    It is useful to have the CPP flag ALLOW\_CALENDAR in
    order to switch from the usual MITgcm setup to the
    one that includes the calendar tool. The CPP flag
    USE\_CAL\_NENDITER has been introduced in order to enable
    the use of the calendar for MITgcm releases earlier
    than checkpoint 25 which do not have the global variable
    *nEndIter*.

\subsubsection{The individual calendars}

Simple model calendar:

          This calendar can be used by defining

\begin{verbatim}
c                  TheCalendar='model'
\end{verbatim}

          in the calendar's data file "data.cal".

          In this case a year is assumed to have 360 days. The
          model year is divided into 12 months with 30 days each.

Gregorian Calendar:

          This calendar can be used by defining

\begin{verbatim}
c                  TheCalendar='gregorian'
\end{verbatim}

          in the calendar's data file "data.cal".

\subsubsection{Short routine description}

{\footnotesize
\begin{verbatim}
c      o  cal_Init          - Initialise the calendar. This is the interface
c                             to MITgcm.
c
c      o  cal_Set           - Sets the calendar according to the user
c                             specifications.
c
c      o  cal_GetDate       - Given the model's current timestep or the
c                             model's current time return the corresponding
c                             calendar date.
c
c      o  cal_FullDate      - Complete a date specification (leap year and
c                             day of the week).
c
c      o  cal_IsLeap        - Determine whether a given year is a leap year.
c
c      o  cal_TimePassed    - Determine the time passed between two dates.
c
c      o  cal_AddTime       - Add a time interval either to a time interval
c                             or to a date.
c
c      o  cal_TimeInterval  - Given a time interval return the corresponding
c                             date array.
c
c      o  cal_SubDates      - Determine the time interval between two dates
c                             or between two time intervals.
c
c      o  cal_ConvDate      - Decompose a date array or a time interval
c                             array into its components.
c
c      o  cal_CopyDate      - Copy a date array or a time interval array to
c                             another array.
c
c      o  cal_CompDates     - Compare two calendar dates or time intervals. 
c
c      o  cal_ToSeconds     - Given a time interval array return the number
c                             of seconds.
c
c      o  cal_WeekDay       - Return the weekday as a string given the
c                             calendar date.
c
c      o  cal_NumInts       - Return the number of time intervals between two
c                             given dates.
c
c      o  cal_StepsPerDay   - Given an iteration number or the current
c                             integration time return the number of time
c                             steps to integrate in the current calendar day.
c
c      o  cal_DaysPerMonth  - Given an iteration number or the current
c                             integration time return the number of days
c                             to integrate in this calendar month.
c
c      o  cal_MonthsPerYear - Given an iteration number or the current
c                             integration time return the number of months
c                             to integrate in the current calendar year.
c
c      o  cal_StepsForDay   - Given the integration day return the number
c                             of steps to be integrated, the first step,
c                             and the last step in the day specified. The
c                             first and the last step refer to the total
c                             number of steps (1, ... , cal_IntSteps).
c
c      o  cal_DaysForMonth  - Given the integration month return the number
c                             of days to be integrated, the first day,
c                             and the last day in the month specified. The
c                             first and the last day refer to the total
c                             number of steps (1, ... , cal_IntDays).
c
c      o  cal_MonthsForYear - Given the integration year return the number
c                             of months to be integrated, the first month,
c                             and the last month in the year specified. The
c                             first and the last step refer to the total
c                             number of steps (1, ... , cal_IntMonths).
c
c      o  cal_Intsteps      - Return the number of calendar years that are
c                             affected by the current integration.
c
c      o  cal_IntDays       - Return the number of calendar days that are
c                             affected by the current integration.
c
c      o  cal_IntMonths     - Return the number of calendar months that are
c                             affected by the current integration.
c
c      o  cal_IntYears      - Return the number of calendar years that are
c                             affected by the current integration.
c
c      o  cal_nStepDay      - Return the number of time steps that can be
c                             performed during one calendar day.
c
c      o  cal_CheckDate     - Do some simple checks on a date array or on a
c                             time interval array.
c
c      o  cal_PrintError    - Print error messages according to the flags
c                             raised by the calendar routines.
c
c      o  cal_PrintDate     - Print a date array in some format suitable for
c                             MITgcm's protocol output.
c
c      o  cal_TimeStamp     - Given the time and the iteration number return
c                             the date and print all the above numbers.
c
c      o  cal_Summary       - List all the setttings of the calendar tool.
\end{verbatim}
}

1	molod	1.2	\subsection{CAL: The calendar package
2	heimbach	1.1	\label{sectioncal}}
3			\begin{rawhtml}
4			<!-- CMIREDIR:sectioncal: -->
5			\end{rawhtml}
6
7	heimbach	1.3	Authors: Christian Eckert and Patrick Heimbach
8	heimbach	1.1
9			This calendar tool was originally intended to enable the use of
10	edhill	1.4	absolute dates (Gregorian Calendar dates) in MITgcm. There is,
11			however, a fair number of routines that can be used independently of
12			the main MITgcm executable. After some minor modifications the whole
13			package can be used either as a stand-alone calendar or in connection
14			with any dynamical model that needs calendar dates. Some
15			straightforward extensions are still pending e.g. the availability of
16			the Julian Calendar, to be able to resolve fractions of a second, and
17			to have a time- step that is longer than one day.
18	heimbach	1.1
19	molod	1.2	\subsubsection{Basic assumptions for the calendar tool}
20	heimbach	1.1
21			It is assumed that the SMALLEST TIME INTERVAL to be resolved is
22			ONE SECOND.
23
24			Further assumptions are that there is an INTEGER NUMBER OF
25			MODEL STEPS EACH DAY, and that AT LEAST ONE STEP EACH DAY is
26			made.
27
28			Not each individual routine depends on these assumptions; there
29			are only a few places where they enter.
30
31	molod	1.2	\subsubsection{Format of calendar dates}
32	heimbach	1.1
33			In this calendar tool a complete date specification is defined
34			as the following integer array:
35
36			\begin{verbatim}
37			c integer date(4)
38			c
39			c ( yyyymmdd, hhmmss, leap_year, dayofweek )
40			c
41			c date(1) = yyyymmdd <-- Year-Month-Day
42			c date(2) = hhmmss <-- Hours-Minutes-Seconds
43			c date(3) = leap_year <-- Leap Year/No Leap Year
44			c date(4) = dayofweek <-- Day of the Week
45			c
46			c leap_year is either equal to 1 (normal year)
47			c or equal to 2 (leap year)
48			c
49			c dayofweek has a range of 1 to 7.
50			\end{verbatim}
51
52			In case the Gregorian Calendar is used, the first
53			day of the week is Friday, since day of the Gregorian
54			Calendar was Friday, 15 Oct. 1582. As a date array
55			this date would be specified as
56
57			\begin{verbatim}
58			c refdate(1) = 15821015
59			c refdate(2) = 0
60			c refdate(3) = 1
61			c refdate(4) = 1
62			\end{verbatim}
63
64	molod	1.2	\subsubsection{Calendar dates and time intervals}
65	heimbach	1.1
66			Subtracting calendar dates yields time intervals.
67			Time intervals have the following format:
68
69			\begin{verbatim}
70			c integer datediff(4)
71			c
72			c datediff(1) = # Days
73			c datediff(2) = hhmmss
74			c datediff(3) = 0
75			c datediff(4) = -1
76			\end{verbatim}
77
78			Such time intervals can be added to or can be subtracted from
79			calendar dates. Time intervals can be added to and be
80			subtracted from each other.
81
82	molod	1.2	\subsubsection{Using the calendar together with MITgcm}
83	heimbach	1.1
84			Each routine has as an argument the thread number that it is
85			belonging to, even if this number is not used in the routine
86			itself.
87
88			In order to include the calendar tool into the MITgcm
89			setup the MITgcm subroutine "initialise.F" or the routine
90			"initilise\_fixed.F", depending on the MITgcm release, has
91			to be modified in the following way:
92
93			{\footnotesize
94			\begin{verbatim}
95			c #ifdef ALLOW_CALENDAR
96			c C-- Initialise the calendar package.
97			c #ifdef USE_CAL_NENDITER
98			c CALL cal_Init(
99			c I startTime,
100			c I endTime,
101			c I deltaTclock,
102			c I nIter0,
103			c I nEndIter,
104			c I nTimeSteps,
105			c I myThid
106			c & )
107			c #else
108			c CALL cal_Init(
109			c I startTime,
110			c I endTime,
111			c I deltaTclock,
112			c I nIter0,
113			c I nTimeSteps,
114			c I myThid
115			c & )
116			c #endif
117			c _BARRIER
118			c #endif
119			\end{verbatim}
120			}
121
122			It is useful to have the CPP flag ALLOW\_CALENDAR in
123			order to switch from the usual MITgcm setup to the
124			one that includes the calendar tool. The CPP flag
125			USE\_CAL\_NENDITER has been introduced in order to enable
126			the use of the calendar for MITgcm releases earlier
127			than checkpoint 25 which do not have the global variable
128			nEndIter.
129
130	molod	1.2	\subsubsection{The individual calendars}
131	heimbach	1.1
132	molod	1.2	Simple model calendar:
133	heimbach	1.1
134			This calendar can be used by defining
135
136			\begin{verbatim}
137			c TheCalendar='model'
138			\end{verbatim}
139
140			in the calendar's data file "data.cal".
141
142			In this case a year is assumed to have 360 days. The
143			model year is divided into 12 months with 30 days each.
144
145	molod	1.2	Gregorian Calendar:
146	heimbach	1.1
147			This calendar can be used by defining
148
149			\begin{verbatim}
150			c TheCalendar='gregorian'
151			\end{verbatim}
152
153			in the calendar's data file "data.cal".
154
155	molod	1.2	\subsubsection{Short routine description}
156	heimbach	1.1
157			{\footnotesize
158			\begin{verbatim}
159			c o cal_Init - Initialise the calendar. This is the interface
160	edhill	1.4	c to MITgcm.
161	heimbach	1.1	c
162			c o cal_Set - Sets the calendar according to the user
163			c specifications.
164			c
165			c o cal_GetDate - Given the model's current timestep or the
166			c model's current time return the corresponding
167			c calendar date.
168			c
169			c o cal_FullDate - Complete a date specification (leap year and
170			c day of the week).
171			c
172			c o cal_IsLeap - Determine whether a given year is a leap year.
173			c
174			c o cal_TimePassed - Determine the time passed between two dates.
175			c
176			c o cal_AddTime - Add a time interval either to a time interval
177			c or to a date.
178			c
179			c o cal_TimeInterval - Given a time interval return the corresponding
180			c date array.
181			c
182			c o cal_SubDates - Determine the time interval between two dates
183			c or between two time intervals.
184			c
185			c o cal_ConvDate - Decompose a date array or a time interval
186			c array into its components.
187			c
188			c o cal_CopyDate - Copy a date array or a time interval array to
189			c another array.
190			c
191			c o cal_CompDates - Compare two calendar dates or time intervals.
192			c
193			c o cal_ToSeconds - Given a time interval array return the number
194			c of seconds.
195			c
196			c o cal_WeekDay - Return the weekday as a string given the
197			c calendar date.
198			c
199			c o cal_NumInts - Return the number of time intervals between two
200			c given dates.
201			c
202			c o cal_StepsPerDay - Given an iteration number or the current
203			c integration time return the number of time
204			c steps to integrate in the current calendar day.
205			c
206			c o cal_DaysPerMonth - Given an iteration number or the current
207			c integration time return the number of days
208			c to integrate in this calendar month.
209			c
210			c o cal_MonthsPerYear - Given an iteration number or the current
211			c integration time return the number of months
212			c to integrate in the current calendar year.
213			c
214			c o cal_StepsForDay - Given the integration day return the number
215			c of steps to be integrated, the first step,
216			c and the last step in the day specified. The
217			c first and the last step refer to the total
218			c number of steps (1, ... , cal_IntSteps).
219			c
220			c o cal_DaysForMonth - Given the integration month return the number
221			c of days to be integrated, the first day,
222			c and the last day in the month specified. The
223			c first and the last day refer to the total
224			c number of steps (1, ... , cal_IntDays).
225			c
226			c o cal_MonthsForYear - Given the integration year return the number
227			c of months to be integrated, the first month,
228			c and the last month in the year specified. The
229			c first and the last step refer to the total
230			c number of steps (1, ... , cal_IntMonths).
231			c
232			c o cal_Intsteps - Return the number of calendar years that are
233			c affected by the current integration.
234			c
235			c o cal_IntDays - Return the number of calendar days that are
236			c affected by the current integration.
237			c
238			c o cal_IntMonths - Return the number of calendar months that are
239			c affected by the current integration.
240			c
241			c o cal_IntYears - Return the number of calendar years that are
242			c affected by the current integration.
243			c
244			c o cal_nStepDay - Return the number of time steps that can be
245			c performed during one calendar day.
246			c
247			c o cal_CheckDate - Do some simple checks on a date array or on a
248			c time interval array.
249			c
250			c o cal_PrintError - Print error messages according to the flags
251			c raised by the calendar routines.
252			c
253			c o cal_PrintDate - Print a date array in some format suitable for
254	edhill	1.4	c MITgcm's protocol output.
255	heimbach	1.1	c
256			c o cal_TimeStamp - Given the time and the iteration number return
257			c the date and print all the above numbers.
258			c
259			c o cal_Summary - List all the setttings of the calendar tool.
260			\end{verbatim}
261			}
262