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WindSpd.h

Go to the documentation of this file.

#ifndef WindSpd_H
#define WindSpd_H

#include <stdlib.h>
#include <math.h>

#include "Units.h"
#include "NLIBRand.h"
#include "FireProp.h"
#include "ChHashTable.h"
#include "KeyVal.h"
#include "DblTwoDArray.h"
#include "FStreamIO.h"
#include "Err.h"

/*
 *********************************************************
 * DEFINES, ENUMS
 *********************************************************
 */

#ifndef DOXYGEN_SHOULD_SKIP_THIS
 
/* used in tokenizing wind azimuth files */
#define WIND_SPD_WSP_COMMENT_CHAR                               ("#")
#define WIND_SPD_SEP_CHARS                                      (" =,;\t")

/* returns corresponding field index in WSP file */
#define WIND_SPD_YR_WSP_TBL_INDEX                               (0)
#define WIND_SPD_MO_WSP_TBL_INDEX                               (1)
#define WIND_SPD_DY_WSP_TBL_INDEX                               (2)
 
/* value of NO DATA used in WSP files */
#define WIND_SPD_WSP_NO_DATA_VALUE                              (-1)

/* keyword indicating units of windspeed stored in .swp */
#define WIND_SPD_WSP_KEYWORD_UNITS                              ("UNITS")
#define WIND_SPD_WSP_KEYWORD_MILEPHR                            ("MILEPHR")
#define WIND_SPD_WSP_KEYWORD_KMPHR                              ("KMPHR")

/* min and max values used to retrieve uniform random number */
#define WIND_SPD_RANDU_MIN_MPS                                  (0.0)
#define WIND_SPD_RANDU_MAX_MPS                                  (10.0)

#endif /* DOXYGEN_SHOULD_SKIP_THIS */

#define WIND_SPD_RAWS_REF_HGT_METERS                            (UNITS_FT_TO_M(20.0))

/*
 *********************************************************
 * STRUCTS, TYPEDEFS
 *********************************************************
 */
 
/*
 *********************************************************
 * MACROS
 *********************************************************
 */

#ifndef DOXYGEN_SHOULD_SKIP_THIS

/* takes an hour 0-23 and returns corresponding field index in WSP file */
#define WIND_SPD_HR_TO_WSP_TBL_INDEX(hour)                      ((hour) + 3)

/*
 * Given a windspeed at reference height, returns windspeed at midflame.
 *
 * Given a windspeed argument assumed to be taken at a reference height (usu. 20 feet, height of RAWS-
 * Remote Automated Weather Station) above the fuel bed, reduces the windspeed using a logarithmic
 * profile according to a value typical of what is experienced halfway between the top of the fuel bed
 * and the top of the flame above the fuel bed.  The formula used approximates a log profile and is 
 * described in (Albini and Baughman, 1979).  Rather than explicitly specify a value for flame height
 * and fuel bed height (the former is usually unavailable until after a prediction for the rate of spread
 * has been made), windspeed in nonforested areas (chaparral and grass fuels) is reduced from 20 ft
 * to a height of 2 * the fuel bed height.  This procedure is described and used in
 * (Finney, 1998).  An alternative approach to explicitly calculating the midflame windspeed is to
 * apply a windspeed adjustment factor (WAF) which corrects the windspeed observed at a height of 20 ft.
 * above the vegetation to that experienced at midflame.  A table of suggested WAF factors for each NFFL
 * fuel model appears in Rothermel (1983). 
 *
 * An example: a windspeed of 10 m/s taken at 6.09 m above the fuel bed of height 1.8288 m is reduced
 * to 3.6 m/s at midflame height using the macro below.  For comparison, Rothermel's (1986) suggested
 * WAF for NFFL 4 (same height as our example) is 0.6 (current standard practice in the field is to use 0.5).
 *
 * WindSpeed At 6.09m (m/s)     Fuel Bed Height (m)     Midflame Windspeed (m/s)
 * 10.0                         1.8288                  3.6408
 * 10.0                         0.9144                  2.9879
 * 10.0                         0.3048                  2.2840
 * 10.0                         0.1524                  1.9787
 *
 * Finney, 1998 has superficially different equation <below>
 *      wsmps / log(((20 + (1.18*(2*fbedhgtm))) / (0.43*(2*fbedhgtm))))
 * Produced identical values as implementation used here.  The log function as referenced here is the 
 * the natural logarithm (ln) because in the ANSI C library the natural log function is named log.
 *
 * Arguments:
 * wsmps- value of windspeed in meters/sec at reference height above fuel bed
 * refhgtm- reference height above fuel bed windspeed has been measured at, in meters
 * fbedhgt- height of the fuel bed, in meters
 *
 * Returns:
 * Windspeed corrected to midflame height, in meters/sec
 */
#define WIND_SPD_REF_HGT_TO_MIDFLAME(wsmps, refhgtm, fbedhgtm)  (ConvertWindSpeedAtRefHgtToArbitraryHgt(wsmps, refhgtm, (2 *(fbedhgtm))))

#endif /* DOXYGEN_SHOULD_SKIP_THIS */
 
/*
 *********************************************************
 * PUBLIC FUNCTIONS
 *********************************************************
 */

int GetWindSpeedMpsFIXEDFromProps(ChHashTable * proptbl, double fbedhgtm, int month, int day, int hour,
                                                unsigned int row, unsigned int col, double * wspmps);

int GetWindSpeedMpsRANDUFromProps(ChHashTable * proptbl, double fbedhgtm, int month, int day, int hour,
                                                unsigned int row, unsigned int col, double * wspmps);

int GetWindSpeedMpsRANDHFromProps(ChHashTable * proptbl, double fbedhgtm, int month, int day, int hour,
                                                unsigned int row, unsigned int col, double * wspmps);

int GetWindSpeedMpsSPATIALFromProps(ChHashTable * proptbl, double fbedhgtm, int month, int day, int hour, 
                                                unsigned int row, unsigned int col, double * wspmps);
double ConvertWindSpeedAtRefHgtToArbitraryHgt(double wsmps, double refhgtm, double hgtm);

int ConvertWindSpeedUnitsToMps(DblTwoDArray * wsp_tbl, const char * units);
                                                 
#endif WindSpd_H        /* end of WindSpd.h */

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