Hi all,
running r.sun on a mountain area with time=8 and day=1, I got negative values for the diffuse radiation fraction.
I even get negative global radiation!
Where am I wrong?
±---------------------------------------------------------------------------+
| Layer: 1_8_d Date: Fri Oct 12 07:53:50 2007 |
| Mapset: zodoardo Login of Creator: zodoardo |
| Location: Valledaosta |
| DataBase: //media/sda7/zodoardo/cartografia/grassdb |
| Title: ( r.sun solar model output ) |
| timestamp: none |
|---|
| Type of Map: raster Number of Categories: 255 |
| Data Type: FCELL |
| Rows: 864 |
| Columns: 1290 |
| Total Cells: 1114560 |
| Projection: UTM (zone 32) |
| N: 5096987.5 S: 5032187.5 Res: 75 |
| E: 422587.5 W: 325837.5 Res: 75 |
| Range of data: min = -18.926418 max = 53.797997 |
| Data Source: |
| Data Description: |
| generated by r.sun |
| Comments: |
| ---------------------------------------------------------------- |
| Day [1-365]: 1 |
| Local (solar) time (decimal hr.): 8.0000 |
| Solar constant (W/m^2): 1367 |
| Extraterrestrial irradiance (W/m^2): 1412.689562 |
| Declination (rad): -0.401581 |
| Latitude min-max(deg): 45.4214 - 46.0199 |
| Sunrise time (hr.): 7.74 |
| Sunset time (hr.): 16.26 |
| Daylight time (hr.): 8.52 |
| Solar altitude (deg): 2.1959 |
| Solar azimuth (deg): 127.0877 |
| Linke turbidity factor: 3.1 |
| Ground albedo: 0.200 |
| ----------------------------------------------------------------- |
| r.sun -s elevin=“DEM” aspin=“DEM_asp” slopein=“DEM_sl” lin=3.1 alb=0\ |
| .2 beam_rad=“1_8_b” diff_rad=“1_8_d” refl_rad=“1_8_r” day=1 step=0.5\ |
| time=8 |
| ±---------------------------------------------------------------------------+ |
±---------------------------------------------------------------------------+
| Layer: 1_8_g Date: Fri Oct 12 08:20:06 2007 |
| Mapset: zodoardo Login of Creator: zodoardo |
| Location: Valledaosta |
| DataBase: //media/sda7/zodoardo/cartografia/grassdb |
| Title: ( 1_8_g ) |
| timestamp: none |
|---|
| Type of Map: raster Number of Categories: 255 |
| Data Type: FCELL |
| Rows: 864 |
| Columns: 1290 |
| Total Cells: 1114560 |
| Projection: UTM (zone 32) |
| N: 5096987.5 S: 5032187.5 Res: 75 |
| E: 422587.5 W: 325837.5 Res: 75 |
| Range of data: min = -10.351157 max = 327.495667 |
| Data Source: |
| Data Description: |
| generated by r.mapcalc |
| Comments: |
| 1_8_b + 1_8_d + 1_8_r |
| ±---------------------------------------------------------------------------+ |
Thanks in advance for your help.