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=3.1alb=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.
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