PRECIPITATION-RUNOFF MODELING SYSTEM (PRMS)

1. PRECIPITATION-RUNOFF MODELING SYSTEM(PRMS) SNOW MODELING OVERVIEW

2. PRMS

3. PRMS Parametersoriginal version

4. PRMSParameters MMS Version

5. SNOW PROPERTIES • Porous media • Undergoes metamorphosis • Surface albedo changes with time • Density increases with time • Has a free-water holding capacity

6. Energy Balance Formulation Hm = Hsn + Hln + Hc + He + Hg + Hp + Hq Temperature-Index Formulation M = Cm * ( Ta - Tb) Modifications Seasonal adjustment to Cm Vary Cm for forest and open Use equation only for non rain days Account for Hg and Hq

7. Snowpack Energy Balance Components

8. PRMS SNOW MODEL Energy Balance Formulation Hm = Hsn + Hln + Hc + He + Hg + Hp + Hq Model Formulation (on each HRU) Hsn = swrad * (1. - albedo) * rad_trncf Hln = emis * sb_const * tavg4 (es T4) Hc + He = cecn_coef(mo) * tavg (ppt days) = 0 (dry days) Hp = tavg * net_precip Hg assumed 0 Hq is computed

9. Snow Surface Albedo vs Time

10. Solar Radiation Transmission Coefficient vs Cover Density

11. Net Longwave Radiation Hlw = (1. - covden_win) * [(emis * air) -snow)] + covden_win * (air -snow) air and snow = sb_const * tavg4 [ (es T4) e = 1.] where tavg is temp of air and temp of snow surface emis = emis_noppt no precip = 1.0 precip

12. PRMS SNOW MODEL Energy Balance Formulation Hm = Hsn + Hln + Hc + He + Hg + Hp + Hq Model Formulation Hsn = SWRin * (1. - ALBEDO) * TRNCF Hln = es T4 Hc + He = Cce * Tavg (ppt days) = 0 (dry days) Hp = Tavg * PTN Hg assumed 0 Hq is computed

13. SNOWPACK DYNAMICS • 2-layered system • energy balance: 2 12-hour periods • energy exchange between layers -- conduction and mass transfer • Tsurface = min(tavg or 0o C) • Tpack is computed • density = f(time, settlement constant) • albedo decay = f(time, melt) • melt volume: use depth-area depletion curve

14. Areal Snow Depletion Curve

15. MELT SEQUENCE cal_net > 0 snowmelt = cal_net / 203.2 pk_temp < 0o C refreeze to satisfy pk_def pk_temp = 0o C satisfy free water holding capacity(freeh2o_cap) remaining snowmelt reaches the soil surface

16. Max Temperature-Elevation Relations

17. TEMPERATURE For each HRU tmax(hru) = obs_tmax(hru_tsta) - tcrx(mo) tmin(hru) = obs_tmin(hru_tsta) - tcrx(mo) where tcrx(mo) = [ tmax_lapse(mo) * elfac(hru)] - -------------tmax_adj(hru) elfac(hru) = [hru_elev - tsta_elev(hru_tsta)] / 1000.

18. Precipitation-Elevation Relations

19. Mean Daily Precipitation Schofield Pass (10,700 ft) vs Crested Butte (9031 ft) Mean daily precip, in. MONTH

20. Precipitation Gage Catch Error vs Wind Speed (Larsen and Peck, 1972) Rain (shield makes little difference) Snow (shielded) Snow (unshielded)

21. Precipitation Gauge Intercomparison Rabbit Ears Pass, Colorado

22. PRECIPITATION For each HRU - DEPTH hru_precip(hru) = precip(hru_psta) * pcor(mo) pcor(mo) = Rain_correction or Snow_correction

23. PCORComputation Precipitation Distribution Methods(module) • Manual (precip_prms.f) • Auto Elevation Lapse Rate (precip_laps_prms.f) • XYZ (xyz_dist.f)

24. PCORComputation hru_plaps • Auto Elevation Lapse Rate For each HRU hru_psta hru_psta = precip station used to compute hru_precip [ hru_precip = precip(hru_psta) * pcor] hru_plaps = precip station used with hru_psta to compute ------ -------preciplapse rate by month [pmo_rate(mo)]

25. PCORComputation Auto Elevation Lapse Rate Parameters pmn_mo elv_plaps padj_sn or padj_rn

26. PCORComputation pmn_mo(hru_plaps) - pmn_mo(hru_psta) pmo_rate(mo) = elv_plaps(hru_plaps)-elv_plaps(hru_psta) For each HRU • Auto Elevation Lapse Rate hru_elev - elv_plaps(hru_psta) adj_p = pmo_rate * pmn_mo(hru_psta) snow_adj(mo) = 1. + (padj_sn(mo) * adj_p) if padj_sn(mo) < 0. then snow_adj(mo) = - padj_sn(mo)

27. PRECIPITATION For each HRU - FORM (rain, snow, mixture of both) RAIN tmin(hru) > tmax_allsnow tmax(hru) > tmax_allrain(mo) SNOW tmax(hru) <= tmax_allsnow

28. PRECIPITATION For each HRU - FORM (rain, snow, mixture of both) MIXTURE prmx = [(tmax(hru) - tmax_allsnow) / -------------------------(tmax(hru) - tmin(hru)] * adjmix_rain(mo) OTHER Precipitation Form Variable Snowpack Adjustment

29. PARAMETER ESTIMATION

31. PRMS Parameters Estimated • 9 topographic (slope, aspect, area, x,y,z, …) • 3 soils (texture, water holding capacity) • 8 vegetation (type, density, seasonal interception, radiation transmission) • 2 evapotranspiration • 5 indices to spatial relations among HRUs, gw and subsurface reservoirs, channel reaches, and point measurement stations

32. BASIN DELINEATION AND CHARACTERIZATION Polygon Hydrologic Response Units (HRUs) (based on slope, aspect, elevation, vegetation) Grid Cell Hydrologic Response Units (HRUs) (Equal to Image Grid Mesh) Focus of research modeling Focus of operational modeling

36. Upper San Joaquin River, CAEl Nino Year

37. SUBSURFACE SURFACE GW ANIMAS RIVER, CO PREDICTED MEASURED

38. EAST FORK CARSON RIVER, CA SURFACE SUBSURFACE GW

39. CLE ELUM RIVER, WA SUBSURFACE SURFACE GW

40. REMOTELY SENSED SNOW-COVERED AREA AND SNOWPACK WATER EQUIVALENT

41. Satellite Image for Snow-Covered Area Computation

45. NASA Regional Earth Science Applications Center Objective - Integrate remotely sensed data into operational resource management applications SW Center - U of AZ, U of CO, USGS, --------------Lawrence Berkeley Labs ~ 1 km pixel resolution of NOAA snow-covered area product on 750 km2 basin

47. East Fork Carson River, CA 1986 1988 1986

48. Observed and Simulated Basin Snow-Covered Area

49. SIMULATED vs SATELLITE-OBSERVED SNOW-COVERED AREA

50. SIMULATED vs SATELLITE-OBSERVED SNOW-COVERED AREA