On the Closure of the Surface Energy Balance in Highly Complex Terrain Mathias W. Rotach, Pierluigi Calanca, Andreas Weigel, Marco Andretta Swiss Federal Institute of Technology Institute for Atmospheric and Climate Science

Layout Surface energy balance Data: MAP -Riviera project Energy balance for a layer Implications for modeling

MAP-Riviera Valley FloorSlope site Average 15 fair-weather days

Surface Energy balance NR G HoHo LvEoLvEo NR-G=H o +L v E o

Surface Energy balance horizontally homogeneous surfaces --> constant turbulent fluxes --> no advection --> closure! z0...] NR-G=H o +L v E o

Surface Energy balance horizontally homogeneous surfaces --> constant turbulent fluxes --> no advection --> closure! z0...] --> non-closure: measurement error turbulence time scales NR-G=H o +L v E o

Surface Energy balance horizontally homogeneous surfaces --> constant turbulent fluxes --> no advection --> closure! z0...] --> non-closure: measurement error turbulence time scales complex terrain... NR-G=H o +L v E o

Bellinzona Biasca Riviera MAP Riviera project Lago Maggiore

MAP Riviera project

MAP Riviera Project

MAP-Riviera: Bosco di Sotto 4 / 16 / 28 m Local surface: corn, grass Full radiation comp, precip, profiles,sfc. hydrology Local slope app. 0.5°

NR G HoHo LvEoLvEo zrzr H(z r )L v E(z r ) Near-Surface Energy Balance

NR G HoHo LvEoLvEo NR-G=Storage+horiz.Adv +vert.Adv HrHr LvErLvEr z=z r

Corrections Sensible Heat flux: --> frequency response (Moore 1986) --> humidity cross-correlation (Schotanus et al. 1983) Latent heat flux: --> frequency response (Moore 1986) --> Oxygen (Dijk et al. 2003) --> WPL-correction (Webb et al. 1980)

Horizontal Advection Comprovasco Magadino Riviera

Vertical Advection zrzr Mean vertical wind: from planar fit

Results...

Energy balance terms NR H+LE+G New sum LE G H Average 7 clear sky days

Contributing terms Sum new terms Storage air / horiz. advection Storage soil Sum corrections Vertical advection Average 7 clear sky days

Vertical advection Proprtional Difference in, q....

Vertical advection Proprtional mean vertical wind

Energy balance terms NR H+LE+G New sum LE G H Average 7 clear sky days

Conclusions Sfc. energy balance in really complex terrain: good to detect processes Corrections to turbulent fluxes important Soil storage term important Vertical advection! --> largest --> most uncertain!

Outlook If indeed vertical advection is substantial > too large a fraction of NR --> H, LE --> cold / dry bias

RAMS simulations - August UTC UTC observations model De Wekker et al. 2003

Salt Lake Valley - VTMX Different models: RAMS MM5 ETA Zhong and Fast 2002 IOPs 6,7,10

Outlook If indeed vertical advection is substantial > too large a fraction of NR --> H, LE --> cold / dry bias How to parameterize in numerical models?

Comparisons of observed and simulated sensible heat fluxes

Hydrological modeling – valley floor Soil moisture (.5m) ET und LE [mm/h] Precipitation [mm/h] ET und LE [W/m2] Sept Sept

ET und LE [W/m 2 ] time Observation (Bowen Ratio) Model (Penman- Monteith) Eddy Correlation Hydrological modeling – valley floor

Closed energy balance Bowen ratio method: --> if and

Planar fit Plot w as a function of (u,v)....

Planar fit on a slope

Common plane vs. local planes Planar fit vs. Double rotation ( PFC - DR )/ DR ( PFC - PF )/ PFC Andretta et al. (2002)

Finnigan et al Energy Balance closure Data from a flux site in Manaus, Brazil