Hans-F Graf, University of Cambridge With contributions from Tobias Gerken, Michael Herzog, and the DFG-TiP team Very High Resolution Modelling of Tibetan Plateau Land Use Change Effects on Clouds, Precipitation and Surface Energy balance TPE, Berlin, Dec 2014

Eddy covariance system for measurement of turbulent fluxes at NamCo Lake on Tibetan Plateau in July Photo: Dep. of Micromet. Univ. Bayreuth Land cover of TP in 1950 (a) and 2000 (b). (Cui and Graf, 2009) Energy Balance of the Tibetan Plateau What are the effects of degraded vegetation and soil on the turbulent fluxes, radiation, clouds and precipitation? Use local flux measurements, plant ecological observations and very high resolution modelling to find an answer.

Further questions 1:

Further questions 2: Overshooting Cumulonimbus

Dynamical Core Surface - Fluxes Atmos- pheric Profiles Turbulence Cloud- Microphysics Nudging Radiation Graphic Output/ Budgets The ATHAM model resolves decametres and includes relevant modules for turbulent fluxes and clouds New Soil- Vegetation Module

Daily cycle of clouds, radiation and sea breeze studied in Gerken et al. Theor Appl Clim, 2013 a) Downwelling solar radiation (SWD, [Wm 2 ]) measured on the Tibetan Plateau on 10 Aug b) Land-use map of Nam Co Lake basin created from Landsat data; c) Modis-terra composite of Nam Co Lake captured at 12:45h BST on 6 Aug 2009; d) Modis-aqua composite for the same day and region as panel c), but at 14:20 and 16:00 h BST. The red circles indicate the location of the Nam Co Lake research station.

With large scale winds blowing from N towards Nyentschen Tanghla Shan deep convection develops in the early afternoon over the southern part of the mountain range. A good sea breeze develops. Observations are met nicely.

With large scale winds blowing towards the North, a weaker sea breeze develops, but the convective activity still is close to the mountain range. Convection is weaker in this case. Hence, the sea breeze concept works well, but depends on large scale wind direction. Important is that most precipitation without strong synoptic forcing happens over the mountains. This is important since observations are normally made in the centre of the valleys!

Measurements and simulation (SEWAB model) of evapotranspiration at Kema station Note the high impact of vegetation state (reduced transpiration, enhanced evaporation for degraded vegetation) in the moister year 2012! More such measurements are necessary to cover the whole spectrum of environmental conditions!

Impact of vegetation cover (25% and 75%) and soil moisture (1.0 and 0.5 soil field capacity) on convective clouds and precipitation (Gerken et al., 2014) In the less vegetated case for dry and wet soil earlier thick cloud cover develops reducing incoming solar radiation at ground between 10:00 and 14:00 LST. Wet soil increases precipitation, but this again is modulated by the vegetation coverage. A complex interplay between soil moisture, surface fluxes vegetation, cloudiness and radiation becomes apparent. More vegetation leads to more precipitation in the afternoon hours. Field capacity Vegetation cover 25%75%

K. Yang et al. / Global and Planetary Change 112 (2014) 79–91 Model simulations have shown that degradation of Kobresia mats leads to more evaporation, 2 hrs earlier cloud formation reducing radiation, increased precipitation and reduced temperature. This has been observed especially for the regions with Kobresia (Yang et al. 2014).

Summary -Deep clouds and heavy rainfall develop mainly close to mountain ranges. That is important since normally observations are made in the centre of the basin, where the settlements are located. - Degradation of vegetation has complex effects on turbulent fluxes, evolution of clouds during the day, incoming solar radiation and precipitation. Less vegetation results in earlier and more intense rainfall, reduced incoming solar radiation and lower temperatures. - Model simulations compare very well (at least qualitatively) with observations. - Degradation of vegetation on the Tibetan Plateau has significant impact on its energy balance – and this also has repercussions on the larger scale monsoon circulation (not shown here, but published in a number of papers with Cui Xuefeng)

Modell ATHAM für Konvektionsentwickungen 2-D meso-maßstäbliches Atmosphärenmodell Hybrid Vegetationsdynamisches Biosphärenmodell (Friend et al., 1997; Friend und Kiang, 2005) Wolken auflösendes aktives Tracer Modell (Oberhuber et al., 1998; Herzog et al., 2003) Meso-maßstäbliche Auflösung von Zirkulationen und Konvektionsentwicklungen für das Nam Co Gebiet (Gerken et al., 2013, 2014) Anpassung des Bodenmodells an SEWAB (Gerken, et al., 2012)