MATERHORN

Mountain Terrain Atmospheric Modeling and Observations Program.

Granite Peak - seen from Ibapah Peak

Figure 1.: Granite Peak at sunset - seen from Ibapah Peak, Deep Creek Mountains, UT.                               

The Mountain Terrain Atmospheric Modeling and Observations Program (MATERHORN) is a multidisciplinary University Research Initiative (MURI) sponsered by the Office of Naval Research. Please check the official web-page of the MATERHORN program at the University of Notre Dame, with links to other research groups. This webpage is an overview of work planned and conducted at the University of Utah by the Hoch & Whiteman research groups as part of the MATERHORN-X team.

Introduction

MATERHORN is a three-year meteorological research program to identify and study the limitations of current state-of-the-science mesoscale models for mountain terrain weather prediction and to develop scientific tools to help gain advances in predictability. It consists of four synergistic components:  a modeling component (MATERHORN-M), a technology component (MATERHORN-T), a parameterization component (MATERHORN-P) and a field experimental component (MATERHORN-X)

The core scientific objective of MATERHORN-X is to gain a fundamental understanding of the interaction of small and large-scale motions in the complex terrain of the Granite Mountain Atmospheric Science Testbed (GMAST) facility at Dugway Proving Ground (DPG), and to improve the predictability of complex terrain weather by gaining an improved understanding of model errors, error growth and predictability limits. The data collected in MATERHORN-X will facilitate model validation, data assimilation and development of physics-based parameterizations.
muri-schematic
Figure 2.: Schematic of the land-surface contrasts and flow interactions around Granite Peak, UT.
The surroundings of Granite Peak are characterized by the land surface contrasts beween vegetated areas ("sparse sagebrush" - actually a mixture of vegetation of greasewood, saltbush, rabbitbrush, blackbrush, ephedra and sage brush) and the non-vegetated playa located west of Granite Mountain. A playa is an undrained flat basin floor between desert mountain ranges that seasonally becomes temporarily covered with water. Because the playa soil develops a salty white crust that is highly reflective during dry periods and becomes moist during wet periods, large energy budget contrasts occur between the playa and its drier surroundings. These surface contrasts drive "playa breezes" - circulations that are similar to the better-known land-sea breeze circulations.

The study site at DPG is surrounded by higher topography to the northeast (Cedar Mountains), the Simpson Mountains, Keg Mountains and the Dugway Range to the south, and Granite Mountain to the west. This geographic setup leads to a characteristic diurnal pattern of thermally driven circulation during synoptically quiescent times, with north-westerly up-valley flow at daytime and a south-easterly down-valley flow during the night.

Previous studies at DPG have shown the occurrence of up-and downslope flows along the eastern slopes of Granite Peak. The east slope of Granite Peak is on of the hot-spots for field observations during MATERHORN-X

Activities

Our activities during the MATERHORN-X campaigns include surface energy balance observations, radiosonde and tethered balloon launches, LiDAR observations on the east slope of Granite Peak, and SoDAR measurements. As data analysis progresses we will update this section.

Surface Winds

The network of 10-m meteorological towers "SAMS" operated by DPG reveals the typical diurnal wind pattern that is dominated by thermally driven circulations under synoptically quiescent conditions, as seen in Figure 3.
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Figure 3.: Animation of temperature and winds at each SAMS station for days in September, October and November (SON) under quiescent conditions. Quiescent conditions are defined by NCEP/NCAR 700 mb wind speed of less than 5 m/s (10 kts). Days are defined as 18 UTC -18 UTC, and both the 00 UTC and 12 UTC times on that day must have 700mb winds less than 5 m/s to qualify.  This is fairly restrictive, with less than 10% of days qualifying.  N for each station varies due to period-of-record differences. Source: Matt Jeglum, University of Utah


Energy Balance Studies

All components of the surface energy balance will be observed at three Extended Flux Sites (EFS), EFS Playa, EFS Sagebrush, and EFS Slope.
At all three sites, observations of the four components of the surface radiation balance are observed with state-of-the-art radiation instrumentation. Net radiation is  the sum of the four (incoming and outgoing / longwave and shortwave) components.

The turbulent fluxes, sensible (H) and latent (L) heat fluxes are measured using eddy-flux instrumentation by Eric Pardyjak's group in the University of Utah's Mechanical Engineering department.

Special care is taken to properly evaluate the subsurface heat flux, using self-calibrating heat flux plates and correcting for the energy storage change in the soil layers above the plates. Special probes are used to measure the thermal diffusivity and heat capacity of the soil.
Diurnal Cycle of Shortwave Fluxes - 7 Oct 2012
 energy balance - 7 Oct 2012
Figure 4: Diurnal cycle of shortwave incoming and shortwave outgoing radiative fluxes observed at EFS Sage and EFS-Playa, 7 October 2012.
Figure 5: Diurnal cycle of energy balance components observed at EFS Sage and EFS-Playa, 7 October 2012.

Global Radiation in Complex Terrain

The spatial variation of global radiation in complex terrain is generally considered the driving forcing for temperature contrasts and the formation of micro-climates in mountainous terrain. We have developed a simple computer code that calculates global radiation as a function of the solar position and the slope angles derived from a digital elevation model. Animations of global radiation for Granite Peak and its surroundings can be found here.

Slope Flow Studies

 Slope flows on the east slope of Granite Peak were made using a line of 5 tall (≥20 m) meteorological towers, ~20 weather stations and several Doppler wind LiDARs. 

Visualisation of LiDAR scans up the east slope of Granite Peak.
 Visualization of LiDAR scans on 2 Oct 2012 on the east slope of Granite Peak (Fig. 6). Color contours give the wind speed along the LiDAR beam - Blue colors indicate flow towards the LiDAR (i.e. down-slope).

While additional analysis is needed for this 2156 MST case, the LiDAR data depicts the interaction between a shallow downslope drainage flow and an apparent colder pool of air that is sloshing up the slope and undercutting the downslope flow layer. Patterns resembling Kelvin-Helmholtz waves can be seen at the top of the colder air layer.
Figure 6: LiDAR scan 2 October 0456 UTC.


Near-Surface Temperature Evolution

Arrays of fine-wire thermocouples are being used to determine the temporal evolution of the detailed temperature structure in the near-ground layer (lowest 3 m) at the three EFS sites.


Results & Presentations
last edits 31 Jan. 2013 - SWH