Observations and numerical modeling of mountain waves over the Organ and San Andres Mountains of New Mexico

White Sand Missile Range (WSMR) lies mainly in the lee of the Organ and San Andres Mountains in south central New Mexico. Together, these two mountain ranges form a nearly unbroken 150 km long south to north oriented barrier that rises 1 to 1.5 km above the surrounding terrain. This barrier is both quite steep and generally quite narrow ranging from a maximum width of 20 km down to 5 km. During late winter and much of the spring, there is often strong westerly flow aloft over the southwestern US. Frequently, strong inversions at heights somewhat above that of the highest terrain complicate the flow's response as it traverses the steep barrier. Consequently, WSMR experiences many mountain and lee wind events in this part of the year.

Many US Army missions are significantly impacted by the highly variable weather conditions in and around complex terrain such as at WSMR, but the Army's capability to forecast and diagnose such conditions remains limited. To better understand and to evaluate and improve the capability of high resolution numerical models to forecast the effects of terrain on weather conditions, the Army Research Laboratory collected surface data from five 10 m instrumented towers sited in the lee of the Organ Mountains during the first three months of 2004. In addition, data from the White Sands Missile Range (WSMR) Surface Automated Meteorological System (SAMS) and other nearby surface stations such as the Remote Automated Weather Stations (RAWS) and the NOAA Profiling Network wind profiling radar at WSMR were collected. The total data set enables meso-b and -ggamma scale depiction of the wind flow in the lee of the Organ mountains; this is augmented in the vertical using horizontal and vertical wind components from the WSMR wind profiling radar.

We will show high resolution (~1 km grid spacing) results from the National Taiwan University/ Purdue, WRF and CaMEL flow solver models for flow situations including hydraulic jumps, lee waves and so on. For example, on January 25, 2004, strong downslope winds on the leeward side of the Organ Mountains transitioned into a flow reversal associated with the first of the lee waves. The modeled lee wave train downwind of the mountains is consistent with an observed decrease with height of the Scorer Parameter

(l² = N²/U² - 1/U D²U /dz²), are well represented by the model's surface winds, and are in agreement with the wind profiler observations. The complete results for this day, including comparison of the models' results and the observations, and those for other days and different situations will be shown in detail.