Site Name

IMPROVE: WARI (Tribal Protocol Site, started 5/22/03)

Region

Great Basin

Terrain

Terrain is shown in the 2 km terrain map and the 20 km terrain map.

The Walker River Indian Reservation is located in western Nevada. Walker River Paiute Tribe governmental and administrative offices are located in the town of Schurz. The Walker River Protocol site, WARI, is located in the Walker River valley near Schurz. Site elevation is 1,280 m (4,198 ft). The Walker River flows from Walker Reservoir, 12 km (8 mi) north of the site, southward to Walker Lake, 20 km (12 mi) south of the site. Surrounding terrain is flat to the east. To the west elevation rises along the eastern slope of a northern extension of the Wassuk Range up to elevations near 2,000 to 2,200 m (6,500 to 7,000 ft), 650 to 700 m higher than the monitoring site, at a distance of 20 km.

Representativeness

The WARI IMPROVE site should be very representative of regional aerosol composition and concentration

Nearby Population/Industrial Centers and Local Sources

The area around the Walker River Indian Reservation and the WARI IMPROVE site is relatively sparse in population, with few nearby area sources. The central California valley, separated from the monitoring site by the intervening Sierra Nevada Range, is the nearest major industrial and population region. Particulate matter from that source region could be mixed upwards and transported aloft by upper level westerly winds. Reno, Nevada is located 100 km northwest of the monitoring site. The Fallon Naval Air Station Bravo bombing range shares the northern border of the Reservation, 20 km north of the monitoring site. Exposed desert surfaces may be a source of entrained crustal material potentially impacting particulate measurements at the site. High aerosol concentrations may also occur during regional wildfire episodes.

Nearby Meteorological Data Stations

Nearby meteorological monitoring network stations are shown in the data network map and at the RAWS station US Climate Archive site. Data collected since 1987 at the Dead Camel Mountain Nevada RAWS site 35 km (22 mi) north of WARI, elevation 1,369 m (4,490 ft) should be representative of meteorological conditions concurrent with aerosol monitoring. Nearby representative meteorological data is also now collected as part of the Tribal Air Program for the Walker River Paiute Tribe.

The nearest upper air data collection site is the Reno (REV) RAOB site, about 100 km (60 mi) northwest.

Wind and Transport Patterns

Synoptic scale winds in the Great Basin are predominantly westerly. At lower atmospheric levels, there can be a significant southerly to easterly component in the winter. Surface monthly Tonopah Nevada Wind Roses are an indication of regional patterns, although surface winds are subject to terrain effects. These wind roses show a predominance of northwesterly surface flow, with a southerly component in the summer.

Locally, surface wind directions may be steered by the nearby Wassuk Range to more north and south directions. In the absence of strong synoptic pressure gradients this higher mountainous terrain may cause mountain/valley circulation, with westerly nighttime drainage flow.

Inversions/Trapping

The spacious Walker River valley, bounded by mountainous terrain to the west, may at times see surface trapping inversions that contain locally generated pollutants at the WARI monitoring site elevation. The area is subject to large scale subsidence inversion conditions associated with regional surface high pressure over the Great Basin that can cause buildup and stagnation of aerosols over periods of days. Highest concentrations may result when this warming and drying condition leads to major western wildland fire episodes.

Climatological Statistics

Long term Hawthorne Nevada Airport climate data are reasonably representative of the climate at the WARI monitoring site. The Walker River Paiute Tribe’s Tribal Air Program is a source for shorter term data collected nearer to the site. Other Nevada Climate Summaries are available from the Western Regional Climate Center.

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