Upslope wind

Upslope wind (daytime) due to greater solar heating on the valley s side than... 

In the mountains, differential heating during the day causes upslope winds, which move up both sides of a valley, and upvalley winds that blow along the valley. During the night, the directions reverse to downslope and downvalley winds (Geiger, 1965 Fig. 1.3). 

Cyclical changes over shorter time scales are harder to spot in the records because they are usually much weaker than seasonal oscillations and can be masked by random variations in the data. Daily cycles have not been observed but possible ambient error sources at Mauna Loa include volcanic, vegetative and man-made effects (e. g. vehicular traffic and industry). Daily peaks in measured concentrations occur because of complex wind currents. Downslope winds often transport CO2 from distant volcanic vents, causing elevations in measured CO2 concentrations. Upslope winds during afternoon hours are often low in CO2 because of photosyn-... 

Perpendicular Day South-facing slope is heated. 5a North wind—stationary eddy fills valley 5b South wind—eddy suppressed, flow without separation 6 Upslope flow on both heated slopes— stationary eddy on one side of valley... 

Figure 11.28 shows similar data for measurements made at Idaho Hill, Colorado, in the fall of 1993 (Williams et al., 1997). Measurements were made of NO, N02, PAN, PPN, HN03, and particulate nitrate, as well as total NO. Two sets of meteorological conditions were encountered, one where the wind was downslope and from the west where there were few sources nearby, and one where the wind was upslope, carrying pollutants from urban areas to the east. Figure 11.28a shows that for upslope air masses from the east with relatively fresh emissions, the sum of the measured compounds accounts, within experimental error, for the total NOy. The average ratio of NOy/total NOy was 1.06 + 0.15. On the other hand, during periods with cleaner, downslope air from the west (which has also had more time to react), the sum of the individual compounds frequently does not add up to the total measured NOy (Fig. 11.28b). The deficit ranges...

When winds move upslope, the air expands and cools ten degrees Celsius per kilometer or five and a half degrees Fahrenheit per thousand feet. When moist air is lifted it cools at the same rate as dry air until the temperature falls to the dew point, at which point water vapor begins to condense to form clouds. When winds move downslope, the air temperature increases ten degrees Celcius per kilometer or five and a half degrees Fahrenheit per thousand feet, and lateral expansion of this heated air increases the wind velocity. In the Los Angeles area, these hot dry winds are called Santa Anna winds. Such winds have other local names over many regions of the earth. 

SNL/NM precipitation and wind information varies from NWS data. Topographic features such as mountains, canyons, and arroyos influence local wind patterns across SNL7NM. Canyons and arroyos tend to channel or funnel wind, whereas mountains create upslope-downslope diurnal wind flows. A more detailed climatic description for the TA-V site is given in the following section. 

---