Thursday, January 13, 2011

Jan. 13 - Low wind, high evening PM  - Low of 23F at the NMSU Coop site this morning. I can feel it warming up. We also had a high of 57F. The forecast for today called for a mild day. Below is the afternoon MODIS image showing our clear skies.
Winds were forecasted to be low today in the eastern part of the study area and increase as you go west. Below is the wind speed trace starting at 14 UTC (7 am) for Las Cruces based on the RUC model. I use Z and UTC interchangeably for noting time. Maximum winds at 16 UTC are 2.8 m/s in Las Cruces.
And here is the trace for Lordsburg for the same time period. Maximum winds at 20 UTC are 6.6 m/s.
So far this morning we have a low wind peak in particulates at the Sunland Park City Yard and Anthony sites.We also have a fairly strong temperature inversion based on the 12 UTC sounding at Santa Teresa. Graphic was obtained from the NCAR Real-Time Weather page.
I thought this is a nice example of a cold core high pressure over Chihuahua at 20 UTC (1 pm MST) today. You can see the surface wind divergence associated with high pressure. Remember that wind flows out of high pressure to low pressure. Temperatures are color coded with coldest temperatures in the blue/green and warm in yellows/orange. This is from the 14 UTC RUC model run.
The surface high was clearly marked in the 15 UTC weather map
At the NMSU core site we saw an evening PM10 peak of 93 µg/m3 and PM2.5 of 30 µg/m3. The PM2.5 MetOne BAM has been missing a few hours here and there over the past few days. I'll have to take a look at it tomorrow. This instrument has been very reliable in the past 6 months.
And another low wind PM spike at the Sunland Park City Yard
and also at the NMED Anthony Elementary site
The evening peak signature goes away at the Las Cruces West Mesa station. This goes to show that PM tends to be higher in the valley than at the West Mesa site. The West Mesa site is 8.5 km directly west of the core site at the Garcia Horticultural farm.
The Las Cruces Holman Road site showed a different story with a 6 pm peak PM10 of 316 µg/m3. Winds were blowing from the east at the time of the spike and wind gusts were around 4 m/s.
The Holman Road site is surrounded by disturbed desert with unpaved roads to the east as shown below from Google Earth. I tend to think that this was caused by a local source rather than representative of the east mesa area although the timing is right and coincides with the other PM spikes across the valley.
The AQI at 11 pm MST shows a patch of moderate air quality over El Paso.
Tomorrow's AQI forecast looks like green (good) air quality.

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