Discussion of

Natural Event DocumentationHigh Winds, Corcoran and Bakersfield, California

September 22, 2006

Rudolf B. Husar

March 10, 2006

Key Evidence: High Winds -> High PM10

• The SJV APCD makes a good case that high winds and high PM10 occurred in Corcoran & Bakersfield

MODIS Terra, 10:30 Local Time MODIS Terra, 13:30 Local Time

MODIS Terra shows some pollution/smoke in the Southern SJV

MODIS Aqua, 3 hours later shows that the pollution/smoke has been cleared by the high winds

Neither image shows evidence of dust – not surprising since dust is hard to see over land

AIRNOW PM2.5, Sep. 22, 2006, Local time

• AIRNOW data are available along the SJ Valley

2006-09-22:14

2006-09-22:22

2006-09-22:16 2006-09-22:18 2006-09-22:20

2006-09-23:00 2006-09-23:02

AIRNOW PM2.5

• There is an issue with the absolute times – don’t match with the SJV report

Corcoran, 16:00 peak

Bakersfield, 20:00 peak

Modesto, 12:00 peak

Sacramento, ?? peak

The dust peak is progressing from 12:00 in Modesto to 20:00 in Bakersfield

Transport speed 0f 25 MPH would do it

Surface Visibility (Bext), Winds – Local Eastern Time ??

• The high winds were also ‘transported’ – moving southward• So, as the gust move southward it could create local dust wherever it peaks

2006-09-22:16 2006-09-22:18 2006-09-22:20 2006-09-22:22

NAAPS Dust Model, Sep 22, 2006 (Times are GMT)

• High surface dust concentrations are forecasted for California• In the early morning the highest winds & surface dust conc. Highest in N. California• By the afternoon, the winds & surface conc. highest over S. California

2006-09-22 00:00 2006-09-22 06:00 2006-09-22 12:00

2006-09-22 18:00 2006-09-23 00:00 2006-09-23 06:00

PM10-PM25 Obs from the SJV Report

• The PM10/PM2.5 ratio of 5-10 indicates fresh dust• But the broad peak in Bakersfield suggests that the dust there has been dispersed..

Tentative Conclusion

Tentative Conclusions• High winds were present to cause windblown dust• Short-term PM10 peaks are indicative of windblown dust• It was a Natural Dust Event

Questions

• Why is PM10 highest in Corcoran-Bakersfield? • Transport from the North is plausible

Alternative Speculative Explanation by RBH (may be off)

• The high wind gusts were moving southward

• As the gust progressed, it kicked up local dust and caused the very high PM10

•