Meeting Minutes: Test Criteria for the Mountain Counties Air Basin

This page last reviewed June 20, 2008


Effective May 1, 2003 the Air Resources Board Meteorology Section implemented new test criteria for the Mountain Counties Air Basin (MCAB). Burn decisions based on Title 17 criteria were previously made for the entire air basin as a whole. Under the new test criteria, burn decisions are made for two zones in the MCAB, as follows:

1. North Section
2. South Section

The North Section includes Plumas, Sierra, Nevada, Placer, and El Dorado Counties. The South Section includes Amador, Calaveras, Tuolumne, and Mariposa Counties. See map.

For both the North and South Sections of the MCAB, a permissive burn day will be declared when the following test criteria are met:

  1. Near 4:00 a.m., the mean 500 millibar (mb) height over the Basin is less than the limiting mean height given in the following table
  2. The expected 4:00 p.m. mean 500 mb height over the Basin is less than the limiting mean height given in the following table.

500 mb Height Test Criteria

Month

No Burn

Marginal

Fair

Good

Superior

January

Old > 571
New > 574

Range:
> 571
< 574

Range:
> 567
< 571

Range:
> 558
< 567

< 558

February

Old > 571
New > 574

Range:
> 571
< 574

Range:
> 567
< 571

Range:
> 558
< 567

< 558

March

Old > 571
New > 574

Range:
> 571
< 574

Range:
> 567
< 571

Range:
> 558
< 567

< 558

April

Old > 572
New > 576

Range:
> 572
< 576

Range:
> 568
< 572

Range:
> 564
< 568

< 564

May

Old > 577
New > 579

Range:
> 577
< 579

Range:
> 572
< 577

Range:
> 567
< 572

< 567

June

Old > 582
New > 585

Range:
> 582
< 585

Range:
> 579
< 582

Range:
> 573
< 579

< 573

July

Old > 585
New > 588

Range:
> 585
<588

Range:
> 582
< 585

Range:
> 579
< 582

< 579

August

Old > 587
New > 588

Range:
> 587
< 588

Range:
> 583
< 587

Range:
> 579
< 583

< 579

September

Old > 585
New > 587

Range:
> 585
< 587

Range:
> 579
< 585

Range:
> 573
< 579

< 573

October

Old > 582
New > 585

Range:
> 582
< 585

Range:
>576
< 582

Range:
> 570
< 576

< 570

November

Old > 577
New > 581

Range:
> 577
< 581

Range:
>571
< 577

Range:
> 565
< 571

< 565

December

Old > 573
New > 576

Range:
> 573
< 576

Range:
> 567
<573

Range:
> 558
< 567

< 558

Additional proposed changes to the North and South Sections include dividing each section into two additional sections. The data for the proposed changes are being collected and analyzed internally before test decisions are made. The proposed changes are as follows:

  1. Above 4,000 feet mean sea level (msl) in the North Section
  2. Below 4,000 feet msl in the North Section
  3. Above 4,000 feet msl in the South Section
  4. Below 4,000 feet msl in the South Section.

Above 4,000 feet msl in the North Section, a permissive burn day will be declared when the following criteria are met:

  1. Near 4:00 a.m., the mean 500 millibar (mb) height over the Basin is less than the limiting mean height given in the table above
  2. The expected 4:00 p.m. mean 500 mb height over the Basin is less than the limiting mean height given in the table above.

Below 4,000 feet msl in the North Section, a permissive burn day will be declared when both of the following criteria are met:

  1. The maximum mixing depth is expected to be at least 1,500 feet above ground level (agl).
  2. The expected afternoon onshore airflow is expected to be at least five miles per hour.

Above 4,000 feet msl in the South Section, a permissive burn day will be declared when the following criteria are met:

  1. Near 4:00 a.m., the mean 500 millibar (mb) height over the Basin is less than the limiting mean height given in the table above
  2. The expected 4:00 p.m. mean 500 mb height over the Basin is less than the limiting mean height given in the table above.

Below 4,000 feet msl in the South Section, a permissive burn day will be declared when both of the following criteria are met:

  1. The maximum mixing depth is expected to be at least 1,500 feet agl.
  2. The expected afternoon onshore airflow is expected to be at least five miles per hour.

In cooperation with the Mountain Counties Air Basin, the ARB has three years to develop new criteria or to use alternate criteria to those specified to establish burn days, no-burn days, and marginal burn days.

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