|Rice Straw Burning
Program - 98
Donald Schukraft, WeatherNews, Inc.
|The 1998 Fall Burn Program was characterized by steady,
methodical burning of agricultural waste with very little downtime due to poor air
circulation or extended periods of rain. Total acreage burned was second lowest since the
program began in 1981. Complaints to the Air Resources Board were almost nonexistent.
The program got under way on Tuesday, September 15 and concluded 56 days later on Monday, November 9. During this two-month period, 85,000 acres of agricultural waste was burned, 75 percent of which was rice stubble. Air quality, as measured by the coefficient of haze, was the best since the programs inception, resulting in only two complaints to the ARB. Only one day, October 23, was declared a no burn day due to excessively high morning stability and poor basin air quality.El Niņo Hangover
Despite reasonably good atmospheric conditions, the fall burn got off to a slow start. An El Niņo-induced short growing season left few fields ready to burn, much less ready to harvest in mid-September. Sharply cooler weather along with some precipitation the last week of September improved atmospheric conditions but unfortunately slowed the rate of harvest and interfered with subsequent drying of stubble. Nevertheless, more than 18,000 acres were burned in September, an amount fairly typical for the month.
Dry weather dominated in October, accelerating the harvest. Weak frontal passages the first half of the month prevented the Sacramento Valley from becoming excessively stagnant, allowing a small but consistent amount of acreage to be burned each day. Sharply warmer weather led to the only no burn day on October 23. These very stable conditions quickly reversed the following day when a surprisingly vigorous storm system dumped up to two inches of rain on the valley. Fortunately, fields dried quickly in the systems wake. Overall, more than 48,000 acres were burned in October.
The first week of November was the most productive period of burning for the entire burn program. More than 18,000 acres were burned in a six-day period culminating on Nov. 6. A frontal passage brought widespread rain on the 7th. After a couple of days of "meager burning," the organized phase of the program concluded Nov. 9.Air Quality Monitoring
Air quality is measured by the "coefficient of haze" (COH). The accompanying graph shows a general increase in COH as the burn season progressed. However, the graph also illustrates how this increase is not directly linked to the amount of acreage burned. As in years past, burning has had little direct impact on the air quality of the Sacramento Valley. Meteorologists point out that shorter day length as the fall progresses leads to stronger inversions at night, which become increasingly more difficult to break. Another surprising development illuminated by the graph is the consistency of burning that took place last fall. Few days were missed because of rain or changes in air quality. This is partially a reflection of the conservative management style of the program and a strong commitment to maintaining the air quality of the Sacramento Valley. The big dips in air quality and daily burn acreage were caused primarily by either periods of wet or excessively windy weather.
Preparations for the 1998 fall burn began with late summer visits to the Automatic Meteorological Observing Stations (AMOS) scattered throughout the Sacramento Valley. All stations were checked for proper operation. Weathernews personnel attended a coordination meeting August 31 with representatives of the Air Resources Board, Fife Environmental and participating counties.
Many improvements were made to the Weathernews Fall Burn Web page (located at www.wxnet.com/fallburn) prior to the start of the 1998 fall burn. Expanded access was made to weather forecasts, observations and other files. Additional links to other weather resources, such as radar and satellite imagery were also provided. Regularly updated hourly observations and daily summaries for all airport and automatic weather station sites in the Sacramento Valley were added. A point and click map of weather station locations made accessing this wealth of valley weather information very convenient.