# Presentation: 893419

## South Carolina Forestry Commission

- February 16, 2006
- Smoke Simulation Analysis
- Gary L. Achtemeier
- USDA Forest Service
- Athens, GA

## Task Description

- The following set of slides summarize a PB-Piedmont post-burn analysis of smoke movement in the aftermath of a 170 acre prescribed burn conducted by the South Carolina Forestry Commission. The burn was conducted on 16 February 2006 in terrain characterized by that of the lower coastal plain. The model simulations run from 1600 EST 16 February through 0800 EST 17 February.

## Weather

- Weather during the burn and the post-burn smoke movement period was mostly clear early becoming cloudy after 0400 EST. A high pressure system over the Atlantic Ocean southeast of the Carolinas stretched westward into South Carolina as a strong low pressure system passed north up the Ohio River valley. The result was southerly winds early slowly shifting to blow from the southwest over the burn site. The geostrophic wind speed, a measure of the strength of the forcing by the large scale (synoptic) wind field decreased from approximately 10.0 m/sec to 1.9 m/sec at 0300 EST. The moderately strong forcing early would have been sufficient to ventilate the burn site while the weaker forcing would have allowed for drainage forcing in the valleys. After 0500 EST, synoptic forcing increased to 12.0 m/sec as a cold front approached the area.

## Modeling Information

- PB-Piedmont Version 5.0-2006
- Grid spacing = 60 m
- Domain size = 271x247 -> 16.3x14.8 km
- Visual domain = 6.9x5.5 km
- Weather data: Hourly METAR
- Elevation data: USGS 30 m DEM
- Elevation contour interval = 2 meters
- Elevation range is 0-38 meters

## The full 16.3x14.8 km model domain captures the broad flat coastal plain of South Carolina. The burn site (white square) is located adjacent to a shallow side valley. 

- The full 16.3x14.8 km model domain captures the broad flat coastal plain of South Carolina. The burn site (white square) is located adjacent to a shallow side valley.

## The PB-Piedmont viewing domain and observation points for 16 February 2006. Observation Point 1 is located over the brown area northeast of the burn site outlined by the white square. Points 2 & 3 are co-located at the end of the drainage north-northwest of the burn site. Observations were taken at different times: Point 1 at 1741 EST, Point 2 at 2221 EST 16 February, and Point 3 at 0503 17 February.

## The simulated plume at 1800 EST, 5 minutes before sunset. An observation of “very light haze” had been made at Point 1 (white circle). PB-Piedmont carries the smoke plume to the northwest over Point 2 well away from Point 1.

## The simulated plume at 2200 EST. Observation at Point 2 of “light to moderate smoke” was made at 2221 EST. PB-Piedmont had shifted winds to blow the plume more to the west bypassing Point 2.

## The simulated plume at 0500 EST 17 February 2006. The observation at Point 3 was “little to no smoke mixed with a little fog”. PB-Piedmont places red dots over Point 3. Red dots mean that weather conditions are such that fog and smoke can coexist.

## Summary:

- PB-Piedmont applied to the coastal plain so far tends to shift winds to blow smoke to the left of where smoke is observed. This tendency appeared with the 2221 EST observation (Point 2) but not with the 0503 EST observation (Point 3 – co-located with Point 2).
- PB-Piedmont also tracks local relative humidity. When the relative humidity reaches 100%, the simulated smoke is displayed as red dots meaning that smoke and fog can coexist. The 0500 EST simulated smoke was almost entirely red dots. The 0503 EST observation noted a mixture of smoke and fog.