Lab 12.3

Lab 12.3 – How can we tell when the ash plume is over the Endurance Array?

Fundamental concept: Describe variations in atmospheric conditions indicative of wildfire ash plumes and identify the arrival date/time of the plume over the Endurance Array. 
Estimated time to complete: 20-30 minutes
Data skills Preparation: Lab 2
Materials needed: None

In activity 12.1 you will examine OOI data, which indicates the arrival of the 2020 Labor Day Fire’s ash plume over the Endurance Array.  Again, think about your experiences around a campfire. What characteristics of the smoke plume would the air above the Endurance Array experience? In this lab section, you will determine the arrival date of the smoke plume based on physical characteristics of the air above the array, observed by the Bulk Meteorology Package on the Oregon Offshore Surface Mooring.

Winds at the latitude of the Endurance Array are typically west winds, meaning they are commonly coming from the west. However, during the period when the smoke plume drifted over the Endurance array, the winds temporarily shifted and east winds prevailed for a period, meaning that the winds were coming from the east and pushing the plume out to sea.

Wind Speed and Direction:

You may have already learned that winds are named for the direction from which they are coming. For instance, a west wind is blowing from the west to the east. You may have also learned that wind direction can be named using a 360 degree compass. In that case, wind coming from due west would be indicated by a value of 270 degrees. To avoid confusion, the parameter we will use is named by OOI as “Eastward wind” velocity which is the same as “west wind” velocity.

The eastward wind velocity can be positive or negative: positive values indicate wind blowing from the west to the east, while negative values indicate wind blowing from the east to the west.

For example:

• +5 m/s on the chart means wind is moving from west to east at 5 meters per second
• -5 m/s on the chart means wind is moving from east to west at 5 meters per second

Relative humidity:

Relative humidity (RH) is the amount of water vapor present in air expressed as a percentage of the amount needed for saturation at the same temperature. The warmer the air, the more water vapor it can hold.

For example, given the same amount of water vapor in an air mass, relative humidity would be higher in cooler air and lower in warmer air. When the air is cool, it can hold less moisture, resulting in higher relative humidity. Conversely, warm air can hold more moisture, leading to lower relative humidity. Smoke plumes contain dark carbon particulates, which absorb light and radiate heat, impacting relative humidity in the smoke plume.

Air temperature:

Air temperature is the measure of the warmth or coolness of the air in the atmosphere. It is a fundamental aspect of weather and plays a crucial role in shaping our climate and environment.

Factors Influencing Air Temperature: Although air temperature is affected by a number of factors, including solar radiation, latitude, altitude, time of day, and seasonal changes, smoke plumes can increase the temperatures by absorbing sunlight and emitting the absorbed energy as heat.

Net Shortwave Irradiance:

Net shortwave irradiance is a measure of solar radiant energy in the visible and near-ultraviolet wavelengths less any outgoing (upward) short-wave radiation from the ocean surface. Net shortwave irradiance increases during the daytime and decreases at night.

Quick Check Questions

 

Interpretation Questions

Use the interactive graphs to answer the questions below:

[open in new window]

1. Select “Eastward Wind” for Graph 1. On what date does it appear that the wind changes direction significantly?
2. Now select “Air Temperature” as the parameter for Graph 2. How does the air temperature change at the time of the wind shift?
3. Select “Relative Humidity” for Graph 2, and compare the two graphs. Does there appear to be a change in relative humidity with a correlation to the change in easterly winds?  If so, what change occurs?
4. On what date does relative humidity change, indicating the arrival of the smoke plume over the array?
5. What causes the observed change in relative humidity over the Endurance Array as the smoke plume moves in? Consider the properties of smoke—how it absorbs and emits light and heat energy,and how these factors could influence temperature and, consequently, relative humidity.
6. Select net shortwave irradiance in Graph 2, does the net shortwave radiation decrease or increase with the arrival of the smoke plume. Explain why this is or is not the anticipated response.
7. On what date does NETSIRR indicate the arrival of the smoke plume? Based on the data, on which day was the smoke plume the thickest (most dense) over the array.
8. Based on all the parameters, what day did the smoke plume arrive over the array?

Application Questions

1. Watch the GOES satellite video below and stop it when you see the smoke plume arrive along the coast of Oregon. Record the date and time that the smoke plume, driven by the atypical east winds, first arrives at the coast of Oregon and above the Endurance Array. Does  the GOES video confirm the date you estimated based on evidence observed on the arrays bulk meteorology package?

GOES Satellite Imaging:The GOES satellite has a suite of imaging instruments including visible, near infrared, and infrared wavelengths. This allows the satellite to image during both daylight and darkness, and to indicate various elements at Earth’s surface or in the atmosphere, such as trees, water, clouds, moisture or smoke.