Valley Fog, Hoar Frost, and Inversion

Fog has settled thick in the Salt Lake Valley. Cache valley has had days of fog.

December 7th, 2017

NASA MODIS

December 12th, 2017

NASA MODIS

Freezing fog often causes hoar frost which is the thick white frost that deposits on trees. If the fog droplets are supercooled, meaning the liquid water is below freezing, it will freeze on contact to surfaces. My brother took this picture from Logan:

Photo Credit: Nathan Blaylock

Oh, and the air is getting pretty bad out there. Check out the PM 2.5 trends across northern Utah. Yuck.

airquality.utah.gov

Snow cover

We finally had a sunny day in Utah (though it is quite smoggy). Now we can see the extent of the snow cover in Utah.

N. Utah Snow on November 25th, 2016

MODIS Image, 25 Nov 2016

https://worldview.earthdata.nasa.gov/

When the clouds clear out, we'll be able to see the snow cover after the last two snow storms :)


Update:
Here is the snow on December 2nd

HRRR Land Use

For reference, here is the land use in the HRRR model:

Categories are based on the MODIS 21 Category data set as indicated below:
1 Evergreen Needleleaf Forest
2 Evergreen Broadleaf Forest
3 Deciduous Needleleaf Forest
4 Deciduous Broadleaf Forest
5 Mixed Forests
6 Closed Shrublands
7 Open Shrublands
8 Woody Savannas
9 Savannas
10 Grasslands
11 Permanent Wetlands
12 Croplands
13 Urban and Built-Up
14 Cropland/Natural Vegetation Mosaic
15 Snow and Ice
16 Barren or Sparsely Vegetated
17 Water
18 Wooded Tundra
19 Mixed Tundra
20 Barren Tundra
21 Lake

Can find other MODIS landuse products here: http://webmap.ornl.gov/ogcdown/dataset.jsp?ds_id=10004&startPos=0&maxRecords=100&orderBy=category_name&bAscend=false

Turbulent Flight--Caused by Gravity Waves?

I'm preparing a presentation on mountain waves and why they are concerning for pilots. Thinking back on my most turbulent flight I wonder if there were any mountain waves involved. That is a possibility.

Our approach was from the south and we flew over Utah Lake. The plane began to say, bump, and drop suddenly. There was one time that the stewardesses all fell to the floor and grabbed onto the seat around them.

This is the MODIS image for the day I flew into Salt Lake City on June 14, 2014. There is evidence of wave like structure in the clouds on that day...

The sounding appears to have the ingredients of a mountain wave--stable air at mountain peak and cross mountain winds with winds from the west.

Here is a view from the plane and from near the airport after landing. Kind of hard to determine if there were mountain waves.

Smoke Week: August 16 - August 23

Smoke from fires in the Washington, Oregon, Idaho, and California was transported into Utah starting August 15th and didn't clear out for over a week. The red dots in the image below show the location of fires based on MODIS observations on August 20th. These fires include the largest fire in Washington's history. Air quality across Utah was impacted by the smoke. At MtMet between the 18th and 22nd PM 2.5 concentrations were in the moderate range and unhealthy for sensitive groups range. Also shown is the ozone at MtMet during the same time. Other observations at MtMet are here. University of Utah trucks, KSL Chopper, and TRAX drove around measuring ozone on August 19th. All observations available here. Looking towards valley from near Bountiful Peak. Lidar observations on August 20th. On the day with the highest backscatter you can see the upper levels winds from the northwest were relatively strong. Lidar backscatter and winds on August 20, 2015[/caption]   On the bright side, we I enjoyed the orange sunsets! Moab Sunset, August 15, 2015 Mapleton Sunset, August 22, 2015

Transported Smoke

Aqua Satellite: August 16, 2015

My allergies have been acting up. I'll bet it is caused by all the smoke in the air. Some of this smoke is likely transported from the northern California fires.

PM 2.5 levels increased across northern Utah, as indicated by several air quality monitoring stations:

At the University of Utah you can see the particulate mater and black carbon concentrations rise late in the evening on August 15th and then drop back down. However, PM concentrations have stayed elevated.

The MTMET ceilometer also shows the smoke increasing particles in the air Saturday evening.

You can see a difference in the air quality in this time lapse video from the Neil Armstrong Academy. Looking at the beginning of the video you can clearly see the mountains in the distance. Fast forward to the next day and the smoke has blown in and the thick smoke obstructs the view.



I was in Moab the evening the smoke blew in and witnessed an amazing sunset. Small particles of smoke scatter light which produces these warm orange and red colors in the horizon in the evening.

Large fires in the west are producing a lot of smoke. Not much of the smoke has been transported to Utah, yet. Early next week we may see some smoke as the upper level flow turns more zonal which will blow the smoke directly east of California.

GFS forecast for Monday at Midnight

From yesterday's satellite image you can see from the MODIS satellite images the fire hot-spots and the smoke plume dispersion.

From the satellites we can calculate the optical depth of the atmosphere. Optical depth is a measure of how much light can penetrate a layer of atmosphere. Below shows the same area with high optical depths (reds) at the location of smoke plumes and low optical depth (blues and purples) over clear skies, meaning light goes all the way to the surface without much depletion. Optical depth isn't calculated for clouded areas.

Smoke from San Bernardino Fires

MODIS Satellite images show the extent of smoke from fires in the San Bernardino mountains. Tomorrows weather will likely blow the smoke to the four corners region, not impacting Northern Utah.

MODIS Terra Satellite: 12:00 noon MST

MODIS Aqua Satellite: 3:24 MST