Monday, October 31, 2011

Photos from IOP3

The DOW has probably never been deployed in conditions like yesterday's.  Severe clear all around, but enough returns for us to be able to look at the structure of the lake breeze and gap flows.

Stansbury Island Road Deployment Site (Photo: John Lawson)
Looking into the Tooele Valley with pollution in low levels
(Photo: John Lawson)
Deployment site in the Rush Valley
(Photo: John Lawson)
Looking at the Stockton Gap flow with pollution in low levels
(Photo: John Lawson)
Evidence for our friends at the Center for Severe
Weather Research that we are taking good care
of their baby (Photo: John Lawson)

Sunday, October 30, 2011

SCHUSS IOP3 Concludes

Shortly after 9 PM, our team shut the DOW down and called an end to IOP3.  We got some good data on the lake-breeze, as well as gap flow near Stockton Bar.

All this clear-air stuff is fun, but we're looking forward to looking and precipitation soon!

IOP3 Update

Our IOP3 team collected data on the lake breeze until about 3 PM MDT and have since relocated to about 9 km south of Stockton Bar where they are looking at the gap flow pouring into the Rush Valley.  The Stockton Bar site shows the persistent northerly flow, but is probably not well located to get the full intensity of the northerlies as they accelerate into the Rush Valley.

Remember that tomorrow (Monday) will be a down day, with a meeting at 3 PM in 711 WBB to discuss possible deployment on Tuesday to observe the frontal passage.

IOP3 and Storm Chasing Plans

Our team in the Tooele Valley is apparently getting some interesting data.  They are opting to do a weather balloon launch for upper-air thermodynamic data and have decided to stay out this evening and examined flow transitions near Stockton Bar.

As such, we will have a down day tomorrow with no operations, but will meet at 3 PM in 711 WBB to discuss a possible deployment on Tuesday to examine a cold-frontal passage.  The DOW will be leaving for San Francisco for a few days this week, but it looks quite active for when it returns.  Finally, some precip appears to be on the way!

SCHUSS IOP3 Lake Breeze Initiation

It doesn't take long for a lake-breeze to form in the Tooele Valley.  We're already seeing northerly flow along I-80, in clear opposition to the continuing down valley flow over the rest of the Tooele Valley.

Hopefully there's enough junk in the air for the radar to get good Doppler velocity returns as they are well positioned on the Stansbury Island Road to observe the along-valley flow.


We have a team with the Doppler on Wheels (DOW) deploying to examine the lake-breeze penetration into the Tooele Valley this morning.  It appears we have just what we are looking for: clear skies, a ridge building in aloft, and very weak flow up to mountaintop level.

Source: NCAR/RAL
Source: NCAR/RAL
The sounding above shows an intense surface-based nocturnal inversion surmounted by a near-isothermal layer that extends to around 810 mb, with light flow throughout.  Hopefully we will get good clear-air returns and can examine the lake breeze development and ultimate penetration into the Tooele Valley.

Saturday, October 29, 2011

Sampling the October Gunk

The meteorological transition that occurs in Salt Lake during October is quite remarkable.  Early in the month we're able to do a pretty good job of mixing out the pollution, but by the end of the month, it gets pretty stingy.

Up high in the foothills, conditions were perfect for a long ride.  The views were great, but plenty of smog could be seen in the lowlands to the west

to the north

or, alternatively, all around (it's amazing what you can do with a phone these days).

Although I normally hope the pollution scours out, I confess I'm hoping it will hang on through tomorrow.  In the morning, we will be deploying the Doppler on Wheels to examine the penetration of the lake breeze into the Tooele Valley.  We'd like the boundary layer to be good and dirty so we get good returns of the Doppler velocity and can examine the structure of the lake breeze, especially as it interacts with the surrounding topography.

Prospects for Snow

The computer models are showing some hints that we may see some of the white stuff flying in the coming days.  Other than a few flakes today, the only stuff flying in the Wasatch right now is coming out of a hose.

The latest GFS, however, has a decent cold front coming through on Tuesday.  It doesn't look like a huge event, but it's more than we've had recently.

Looking out into the far range, the GFS brings a deep, cold trough across Utah late in the week and early next weekend.

The ECMWF model does this as well.

Source: Penn State E-wall
I don't get too excited about 7 day forecast, but the forecast bears watching during the coming week.

Friday, October 28, 2011

DOW Outreach and Plans

We gave about 180 students at Newman Elementary School and the Salt Lake Center for Science Education an education in radar meteorology and an up close tour of the Doppler on Wheels (DOW) today.

We're taking a day off tomorrow, but will be investigating the penetration of the lake breeze into Tooele Valley on Sunday.

Thursday, October 27, 2011

University of Utah Meet and Greet

Some photos from today's Doppler on Wheels (DOW) meet and greet on the University of Utah campus.  We brought a couple of classes through, plus enjoyed quite a bit of walk up traffic, including some readers of this blog.  If you missed it, perhaps we'll do another in a week or two.

The DOW with the Sutton Building
Yours truly with the Atmos 1010 (Severe and Unusual
Weather) class
Atmos 1010 class getting wowed by the DOW 
Atmos 5110/6110 (Synoptic–Dynamic Meteorology) class

Come Visit Us

We'll be showing off the Doppler on Wheels (DOW) outside the Frederick A. Sutton and William Browning Buildings from 9 am to 1 pm today on the University of Utah campus.  Come by and check out this meteorological beast on wheels.

Wednesday, October 26, 2011

SCHUSS IOP2: Cumulus Patheticus

Desperate times call for desperate measures.  When some surprise cumulus clouds popped up today, we dashed off into the field and got some data with the DOW of the "cumulus patheticus" and sublimation/evaporation of snow/rain falling below cloud base.

Photo Credit: John McMillen

Live and Learn

This morning's DOW deployment at the mouth of Weber Canyon was both windy and cold.

Photo Credit: John McMillen
We learned that the radar is not very useful at this short range and that the boundary layer was perhaps too clean for good clear air returns.  As I like to say, an expert is someone who makes all the mistakes, so this was a good experience.

We're running out the door shortly to see if we can get some data on these snow/rain showers that are moving across the Wasatch range from the north-northeast.

Yes, from the north-northeast.  We're on the back side of a deep trough and that's where the flow aloft is coming from and we're seeing some weak convection pop up in the cold air.

This won't be a case to write home about, but we'll get more experience using the polarimetric capabilities of the radar in complex terrain.

Where Is the DOW?

Given the lack of exciting weather, we are concentrating for now on learning the system so we are ready when the big storm hits.  Yesterday afternoon we deployed to a site along SR-111 that we can use to survey the entire Salt Lake Valley and Wasatch Mountains and spent some time slicing and dicing what wimpy clouds we could find.

This morning we have a team setting up at the mouth of Weber Canyon where we will see how the DOW does examining the valley exit jet.  Down canyon flow is evident at the Power Canyon site within the canyon, but Hill AFB as a light north wind.

At the Power Plant, winds are currently gusting to just over 20 miles per hour.  I suspect the flow is stronger at the canyon mouth, but this will probably end up being a moderate event.  Nevertheless, we'll see how the radar does in this environment.

Tomorrow (Thursday) we will hold an open house with the DOW on the east side of the Sutton and Browning Buildings on the University of Utah campus from 9 am to 1 pm.  Feel free to stop by and have a look.  

Tuesday, October 25, 2011

SCHUSS IOP1: A Freaky Front

Disclaimer: This post is long, technical, and for the weeniest of Wasatch Weather Weenies, but you should read it anyway if you want to see just how complicated the atmosphere can be over and around the Great Salt Lake.

For the first Intensive Observing Period (IOP1) of the Storm CHasing Utah Style Study (SCHUSS), we spent yesterday evening near Lake Point on the southern shore of the Great Salt Lake examining the dry cold front as it moved southward into northern Utah.   I'm sure there were heads turning along I-80 as they drove past the rest stop.

As we deployed in the late afternoon (~2300 UTC, 1700 MDT), the front passed Locomotive Springs at the northern tip of the Great Salt Lake.  Temperatures over and near the lake were much cooler than over the surrounding landmass.  For example, it was only 62F at Hat Island, but 70F at the Salt Lake airport and in the mid 70s over Dugway Proving Grounds.

A shallow layer of haze was also evident over the Great Salt Lake.

These observations suggest that the cold front would be moving into a cooler, shallower, and possibly more stable low-level airmass over the lake.  Sometimes this leads to the development of what is known as an undular bore, a gravity wave that can develop as a cold front moves into a stable layer.

The front passed the northern tip of Antelope Island just before 0230 UTC (2030 PM MDT).  At that time, the prefrontal surface flow was transitioning from the daytime upvalley/upslope regime to the nighttime downvalley/downslope regime.  Most stations in the Tooele Valley had reversed to southerly (downvalley).  Along I-80 near the Oquirrhs in the Salt Lake Valley, most stations were southerly, southeasterly, or easterly.  In other words, near our observing site on the south shore of the Great Salt Lake, the surface flow was offshore as the front approached.

A vertical scan from the DOW radar from our site near Lake Point northward toward Promontory Point showed both the offshore flow and the front remarkably well.  In the Doppler velocity image below, warm colors indicate flow toward the radar, cool colors flow away from the radar.  The front was approximately 14 km offshore (blue line, range rings below every 2 km), as indicated by an abrupt transition to strong flow toward the radar.  Ahead of it, a shallow layer of offshore flow was surmounted by a layer with strong flow toward the radar.  In other words, the flow at this level had a northerly component even ahead of the front.

This pre-frontal northerly flow aloft existed for some time as the front approached and extended to the surface earlier during the day.  It is unclear if it is the last gasp of the lake-breeze circulation from the prior day, or if other processes were contributing.  The bulge in the layer of northerly flow roughly 10-12 km from the radar is also interesting.  It could be a gravity wave initiated as the front pushed into the stable layer, or perhaps reflects convergence near the land-breeze front (note how the offshore flow weakens just below it).

The front and the pre-frontal bulge move closer to the radar by 0243 UTC (2043 MDT).   During this period, and the time leading up to the frontal passage, we experienced intermittent bursts of northerly flow with nasty lake stink.    We hypothesize that these bursts were driven by shear near the top of the shallow offshore flow, which may have been enhanced as the northerlies intensified aloft.

A curious aspect of this case is the abrupt nature of the wind transition at the front, wheras the temperature transition was modest and less abrupt.  At Hat Island, for example, the pre-frontal flow was northerly (as mentioned above), but the speed increased dramatically with the frontal passage.  The temperature, however, only dropped about 6F in 30 min.  In part, this reflects the cool pre-frontal airmass over the lake.

Hat Island Fropa at ~0120 UTC (1920 MDT)
We didn't expect much as we ventured out into the field, but as usual, mother nature delivered.  For Atmospheric Sciences undergraduates, investigating this case would make for a great senior capstone project.

Monday, October 24, 2011

"Storm Chasing" Plans for the Coming Week

Mother nature is not cooperating this week by giving us a big storm, but we will be doing some "storm chasing" anyway with the Doppler on Wheels (DOW).

Today we are planning to deploy around 2 PM, check out the site lines at a possible lake-effect observing site in the west valley, and then setup along I-80 near Salt Air and Lake Point to examine the cold front as it moves across the Great Salt Lake.  We anticipate this will be a dry cold-front passage, so we'll be using the clear-air Doppler velocity capabilities of the DOW to examine the flow associated with the cold front and it's interaction with the stable boundary layer over the Great Salt Lake.

Tomorrow we hope to deploy, possibly east of the Wasatch, to examine whatever clouds and precipitation develop during the afternoon.  The NAM model is optimistic of some action over the Uintas, which perhaps we'll be able to sample from the ridge between Park City and Kamas, but we'll see if Mother Nature cooperates.

On Wednesday we may try to examine canyon outflows in the morning, before napping in the afternoon.

Finally, on Thursday, we will have an open house on the University of Utah campus from about 9 am to 1 pm next to the Frederick Albert Sutton and William Browning Buildings.  Come by and visit us.

Sunday, October 23, 2011

Getting to Know the DOW

Being a meteorologist isn't just a job, it's an adventure, and we had one this weekend as we got to know the Center for Severe Weather Research Doppler on Wheels (DOW) Radar.

First, we had the pleasure of watching heads spin as we drove it through campus and downtown Salt Lake City.  As can be seen below, the DOW is something that seems to be right out of science fiction and we got more attention than a Jennifer Aniston siting during the Sundance Film Festival.

With no precipitation in sight, we set up the DOW in an area where we hope to observe lake-effect precipitation in the future to see what sorts of ground clutter we were dealing with.  

Ground clutter is radar returned produced by the Earth's surface and other ground-based obstacles, such as telephone and power poles, trees, houses, etc.  You don't want alot of that stuff in the way as it makes it more difficult to get good observations of precipitation.  Based on our recon, the site above appears to be great for looking at lake-effect bands that extend into the eastern Salt Lake Valley and Davis County.  

The beauty of the DOW is that it is user configurable and we can have it scan pretty much any way we want.  Further, although most people are aware of the use of radar to examine precipitation systems, the DOW is sensitive enough that we get some pretty interesting information on airflows even when the air is clear.  It didn't take long on Saturday for the students to start slicing and dicing the morning drainage flow from the Salt Lake Valley out over the Great Salt Lake and the outflow from Weber Canyon.

I took a quick snapshot of this vertically oriented scan taken towards the Great Salt Lake showing a shallow layer of offshore flow (purple) and oppositely directed return flow aloft (yellows).  

We are hopeful based on this data that we may be able to use the DOW to examine slope, valley, and lake driven flows during periods where Mother Nature is not cooperating and keeping us dry.

We also tried to have some fun identifying flocks of birds on the radar.  I'm not sure we were successful, but if anyone knows a good ornithologist in Salt Lake, have them give me a call.

Friday, October 21, 2011

Got Doppler?

The Center for Severe Weather Research Doppler on Wheels (DOW6) arrived on the University of Utah campus last night.  We are so looking forward to driving this thing around town and turning heads.  Perhaps we'll park it in front of Steve Harris Imports, the local Ferrari dealership, and see if we get more attention!

For those of you interested in the gory details, this is an X-band polarimetric Doppler radar.  X-band refers to the wavelength of the radar, which is 3 cm compared to 10 cm for a National Weather Service radar, enabling a smaller dish (desirable if you want to put it on a truck!) and increased sensitivity.  Polarimetric means that radar energy is emitted and received in two planes, horizontal and vertical, which provides information about the shape of the raindrops, snowflakes, bugs, or whatever else the intercepts the radar signal.  Most National Weather Service radars are not presently polarimetric, but will be upgraded with this capability in the next few years.  Doppler means that we can measure the speed of those raindrops, snowflakes, and bugs towards or away from the radar.   Most radars today are Doppler, but DOW6 offers higher spatial and temporal resolution.

A big advantage of the DOW is that we can position it where we want and scan storms as we want.  In addition to horizontal scans, we can take vertical slices through storms and do so at very high frequency.  University of Utah students will be using these capabilities to probe mountain storms, cold fronts, lake-effect storms, melting-band microphysics, and lake-breeze fronts.

We spent the day today learning the basics of running the DOW and will be doing a bit of testing out in the field over the weekend.  If you see us, give us a honk and wave!

U graduate students in the DOW 
Stay tuned to this blog for information on deployments and an on-campus open house that we hope to hold next week.

Urban Haze All in My Brain

We're not quite into inversion season yet, but we've reached that time of year where the incoming solar radiation is simply not sufficient to build a deep convective boundary layer in the afternoon.  As a result, considerable urban smog (I shouldn't call it haze, but I like Jimi Hendrix too much) is developing over the Salt Lake Valley during quiescent weather periods.

Yesterday afternoon, for example, there was noticeable smog as one looked south toward the Oquirrh Mountains from near Ensign Peak.

In the afternoon sounding from Salt Lake City airport, it appears that the convective boundary layer extends to just below 700 mb (~10,000 ft) which is close to the crest of the surrounding mountains.  Thus, we're getting decent mixing, but perhaps not enough to pump everything out.  Hence the smog.

The good news is that PM2.5 levels remain relatively low.

Source: Utah Division of Air Quality
It's only a matter of time, however, until the sun angle and day length decrease to a point that things start to get ugly.  The best thing that we can hope for is a winter with limited snowcover (in the valley, not the mountains!) and frequent storms to clean things out.

Thursday, October 20, 2011

The Earth is Warming, But We Already Knew That

Are trends in the Earth's surface temperature derived from instrumented records reliable?  At least three groups, the Climate Research Unit at East Anglia University (HadCRUT), NASA's Goddard Institute for Space Studies (GISS), and the NOAA/National Climatic Data Center (NCDC) produce analyses of the Earth's surface temperature during the instrumented period.  This is a difficult job.  Observing sites move, the land-surface changes around them (e.g., urbanization), instruments change, etc., and these changes need to be considered.  Hansen et al. (2010) provide a detailed overview of the process used by NASA/GISS and it is extensive and exhaustive.  Although the three groups have differing approaches, their results are generally quite similar and show a consistent picture of a warming planet.

Source: Hansen et al. (2010)
Another group, The Berkeley Earth team, has recently developed its own analysis and, as reported today in the Guardian, has just submitted four papers to Geophysical Research Letters that describe their work to date.  These papers are available here, and they report trends consistent with the analyses above.  Yes, minor adjustments will continue to be made as analysis approaches are refined, but the big picture is quite clear.  The Earth is warming, but we already knew that.

Storm Chasing Utah Style Begins

Photo: Josh Wurman, Center for Severe Weather Research
The Center for Severe Weather Research Doppler on Wheels polarimetric research radar arrives in Salt Lake City this evening, marking the beginning of what I am jokingly calling the Storm CHasing Utah Style Study (SCHUSS).   Let me know if this is too weird, or you can suggest something better.

Friday and Saturday will be training days for several of our students, followed by a down day on Sunday.  After that, everything depends on the weather.  Right now, I can summarize the forecast for next week in one word, DRY.  Some of the GEFS ensemble members call for a weak upper-level trough passage on Monday that is expected to be dry.

Source: Penn State E-Wall
After that, all the members park a big ridge over the western United States.

Source: Penn State E-Wall
This is how it works in storm chasing.  Arrival of DOW + Excited Scientists = Development of Ridge.  This isn't all bad news as it will give us a chance to get some experience with the system and conduct some outreach activities on campus and at area schools.  Stay tuned for details.