2019 - Robert's botanical adventures in Northern California

[ian mcdonald]

On the site today we were counting adders and measured the ground surface temperature at 22C.

[Robert]

Temperatures in the 10C range is not uncommon at the south and west coast in February (the record highest is 18.8C from 1990). What is uncommon is the prolonged warm spell. This February seems to be the warmest for decades. Usually one or two mild days are followed by frost and occasionally snow.
Not so this year so far!

Trond,

This is all very interesting information. Thank you for sharing.

We have been under a persistent Polar to Arctic North flow for the last 7 days. At times 500 mb temperatures have dropped to -35 C, which is fairly cold for us. The GFS forecast is for the pattern to start shifting, first to the NW, then to zonal, and then eventually we are forecast to get another hit of subtropical moisture. With all the wintertime numerical forecasts, we shall see what actually happens, especially past day 3 to 4. Sometimes they are spot on, at other times the scenario in the 4 to 7 day range change every 6 hours to something very different than expected. The Pacific-North American Pattern index has been negative for the past few days. Generally this leads to a split in the jet stream over the western Pacific Ocean and cold generally dry conditions on the west coast of the U.S.A. The Arctic Oscillation has been strongly positive which is generally indicative of mostly low amplitude planetary waves.

[Robert]

On the site today we were counting adders and measured the ground surface temperature at 22C.

Hi Ian,

Thank you for sharing this bit of information.    I look forward to your next report.

Due to the declination of the sun this time of year and the low elevation of your site, 22 C does not seem like an unreasonable temperature, even if the direct beam solar radiation is not blocked by any cloud cover.

I think that those that grow true high elevation alpine species would be interested to know that ground temperatures can soar to very high levels during the summer at high elevations when the direct beam solar radiation is not blocked by cloud cover. Water vapor, aerosols, etc. absorb a fair amount of IR radiation as it passes through the lower portions of the troposphere.

[ian mcdonald]

Thanks Robert, the temperature in this area at this time of year would be in the region of 12C-18C. The forecast is for the warmest weekend February temperatures for many years. Last Spring was cold and wet.

[Robert]

23 February 2019
1300 UTC

Yesterday was my first opportunity to observe snow conditions on Peavine Ridge in about 2 weeks. The snow totals are very impressive. I measured 117 cm of snow on the ground on the crest of Peavine Ridge, 5,146 feet (1,569 meters). The water content of the snow was also very high, ≈ 12.00 inches. Both my wife and I commented that we have not seen conditions like this, at this elevation, for decades. I am working on quantifying this idea. There have certainly been perceptible changes in the snowfall and other climatic patterns in the Sierra Nevada over the past 40 years or so. I currently have proxy data suggesting a considerable upward shift in snow levels over the past 35 years. In addition, there are indications that the duration of snow cover each season has been declining over this same time period. The climatic pattern shifts (and other variables) are certainly impacting the ecosystems in this region and by extension of this idea, our gardens.



Down the mountain near Riverton, 3,625 feet (1,105 meters) there was 29.5 cm of snow on the ground with a liquid equivalent of 2.23 inches. The snow amounts at this elevation are not impressive, however the persistence of the snow cover is. To date, there have been 18 snow cover days during February at this site. This number is impressive!

Now it will be interesting to see how much longer the snow cover at these two sites persists. Current weather forecasts suggest that we will be impacted by moisture of a tropical/subtropical origin over the next week. If this scenario holds, this will be a heavy rainfall event for all locations except for the higher elevations of the Sierra Nevada. The snow at the Riverton site will not persist long under these conditions. On the crest of Peavine Ridge, the snow will likely be eroded to a certain extent and become compacted by the rain event. Generally under these conditions a hard layer of ice develops in the upper layers of the snow, but all of this depends on what actually occurs. I will be monitoring the snow and storm conditions and will keep you posted.

As a side note, last year on 1 February there were 2 species of Arctostaphylos, Manzanita, in bloom on the crest of Peavine Ridge. This year they are buried under 117 cm of snow. Snow cover and temperatures (and certainly other variables) will dictate their blooming period this season.

[Robert]

2 March 2019
2123 UTC

My wife and I did the weekly snow survey yesterday, however before posting the results from this outing I will revisit the odd site where snow does not accumulate despite abundant snowfall. After further investigation yesterday this site remains quite the mystery.



This is the site as it appeared on 8 February 2019 after >78 cm of snowfall. Since this time there has been an additional >39 cm of snow accumulation, which has now been reduced to 83 cm of snow as of 1 March.



This is the site, as it appeared yesterday, 1 March.

Yesterday, my approach was to survey the area to see if there were similar sites where snow does not accumulate.

I am not sure what I was thinking when I made my first evaluation of this phenomena. Latent heat (fusion – liquid to ice) may be a minor factor in slowing snow accumulation at this location, but is not the primary factor involved. The high heat holding capacity of water seems the logical answer, however the whole area is water logged during the winter with standing water, which slowly oozes and seeps down the slope. This site does not seem any different from many other locations on this slope. It seems logical to assume that there would be additional locations where snow accumulation is inhibited by the heat holding capacity of a large amount of water. This is not what I observed. In addition, this is not the ocean. I do not have any clear indication how extensive water accumulation might be below the surface of the ground. In the summer the site is xeric.

Another factor might be the albedo of the soil. The andesite based soil at this site is a medium gray color when dry. When wet the same soil can be very dark, almost black in color. Certainly this would enhance the absorption of solar radiation providing the ground is not covered with snow. Without snow cover, the moist soil would certainly absorb a fair amount of heat. Whether this would be enough to consistently inhibit the accumulation of snow at this site I am uncertain.

Yet another factor may be the large rocks and boulders throughout the area. Some of the larger boulders are large enough to protrude above the ground shortly after deep snowfall. They would absorb some solar radiation and accelerate the melting of snow very close to the rock surface for a period of time.   There are no large boulders near the site. Some other form of heat sink is possible as well as a combination of all the factors above.

I guess this is one of those things I never learned, forgot, or who knows. Anyway, if anyone has a good hypothesis on the lack of snow accumulation at this site, please share it with me.

[Hoy]

Robert, I am used to see such spots were snow doesn't accumulate and the water doesn't freeze during winter. They are all connected to water seeping up from underground. Such holes can occur in the middle of a bog or at the foot of hills etc. A similar kind of "holes" can occur along a creek or similar where some spots do not freeze or are covered by snow unless it is very cold for a long time.

[Robert]

Hi Trond,

My wife keeps telling me that this site stays very moist late into the spring/early summer season. The water does freeze over at this site. During the past week low temperatures fell to 9 F (-12.8 C) at this site and the surface was completely iced over. I did not probe around to see how far the ice penetrated into the ground. Generally the ground does not freeze deeply in this area. I will know much more in the future when I get the soil temperature loggers set up. Not far from this area there are natural springs where the water never freezes even with extreme cold weather. Given all the seepage in the area I am still wondering what exactly is going on at the "site". I'm sure that eventually you and my wife can tell me "I told you so".   

[Hoy]

..... I'm sure that eventually you and my wife can tell me "I told you so".   

Yes, of course we will

[Robert]

Yes, of course we will

Ah, Yes!     

[Robert]

5 March 2019
2300 UTC




I finally crunched the WX numbers for February 2019.

February 2019 turned out to be the coldest February at the El Dorado County, California farm since I started keeping detailed WX records at this site in 1983.
The mean temperature for February 2019 was 42.54 F (5.86 C), 5.52 F (3.07 C) below the 30-year mean of 48.06 F (8.92 C).



February 2019 was also a very snowy month. Although the farm only recorded 3.80 cm of snow during the month, the higher elevations in our area recorded much more. As an example, a short distance from the farm at Pollock Pines, California, 4,000 feet (1,219 meters), > 3 feet (91 cm) of snow was recorded. Not only were there copious amounts of snow but it also lingered. 24 snow cover days were recorded at Pollock Pines during the month of February, and this snow lingered until 4 March.

It has been many years since we have seen abundant low elevation snow accumulations. It has also been many years since such snow accumulations have lingered at and below the 4,000-foot (1,219 meters) level. February of 1990 was one of our previous banner snow months. During this snow event 19 cm of snow fell at the farm, 1,460 feet (445 meters), with much more in Pollock Pines and the higher Sierra Nevada.



There are also large accumulations of snow in the Sierra Nevada.

Higher in the Crystal Range:

At 8,600 feet (2,621 meters) there are ≈15 feet (457 cm) of snow on the ground at this time. The liquid equivalent is 58.41 inches (148.36 cm).

At 6,700 feet (2,042 meters) there are 12.50 feet (381 cm) of snow on the ground with a liquid equivalent of 55.95 inches (142.11 cm).

The above totals are well above average for this time of year and even above the 2016-2017 snow depth totals on this date. 2016-2017 was a banner precipitation season, however snow levels were frequently quite high.



February 2019 was consistently cold but not extreme. As an example -1 F (-18.3 C) was the coldest low temperature recorded at 6,700 feet (2,042 meters) in the Crystal Range.



Currently the rainy and stormy weather have returned. Snow levels are high, above 5,500 feet (1,676meters), due to the subtropical origin of this air mass. The numerical models are having difficulty forecasting the next 7 days. Currently, it appears that much of the moisture from the current storm will move south of our area. The forecast models are having more difficulty with the following storm. This storm will be dropping southward from the Gulf of Alaska. This system will bring us much cooler temperatures, but precipitation amounts are contingent on its trajectory. It now appears that we will have a period of dry weather once this storm system exits the region.

Now it is time for me to make a guess at our WX beyond this time frame.
Currently we are experiencing El Niño teleconnection conditions. The Walker Circulation pattern has shifted eastward and is currently centered ≈ 170 W longitude. In addition, SST (Surface Sea Temperatures) remain well above average in this area as well as farther to the east, centered ≈ 140 W longitude. The downwelling Oceanic Kelvin wave currently moving eastward across the equatorial Pacific will likely sustain the warm SST in the equatorial eastern Pacific for the short term. This pattern increases the possibilities of additional AR (Atmospheric River) directed into our portion of California. Whether this will indeed happen is something else.

Currently the Pacific North American Pattern index is -0.75. This is suggestive of much cooler and drier conditions and a spilt Jet Stream in the western Pacific. The Arctic Oscillation Index is currently 2.25. This suggests a much more zonal jet stream pattern. The PNA and AO were at the same levels during our last AR event, however this time around I believe conditions will be drier. So my big guess is that the mid-portion of March will be cooler and drier than what we have experienced during the past week. Beyond this point my guess is that another AR MIGHT impact our portion of California.

Currently this is the best I can do with my very crude statistical model (using current conditions and past patterns). For me this is a fun and challenging endeavor. I learn a great deal too even (and especially) if I make mistakes. For me the best way to learn something is to do it.

Soon I will be able to get back to field botany.   

[Hoy]

Robert,

The mean February temperature here was 5.0C, one of the warmest ever! The 30 year average (1960-90) is 0.6C.

Here is what Yr says about your weather the next week:

https://www.yr.no/place/United_States/California/Placerville/long.html?spr=eng

[Robert]

Robert,

The mean February temperature here was 5.0C, one of the warmest ever! The 30 year average (1960-90) is 0.6C.

Here is what Yr says about your weather the next week:

https://www.yr.no/place/United_States/California/Placerville/long.html?spr=eng

Hi Trond,

Currently I calculate the 30-year temperature mean at the farm from 1985-2015.

Do you know what the extreme high mean temperature is in your area during the 1960-1990 time period?

[Robert]

19 March 2019
0500 UTC



Today was snow survey day. I traveled to Peavine Ridge to check the snow depth, snow water content, and precipitation totals. Despite the warm spring-like weather over the past few days the snow pack is hold up extremely well, even on exposed sites (such as pictured above).



I recorded 50 cm of snow on the ground. The snow cover is holding up well despite solar radiation peaking at ≈ 900 W / m² each day over the past 6 days.

Last year, on 18 March, I recorded 65 cm of snow at my usual site, but then winter did not arrive until March last year. The water content of the snow pack last year was 8.00 inches (203.2 mm), vs. 8.60 inches (218.4 mm) this year. The total snow cover days this year are 99 days as of 18 March. I do not have a complete number of snow cover days for last year.



I get to eat crow on this one!   

My wife and Trond were correct there was a seasonal spring where the snow did not accumulate. My wife has such a great memory; I wish she could accompany me more often. 



It is hard to detect with this photograph, but there is a good head of water flowing from the spring. Come summer the whole area will be bone dry.



It is great to see abundant snow in the Sierra Nevada. I checked one of several high elevation sites that I monitor. As of 18 March, the current snow pack has a water equivalent of 61.15 inches. This compares favorably to the banner snow season of 2016-2017 when there was 65.07 inches at the same site on the same date. Unfortunately I do not have exact numbers, but this is somewhere ≈ 150% of average to date. I do know that the totals are ≈ 200% the 5 year average, however this includes some of the drought years. Soon I will have more comprehensive figures.

[Robert]

While I was on the Ridge a few clouds started to form. I calculated a surface based LCL, ≈ 760 mb. I also checked the 2200 UTC Sacramento and Carson City GOES Skew-T charts and found 760 mb to be a reasonable number. Clearly a bit of moisture from the next advancing storm system is starting to trickle into our region. This morning when I check the 850 mb precipitable water transport it was 0.3 inches (0.76 mm) By this afternoon it was 0.4 inches (1.0 mm), I guess just enough moisture for a few clouds to form as the air parcels were lifted by the mountains. The clouds are beautiful and I like watching them.

About 10 days ago, my primitive/crude statistical model forecasted rain for our region about now. With rain forecasted to arrive in a day or two, I was a bit surprised that the model might work, especially so far in advance. But then it could have been blind luck. Checking other atmospheric features, the chances of another AR (Atmospheric River) arriving this season have diminished. Well, it will be nice to get some more precipitation over the next 3-5 days, even if the totals are not great (the second storm to arrive looked promising, however if it becomes negatively titled as currently forecast <always changeable>, well this generally does not encourage large precipitations totals). We shall see.

I hope to have another field botany day soon. The wildflowers at the lower elevations are starting to bloom.