Saturday, September 19, 2015

El Niño and Buoy 46012 Half Moon Bay

Buoy 46012 HMB
Right now in the Pacific specifically the waters from Monterey to Point Reyes and out to the Farallones have temperatures historically high and persistent with temperatures around or above 60° F. The Half Moon Bay buoy 46012 has recorded as high as 65°F water temperatures numerous times. From the past records of buoy 46012 (1980-present) the highest temperature I have found is 67°F. So not only are we flirting with record high temperatures they have been in record territory consistently since early July! There is a lot of talk about the possible historic El Niño  event brewing in the Pacific plus the Pacific Blob that has parked itself right in our local coastal waters. In addition the Ridiculously Resilient Ridge (RRR)   has been batting storms away from the Bay Area and most of California now for about 4 years!

The purpose of this exercise is to monitor buoy data as we approach the winter season and compare data from previous years, especially El Niño  and in particular 1997-98 our last El Niño  year. Unfortunately buoy 46012 (HMB) did not record water temperatures for the entire 1997 year probably because of a technical glitch. However buoy 46026 (SF) had useful water temperatures for this period. 

Some Technical Data on Buoy 46012

Owned and maintained by National Data   Buoy Center
3-meter discus buoy
ARES payload
37.363 N 122.881 W (37°21'45" N 122°52'52" W)

Site elevation: sea level
Air temp height: 4 m above site elevation
Anemometer height: 5 m above site elevation
Barometer elevation: sea level
Sea temp depth: 0.6 m below site elevation
Water depth: 208.8 m
Watch circle radius: 170 yards

NOAA has been collecting Historical Data from this buoy since 1980. Some parameters of interest are sea and air temperatures wind velocity and direction, wave heights and periods dew points and pressure readings. I will be exploring data from this buoy as well as Buoy 46013 Bodega Bay located 48 NM NW of San Francisco, buoy 46026 San Francisco located 18NM West of San Francisco, buoy 46237 San Francisco Bar located about 7 miles West of San Francisco and Weather Station FTPC1 located at Crissy Field Presidio! In the future I may also include data from the Point Reyes, Monterey and Point Arena stations.     

I'm going to focus initially here from July 1st 2015 thru the present date which as I write is September 7th 2015. I'm using this period because a historical spike in the ocean temperature appeared about July 7th 2015 and was 18.0 C (64.4 F) after a long period of temperatures well under 60 F.  The water temperature spike of July 7th is significant to me because it's the first time I could feel a change in my local climate and relate it to the ocean temperature. This seems obvious if after thought but was a surprise to me and at the same time gives me a metric to relate my climate to the local ocean behavior. Having lived on or near the California Coast for near 50 years, I was convinced the coastal cool Mediterranean climate was rock solid in its persistence and seemed impervious to change!

Looking at the historical records of buoy 46012 from  11/1980 thru 7/2007 below we see the Mean and Standard Deviation Plot. The water starts to warm from July reaching a peak in September. From this chart we see a range of temperatures of almost 20 F with a low of 47.6 F to a high of close to 68F.
Buoy 46012 Mean and Standard Deviation
HMB 11/1980-7/2007

The last major El Nino event occurred in the winter 1997-1998. Having been a coastal resident in those years I can remember similarities in climate, temperature/humidity as well as the very high rain totals about twice normal. There is ocean temperature data from buoy's 46012 (HMB) and 46026 (SF) readily available over the last 17 years. However water temperature data for buoy 46012 (HMB) was not operational (for some unknown reason) in 1997. Fortunately buoy 46026 (SF) does have some data for 1997.

I'm curious as to water temperatures in 1997 and today to see what can be wrung out from the data. To simplify this process I used 60 F as a temperature to search for knowing the water temperature for those years rarely topped 60F.   It should be noted that these buoy records record data hourly throughout the year so data can be daunting. Basically over 8000 observations are made yearly on about 13 parameters including air and water temperatures, wave height and period and more.    

I used data from both the HMB and SF buoys to compare how often the water temperature rose above 60F over comparison years. First looking at the data for buoy 46012 (HMB) for years 1991-2013 which is full records are available. For this 23 year period the average number of records for temperatures over 60F is 184 per year. Four of those years had zero records over 60F! In that period 1992 had the most 60F records which were 1077. In 2014 the total records over 60F was 3553 which is magnitudes greater than the 23 year average and is almost 4 times greater than the previous high of 1077. So far in 2015 records are up to date thru July and 714 records have exceeded 60F. This does not include August and September typically the hottest water temperature months. So it appears 2015 will probably have 60F plus records similar to 2014 which is historically high!

Examination of the data for buoy 46026(SF) shows a yearly average from 1998-2013 of 116.5 records. As previously mentioned the HMB buoy was nonfunctional in 1997 for water temperature. However the SF buoy was operational and there were 1765 records for 60F in that El-nino  year. In 2014 there were 1431 records of 60F. Although the HMB buoy had over twice the number of records in 2014 , 3553 as the SF buoy which was 1765! 

Buoy Comparisons 1980-Present
Buoys Ave Yearly Records
>60 F
High Record Year 2014 2015
Buoy 46012 (HMB) 184 1077 (1992) 3553 1320
Buoy 46026(SF) 116 1765 (1997 El Nino Yr) 1431 714

In summary we can see that 2014 and 2015 have significantly higher water temperatures and historical persistence!Buoy 46012 had 3553 records above 60F, the previous record being 1077 records in 1992. With 1320 records above 60F to date looks like 2015 will match 2014 for longevity of the record ocean temperatures.

No comments:

Post a Comment