The last several weeks have been hard on the satellites people like me use most for determining sea ice coverage. We use passive microwave instruments on a number of different satellites. The 'passive' in its name means that it doesn't emit microwaves. It just sits back and collects the emissions from where it's looking. In this, the instrument is rather like our eyes.
Different centers use different instruments and different combinations of instruments. The main ones are:
SSMI on DMSP F-15, launched on 12 December 1999 (pushing 17 years!)
SSMI-S on DMSP F-16, launched 18 October 2003 (pushing 13!)
SSMI-S on DMSP F-17, 4 November 2006 (almost 10!)
SSMI-S on DMSP F-18, 18 October 2009 (approaching 7)
SSMI-S on DMSP F-19, 3 April 2014 (only 2)
AMSR2 on GCOM-W, 18 May 2012 (nearly 4)
A word about the names. SSMI is Special Sensor Microwave Imager. 'Imager' is the key word. With satellites, 'imager' means that the instrument is designed to be able to see (mostly) the surface. Handy for us sea ice people. DMSP is the Defense Meteorological Satellite Program -- the US Department of Defense operates these satellites. SSMI-S (or SSMI-SU) is the SSMI -- Sounder (or Sounding Unit). Means that in addition to the regular SSMI observing of the surface, it also carries some sensors that can do 'sounding'. Sounding is to see what's going on in the atmosphere rather than mostly the surface. (Name comes from the weather balloons -- which collect data known as soundings.) AMSR is Advanced Microwave Sounding Radiometer. It's operated by the Japanese Space Agency (JAXA). The advance is that it is able to see more detail and the much older designs in the SSMI and SSMI-S.
So, to our stories of woe. All of these instruments are designed for 5 years' operation. F-15 giving (mostly) good data after 17 years is spectacular for this type of satellite. Notice that most of these potential data sources are already past their design life. Since February 2016:
F-16: the sounding channels quit working early February
F-17: April 5th data quality impaired on one of the surface imaging channels, data volumes sent are greatly reduced.
F-18: Mostly ok, but reduced volume of data. Many orbits' data not making it through.
F-19: Data ceased flowing February 2
AMSR2: Data outage afternoon of April 15th through morning of April 16th.
F-15, the oldest of the crowd, is still sending basically normal data volumes at basically normal volumes.
So, hiccups all around the sea ice analysis world. The NSIDC was using only the F-17 SSMI-S, so has to rebuild their system to work with another instrument. The AMSR2 temporary outage affected some centers seriously as they relied only on that instrument. The US NWS uses both F-15 and F-17, and so far seems to be ok. I haven't checked the operating status of the OSI-SAF sea ice (European analysis). If I remember correctly, they also use more than one instrument, so should also be ok.
More gory details below the fold ...
17 April 2016
15 April 2016
Autism Awareness Month, 2016
A heads up that it's autism awareness month again. Autism hasn't changed much in the past year, so I don't have much new to say. My 2015 post covers what I have to say myself. In brief: people are people, including autistic people. People are all similar, because we're people. And people are all different, because we are people. All of this applies to autistic people too, no more, no less.
13 April 2016
Chapter one and Ted Fujita
Dr. Tetsuya Fujita, a.k.a. Ted, a.k.a. Mr Tornado was a meteorologist who spent most of his career at the University of Chicago. When I was in graduate school, I was down the hall from him and a friend (Eric) was one of his students. One day, Eric told me a Ted story.
Dr. Fujita held up a book on fluid dynamics (one of the central subjects for studying meteorology) and said to Eric "See this book? I only know chapter one." (maybe it was 'use'. Been a few years.) At the time, I thought it was more than a little exaggerated. And it probably did have a fair amount of exaggeration (Ted wasn't above such things). But, as I've continued my career and studies, I see more and more truth and wisdom in that comment.
I don't know about that particular book. But as I re-open math and science books I read years or decades ago, I'm continuing to find meaning and importance very early in the text. Not because I didn't learn enough of the early chapters to do well in class and tests, or to be able to apply the knowledge in later years at work. Rather, because as I've worked more on the subject, or learned more outside it, I see that there are more and more connections to 'chapter one' material. In that case, there's a lot of merit to looking back at chapter one and seeing how much deeper a knowledge I (you too, probably) can get from the later viewing.
Dr. Fujita held up a book on fluid dynamics (one of the central subjects for studying meteorology) and said to Eric "See this book? I only know chapter one." (maybe it was 'use'. Been a few years.) At the time, I thought it was more than a little exaggerated. And it probably did have a fair amount of exaggeration (Ted wasn't above such things). But, as I've continued my career and studies, I see more and more truth and wisdom in that comment.
I don't know about that particular book. But as I re-open math and science books I read years or decades ago, I'm continuing to find meaning and importance very early in the text. Not because I didn't learn enough of the early chapters to do well in class and tests, or to be able to apply the knowledge in later years at work. Rather, because as I've worked more on the subject, or learned more outside it, I see that there are more and more connections to 'chapter one' material. In that case, there's a lot of merit to looking back at chapter one and seeing how much deeper a knowledge I (you too, probably) can get from the later viewing.
11 April 2016
Recent reading
I'm a bookaholic, I confess. I have far more books than are strictly needed. And I'm acquiring more essentially all the time. (The freebies available via google, ibooks, kindle, nook, and many other venues don't exactly slow down my acquisition.) On the other hand, I do eventually read them. From recent (-ish) reading:
Hands on Meteorology by Zbigniew Sorbjan -- a book with something of everything for meteorology and middle school students (or older). Some history, some biography, and a substantial chunk of hands on meteorology. Plenty of experiments that you can do with minimal experience and equipment.
Street-Fighting Mathematics: The Art of Educated Guessing and Opportunistic Problem Solving, Sanjoy Mahajan -- To get through to the end of this book, you'll want at least integral calculus. But I mention it here because a) some of you have that background and b) those who don't: consider the title. You can choose to consider mathematical problem solving as being something like a mixed martial arts, steel cage, match. No holds barred either. While math is often taught as a matter of exactness, and the one and only one correct answer, there's a broad swath in which coming up with a pretty good approximation is an excellent thing. In practice, this is an enormous swath of science*. See also my old post Fermi Estimate Challenge.
Native American Crafts and Skills, 2nd Ed., David Montgomery -- It's easy to make, say, a house when you already have plans, bricks, saws, (pre-cut!) lumber, plumbing, electricity, and so on. But what do you do when you only have stone tools? How about when you also have to make the tools themselves? There's some serious intelligence involved in solving these problems. This book has some of the solutions. In a few cases, such as the shape and orientation of a Tipi, there's also a connection to meteorology and climate.
What We know About Climate Change, Kerry Emanuel -- This is a far smaller book than I expected from the title. It also includes no math. It's a good place to start reading on climate. It won't take you long, and won't bury you in detail or math.
More to come ...
* Post to come about Ted Fujita, and his 'chapter one' rule.
Hands on Meteorology by Zbigniew Sorbjan -- a book with something of everything for meteorology and middle school students (or older). Some history, some biography, and a substantial chunk of hands on meteorology. Plenty of experiments that you can do with minimal experience and equipment.
Street-Fighting Mathematics: The Art of Educated Guessing and Opportunistic Problem Solving, Sanjoy Mahajan -- To get through to the end of this book, you'll want at least integral calculus. But I mention it here because a) some of you have that background and b) those who don't: consider the title. You can choose to consider mathematical problem solving as being something like a mixed martial arts, steel cage, match. No holds barred either. While math is often taught as a matter of exactness, and the one and only one correct answer, there's a broad swath in which coming up with a pretty good approximation is an excellent thing. In practice, this is an enormous swath of science*. See also my old post Fermi Estimate Challenge.
Native American Crafts and Skills, 2nd Ed., David Montgomery -- It's easy to make, say, a house when you already have plans, bricks, saws, (pre-cut!) lumber, plumbing, electricity, and so on. But what do you do when you only have stone tools? How about when you also have to make the tools themselves? There's some serious intelligence involved in solving these problems. This book has some of the solutions. In a few cases, such as the shape and orientation of a Tipi, there's also a connection to meteorology and climate.
What We know About Climate Change, Kerry Emanuel -- This is a far smaller book than I expected from the title. It also includes no math. It's a good place to start reading on climate. It won't take you long, and won't bury you in detail or math.
More to come ...
* Post to come about Ted Fujita, and his 'chapter one' rule.
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