23 April 2013

Was ESMR screwy?

A reader here also asked about the pre-1979 satellite data over at my question place. The thing is, we do have pre-1979 satellite sea ice data -- the ESMR (Electrically Scanning Microwave Radiometer) 1973-1976.  It was a much simpler instrument than the SMMR, SSMI, SSMI-S, and AMSR which started flying in 1978 and since.  The more recent ones have two very important improvements over the ESMR -- they use multiple channels (think of it as colors) and they use both horizontal and vertical polarizations rather than just total power.

Ok, translation to English.  Our eyes look in three channels -- red, green, and blue.  Different creatures use different numbers of channels.  Dogs use only one, black and white (as we do if the lighting is very low).  Mantis shrimp use 10 channels.  Bees use ultraviolet.  And so forth.  The key is that the eyes respond to some number of colors.  Numbers vary, and what color band also varies. 

The other thing about electromagnetic radiation is that it can be polarized -- vibrating in one way versus another.  The two linear polarizations are horizontal and vertical.  ESMR just lumped them together and measured total power.  SMMR and the rest measure horizontal and vertical polarization separately at most of the channels.  Basically, SMMR and all the more recent instruments have high quality color vision versus ESMR being a rather fuzzy black and white.

But ... black and white is still better than not being able to see at all.  The question then arises in retrospect whether we can use the black and white instrument, ESMR, like our more recent color vision instruments.  Now, in part, I know the answer already -- you can't.  More precisely, you can't do it well enough to satisfy my colleagues at NASA-Goddard.  Perhaps, though, it can be done accurately enough to answer some questions of interest, even if not accurately enough to be entirely comparable to the modern instruments.

I have some ideas, naturally, and have been been pursuing them a bit -- enough to know that there's a fair chance of getting useful answers.  Whether it's useful enough to answer questions of interest ... well, I'll also invite questions you all find of interest.

22 April 2013

Forecast Contests

I'll invite your suggestions for forecast contests to hold.  In the mean time, some results from forecast contests at my work. 

The winter contest was to predict the date of the first 2 inch (5 cm) snowfall at our official weather station.  It never happened.  I came close to predicting the date, sort of.  Since we've had some memorable storms on or near President's day (February 18th this year), I went with that.  Nothing noteworthy that day this year.  But the next guesser was for May 1, so when we were getting forecasts of significant snow (4-8 inches, 10-20 cm) in mid-March, I was hopeful.  Only 1.7" at the official station, though, so no luck for me.  (If only we'd used any of the other area stations!  All beat 2".)  This is our second straight year of not having even one day with 2" of snow.  Should probably adjust the standards to 1" (2.5 cm).

The summer contest had a winner before entries had even closed.  One of the contests was to predict the first day that the official station would exceed 90 F (32 C).  Entries open to the 30th of April, it happened the 10th if I remember correctly.  The 7th earliest date ever.  Spring here, apparently was April 8th and 9th.  We're now on summer.  Note to future: have to close entries on the summer forecast contest on April 1st or earlier.  (Our earliest ever 90 F day was apparently late March -- 27th, iirc).

Both contests suggest that traditional weather forecast contests need some updating for changing climate.

For here, a couple of contests that came to mind, in addition to the 'traditional' guessing of the September average Arctic sea ice extent, are to guess when the atmospheric CO2 levels for Mauna Loa monthly average will pass 400 ppm, and when it will pass 150% of pre-industrial (420 ppm).  One that can be done annually, guess the first week when Arctic sea ice extent will fall below the climatological (1979-2000) minimum extent, and guess how many weeks the ice will remain below that minimum.

Other ideas?

11 April 2013

Life isn't simple even for a coral

Heard an interesting talk yesterday about coral, and remote sensing of water temperatures and light levels as a means of tracking how they're doing.  The effort was prompted by the major coral bleaching events in the last decade.  I'm a physical, rather than biological, oceanographer, so my prior knowledge of corals is well-covered by a) coral bleaching events are bad for coral and b) coral are pretty.  A good entry point on the web for the coral monitoring efforts is NOAA Coral Reef Watch, where you can find out much more.

One of the things that is important for coral is water temperatures.  If water gets too hot, it's bad for the coral.  That's old news at this point.  The addition from this presentation was that coral also care about light levels.  If it's too bright, that's also bad for the coral.  They can adapt to some degree, over time, to high light levels. 

As I suggest in the title, the situation is not simply those two things.  High temperatures aren't good.  But if the lighting isn't too strong, it's survivable.  The presentation included observation of a time that had prolonged high temperatures, but the lighting wasn't very strong and the coral survived ok.  A situation that didn't have as high temperatures (though still high) but did have excessive lighting resulted in much more bleaching.

It's also the case for coral, as for people, that it is sustained extreme conditions which matter.  So, again, the concern is for heat waves, not hot individual days.

10 April 2013

Consequences of the abnormal normal climate

In last Monday's note, I concluded that climate was only 'normal' from 1936-1977.  As with any science conclusion, this is not past discussion.  But, as we often do in science, let's take that part as true and see where it leads us.  If it leads us to something silly, then we have (more) reason to question our original conclusion.  On the other hand, if it leads us to things that make sense, it suggests that the original, tentative, conclusion is possibly better than we originally thought.

So, if climate were 'normal' only between that span, give or take, is there anything else that can be concluded?  Two things occurred to me pretty quickly; please do add more that you think of!  One is about psychology and the other is engineering.

01 April 2013

When was climate normal?

It's been a couple years since I took up the question of normal climate, so time for another go.  At that time, I used monthly data from Hadley, and arrived at the observation that if you're younger than 26, you've never seen a month where the global average as as cold as the 1850-2011 average, 317 consecutive months (at that point, now over 330) of warmer than 'normal' temperatures.  I'll cheat and give you some answers first, read on to see how they're established:
  • Climate was 'normal' only between 1936-1977
  • Every year 1987-present has been warmer than any year before that
  • 1976 was warmer than any year before 1926
  • 1978 (next coldest year of the recent run) was warmer than any year before 1940
Do read on to see what 'normal' winds up meaning; it's important!  One part of 'normal', as we intuitively think about it, is that you should some times above it, and sometimes below.  Having many consecutive years above 'normal' says that normal isn't really very good.  To help get quantitative about how to proceed, consider this plot of NCDC's data (warmer/colder than the 1880-2012 average -- the length of the entire record).