2011-08-03 03:04:39Information about HITRAN...
Rob Honeycutt

robhon@mac...
98.207.62.223

I have this discussion going with a climate denier regarding Evans 2006, MEASUREMENTS OF THE RADIATIVE SURFACE FORCING OF CLIMATE.

He is claiming that since Evans uses HITRAN that the whole thing is based on models.  The study is obviously all about using empirical data but I'm at a loss as to how to most effectively counter his argument because I don't have a full understanding of what HITRAN is or does.

This is from the paper...

"In order to extract the greenhouse flux from individual gases, the background emission of the atmosphere was simulated using the radiative transfer code, FASCOD3 (Clough et al., 1988). The simulations incorporated the temperature, relative humidity and pressure profiles from radiosonde measurements obtained at Maniwaki, Quebec, a location 280 km distant from Peterborough. A constant mixing ratio profile of 360 ppmv was used for carbon dioxide (IPCC, 1995) and the concentrations of other background gases were taken from the AFGL Atmospheric Constituent profiles (Anderson et al., 1986) and scaled to current tropospheric concentrations (IPCC, 1995). The line transition parameters for the molecules were provided from the 1992 AFGL HITRAN database (Rothman et al., 1992). The model utilized an aerosol profile that was representative of the visibility conditions as monitored by the local weather office. An example using this procedure is illustrated for CFC-12."

2011-08-03 03:11:13
Rob Honeycutt

robhon@mac...
98.207.62.223

I guess, specifically, what do they mean by "line transition parameters?"

2011-08-03 03:54:04An interview with: Dr. Laurence Rothman
nealjking

nealjking@gmail...
91.33.115.88
An interview with:
Dr. Laurence Rothman
           

In the interview below, in-cites correspondent Gary Taubes talks with Dr. Laurence Rothman of the Harvard-Smithsonian Center for Astrophysics about his highly cited paper, "The HITRAN molecular spectroscopic database and HAWKS (HITRAN Atmospheric Workstation): 1996 edition" (J. Quant. Spectrosc. Radiat. 60[5]: 665-710, November 1998). According to the ISI Essential Science Indicators Web product, this paper has been cited 688 times to date, and is currently the most-cited paper of the past decade in the field of Engineering. Dr. Rothman has 12 highly cited papers in this field, with a total of 863 citations to date.

   Would you please tell us about how HITRAN got started and what it is?

HITRAN stands for HIgh-resolution TRANsmission molecular absorption database, and it goes all the way back to 1961, before I did my Ph.D. on an aspect of molecular spectroscopy. Through some prior research I had done with an Air Force lab nearby in Bedford, Massachusetts, I got a job out there. This Air Force lab was interested in detecting jet aircraft from a distance, with detectors, say, from another aircraft. But you have the Earth’s atmosphere in between, obviously, with a lot of absorption at different frequencies. Hot sources give out a lot of energy in the infrared region of the spectrum, but if you happen to tune your detector, for instance, to where there’s major water-vapor absorption, you’re not going to see anything. What the Air Force needed was a database, a whole compendium of the major absorbers in the Earth’s atmosphere, where they are and how strong they are. The thing you have to realize is that the molecules in gasses have discrete frequencies of absorption; all these guys—water vapor, carbon dioxide—absorb electro-magnetic radiation at discrete frequencies, but they’re smeared out a little because they’re colliding all the time. If you had a database of all this information, you’d have a fingerprint of what’s going on in the atmosphere. It can be an incredible amount of information.


HITRAN is like the human genome of gasses, if you will.”

 

I should also mention that these absorbers in the infrared range are what some people call the minor constituents of the atmosphere. These are the trace constituents, like water vapor, methane, and carbon dioxide, which happen to be incredibly efficient absorbers.

   This was over 40 years ago. How did it develop once you got this assignment?

Well, we assembled a kind of committee from around the States, key people to work on this. Not just from our lab. We had sufficient funding at the time. We could have contracts with them. Someone from Ohio State, from the University of Maryland, from a major company in California. We had the research department at Hanscom Air Force Base in Bedford Massachusetts. Together, we developed this big database and then made it public domain. The first edition of this came out on a magnetic tape in 1973, and we freely distributed it.

   Who were the original users?

Certainly the military. It started out a military project. But then NASA immediately realized they could use it for remote sensing of the Earth’s atmosphere. And very early on the Department of Transportation (DOT) got involved. They had this very special problem. Nixon wanted to build a supersonic transport (SST), and the critics worried that it would destroy the ozone layer by giving out nitric oxide and some other gasses. So we got funding from the DOT and that enabled me to expand on this HITRAN database from the original seven gasses we had. Meteorologists started getting into it, so that pushed it to spectral regions beyond the infrared. This was over the course of time. HITRAN is like the human genome of gasses, if you will. And over the years, an unbelievable number of applications were developed to make use of it.

   It sounds like it was driven as much by the applications as anything else?

Applications did tend to drive it. In 1973 we came out with a database that involved only seven molecules in the infrared—water vapor, carbon dioxide, ozone, nitrous oxide, carbon monoxide, methane, and oxygen, which has a couple of weak bands. I jokingly call these the original seven sins. They are the major absorbers in the infrared. That application was driven by the Air Force. In 1978 we had this input from the DOT because of the SST. In the early 1980s, the Air Force started thinking maybe we should be looking at things in the microwave, so we extended the spectral coverage to microwave. In the 1980s NASA came in with this whole idea of remote sensing. They have been the biggest driver to me; they also have taken on the major funding support for this program. Using my database, they can calculate what the constituent quantities are in the Earth’s atmosphere. That meant I had to expand beyond the original seven gasses to the real trace gasses—the anthropogenic things in the atmosphere. We want to see if they’re increasing or decreasing or have odd geographical or altitude distributions. Now the project has become really big. We also have more parameters than we started with. Originally, we tried to catalog the exact wavelength, the intensity of the line and its width, and the lower state energy. That was four parameters. For the sophisticated remote sensing NASA is doing, they needed more. So in addition to having to add many, many gasses, we had to expand the parameter set and get better accuracy.

   How accurate are the HITRAN measurements?

We require these things, because of the instrumental capabilities of NASA satellites, to have incredible accuracy. That means we want to know line positions to one part in 10 million or even better. That’s a tough demand. We want to know the intensities to better than two percent. That’s tough, too. There are so many sources of error. For example, the pressure and the temperature in the cells that we’re using to measure these quantities. We’re pushing the envelope.

   You’re working at an astrophysical laboratory but you’re highly cited in engineering. How does that happen?

Well, the engineering citations are simple. There are so many applications and a lot of them are industrial, and so this is where it shows up. The Environmental Protection Agency is now using it. They’re worried about what’s coming out of various smoke stacks, for example. It’s everything about gasses and so everybody is using it. Now why is it here? A place called the Harvard-Smithsonian Center for Astrophysics. We have a division here called atomic and molecular physics. A lot of people here do spectroscopy and, in fact, most of the people on my floor don’t do traditional astrophysics; we do atmospheric physics. We have experts in the ultraviolet, microwave, infrared. Also this facility has a tradition in building databases. The archiving of mankind’s knowledge and achievements fits very well with the Smithsonian mission in this joint facility.

   How do you see HITRAN evolving over the next five years?

One thing, which some people say is just crossing ts and dotting is, is replacing a lot of our stuff with much more accurate data. That’s needed for upcoming satellites. I also see adding a lot of spectroscopic features that are important but that I’ve never gotten into—effects due to the collisions of molecules, for instance. These have been seen, but they haven’t been very well characterized up to now. I’d also like to push this toward higher temperature parameters. I recently had some calls from a Nobel Prize winner studying red giant stars, and he needs something like my database, but pushed to higher temperatures.

   What’s been the biggest surprise over the last 40 years?

Well, one of them is how many things man is putting up there. It makes my job never-ending. I just added a new molecule to the database that I can’t even pronounce. It gets a little strange. We have all these new gasses that replace CFCs, which attack the ozone, but the new gasses are long-lived and have other effects. They become greenhouse gasses. The only solution is to have fewer humans.

   Is there a global message about HITRAN that you’d like to leave for the public?

Well, I’ve been managing HITRAN for more than 30 years almost on a shoestring. I get support. I now have one or two post-docs. I rely a lot on goodwill from various countries. But one thing is that all of us involved are getting older, and so I need to make sure this carries on. Ideally it should be run internationally with an institute. But that needs to be pursued. Everyone recognizes it has incredible applications. We need to put more molecules in. We need to cover more of the spectral region. We need even more accuracy. But we have to keep it alive. And many people are getting a free ride on this. I have 6,000 people on my mailing list from academia to industry. They’re all getting a free ride, which is okay but it doesn’t keep things going. NASA has been great, but you can’t expect them to take on the entire burden. In recent years they have taken the lion’s share. They get a lot, and they need it. But they shouldn’t be the only ones. They know it, and so they ask me, "Who else is funding you?" And so I go ask the other users, and they say, "You don’t need more money. NASA is supporting you. Just give us the data."End of interview

Dr. Laurence S. Rothman
Harvard-Smithsonian Center for Astrophysics
Atomic and Molecular Physics Division
Cambridge, MA, USA

2011-08-03 03:56:45Line transition parameters
nealjking

nealjking@gmail...
91.33.115.88

Rob,

from the above: "We also have more parameters than we started with. Originally, we tried to catalog the exact wavelength, the intensity of the line and its width, and the lower state energy. That was four parameters. For the sophisticated remote sensing NASA is doing, they needed more. So in addition to having to add many, many gasses, we had to expand the parameter set and get better accuracy."

2011-08-03 04:37:01
Rob Honeycutt

robhon@mac...
98.207.62.223

Thanks Neal...  I also just found this FAQ a the HITRAN database website with lots of information.  

You gottal love the last bit of this interview.. "And so I go ask the other users, and they say, 'You don’t need more money. NASA is supporting you. Just give us the data.'"