Like for many of us, words cannot truly describe the horrible shock being felt at losing our dear friend Paul. Having met Paul for the first time some 15 years ago when in Massachusetts and interacted with him along with other colleagues Tony Clough, Jean-Luc Moncet, Eli Mlawer on matters related to his life achievement CRTM, he became a great friend and a huge support when I moved to DC. He was passionate about software. And not just CRTM. Never seen something like that. He taught people (including myself) how to code properly and how to manage software. He was always ahead: By the time I caught up with configuration management based on CVS, he had already moved on to SVN, and by the time I learned how to use SVN, he was already doing TRAC and other stauu (I lost track...). He was the author of the NOAA Fortran coding standards and that had a widespread impact in the organization. A regular to the ITOVS and other conferences, so many of us relied on him and benefited from his contributions over the years. Scientifically, but also for fun. He was an impressive learner, a joyful soul, and a generous man with his skills, his time, smiles and almost contagious happiness. So many memories! So long mate, you mill be missed dearly.
Sid Boukabara

A great Paul story from ITSC-VI:
I remember when Paul accompanied me on his first trip to the US to a TOVS Workshop in the Appalachian Mountains. The Workshop folk scheduled a baseball game one afternoon. It was the USA versus the rest (ie international visitors). Paul lined up to bat for the Internationals. He hit the ball fair and square and sent it so far into the treed park that we lost sight of it. Well the Internationals won the match but the more interesting outcome from my perspective was that Tom Achtor, who was the Manager for the CIMSS program at SSEC, walked up to Paul at the end of the game and said something like:
"Hi, I'm Tom. I don't know anything about the quality of your science but with a hit like that with a baseball bat you are working for us at SSEC."
Merv Lynch
Curtin University

I will share another Paul story from ITSC-VI in Airlie, VA:
Paul and I were both students at the time attending the ITSC for the first time. The conference site pub closed early every evening, and Paul and I would be there to the end. The local sheriff was usually there at closing time as well and would chat with the conference attendees as well as the bartender. The sheriff really took a liking to Paul (as we all did) during that brief amount of interaction at the pub. At the conference end, the sheriff made Paul an honorary deputy and presented him with a badge to take home! Paul had a positive impact on everyone around him. I am so happy I was able to make Paul's acquaintance, even but for a brief fleeting week at ITSC-VI. I cherish those memories even now.
Richard Slonaker

... the Airlie keeps coming up in remembering Paul... I surely remember the bar scene with Paul, Richard a few others notably Dave Wark who would be there real late and be causing quit a stir...
The softball game also featured Dave Steinbergen (Canada) tearing up his knee chasing a long deep fly ball when he all of a sudden disappeared ... and there was the canoe trip in which Paul was one of the river captains as I recall; who was in his boat?
Paul was visible here at NCW and we will miss him. I think we should put a plack where he parked his bike.
Tony Reale

This is a tremendous shock. I have been out cycling with Paul several times when he was visiting the Met Office in England (trying to keep up with him...). I am really shocked. My heart felt condolences go to all who know and appreciated Paul. He will be much missed. He was talented and an outstanding colleague to all who worked with him in our community... I am struggling to take it in.
Stephen English

So sad, I was so fond of Paul as everyone was. For some reason just yesterday I mentioned to my wife that I hoped she got to meet Paul one day.
Larrabee Strow
Physics, UMBC

Terrible news... I am very sad to hear this. I did get to know Paul a bit when he came here from Curtin many years ago. Please convey my sympathies.
Sanjay Limaye
SSEC, UW-Madison

As you can imagine everyone here at NOAA is in deep shock.
This is a huge loss personal and professional loss to us all. He will be deeply missed.

As many of you know, Paul was about to leave us after over a decade to work at the University of Wisconsin. So a lot of what I am going to say today are things I was going to use to embarrass Paul at his leaving celebration. Hopefully he is listening in to what we have to say.
I have known Paul for 23 years. We first came across each other at the University of Wisconsin where we both worked in our late twenties. He had arrived not long before me from Curtin University in Perth. My first memory was Paul and I both being introduced to skiing by a French visiting scientist named Francois. We went to Cascade Mountain which is a ski hill just outside Madison. It turns out that growing up in Western Australia or Southern England does not mean you're a natural at winter sports. I remember a long frustrating day and I think we both mastered turning right, but turning left was a step too far.
Paul was famously recruited by Wisconsin based on his ability to hit a baseball at the 1991 TOVS conference. At Madison, Paul quickly established himself as a rising star in the department including his early mastery of radiative transfer codes and his mastery of computer science. His reputation went from strength to strength both in Madison and beyond.
After a few more years, and a PhD from Curtin University in Australia on retrieval of ozone from ground based hyperspectral sounders, Paul made his way to EMC, working originally for UW, then SAIC and, for the last six years, for IMSG.
It was here that he started work on the CRTM radiative transfer code. His deep subject knowledge, attention to detail and his insistence on high quality programming, testing and documentation procedures (from himself and from others) made it the the highly respected utility that it is today. In most peoples' minds Paul WAS the CRTM.
Paul combined that rare talent that combines both close attention to detail and an appreciation of the big picture. He saw the need at EMC to introduce more modern change control procedures (which were previously non-existent) and made it his mission to change the way we all worked. He worked tirelessly to convince often reluctant co-workers that Trac, SVN and the like were not only desirable but necessary for a modern NWP centre. Despite many frustrations, through his positive personality and sheer force of will this is an argument he largely won and the centre is much, much better off for it.
Paul worked with an openness, a sense of humour and a positive attitude. His work was of the highest standard, of course, but even so he understood that to produce the best required a willingness to actively seek out and accept scrutiny and alternative suggestions. It was all about the final deliverable regardless of who got the credit  -  or the blame. Nothing seemed more exciting than discovering some apparent bug or feature that needed to be fixed or explained in his own code. And he also treated everyone with respect and patience  -  and many of us have had difficult concepts explained to us over many iterations. There was no such thing as a stupid question  -  much as I tried to prove that wrong.
But most of all we will remember Paul's positive energy and sense of humour. The light-hearted banter that seemed to be a fixture of our days will be missed. For me it was great simply having someone that understood terms like "fortnight" and "leg before wicket". When he would make a joke at someone's expense he would always say "Just pulling your wizzer!". I was never quite clear what that meant.
And, of course, Paul was a very avid bicyclist. It was always a wonder to me how he would ride to work year-round, battling the insane Washington drivers and some not so bicycle friendly neighbourhoods. We will certainly miss the sight of Paul sitting in the corner of an early morning meeting (10am) in full bicycle gear, as ever bringing his own brand of humour and sanity to proceedings.
Finally, Paul was loved and admired throughout the international community. Like a number of us here, Paul was an active member of the International TOVS Study Group, which runs a conference every couple of years, but also a close international community of satellite retrieval and assimilation experts. The webpage set up in memory of Paul is already overflowing with tributes from four continents. The community remembers a great scientist and a wonderful friend. There is a huge Paul-shaped hole in our work lives and our community and he will be sorely missed by us all.
Andrew Collard

I am so shocked by this news! I have been so helped by him not only from the masterpiece of CRTM but also from his numerous answers on many tech boards over the internet. May his soul rest in peace!
Xin Jin

It is of great sadness and shock what happened to Paul, he was health conscious man who told me he always use B(ike), M(etro) and W(alk). I will miss him so much.
Dongsoo Kim

What a shock to read these sad news. I knew Paul since the Airlee meeting 1991. My deepest thoughts are with his family and his friends. He will be missed very much.
Dieter Klaes

It with great shock and sadness to receive this bad news. Paul was a wonderful colleague. Always kind and gentle, Paul made friends with all those that he came into contact with. As you know,I was personally blessed to have known and interacted with Paul ever since he came to SSEC/CIMSS in the early 90's as a student of Curtain University. He contributed greatly to our profession with his radiative transfer modeling achievements and the code that he provided. It was obvious that he loved his work from his enthusiasm for it and from the smile on his face when he discussed it.
My sincere condolences to you, who I know is a very close friend of Paul's. Please pass on my condolences to Leah. He will be greatly missed.
With the faith that he now enjoys eternal happiness with the angels in the life that he has passed on to,
Bill Smith
Hampton University/SSEC

This is a complete shock. Paul has been such an enthusiastic long-time member of ITWG, a great colleague to be with, and a dedicated RT Working Group co-chair. He will be terribly missed. My sincere condolences go to his family and everyone who knows him. I really struggle to take this in.
Niels Bormann

Yes, I remember driving with him down to one of the FIRE programs in KS/OK in the 1990s. It was a fun road trip. This is very sad news. A wonderful person is lost to us.
Steve Ackerman
CIMSS, UW-Madison

It's hard to come to terms with Paul's passing. He was a really great person.
Before Paul left DC a year and change ago to go back to Australia for several weeks and help care for his dying father, I remember him saying that he had to laugh about it; that laughter was how he could deal with the gravity of the situation and still be able to carry on. I actually don't think I ever saw him without a smile on his face or unprepared to crack a joke.
In going through some things to find a photo of Paul for an internal website, I came across a slide he tacked on to a presentation he did about a year ago for one of our quarterly meetings. It made me laugh. There was a request that I pass it on here, as some of you may also enjoy seeing it.
Erin Jones

I have so many fond memories of working on AIRS science team efforts with Paul in the 90s. He made numerous significant contributions, especially conducting all of our simulations of the double difference concept for accurately intercomparing aircraft spectra with AIRS. It is very painful to have to say goodbye to a wonderful friend and colleague. I have always though of Paul as a special member of SSEC.
Hank Revercomb
SSEC, UW-Madison

The year I started at SSEC was the same, the caring email streams I saw in several posts testified to the impact (even remotely) that Paul van Delst had in many of our lives. With a heavy heart,
Wayne Feltz
SSEC, UW-Madison

What a great shock and sadness to receive this bad news. Paul was a wonderful scientist and scholar in atmosphere remote sensing. He had visited Taiwan twice. His polite, gentle manner was an admiration to me. Yes, he was talented and an outstanding colleague to all of us.
Kunghwa "Peter" Wang
University of Taiwan

I have worked for many years liaising with Paul through the ITWG on atmospheric radiative transfer problems and although we were working on different models Paul always collaborated with us to share the knowledge for the good of all. We did an exchange in 2006 where I worked with him in Washington for 6 weeks comparing both RTTOV and CRTM and he came to Exeter doing the same where he discovered the joys of cycling up Devon hills!. He was always optimistic in his outlook to get things done despite the barriers in the way. He will be greatly missed and we send our condolences to his family.
Roger Saunders
UK Met Office

I have many memories of Paul. A few of them come to mind   -   sharing stories about his hometown, Perth, Australia, playing softball at ITSC-6 after he first arrived in the US, going out for Mexican food and seeing his enjoyment of spicy food, and watching his affection for animals as he interacted with our housecats. Paul was a seeker of knowledge, a keeper of the radiative transfer code, a friend to all in the International TOVS Working Group, an enjoyer of life, and a gentle soul. He added something special. He left us too soon.
Paul Menzel
SSEC, UW-Madison

Paul was my office "mate" when he came to SSEC as a PhD student for Merv Lynch in Curtain University in Perth, Australia and I was an assistant researcher. I have many fond memories of his Aussie sense of humor and curious turn of phrase but also of his personal kindness, e.g. when he patiently waited for me at the top of every hill near New Glarus as I slowly toiled my way up and then would effortlessly zoom on up the next hill and patiently wait for me again. But the thing that impressed me the most was when I somewhat proudly gave him all the FORTRAN77 code that I had spent the last three years developing and getting to work so he could use it in his thesis studies. About a month later he gave it back completely re-written in FORTRAN90, beautifully modular, and about 10x more readable an reusable than what I had given him. PVD was one of a kind and I will sorry miss him. I know I speak for many of us who were very excited that Paul was returning to SSEC so we could make new memories together and to have him snatched away at this moment in time just makes me more thankful for the time he did spend with us at SSEC and at NOAA and in the ITOVS community.
Bob Knuteson
SSEC, UW-Madison

Paul's influence and magnetism extended beyond adults. On a few occasions when he was back in Madison (he was mostly in DC Land by this time), Chia and I had him over for dinner. Our kids, Alex and Isabelle, were totally entertained by Paul, with all his quirkiness combined with his difficult-to-describe yet unmistakeable ability to connect with the kids. He was sort of able to become one of them when he was around them. Since it was often long stretches between his visits, whenever he was coming to our house, we would tell them "Paul from Australia" was coming for dinner and they would reply "oh, you mean that guy with the accent that curses a lot?". Only Paul could appropriately and unoffensively mix cursing into his interaction with kids (and he was careful always to tell them not to repeat what he said!). We as a family enjoyed many laughs and good times with Paul that will not be erased with his passing, and yes, we were looking forward to having him over sometime for a dinner upon his return to Madison.
I haven't had the heart yet to tell our kids of Paul's passing. I think I may wait for some time to elapse before doing so....
Chris (and Chia) Moeller
SSEC, UW-Madison

Paul was without a doubt one of the most friendly and welcoming people in the ITWG community. The sort of guy who, when you meet him, makes you feel like you've known each other forever and have loads in common. I was really impressed by his ability to include the new young members of our group as well as keep up with his old friends. He was a very special guy, and it is such a shock that we have lost him. At least he was enjoying himself to the end.
Fiona Smith
UK Met Office

My colleagues and I from Environment Canada are very saddened par the passing of Paul.
I have been working closely with Paul in the RT group since the Boulder conference. Always in good spirit. This seems unreal.
He brought so much to our community through his excellent work and friendship.
Our condolences to his family,
Louis Garand
Environment Canada

We too, as has been said many times, are still in shock over the news. We've all been lucky to have known Paul, and to have worked with him as Paul has set an example of cooperation and just being a pleasure to interact with both socially and for working relationships. He has given me some memorable one liners for my wall of quotes, but they just never are as funny and pointed as when you were there to hear them straight from the source.
He will truly be missed.
Benjamin Ruston
Naval Research Lab

It is almost unthinkable that a man as fit as Paul should die of a heart attack. But these things happen.
When I passed the CRTM over to Paul, I knew it was going to good hands. He was an excellent programmer as well as a very good scientist. He will be sorely missed.
Tom Kleespies
NOAA (ret)

This is indeed very sad news. So sorry for the loss. We will miss him.
Ashim Kumar Mitra
India Meteorological Department

I first met Paul in 2005 at a MURI meeting, in Madison. Of course, we focused on the after work hours socializing. I was most entertained by how swiftly he would switch between being professional and goofy.
I was excited to find out we are going to be part of the same team at EMC, when I moved from Australia to Washington,DC. I was impressed by his high integrity and professional code at work. Even when venting about the things at work that frustrated us he always remained respectful.
I got to know Paul outside of work too and I will miss that Paul most of all! Humble and caring, always there for me, even when faced with his father's health hardship. And always ready for a laugh!
What I appreciated most about him was his genuine joy for the simple things in life - crossing Washington, DC on a rental city bike, having oysters for breakfast by the Potomac, planting a raspberry bush in his back yard, discovering yet another brand of Gin  -  his favourite drink.
I will miss him immensely and forever cherish the memories we made in these 18 months in Washington, DC.
Iliana Genkova

When trying to navigate my way through the maze of cubicles at NCWCP I somehow always managed to end up in Paul's cubicle, like a ship sailing toward a beacon at sea.
I would inevitably find Paul sitting behind his computer, always good-humored, ready to take the time to answer questions and discuss the "future"... cracking a few jokes on every occasion.
Every time I bring back memories of a RT working group session, I see Paul in the picture, here, with us at the table, taking notes and laughing at himself and apologizing when he missed something that was said.
Paul was a constant.
No word will bring Paul back but friendly, honest, truthful, humble, dedicated, reliable, funny... is how he will continue to live in my memory...
I will keep smiling when remembering how I would always scroll down to the end of every email he sent when opening them looking for the "Cheers, paulv" as a mark of authenticity...
We lost a great guy!
Cheers my friend!
Jean-Luc Moncet
Atmospheric and Environmental Research

It is quite some years since I attended a ITWG meeting. I have enjoyed reading the many emails that have circulated on the ITWG following Paul's untimely death.
I did introduce Paul van Delst to the ITWG when he accompanied me to ITWG VI in Airlie, VA and at the time had no idea how that introduction would bloom into his full-on and productive career.
Paul van Delst was an undergraduate student at Curtin University, Perth, Western Australia (as was Liam; same student cohort). Paul continued at Curtin studying his PhD and I was his Principle Supervisor ably assisted by my colleague Brian While for the Dept of Mathematics and Statistics, Curtin.
During his PhD I sent Paul to SSEC / CIMSS at UW, Madison to participate in a field program that deployed one version of Prof Bill Smith's ground-based AERI hyperspectral radiometers. Paul returned to Perth with Leah to analyse his data sets and write his dissertation:
Ozone concentration profile retrieval from ground-based high-resolution thermal infrared spectra / Paul van Delst [ PhD Thesis : 1996 ]
using the 9.6 micron band. Both Leah and the rich research culture at SSEC/CIMMS attracted him back to the US.
I have clipped in below a Bereavement Notice that appeared in Perth's daily newspaper today that I inserted on behalf of our Remote Sensing and Satellite Research Group in the Department of Physics and Astronomy at Curtin University. Liam and I have managed to contact many of Paul's undergraduate group. It has been impressive to read their sad reaction to the news of his passing and to record their high regard for him as a person and their respect for his calibre as a scientist.
Merv Lynch
Physics and Astronomy, Curtin University

My sincere condolences to everyone who was close to Paul.
We have met on several occasions at various ITSC meetings, and he struck me as a very competent man, however young. It is sad to see him passing.
Alexander Uspensky

Just before the weekend when he passed away, he sent out an email said he had completed some initial code that replicates the ODPS modules but using objects and wanted us to review it. I received that email together with the sad news. I was so shocked and saddened. I'm still not used to the fact that he's gone. But the quietness of his office reminds me that he is no long there anymore. He was a nice guy and willing to help others. Whenever he was in, his office was always busy. People constantly came to his office with various questions and he was always ready to answer them. He was an outstanding programmer and radiative transfer scientist. He had high standards for the code quality. Those codes that are not organized and have tangled control structures are called by him "spaghetti code". (That is what our old LBLRTM looks like). Paul, have a good trip to heaven, you will be long remembered.
Yingtao Ma
Atmospheric and Environmental Research (AER) @NOAA/STAR