GeoInformatics 2012

2012年6月15日至17日，GeoInformatics 2012在香港中文大学举办，由我们实验室承办。GeoInformatics是CPGIS这个华人地理信息协会每年都要举办的国际性会议。1992年，在美国纽约Buffalo大学，几个年轻的留美博士生自发组织成立了这样一个华人协会，领头的就是现在的林珲教授。20年后，当时的协会成员或成为工业界的领头人，或成为国内外顶尖大学的学者、教授，共同支撑着GIS学科的发展。我能想像这种从无到有的成就感，也很感叹这帮人敢想敢干的精神。

这届的会议非常成功，也邀请到了许多国际GIS大佬，如Goodchild, Michael Batty等。甚至还请来了GIS之父Tomlinson. 当2米多高的Tomlinson拄着拐杖颤颤巍巍地走上讲台，以一个父辈的身份，用颤抖的、接近哭腔的口吻对我们说“Now, I talk to you directly, the future of GIS”时，我仿佛接受了一次洗礼，似乎那个学科发展的巨担已传递到了我们肩头。

会上我还意外地碰到了John Radke，让我一下子想起了三年前的我。那会儿我利用寒假的时间去美国UC Davis交流，期间去了UC Berkeley. 因时间仓促，事先没联系好那边的老师，只在网上查了地理系的地址，就凭着一股年轻人的蛮不讲理去了。在系楼的过道上看到了John Radke的名字，只知道是和GIS相关的，就和秘书说我要找他。没想到他并没有怪我来得莽撞。很奇怪的，我们并没有讨论GIS的话题，而是就中国的问题争论起来。他说他小时候在中国长大，对中国很失望，中国的政府和学术很腐败；我便和他说现在已经不一样了，你大可以再去看一下。争论的最后我们都按捺不住脾气了，一小时的谈话就终止了。现在想来，当时的我真是好笑，而John的风度也的确让我印象深刻：一个大牌教授突然被一个不知哪来的毛头小孩打扰，还莫名其妙地和他讨论了一小时中国问题！记得讨论完的我异常兴奋，回去后还给他发了邮件，贴在下面，以供玩味。

Prof. Radke,

     Hello, I'm the Chinese student who met you this afternoon. I'm from Zhejiang University with GIS as my major.

I really admire you, not for your great achievements in GIS, but that you are truly thinking about what we are doing and what we are doing that for. You made me think deep into why I learn GIS. I have too much to say, so it might be a little bit long letter. 

     Money is necessity for life, but I never worry too much about it. I have my dream which means more to me and I keep it all the way I grow up: I want to do something to change the world( big dream, err?) I keep on asking myself: but how? until I met GIS. GIS tools are powerful but  they are not interface friendly and are complicated to use. Why not make it as popular as photoshop, thus pushing GIS research one step forward?

    But after the talk with you today, something new came into my mind. GIS is a tool, and only a tool which can be used in any way or not in any way at all if you are not determined to solve a problem! There exist many problems--both in developing and developed countries--environmental degradation, resource shortage, transportation problem, etc. Actually the government could solve them, but it costs. What we might do is, to make the cost smallest so that the governor is willing to take the risk, with the tool of GIS. And I might turn to politician if necessary.

     I don't know if it is another naive idea. It just hits my mind on my way back home.

    As for the "China" you mentioned today, I just feel sorry. But it's not apology. I just feel sad that you didn't see the other side of the country. That's not real China. There are many problems in China like government corruption and environmental degradation. But we have identified the problems and we have taken action. We just need time. Time is indeed impressing but it's never too late to take action. China is no longer the poor country before. It is a big responsible country, just look at 2008 Olympics and the important role China plays in the Copenhagen conference. I truly   hope you pay a visit to China once more, and perhaps to Zhejiang University, Hangzhou.

     By the way, Beijing is the capital of P.R.China, while Capital Nanjing is history. They are two different periods of China of 5000 years old.

John竟也马上给我回了一封长信：

Dong Chen,


It was good to meet you.  If I could only transfer my experience to you
directly you would see that in my mind I see the beauty of your home
country and in fact all the counties of the world.  I also see the future
and the custodians of the future.  This is my dilemma. It starts with
humans and their inability to see the bigger more important problems.
They are for the most part goal directed and this is their weakness and
downfall.  No doubt China will fix its current problems but will they
learn?  The US is young, has experienced many growing pains and I believe
rarely learns form those experiences.  If we only had time to go into this
further.


To save a life is to save your own.  Save mother earth and look what you
have done.


Governors (politicians) are usually caught up in themselves and by the
time they realize they could have done something good ... their time is up
and a new one enters the scene.  Faith in their ability to see the
problems and articulate a solution is likely naive but this is not a
failure of yours but theirs.


Spatial reasoning and understanding brings us closer to recognition of
what is.  This is why I have embraced GIS.  I see you feel the same.  I
salute you for it.


kind regards,

这次再见，很可惜他已经不记得我了。希望有一天，在我学有所成之时，能再和他"talk around GIS problems"。

这次会议是我认识GIS圈里人的大好机会，在这里把CPGIS的一些会员贴出来，供膜拜学习（不保证信息完整准确）。

1. 宫鹏。19岁即于南京大学地理系本科毕业，21岁于南京大学地理系硕士毕业，25岁于加拿大滑铁卢大学地理系获得博士学位，现任美国UC Berkeley大学教授，清华大学地球系统科学研究中心主任。
2. 丁跃民。美国Verizon Communication公司信息技术部资深经理。Verizon主要运营无限服务，美国最新的4G网络就是他们运营的。
3. 龚健雅。江西人。毕业于华东地质大学（今东华理工大学）。中国科学院院士，武汉大学教授，武汉大学测绘遥感信息工程国家重点实验室主任。吉奥公司总工。
4. 周成虎。福建人。南京大学陆地水文专业学士，中科院地理所博士。陈述彭学生。中科院地理所副所长，资源与环境信息系统国家重点实验室主任。
5. 李荣兴。上海同济大学surveying and mapping专业学士、硕士，Technical University of Berlin 大学 Photogrammetry and Remote Sensing博士。曾是NASA火星探索计划科学家。现任Director, Mapping & GIS Laboratory，Department of Civil and Environmental Engineering and Geodetic Science， The Ohio State University
6. 李斌。广东人。Ph.D., Syracuse University。现为Central Michigan University地理系教授。
7. 柳林。中山大学地理科学与规划学院院长。美国辛辛那提大学教授。
8. 林戈。美国内布拉斯加大学医学中心副教授。
9. 夏福祥。浙江衢州龙游人。浙江大学毕业。现为ESRI 资深构架师。
10. 周启鸣。香港浸会大学地理系教授，地学计算与分析研究中心主任。
11. 王野乔。美国罗德岛大学自然资源科学系教授。
12. 关蔚禾。哈佛大学地理分析中心研究服务部主任。
13. 涂汉明。Octagon Research公司临床信息技术部总监。
14. 陶阅。湖北人。武汉大学毕业，后赴加拿大卡尔加里大学用两年半时间获得博士学位。32岁获终身教授职称。开发了GlobalView等软件，现为PPLIVE的CEO.

A dip into NCL

NCL is an interpreted language designed for scientific data analysis and visualization. I use it mostly for visualization, but not seriously, because there is another developed platform for visualization. For NCL, I just use it to check the model results.

So I just got a dip of NCL for the last three days, in an attempt to plot a wind vertical profile with eta level. The wind vector goes along the terrain and the plot is blank where there is a hill, so that the impact of topography could be seen. Shame on myself, I still haven't gone through it. And in terms of time, I have to give up. Here I'd lie to summarize up what I've learned with NCL.

Coordinate variables are the key information to plot right. Variables from model results (in my case, WRF, CMAQ, and SMOKE) usually bear no coordinate, but columns and rows. It is fine if you just want to see the patterns. However, if you want a base map overlaid, the right coordinates have to be assigned. Coordinates are usually stored in another output variable, e.g. XLAT for latitude and XLONG for longitude in WRF. What you have to do is to assign lat/lon to the right dimension of, say, wind. Here is the code:

f         = addfile(filename, "r")
U        = f->U                             ; wind in east-west direction, time*lev*lat*lon
W        = f->W                            ; wind in bottom-up direction
lat       = f->XLAT(0,:,0)             ; time*lat*lon
lon      = f->XLON(0,0,:)
znu     = f->ZNU(0,:)                 ; time*lev

lat@units  = "degrees_north" 
lon@units = "degrees_east"
lat!0          = "lat"
lon!0         = "lon"
lat&lat      =  lat
lon&lon     =  lon

lev                      = znu*1000            ; [-105.1526..-82.84741]
lev@long_name  = "eta*1000"
lev@units           = "hPa"
lev!0                   = "lev"
lev&lev               =  lev

U!0      = "lev"
U!1      = "lat"
U!2      = "lon"
U&lev    =  lev
U&lat    =  lat
U&lon    =  lon

; And the same for w, left out here

But wait, there is a mistake here. NCL would prompt dimension inconsistent between U and W. Let's take a close look at it. By the funtion printVarSummary we find the dimension of both U and W is time*level*latitude*longitude. So, why inconsistent?

It comes out that there are two grids in WRF, the staggered grid and the mass grid. Value in mass grid is refers to value in the center of the grid while value in staggered grid means value in the boundary of the grid. So the dimension size of staggered grids is always greater than mass grids by 1. To solve the inconsistency, we average the value to mass grid points.

dimU = dimsizes(U)
nlonU = dimU(3)
u = 0.5 * (U(:,:,:,0:nlonU-2) + U(:,:,:,1:nlonU-1))

In this case, u is on the common grid. And the same is for w.

Finally gsn_csm_pres_hgt_vector (example is here and here) is used to plot the vector. However, the result (shown in figure below, at 24.5N along 113-114E) is quite different from the example, mainly for the three points:

 1. I am not sure whether the eta level is terrain-following. Though there are "ups and downs", no specific "hills" are to be found. Of course, it may be a problem of scales.
2. The temperature contour goes along eta level, which is weird.
3. Wind always flows to the east. There seems no "up" wind.

Some other resources:
To plot vectors:
gsn_vector(), gsn_csm_vector(). And the latter is more advanced.
gsn_csm_vector_map() overlays the vector plot on a base map.

To draw vector and scalar simultaneously.
gsn_csm_vector_scalar_map()

完成论文

查看了下上一篇日志，还是在上月初写的。一晃就是50天，时间过得真快。

没写日志的一个原因是这期间确实没取得实质性的进展。除了为WRF和CMAQ写了两个顶层的控制脚本，就为在其他机器上安装CMAQ进行尝试。这不是技术问题，而是沟通与制度的问题。结果实验室新买的电脑因为权限问题到现在还没配置好，而中大的集群也因升级而暂时无法使用。结果白白浪费了一些时间。不过在此期间，发现CMAQ竟然升级了。最新的CMAQ 为5.0版本，加入了 CMAQ-WRF two-way couple 的新特性。这个升级非常让人兴奋。众所周知，气象场对污染物的分布产生很大的影响，是污染物扩散的驱动力；反过来，污染物的浓度也会对局部地区的温度、相对湿度等产生影响。因此，将这种双向的反馈反应到模式中，会使模拟结果更加准确。

在此期间，还写了MSc的毕业论文。本打算非常认真、严谨地对待这篇文章，但是时间紧迫，平时积累不够（想起Robert说的，每天读半小时文献，写半小时文摘，这些积累使他最后写论文时简单的copy-paste就完成了。真是汗颜）。因此论文不是很让我满意，模拟的结果也没有时间再做改善。

在做毕业论文内容的过程中，我也发现了一些问题：

1. 我拿到的污染源数据中，香港的排放源不完整，甚至是空白的。具体的数据还没有分析，但从CMAQ模拟的结果来看，香港地区除了塔门这个监测点，其他监测点的污染浓度值都与模拟值相差较大。这可以用排放源解释：塔门附近没有大型的排放源，它监测的是背景浓度，而且它离深圳较近。相对而言，深圳的排放源更准确，模拟的污染物浓度也更符合实际。所以塔门模拟得较好。而其他站点，因为排放源的缺失，模拟的浓度值大大低于实际值。

2. 跑模式分析污染物是一件很荒诞的事。在我看来，很多这方面的论文就是为了发表而发表。很多人跑模式，是为了分析过去的某个空气污染事件。当模拟值与实际值不符时，就提高或减少排放源的排放量，直到结果较为满意。试问，这样有什么意义？当然，有些人依此得到较为可信的排放源数据，并希望将它用于未来的模拟。可问题是，怎么证明适用于那个事件的污染源同样适用于其他事件、其他时期？

很高兴我今后不再研究这个领域。