城市是車輛、住宅、商業(yè)、工業(yè)匯聚之地，溫室氣體排放量大。
渦度協(xié)方差方法，為準(zhǔn)確測(cè)量這種復(fù)雜“生態(tài)系統(tǒng)”的溫室氣體排放提供了可能。
LI-COR渦度協(xié)方差通量測(cè)量系統(tǒng)
圖片來源/大阪府立大學(xué)http://atmenv.envi.osakafu-u.ac.jp/
這些測(cè)量數(shù)據(jù)，可在評(píng)估城市溫室氣體排放現(xiàn)狀、優(yōu)化交通組織、規(guī)劃城市發(fā)展、制定減排政策等方面發(fā)揮重要作用。
為幫助廣大通量研究工作者深入了解這一新興科研領(lǐng)域，5月13日，LI-COR應(yīng)用科學(xué)家George Burba和Dave Johnson，就這一主題和大家分享了通量測(cè)量系統(tǒng)知識(shí)和相關(guān)案例。
該講座主要內(nèi)容包括：
● 直接測(cè)量方法提供精準(zhǔn)城市溫室氣體排放數(shù)據(jù)
● 渦度協(xié)方差通量測(cè)量系統(tǒng)的組成
● 城市生態(tài)系統(tǒng)溫室氣體排放研究案例
下面是視頻回放和Q&A整理（后附ppt）
Q&A整理
Q1 Derrick Lai: Hi Dave, thanks for your sharing and love the virtual background of Hong Kong! In high-density and heterogeneous cities with high rises like Hong Kong, what is your suggestion of making reliable eddy covariance flux measurements? Would we be making measurements in the roughness sublayer only, instead of in the constant flux layer as the EC method assumes? Thanks.
Derrick Lai：Dave您好！謝謝您的分享。像香港這種“高密度”城市，下墊面復(fù)雜，您能否講一下如何使用渦度協(xié)方差測(cè)量方法進(jìn)行可信的通量觀測(cè)呢？我們是應(yīng)該在粗糙亞層（the Roughness Sublayer）測(cè)量，還是應(yīng)該在EC方法中提到的常通量層（the Constant Flux Layer）呢？
A1 James Kathilankal: I guess it depends upon your experiment, to cover the entire city you probably have to be on top of the highest building, but you could study sections of the city by installing on the tallest building in a particular area. This is a challenge with urban ecosystems, the lack of homogeneity
James Kathilankal：我覺得這取決于您具體的實(shí)驗(yàn)?zāi)康?。如果您的研究區(qū)域是整個(gè)城市，儀器的安裝高度應(yīng)該位于城市最高建筑物的上方；如果您研究城市中的某些區(qū)域，儀器安裝在特定區(qū)域最高建筑物的頂部即可。由于城市下墊面異質(zhì)性大，這對(duì)于測(cè)量來說，確實(shí)是個(gè)挑戰(zhàn)。
Q2 Derrick Lai: Thanks, James. In natural ecosystems, we have to put the sensor at a height of < 1.5 times the canopy height. In the urban ecosystem, say with a mean building height of 100 m, are we measuring the flux properly by placing the sensor at only 1-2 m above the building top?
Derrick Lai：謝謝您的回答。在自然生態(tài)系統(tǒng)中，我們一般把通量測(cè)量?jī)x器架設(shè)在大約1.5倍冠層高度的地方。而在城市生態(tài)系統(tǒng)中，比如建筑物的平均高度為100m，我們?nèi)绻褍x器安裝在建筑物頂部1-2m的地方，貌似不太合適？
A2 James Kathilankal: Choosing the tallest building will help as at that point the building can be considered as part of the tower and when you measure at such heights, some of these requirements can be relaxed as we are measuring much larger eddies which move slowly that what you will find in short ecosystems
James Kathilankal：選取最高的建筑物來架設(shè)儀器是合理的，這個(gè)建筑物可被認(rèn)為是通量觀測(cè)塔的一部分。對(duì)儀器的安裝高度要求可適當(dāng)放寬，儀器可測(cè)量到更多大的渦旋運(yùn)動(dòng)（Larger Eddies）。（編者按：理想情況下應(yīng)該安裝在建筑物平均高度1.5倍的地方，然而實(shí)現(xiàn)起來會(huì)很麻煩。）
Q3 Yingqi Zheng: Wind directions at a 30-minute scale measured by the ultrasonic anemometer, after correction, show great discrepancies from those measured by other devices. Would this cause error in estimating footprint?
Yingqi Zheng：使用超聲風(fēng)速儀測(cè)量得到的30min的風(fēng)向數(shù)據(jù)，和氣象站的風(fēng)向數(shù)據(jù)差異較大。這是否會(huì)影響Footprint計(jì)算呢？
A3 James Kathilankal: ultrasonic measurements will have some discrepancies, but you can get a better temporal resolution from this data, and using diagnostics from the anemometer you can filter out unrealistic values..so average values tend to agree well with slow measuring sensors
James Kathilankal：超聲風(fēng)速儀的數(shù)據(jù)（高時(shí)間分辨率的風(fēng)向數(shù)據(jù)）會(huì)和慢速傳感器的測(cè)量數(shù)據(jù)存在一定差異。使用診斷值，您可以把不可信的數(shù)據(jù)濾掉。理論上，經(jīng)過這種數(shù)據(jù)處理，兩者應(yīng)保持較好的一致性。
Q4 Chaerin Park: Thank you for the good presentation. In the presentation, you mentioned that there is software that can analyze whether the observed co2 flux data originated in a specific area, is this software made by li-cor? Can all the co2 flux data observed through li-cor equipment be analyzed using this software?
Chaerin Park: 謝謝精彩的講座內(nèi)容。您提到有軟件可分析通量數(shù)據(jù)的來源。請(qǐng)問這個(gè)軟件是LI-COR研發(fā)的嗎？所有使用LI-COR儀器獲取的數(shù)據(jù)，都可以使用這個(gè)軟件來做這種分析嗎？
A4 James Kathilankal: The software which is used is the Tovi software (beta version). Flux footprint modeling can be used to allocate fluxes, but this is more for getting average values.
James Kathilankal: 這個(gè)軟件是Tovi，該軟件由LI-COR自主研發(fā)。您可使用其中的Footprint模型來進(jìn)行這種分析。另外，您可登陸https://www.licor.com/tovi/了解有關(guān)這個(gè)軟件的更多詳細(xì)信息（編者按：該軟件可免費(fèi)試用30天）。