涓流細雨

編輯 賈朋群

“Himawari-8 is sending kinds of big data that were not available before. We are now able to build a system that uses those data to improve the way we predict weather. The strength of this system is it gives you accurate weather predictions when natural disasters may happen, and it is updated constantly. For those who are vulnerable to natural disasters, like the elderly and people with disabilities, you want to give them enough time if they have to evacuate their home.”

“葵花-8”衛星獲得了以前無法得到的大數據。我們現在能夠基于這些數據建立改進天氣預報的系統，系統定時更新。對于面對自然災害脆弱的人群，如老人和殘疾人，需要從家中轉移時就能得到更多的時間。”

——日本理化研究所利用“葵花-8'衛星建立的“紅外輻射亮度數據',可用于天氣預報模式,主要能夠提供濃云密布時天氣系統的分布,從而改變之前這類天氣難以有效處理的問題。該項目的負責人Takemasa Miyoshi描述了這個項目可能獲得的結果。

“The rapid and dramatic changes we continue to see in the Arctic present major challenges and opportunities. This year’s Arctic Report Card is a powerful argument for why we need longterm sustained Arctic observations to support the decisions that we will need to make to improve the economic well-being for Arctic communities, national security, environmental health and food security.”

“我們看到的北極快速和強烈的變化帶來了巨大的挑戰和機會。今年的《北極報告》有力地支持了我們為什么需要長期可持續的北極觀測來支持決策，我們需要這些決策改進北極周邊經濟狀況、國家安全、環境健康和糧食安全。”

——美國NOAA連續第12年發布《北極報告》,這份由12個國家85位學者共同完成并且通過同行評議定稿的報告指出,2017年是北極有記錄以來第二高溫年,升溫幅度是全球的兩倍。談到這份報告的價值,NOAA執行局長Gallaudet博士如是說。

“Events like these cause enormous damage. It’s important that we have an accurate understanding of how the hazard posed by these events change as the climate changes.”

“這樣的事件引發巨大損失。我們認識當氣候變化發生時這些事件的改變是如何帶來災害的就非常重要。”

——2017年大西洋颶風季,成為美國歷史上最具破壞力的颶風季節,在11月30日官方颶風季尚未結束,損失已經超過了2000億美元。哥倫比亞大學氣候學者開發了新的全球颶風模式,能夠估計罕見和高影響風暴在不同氣候背景下的長期損失。項目負責人,該校氣候和社會國際研究所的Chia-Ying Lee闡述了他們這項研究的意義所在。

2017年11月舉行的UCAR國會吹風會上，來自美國高校、聯邦實驗室和私企的專家，面對每年數十億天氣相關的市場，就吹風會主題“研究向產業過渡（MOVING RESEARCH TO INDUSTRY）”發表了各自就天氣預報技術、政府投入和天氣市場等的觀點。

“Thanks to a quiet revolution in modern weather prediction,we can all use forecasts to make decisions in ways that wouldn't have been possible just 10 years ago. Now we are looking to the next revolution, which includes giving people longer lead times and communicating risk as effectively as possible.”

“源于現代天氣預報靜悄悄的革命，我們所有人利用預報進行決策的方式在10年前是不可能的。現在我們關注下一場革命，包括讓公眾有更長的提前時間以及盡可能有效的風險告知。”

——NCAR資深學者,該機構MMM實驗室副主任Rebecca Morss發表了自己的看法。

“The future of weather forecasting is very promising. With strategic investments in observations, modeling, data assimilation,and supercomputing, we will see some remarkable achievements.”

“未來天氣預報非常值得期待。在觀測、模擬、數據同化和超級計算方面的投入，能讓我們獲得明顯的進展。”

——賓州州立大學氣象和統計學教授Fuqing Zhang在強調了科學家正在借助更詳盡觀測和計算模擬,特別是利用NOAA的GOES-R衛星和強有力的FV3模式推進對颶風和其他風暴的認識后,給出了他的展望。

“We have a weather and climate enterprise that we can be extremely proud of as a nation, but it's not where it should be.Weather affects every consumer and business, and the public-private partnership can play a pivotal role in providing better weather information that is critically needed.”

“我們為國家的天氣和氣候事業非常驕傲，但是不應停止于此。天氣影響每個消費者和商業，公共—私人伙伴在提供更好的所需天氣信息方面起到重要作用。”

——美國天氣公司科學和預報業務主任Mary Glackin如是說。他認為天氣企業界的目標是幫助消費者和業界做出更好的決策,這可以通過提供自己做出的預報和傳送國家氣象局預警兩個渠道實現。天氣公司目前正在調整基于NCAR的模式,即MPAS (Model for Prediction Across Scales,跨尺度模式)模式用于全球實時天氣預報。

“These essential collaborations between government agencies,universities, and private companies are driving landmark advances in weather forecasting. The investments that taxpayers are making in basic research are paying off many times over by keeping our nation safer and more prosperous.”

“這些在政府部門、大學和私企之間關鍵的合作正在促成天氣預報的重大進展。納稅人在基礎研究上的投入，可以通過保持國際安全和更加繁榮得到數倍的回報。”

——NCAR主席Antonio Busalacchi,強調了多方合作代理的益處,指出NSF、NOAA和其他聯邦機構對研究投入對于改進預報十分關鍵。

2018年初召開的美國氣象學會第98屆年會上，首次舉辦的“小衛星地球觀測第一次學術會”（First Conference on Earth Observing SmallSats）引入注目。會議安排的30個報告，分“立方體衛星和小衛星在推進地球科學、天氣預報、空間天氣預報、水文研究和氣候監測中的進展”（Advances in CubeSats and SmallSats to Improve Earth Science,Weather Forecasting, Space Weather Prediction,Hydrology Studies, or Climate Monitoring）、“觀測系統理念”（Observing System Concepts）和“可行技術及其成熟”（Enabling Technologies and Their Maturation）和“小衛星地球觀測：新常態”（Earth Observing SmallSats: The New Normal）等4個主題（其中，第2、3個主題為與第22屆衛星氣象和海洋學會議聯合舉辦），全面評述了小衛星在地球觀測領域里的優勢、技術開發細節和一些項目規劃在未來可能展示的作用。這里介紹幾位來自NASA的參會學者的發言。

“RainCube (Radar in a CubeSat) is a technology demonstration mission to enable Ka-band precipitation radar technologies on a low-cost, quick-turnaround platform. Radar instruments have often been regarded as unsuitable for small satellite platforms due to their traditionally large size, weight, and power. The Jet Propulsion Laboratory has developed a novel radar architecture compatible with the 6U form factor. The RainCube mission will validate two key technologies in the space environment – a miniaturized Ka-band precipitation pro filing radar that occupies ～3U and a 0.5m Ka-band deployable parabolic antenna stowed within 1.5U.”

“RainCube（即立方體衛星上的雷達）技術，展示了Ka波段降水雷達技術可以應用于低造價和快速轉向的平臺。雷達設備一直被認為不適宜小衛星平臺，因為傳統上該設備具有大尺寸、大重量和大能耗。JPL研發了新的雷達架構可以裝入6U空間。RainCube項目驗證了兩項空間環境下的關鍵技術：小型化的Ka波段降水廓線雷達占據3U空間和一個0.5 m的Ka波段可展開的拋物形天線可放入1.5U的空間內。”

——來自NASA噴氣推進實驗室(JPL)的Shivani S Joshi在會上詳細解釋了RainCube項目,預計該衛星將在2018年5月送往國際空間站,7月送入軌道。

“The CubeSat Infrared Atmospheric Sounder (CIRAS)employs an MWIR spectrometer operating from 4.08-5.13 μm with 625 channels and spectral resolution of 1.2-2.0 cm-1to achieve lower tropospheric temperature and water vapor profiles. The CIRAS is packaged in a 6U CubeSat and uses less than 14 W. CIRAS is under development at NASA JPL and scheduled for launch in 2019.CIRAS technology can be applied to a future Earth Observing Nanosatellite (EON)-Infrared, to address a loss or gap in coverage of CrIS on orbit.”

“立方體衛星紅外大氣探測器（CIRAS）采用MWIR分光儀，工作譜段為4.08～5.13 μm，擁有625個頻道，空間分辨率為1.2～2.0 cm-1，可獲得對流層低層溫度和水平廓線。CIRAS裝入6U立方體衛星，能耗小于14 W。目前CIRAS在NASA JPL開發，計劃2019年發射。CIRAS技術可以在未來地球觀測超小衛星（EON）—紅外項目中應用，作為在軌的CrIS的備份或補足其覆蓋的不足。”

——同樣來自JPL的Thomas Pagano則在討論了紅外譜段探測對于大氣科學研究和氣象預報、氣候變化監測等的重要意義后,以CIRAS 項目為例,說明紅外探測技術也可以通過小衛星平臺來實施,且對于未來地球觀測體系的設計也具有重要意義。

“The National Aeronautics and Space Administration (NASA)Time-Resolved Observations of Precipitation structure and storm Intensity with a Constellation of Smallsats (TROPICS) mission is a constellation of state-of-the-science observing platforms that will measure temperature and humidity soundings and precipitation with spatial resolution comparable to current operational passive microwave sounders but with unprecedented temporal resolution.TROPICS is a cost-capped ($30M) Venture-class mission funded by the NASA Earth Science Division. The mission is comprised of a constellation of 3 unit (3U) SmallSats, each hosting a 12-channel passive microwave spectrometer based on the Micro-sized Microwave Atmospheric Satellite 2 (MicroMAS-2) developed at MIT LL. TROPICS will provide imagery near 91 and 205 GHz,temperature sounding near 118 GHz, and moisture sounding near 183 GHz. Spatial resolution at nadir will be around 27 km for temperature and 17 km for moisture and precipitation. The swath width is approximately 2000 km. TROPICS enables temporal resolution similar to geostationary orbit but at a much lower cost,demonstrating a technology that could impact the design of future Earth-observing missions. The TROPICS satellites for the mission are slated for delivery to NASA in 2019 with potential launch opportunities in 2020. The primary mission objective of TROPICS is to relate temperature, humidity, and precipitation structure to the evolution of tropical cyclone (TC) intensity.”

“NASA的小衛星星座降水結構和風暴加強時間解析觀測（TROPICS）項目是一個科學領先的衛星星座觀測平臺，將以空間分辨率等同于目前業務被動微波探測和空前的時間分辨率實施溫度、濕度和降水探測。TROPICS是NASA地球科學部資助的成本設定（3000萬美元）的企業級項目，項目包括一個含有3個單位（3U）小衛星的星座，每個小衛星載有一個在MIT LL開發的基于MicroMAS-2的12通道被動微波光譜儀，將提供91和205 GHz附近的圖像、118 GHz附近的溫度探測和183 GHz附近的濕度。星下點空間分辨率溫度為27 km，水汽和降水為17 km，掃描帶的寬度約2000 km。TROPICS的時間分辨率類似與地球靜止軌道，但費用低很多，顯示出是對未來地球觀測設計可能產生影響的技術。NASA計劃于2019年或2020年發射TROPICS衛星。TROPICS的主要任務目標，是熱帶氣旋（TC）加強時的溫度、濕度和降水結構演化。”

——來自NASA馬歇爾太空飛行中心(MSFC)的Bradley T. Zavodsky關注的針對熱帶TC加強的小衛星觀測項目,讓小衛星項目走向面對需求進行設計和實施。

“Cloud ice plays important roles in Earth’s energy budget and cloud-precipitation processes. Knowledge of global cloud ice and its properties is critical for understanding and quantifying its roles in Earth’s atmospheric system. It remains a great challenge to measure these variables accurately from space. Submillimeter (submm) wave remote sensing has capability of penetrating clouds and measuring ice mass and microphysical properties. In particular, the 883-GHz frequency is a highest spectral window in microwave frequencies that can be used to fill a sensitivity gap between thermal infrared (IR)and mm-wave sensors in current spaceborne cloud ice observations.IceCube is a cubesat spaceflight demonstration of 883-GHz cloud radiometer technology. Its primary objective is to raise the technology readiness level (TRL) of 883-GHz cloud radiometer for future Earth science missions.”

“云冰在地球能量收支和云—降水過程中起重要作用，全球云冰及其屬性的知識對于認識和量化其在地球大氣系統中的作用十分關鍵。從空間準確測量這些變量還是巨大挑戰。亞毫米（submm）波遙感能夠穿透云測量冰體及微物理屬性。特別是，883 GHz頻率是毫米頻率中的最高譜窗，可用來填補目前天基云冰觀測從熱紅外（IP）到毫米波傳感器的空白。IceCube是一個展示883 GHz云輻射計技術立方體衛星平臺，其主要目標是提升未來地球科學使命883 GHz云輻射計的技術儲備水準（TRL）。”

——來自GSFC 的Dong L. Wu,介紹了NASA針對云中冰晶觀測已經完成實施的小衛星項目——冰立方(IceCube)。據悉,IceCube為3U立方體衛星,經過兩年半的研發,于2017年4月成功送往國際空間站,并于5月進入軌道。IceCube中的云冰輻射計(ICIR)已經開始白天運作并獲取數據。2017年6—7月,ICIR獲得的云圖清晰地展示了ITCZ分布。