A defining milestone for Vietnam’s Hydrometeorology came on October 3, 1945. Shortly after the founding of the Democratic Republic of Vietnam, President Ho Chi Minh signed Decree No. 41, placing the Phu Lien Observatory and the Department of Astronomy under the Ministry of Public Works and Transport, charged with observing wind and rain and forecasting weather and climate nationwide. This date is also recognized as the birth of Vietnam’s Hydrometeorology sector.
Professor Nguyen Duc Ngu, who later served as Director General of the General Department of Hydrometeorology from 1991 to 1999 and represents the sector’s third leadership generation, has often been described as a living bridge across its historical phases.
According to Prof. Ngu, from the moment President Ho signed Decree No. 41, the sector operated under wartime rules. During the resistance war against the French (1945–1954) and throughout the protracted struggle to reunify the country (1954–1975), Hydrometeorology personnel both served production and supported the resistance.
In 1975, after national reunification, Vietnam embarked on post-war reconstruction. The country joined the World Meteorological Organization (WMO) that same year to receive international information and share domestic observation data under international commitments. Only in 1976 did the Hydrometeorology network truly extend across the entire nation. From then on, with the necessary time, people, and resources, the sector was able to build out a nationwide network of meteorological and hydrological stations across land and sea.
Looking back, Prof. Ngu recalls that after Decree 41, Professor Nguyen Xien was assigned to lead the Hydrometeorology service. In 1946, as the nationwide resistance began, Hydrometeorology evacuated to Viet Bac. There, Prof. Nguyen Xien focused on training talent in basic sciences for the Government and on preparing foundational documents to support the future development of Vietnam’s Hydrometeorology sector.
Throughout the wars against the French and the Americans, Prof. Nguyen Xien devoted himself to compiling core technical and professional materials for Hydrometeorology: curricula for training observers; standards; procedures and regulations; the surface meteorological code; rules for surface meteorological observations during wartime; interim rules for hydrological observations and data processing; coastal ocean-meteorological observation regulations; pilot-balloon observation rules, laying the groundwork for later operations.
After the liberation of the North in 1955, the Hydrometeorology service was restored and strengthened. Personnel remained scarce and undertrained, drawn mainly from basic science schools along with “retained” staff, those who had worked in the French-era meteorological service.
In 1955, Prof. Nguyen Xien organized the first three elementary training courses for meteorological observers, personally teaching them. Prof. Nguyen Duc Ngu belonged to this first cohort. At the same time, the service set about repairing and rebuilding war-damaged observation stations.
“I was among Prof. Nguyen Xien’s first students,” Prof. Ngu says. “I was then assigned to establish a meteorological station in Yen Bai in 1956 and to conduct observations there for the next two years. In those early days, we gradually expanded the observation network in the North, but it remained very rudimentary due to a lack of equipment. We had to seek assistance from socialist countries such as China, the Soviet Union, and Eastern Europe.
“At the time, Vietnam could produce only simple instruments: rain gauges, wooden Stevenson screens, and a vane-type ‘Vind’ wind gauge using a slat. When the wind pressed against the slat, its deflection indicated wind speed.
“After 1975, once the South was liberated, the North’s Hydrometeorology service took over and unified operations nationwide. We standardized technical procedures and observation rules. Under embargo and with few international ties, we could not exchange hydrological data with many countries. We received data mainly from the Soviet Union and China through bilateral channels.
“To forecast storms, rain, and monsoons, we had to borrow observation data from the Soviet Union, China, and neighboring countries as a basis. Domestically we had our own data, but not international datasets.”
His two years (1956–1957) building and observing at Yen Bai yielded an unprecedented story. “We were told that the Soviet Deputy Chairman of the Council of Ministers would visit Vietnam and that his plane would pass over Yen Bai. But there was no station there. We needed a station to provide hydrometeorological information for the flight path.
“I brought along a rain gauge and a compass to build a station. With no premises, we borrowed space from the provincial Post Office. First, I went into a village to buy a 10-meter bamboo pole, stripped the leaves, and tied two cross sticks at the top to mark the four points of the compass. We planted the pole in the Post Office yard, used the compass to align it precisely to the cardinal directions, and tied a ribbon at the top to indicate wind direction. Wind speed was estimated using the Beaufort scale; the rain gauge sat below. And that was our meteorological station. After taking measurements, I drafted a coded telegram in Morse and sent it to Hanoi for bulletin preparation, thus providing the data needed for the Soviet leadership’s flight”, he recalls.
The war years and immediate post-war period were so hard that even pencils, the standard instrument for observers to record data per regulations were scarce. “Ink pens were against the rules,” Prof. Ngu notes. “At one meeting attended by Prime Minister Pham Van Dong, we raised the problem. He paced for a while, then laughed: ‘Even the Prime Minister has to concede defeat on this one.’ That’s how tough things were, yet we got through. Step by step, we solved even such small shortages and began making things domestically”.
In 1957, during the International Geophysical Year, Polish experts helped Vietnam build two geophysical observatories at Sa Pa (in the former Hoang Lien Son) and Phu Lien (Hai Phong). Prof. Nguyen Xien reassigned Prof. Ngu from Yen Bai to Phu Lien to work directly on the project, where he served two years as an observer.
At the end of 1959, Prof. Nguyen Xien brought him back to Hanoi to teach elementary meteorological observer courses (cohorts 6 and 7) at the Hanoi Meteorological Vocational School, training more than 500 students, even as Prof. Ngu himself was still classified as an elementary-level observer.
In 1962, he was sent to university in China for four years. Returning in 1966, he was assigned by Prof. Nguyen Xien to compile the climate monograph for Ha Tinh province. “I rode a bicycle from Hanoi to Ha Tinh,” he says, “passing heavily bombed targets on Route 8 and Route 15, over what locals called the ‘crawl-and-roll roads’”.
He traversed every district and commune, completed the Ha Tinh climate report, then under Prof. Nguyen Xien’s strict rules, presented it at a provincial conference for sectoral comments and formal approval before submitting it to the central office. “I delivered the report, received high marks from Prof. Nguyen Xien, and was then encouraged to do the same for Quang Binh,” Prof. Ngu says. “Again, I biked south. I slept and worked in tunnel shelters, did fieldwork by day to gather data. Those years are unforgettable. The people of Vinh Linh were extraordinarily brave and steadfast. Despite fierce bombardment, they remained calm and courageous.”
The Cua Tung Meteorological Station was among the most heavily bombed by U.S. aircraft; its observers were killed in action. Between 1954 and 1975, more than 20 Hydrometeorology personnel fell while on duty. Many stations - Bach Long Vy, Hon Gai, Hon Dau, Pha Din, Cua Tung, Do Dao, Cua Cam, the Phu Ly hydrology post lay in the crosshairs of air raids. “I worked in tunnel shelters that even housed a state store. Each morning a basin of warm water and a face towel would be laid out for me. People cherished and respected meteorological staff”, he recalls.
After 1975, hardship persisted. In 1976, the General Department of Hydrometeorology was created to administer the nationwide sector. Prof. Nguyen Xien retired; Tran Van An was appointed Director General. In wartime, meteorology served not only economic production and agriculture but also the armed services: artillery, air force, navy, infantry, logistics.
In 1976, Prof. Ngu completed his doctoral-equivalent studies in Poland. At home, a prolonged debate raged over the nature of the North’s climate. Some argued it was subtropical, not humid tropical monsoon, citing several consecutive, prolonged cold winters that damaged crops and livestock. Proposals followed to adjust agriculture accordingly: plant wheat and potatoes, raise sheep—instead of wet-rice and sweet potatoes.
That “subtropical” hypothesis led to harmful decisions: wheat was imported but failed to head; potatoes formed tiny tubers; sheep introduced in rainy Quang Ninh died in droves, then in dry spells grew thin coats or coats of poor length and density.
Prof. Nguyen Xien summoned Prof. Ngu and tasked him with settling the question.
At a 1976 climate science conference in Sa Pa, Prof. Ngu presented a report affirming that northern Vietnam has a humid tropical monsoon climate. He laid out the drivers, processes, and mechanisms that shape the region’s climate, and distinguished clearly between subtropical and typical tropical regimes.
The debate ended. From then to today, the North’s agricultural structure has been aligned with the humid tropical monsoon climate: rice remains the mainstay, complemented by winter and winter–spring crops. Over time, the intrinsic stability and proper naming of the North’s climate have only been reinforced.
“Hydrometeorology provides the scientific basis for economic–social strategies and production plans, and underpins sectoral planning across fields. Its role is especially intertwined with agriculture,” Prof. Ngu says.
“I worked on many other projects as well—analyzing Vietnam’s climatic conditions to support a master plan for allocating productive forces based on climate through the year 2000, chaired by the Ministry of Planning and Investment; and studying the climate of the Central Highlands.
“After liberation, remnants of the FULRO insurgency remained in the Highlands. Local leaders told me to change vehicles and issued sidearms to our engineers for field surveys. After three years, we completed the first comprehensive climate study of the Central Highlands, published in 1985.”
In 1991, Prof. Nguyen Duc Ngu was appointed Director General of the General Department of Hydrometeorology—a time when the system had seriously deteriorated due to lack of operating funds, reflecting the broader economic crisis.
“I couldn’t stand by and watch the sector stall,” he says. “Hydrometeorology provides critical inputs for national planning and especially for agricultural production. I petitioned the Council of Ministers—then chaired by Do Muoi, with General Dong Sy Nguyen as Vice Chairman—for a directive to strengthen Hydrometeorology’s capacity and effectiveness, with a focus on supporting agriculture.”
A week later, General Dong Sy Nguyen signed the directive. On that basis, the Ministry of Finance increased funding, enabling upgrades to infrastructure and technology. At the General Department’s request, the Chairman of the Council of Ministers (now the Prime Minister) issued Directive No. 249-CT on August 9, 1991, to enhance Hydrometeorology, improve disaster prevention and mitigation services, and support production and livelihoods.
Implementing this pivotal order, the General Department devised the program “Enhancing the Capacity and Socio-Economic Utility of the Hydrometeorology Sector,” comprising five target programs, including “Ensuring the Volume and Quality of Basic Hydrometeorology Investigations, and of Air and Water Environment Monitoring.” Launched vigorously in 1992 with steadily rising state investment and the sector’s concerted efforts, the program gradually reversed the decline of the observation network.
Prof. Nguyen Duc Ngu retired in 1999, after 45 years of dedicated service.
Entering a new phase marked by professionalization, modernization, and the application of science and technology to forecasting, Prof. Ngu observes that after Vietnam normalized relations with the United States and China, the Hydrometeorology sector adopted modern forecasting models and built high-speed computing facilities, shifting from traditional methods to numerical weather prediction. Vietnam developed warning-oriented forecasts using meteorological radar and satellites, and launched research programs on climate zoning to serve specialized sectors such as agriculture, construction, and aviation; on Vietnam’s overall climate; and on the country’s climate and climate resources.
“Today, every sector uses climate–weather information for planning, drawing on the monograph Climate and Climate Resources of Vietnam, co-authored by Prof. Dr. Sc. Nguyen Duc Ngu and Prof. Nguyen Trong Hieu,” he notes. “It provides the foundation for regional climate resource assessments and sectoral planning nationwide.”
“In the early 1990s, I began studying climate change. In 1992, when the world convened the first Earth Summit in Rio de Janeiro (June 3–14), I served as chief editor of a project to raise awareness and strengthen local capacities for adaptation and mitigation—contributing to Vietnam’s implementation of the UN Framework Convention and the Kyoto Protocol on climate change.
“In that work, we confirmed that Vietnam’s climate had already changed over the prior 100 years. That finding underpinned the Government’s participation in the conference and its signing of the first climate convention, and it spurred subsequent climate-change research. It was Vietnam’s first comprehensive climate-change study—covering global change, national status and impacts, and solutions—and later informed the National Target Program to Respond to Climate Change, approved by the Prime Minister in December 2008. The Party Central Committee’s 7th Plenum later issued a resolution on proactive climate-change response,” Prof. Ngu says.