Taiwan is a middle-sized island, neither very large nor very small. Among the islands of the world, it ranks 39th. Kyushu—one of the main Japanese islands—is slightly larger. Hainan off the coast of South China and Timor in the Malay Archipelago are slightly smaller. Whatever Taiwan lacks in size, it more than makes up for in geographical and especially in climatological diversity. For its mere 13,885 square miles, this uptilted chunk of land tossed into the Pacific athwart the Tropic of Cancer and between the East China and South China Seas has a climatic pattern of immense complexity.
The island is about 250 miles long and 90 miles across at its widest. Mountains run from north to south in ranges and sub-ranges that rise as high as 13,000 feet and occupy about two-thirds of the land area. To the west lies the Chinese mainland with its monsoon system of climate. To the southwest lies the South China Sea and to the southeast the Philippine Sea that contributes a weaker monsoon system during the summer. As if these influences were not climatically complicated enough, the Kuroshio (Japan Current) strikes the southern tip of Taiwan and makes its way along both coasts.
Taiwan's people joke about their climate. They say it never stops raining in Keelung, the northern port, and ask where you can find a longer, hotter summer or a colder two-month winter. Taipei residents complain that they don't see the sun for months on end. On a rainy island, drought stalks the hydroelectric facilities of the south in the spring and power shortages necessitate rationing for some industries. People from the Chinese mainland are apt to remark that there is always good weather on Taiwan but never where you are at the moment.
The winter monsoon from the Asian continent is Taiwan's biggest climate-maker. From October to March, it blows into the northern part of the island. The winds are heavily laden with moisture picked up in the Taiwan Straits. As the air masses rise to pass over the high mountains, they loose much of their moisture in winter rainfall. Rainy, cloudy weather is common in northern Taiwan during these months. But the southwest is caught in a rain shadow; winter there is the dry season. The southwest gets its rain when the gentler, more variable monsoon blows up from the seas to the south. This monsoon affects the climate in the north to a lesser extent. On an island only 250 miles long, the north has a wet winter and a dry summer, and the south has a wet summer and a dry winter.
Temperatures of both summer and winter are moderated by the Kuroshio. But because most of the current flows up the east coast, temperatures there are slightly warmer in winter and cooler in summer as compared with the west coast. The annual mean temperature for the whole island is above 70° F. There is a sharp difference between north and south—about 5° F. from one end of the island to the other. Yet in July—the hottest month—the average temperature is about the same in Keelung (north) as in Hengchun (south). The highest temperatures ever recorded were in excess of 102° F. In the cold months of January and February, the north is nearly 10° colder than the south (nearly 60° F. in Keelung compared with nearly 70° F. in Hengchun).
Snow in the Mountains
Taiwan seems to escape its sub-tropicality in the winter—a fact which is attributable to the mountains as well as to the continental monsoon. Snow occurs in the high mountains. There is even a brief ski season. Frost is unusual but not unknown on the northern plain. In the cold snap of February 13, 1922, both Taipei and Taichung had temperatures below freezing. Temperatures in the high 30s and low 40s are common a few times a year. Minimum mountain temperatures have reached 10° F. at Yushan, the highest peak, and 18° F. at Alishan.
The annual temperature range is about twice as high in the north (23.4° F. at Keelung) as in the south (12.6° at Hengchun). The Kuroshio helps to make the range smaller than on the China mainland coast. Daily temperature variations range from 41° F. to 50° F.
Rainfall patterns are as varied as temperatures. In general, the island has heavy rainfall. But the distribution is uneven. The east coast has more rain than the west cost. Lowlands receive less precipitation than the mountains. Houshaoliao on the northern tip of the island near Keelung has an average of more than 250 inches of rain a year. In 1912, a record of 331 inches was set. The west coast is in the rainshadow and receives only 40 to 60 inches annually. The Penghus (Peseadores islands) off the southwest coast receive less than 40 inches a year and have a minimum figure as low as 16 inches.
Not only are the seasons of rainfall different in north and south, but the character of the precipitation affords a sharp contrast. The continental monsoon of the north brings steady, soaking rains, whereas the summer convectional rain of the south comes mostly in the form of downpours. Occasionally the north also has thunderstorms and heavy convectional rainfall in the summer. The summer monsoon moves along the east coast south of Hualien, bringing cloudiness but not much rain. The central part of the west coast is the driest part of the island because of the rain shadow effect of the Central Range.
Rainfall Variations
Rainfall varies greatly from one year to another. There is an increase from north to south—15 per cent variability at Ilan and 35 per cent at Hengchun. This difference is ac counted for in large part by the heavy rains brought by typhoons, which strike in the south and east more often than in the north and west. The number of rainy days is high, especially in the mountains and the north. Yushan has rain about 270 days a year, Alishan 210 days, and Taipei 190 days. But in the southwest rainshadow area, the averages fall off to 110-120 days.
Taiwan is a windy place. Along the northwest coast and in the Penghus, windbreaks are necessary to protect crops. The wind system also is largely a monsoon product. In the winter the northwest winds from continental China are deflected by the earth's rotation and become a northeast monsoon. In summer, the southeast winds are deflected into the milder southwest monsoon. From October to March, the winds prevail from the northeast and coincide with the northeast trade winds to attain a velocity of more than 150 inches a second in November at Taipei. In the Penghus, the velocity reaches 366 inches in December and there are 140 days of high winds a year, all but about 30 between October and March. The wind velocities of the southwest monsoon average only a little over 100 inches per second. Temperatures of the north are materially affected by these winds. The cold air from the mainland brings the snappy weather of winter and the tropical winds from the south contribute to the heat of the northern summer.
Taiwan lies in the track of Pacific typhoons and has an average of between two and three a year. However, these destructive storms tend to hit the island on the east coast and partially to blow themselves out crossing the high mountains. The narrow east coast plain is not heavily populated, so damage is minimized. Typhoons are fickle storms, however, and sometimes strike from west to east across the southern part of the island. Occasionally they also bore directly in upon northern Taiwan from the east rather than along the northwestern course that takes them through the mountains. The heavy rains of the typhoons may be as damaging as the strong winds.
Destructive Typhoons
The typhoon season is from July to October, although out-of-season storms are not unknown. Taiwan's worst typhoon of the last few years was Gloria on September 11, 1963. More than 200 persons lost their lives and property damage was heavy. One of the most costly in the island's history occurred August 26 and 27, 1911. Wind velocity reached 160 miles an hour. The death toll exceeded 500. Another bad typhoon was that of September 25 and 26, 1946. Horizontal pressures may reach 100 pounds per square foot in a typhoon and water content may equal two quarts per cubic yard of air.
In the past, Taiwan has suffered heavy damage because of the lack of typhoon warnings. Radar now scans the path of approaching typhoons. Watch also is kept by aircraft. Warnings are received from the Philippines and other islands to the south.
Taiwan's absolute humidity ranges from 0.59 to 0.79 of an inch and is generally much higher in summer than in winter. Taipei has average humidity of 0.85 in July and 0.42 in February. Taipei's relative humidity averages 82 per cent annually. The relative humidity decreases from north to south. Relative humidity in the north is higher in winter than in summer. The Taipei figures are 84 per cent in January and February and 78 per cent in July and August. The reverse is true in southern Taiwan.
Northwestern Taiwan and the east coast have cloudy weather on an average of 7 out of 10 days. The west and south are the least cloudy. More than half of Taichung's days are sunny in October and November. September is Taipei's least cloudy month. Although rainfall is not heavy, the Penghus have more cloudiness than Taichung.
260 Days of Fog
Taipei and Keelung have less than 40 per cent of possible sunshine annually: 1,646 and 1,243 hours, respectively. Taichung has 2,477 hours and Tainan 2,593 hours. On the east coast, Taitung has 1,897 hours. Fog is not much of a problem except on Alishan, which is usually shrouded in a "sea of clouds". Foggy days add up to 260 a year atop this mountain. Taipei has only about 13 foggy days annually.
Climatic complications make the famous Koppen system of indifferent value in classifying Taiwan climate. According to Koppen, four types of climate may be distinguished: (1) tropical monsoon in the southern part of the island, (2) humid sub-tropical in the northern part, (3) humid with hot summer in the eastern and western coastal areas, and (4) humid with cool summer in the Central Mountains. But according to the Koppen classification, Taipei and Hualian on the east coast both belong to the same group. Actually, their climates are quite different. Contrariwise, Tainan and Kaohsiung on the southwest coast have almost identical climates, yet are in different zones on the Koppen map.
Any island of Taiwan's size will have a climate that is strongly influenced by the nearness of the sea. What makes Taiwan different is the monsoon pattern, the height and ruggedness of the mountains, and the north-south elongation of the narrow land mass. Ironically, the worst weather is in the north where the population concentration is the densest.
The British often joke about their climate, just as do the people of Taiwan. They call it the worst in the world—and suggest that only mad dogs and Englishmen would endure it. However, the geographer Ellsworth Huntington once formulated a theory that the most progressive peoples were to be found in lands with marked climatic changes. He also believed that violent storms had a creative impact. Huntington can be used to help explain England's rise to world power and Taiwan's energetic society. Not many other subtropical climates have given rise to such a hard-working culture.
Taiwan can be enervatingly tropical in summer and energizingly temperate in winter. It can be damp to a point of mildewed clothing, shoes, and books. But it is never boring. There is no subtropical sameness. Tourists have learned that the ideal time of visitation is in the fall. Fortunately, this coincides with the time of holidays: National Day, Overseas Chinese Day, Taiwan Retrocession Day, the birthday of President Chiang Kai-shek, and the anniversary of the birth of Dr. Sun Yat-sen. Even Taipei lays aside its foul weather and lets the sun shine through in October and November.