Climate

Taiwan sits astride the Tropic of Cancer, positioned uniquely between the Eurasian continent and the Pacific Ocean. This strategic location creates a complex and variable subtropical monsoon climate 亞熱帶季風氣候. This beautiful island enjoys warm and humid characteristics, but due to monsoons, typhoons, and topographic effects, it has developed a rich diversity of local climates, presenting dramatically different climatic conditions from north to south and from mountains to plains.

Climate Zones and Characteristics

Latitude and Climatic Division

Taiwan spans the Tropic of Cancer (23.5°N), an important line that divides the island into two climate zones:

Northern Region (Subtropical Monsoon Climate):

• Coverage: North of the Tropic of Cancer, including Taipei, Taoyuan, Hsinchu, Miaoli
• Features: Four distinct seasons, cooler winters, hot humid summers
• Annual average temperature: Around 22-23°C

Southern Region (Tropical Monsoon Climate):

• Coverage: South of the Tropic of Cancer, including most areas south of Taichung
• Features: Year-round high temperatures, distinct wet and dry seasons
• Annual average temperature: Around 24-25°C

Integration of Maritime and Continental Climate

As an island, Taiwan is influenced by multiple climate systems:

• Maritime climate influence: Warm ocean currents moderate temperature changes
• Continental climate influence: Northeast monsoons bring continental cold air masses in winter
• Island effect: Complex topography creates microclimate diversity

The Domination of Monsoon Systems

Taiwan's climate is deeply controlled by the East Asian monsoon system, showing distinct seasonal variations.

Northeast Monsoon (October to April)

Formation Mechanism: During winter, the Siberian high pressure moves southward, forming strong northeast monsoons that dominate Taiwan's autumn and winter climate.

Climate Characteristics:

• Temperature: Cold and dry, northern areas' coldest monthly average 15-17°C
• Precipitation distribution: Northeastern windward slopes receive abundant rain, southwestern leeward areas remain sunny
• Famous phenomenon: "Hsinchu winds, Yilan rains" 竹風蘭雨 (strong winds in Hsinchu, abundant rain in Yilan)
• Keelung specialty: Known as the "rainy port" 雨港, with annual rainfall reaching 3,000mm

Topographic Effects:

• Windward slopes: Keelung and northeast Yilan receive abundant rainfall
• Leeward slopes: Taichung, Changhua, and Yunlin experience dry, clear weather
• Foehn effect: Warm dry foehn winds occur on leeward slopes of central mountains

Southwest Monsoon (May to September)

Formation Mechanism: During summer, the Pacific subtropical high extends westward, and warm moist air masses from the Indian Ocean and South China Sea form southwest monsoons.

Climate Characteristics:

• Temperature: High temperature and humidity, warmest monthly average 28-29°C
• Humidity: Relative humidity can reach 80-85%
• Precipitation distribution: Southwestern windward slopes receive concentrated rainfall
• Afternoon thunderstorms: Inland areas affected by thermal convection often experience afternoon thundershowers

Regional Differences:

• Southwestern plains: Abundant rainfall, main source of Taiwan's summer precipitation
• Eastern regions: Located on leeward slopes, relatively dry
• Mountain areas: Orographic lifting creates more concentrated rainfall

The Baptism of Plum Rain Season

Plum rain 梅雨 is an important climate phenomenon during Taiwan's spring-summer transition, typically occurring from mid-May to mid-June.

Formation of Plum Rain Front

Meteorological Conditions: When the Pacific subtropical high moves northward and encounters southward-moving cold air masses near Taiwan, a stationary front forms - the plum rain front.

Characteristics:

• Persistent rainfall: Continuous drizzle for several days to weeks
• High humidity: Relative humidity often exceeds 90%
• Moderate temperature: Temperatures between 20-28°C
• Regional differences: Southern areas enter and exit plum rain season earlier than northern areas

Importance of Plum Rain

Water Resource Replenishment: Plum rain period rainfall accounts for about 15-20% of Taiwan's annual precipitation, serving as an important water resource supplement.

Agricultural Impact:

• Positive: Provides necessary moisture for rice growth
• Negative: Excessive rainfall may cause pest and disease problems

Life Impact: High humidity during plum rain season easily causes mold growth, affecting daily life quality.

Empty Plum Phenomenon

In recent years, affected by climate change, "empty plum" 空梅 (insufficient rainfall during plum rain season) phenomena have increased:

• Causes: Overly strong Pacific subtropical high suppresses plum rain front formation
• Impact: May lead to declining reservoir levels and drought crises
• Trends: Plum rain season may be delayed, with fewer rainy days but increased intensity

The Power of Typhoon Season

Typhoons are the most important weather system during Taiwan's summer and autumn seasons, with profound impacts on climate and society.

Typhoon Activity Characteristics

Temporal Distribution:

• Peak period: July-September, with August being most active
• Average number: About 3-4 typhoons directly affect Taiwan annually
• Path types: Westward path, northwest path, northward path

Intensity Classification: Based on maximum wind speed, typhoons are classified as:

• Mild typhoon: Wind speed 17.2-32.6 m/s
• Moderate typhoon: Wind speed 32.7-50.9 m/s
• Severe typhoon: Wind speed 51.0 m/s and above

Dual Impacts of Typhoons

Positive Effects:

• Water resource replenishment: Typhoon rainfall accounts for about 30-40% of Taiwan's annual precipitation
• Atmospheric cleaning: Strong winds help disperse air pollutants
• Ecological balance: Some plants depend on typhoons for seed dispersal

Negative Disasters:

• Wind damage: Strong winds cause building damage and power outages
• Flooding: Heavy rain triggers floods and landslides
• Agricultural losses: Crop lodging and fish farm damage

Notable Typhoon Cases

Typhoon Herb (1996):

• Caused 51 deaths, economic losses of about NT$20 billion
• Triggered severe landslides on Alishan Highway

Typhoon Morakot (2009):

• August 8th flood, caused 677 deaths and disappearances
• 24-hour rainfall reached 1,403mm (Alishan weather station)

Typhoon Soudelor (2015):

• Over 4 million households lost power across Taiwan
• Demonstrated modern society's emphasis on typhoon disaster prevention

Extreme Weather and Climate Change

Significant Climate Change Impacts

Taiwan's recent climate observations show clear change trends:

Temperature Changes:

• Warming trend: Average temperature has risen about 1.6°C over the past 100 years
• Increased heat waves: Days exceeding 38°C have significantly increased
• Warm winter phenomenon: Fewer cold days in winter

Changed Rainfall Patterns:

• Increased extreme rainfall: Events with 24-hour rainfall exceeding 500mm have increased
• Higher drought risk: Consecutive rainless days have lengthened
• Rainfall concentration: Rainy seasons wetter, dry seasons drier

Extreme Weather Events

Record-breaking High Temperatures:

• July 2020, Taipei station reached 39.7°C, a historical record
• Urban heat island effect intensifies, nighttime temperature drop decreases

Extreme Rainfall:

• August 2018 southern Taiwan heavy rain, 24-hour rainfall exceeded 800mm
• Short-duration intense rainfall patterns increase, raising disaster prevention pressure

Drought Events:

• 2021 century drought, reservoir levels reached new lows
• Reduced spring rain, plum rain season delayed or absent

Future Climate Projections

Based on IPCC climate model projections, Taiwan's future climate will show:

Temperature Changes (by 2050):

• Average temperature will rise another 1.5-2.5°C
• Summer high-temperature days will increase dramatically
• Winter temperatures will rise, frost days will decrease

Rainfall Changes:

• Annual total rainfall may increase slightly
• Wet-dry season differences will become more pronounced
• Extreme rainfall events will increase in frequency

Typhoon Changes:

• Typhoon numbers may decrease
• But intensity may strengthen
• Extreme rainfall typhoon events will increase

Topographic Influences on Climate

Vertical Climate Zones

Taiwan's abundant high mountains create distinct vertical climate zones:

Sea Level to 1,000m (Plains Climate):

• Annual average temperature 22-25°C
• Subtropical or tropical characteristics

1,000-2,000m (Mountain Climate):

• Annual average temperature 15-20°C
• Temperate characteristics, four distinct seasons

2,000-3,000m (High Mountain Climate):

• Annual average temperature 8-15°C
• Cold characteristics, possible winter snowfall

Above 3,000m (Alpine Climate):

• Annual average temperature below 8°C
• Polar characteristics, sparse vegetation

Local Climate Phenomena

Valley and Mountain Winds:

• Daytime valley winds: Air flows from plains to mountains
• Nighttime mountain winds: Cold air flows from mountains to plains

Foehn Effect:

• Occurrence locations: Taitung, Hengchun, Taichung
• Characteristics: Temperature rises, humidity drops, wind speed increases

Leeward Dryness:

• During northeast monsoon: Taichung, Changhua, Yunlin are drier
• During southwest monsoon: Eastern Taiwan is relatively dry

Climate and Life

Agricultural Adaptation

Taiwan's agriculture fully adapts to climate characteristics:

• Rice cultivation: Coordinated with plum rain and typhoon seasons for double cropping
• Tropical fruits: Southern development of mangoes, lychees, longans
• Temperate vegetables: High mountain cultivation of cabbage and lettuce

Urban Planning

Climate considerations influence urban development:

• Building design: Considering ventilation, shading, typhoon resistance
• Drainage systems: Designed for extreme rainfall
• Green space planning: Mitigating urban heat island effects

Living Culture

Climate shapes Taiwan's unique lifestyle:

• Dietary habits: Cool foods in summer, hot foods in winter
• Clothing culture: Light clothing adapted to subtropical climate
• Festival activities: Traditional festivals coordinated with seasonal changes

Disaster Prevention and Adaptation

Weather Forecasting System

Taiwan has established a comprehensive meteorological monitoring network:

• Surface stations: Over 400 automatic weather stations
• Upper-air observations: Radiosondes, weather radars
• Ocean buoys: Monitoring sea temperature and waves
• Satellite data: Cloud imagery, temperature, humidity

Disaster Warning Mechanisms

Typhoon Warnings:

• Sea typhoon warning: When typhoon center is within 800km of Taiwan
• Land typhoon warning: When estimated to affect land within 18 hours

Heavy Rain Advisories:

• Heavy rain advisory: 24-hour accumulated rainfall above 80mm
• Torrential rain advisory: 24-hour accumulated rainfall above 200mm
• Extremely torrential rain advisory: 24-hour accumulated rainfall above 350mm

Climate Adaptation Strategies

Water Resource Management:

• Enhancing reservoir storage capacity
• Developing recycled water and desalination
• Promoting rainwater harvesting

Disaster Prevention Infrastructure:

• Strengthening drainage and sewer systems
• Building retention ponds and resilient communities
• Improving building wind and water resistance

Ecological Adaptation:

• Protecting forests for water conservation
• Establishing ecological corridors
• Promoting eco-friendly agriculture

Taiwan's climate is one of this island's most precious natural assets. From mild springs to scorching summers, from the rainy plum rain season to the powerful typhoon season, each season has its unique beauty and challenges. Facing the impacts of climate change, Taiwan is actively developing adaptation strategies, hoping to protect the environment while preserving a livable homeland for future generations.

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References:

• Central Weather Administration 中央氣象署
• National Science and Technology Center for Disaster Reduction 國家災害防救科技中心
• Taiwan Climate Change Projection Information and Adaptation Knowledge Platform 台灣氣候變遷推估資訊與調適知識平台
• Council of Agriculture, Executive Yuan 行政院農業委員會