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DPRK Climate

Extremely cold outbreaks during winter could have a serious impact on ground and air operations. During colder temperatures, hypothermia, frostbite, and cold related injuries will slow the tempo of ground operations. Cold weather also impacts the turnaround time of aircraft as maintenance, refueling, and ammunition loading are affected. Trafficability is favorably impacted by the state of the ground. The ground freezes around 10 November in the extreme north, around 20 December along the DMZ, and not until 30 January in the extreme south. Thawing begins around 30 January in Pusan, mid-February along the DMZ, and not until 20 March in the far north. Ice also impacts naval operations from December until March.

Rain is the biggest problem for military operations in Korea. Heavy rains during the Southwest Monsoon saturate the ground and make conditions ideal for flash flooding. Trafficability is impaired by the wet ground and the effects of suddenly changing shallow, slow moving streams into rapid, deep rivers. In addition, mountain passes and rough mountain terrain become even more difficult to traverse due to the rains. Winter snows have an impact on aircraft takeoff/recovery at coastal bases and in mountainous terrain where snows are normally more significant. With limited highway LOCs available, heavier snowfalls can cause a significant impact on supply/resupply operations. The worst flying weather of the year occurs during the summer rainy season. About half the season, ceilings and visibilities are less than 3,000 ft and 3 mi, respectively.

In determining the effect of surface winds, direction is the most significant criteria. During the Northwest Monsoon (November-March), the effects of nuclear, biological, and chemical (NBC) warfare to the south are heightened. Although temperatures modify the effect of NBC agents at this time, dispersion patterns would be favorable for North Korean use. The Southwest Monsoon (June-September) has temperatures and humidity favorable to North Korean NBC use, but dispersion patterns are less favorable. The Southwest Monsoon pattern also has periods of strong wind speeds which may adversely affect air operations, air defense, and communications which are antenna-dependent.

The best period for air and ground observation is the generally clear winter period, December through March. Flying weather in the winter is the best of any time of the year, although pilots must take note of frequent severe turbulence and icing. Both hazards can be associated with the passage of a trough. The fall period, October through November, permits good air and ground observation; however, air operations are frequently marginal during morning hours due to periods of ground fog in river valleys and low-lying areas. During the spring, April through June, air and ground observation are often limited as a result of increasing cloud cover and precipitation. Additionally, the spring period brings with it an increase in early morning fog that burns off by late morning. Also during the spring, dust resulting from Yellow Wind can reduce visibility at times to less than 1 mile, affecting both ground and air observation. Periods of rain during the summer, when the peninsula receives the majority of its annual precipitation in the form of monsoons, greatly reduce air and ground observation capability.

Korea's climate is defined by its latitude, peninsular shape, terrain, currents and close proximity to the Asian continent. It is characterized by continental winters and monsoonal summers. Though Korea juts far out into the sea, the west coast climate is less maritime due to the shallowness of the Yellow Sea; its shallow (depths average 45 m/150 ft) water basin heats and cools rapidly, contributing little to moderating the climate, where as the East Sea (Sea of Japan) moderates the east coast's climate due to its deeper waters (1,500 m/ 5,000 ft).

The southern climate is less continental and more subtropical with a significant warm period lasting approximately 6 to 7 months. In the north, winter conditions may last for 6 months, while in the south it may only last for 3 months. However, 3 successive cold days are typically followed by 4 successive days of warm weather. The peninsula's west coast is generally open to the influence of the cool air masses that roar out of the Asian mainland, while the east coast is protected by the chain of mountains that parallel the coast (Chungnyong Mountains) and is warmed by the East Sea (Sea of Japan).

In the northernmost regions, the winter lasts a full 6 months and in January the average temperatures may fall below -18 C (0 F). The hottest time of the year is the summer, with average temperature ranges between 25 -27 C (77 -80 F) in most of the southern regions and milder temperatures of 22 C (72 F) along the northeast coast. The range of temperatures is much greater in the north and in the interior than along the coasts. The annual average difference in temperature between the coldest and hottest months for Seoul is approximately 28.3 C (83 F).

Korea is located in the East Asian Monsoon belt. Seasonal monsoon winds affect Korea's weather throughout the year. The Southwest Monsoon blows in from the south and southeast during the summer, bringing hot, humid weather. The cold, dry, Northwest Monsoon blows in from the north and northwest during the winter, bringing cold weather. Korea's massive mountains protect the peninsula's east coast from the winter monsoon, though occasional heavy snows can fall along the eastern mountain ranges. As a result, the east coast generally has warmer winters than the rest of Korea.

Heavy rainfall from June through September accounts for about 70 percent of Korea's yearly precipitation, with annual precipitation averages between less than 500 mm (20 in) in the northeastern inland areas and 1,500 mm (59 in) along the southern coast. Mean precipitation decreases from south to north. Some regions will have particularly heavy rains due to orographic effects (air uplifted by mountains) and the convergence of moist air masses. In most years, one or two typhoons hit the peninsula during July and August.

Spring Pattern (April-May)

April marks the start of the transition from the cold, dry winter to the summer rainy season. This transition lasts nearly 2 months. Low pressure systems start forming near the Gulf of Bo Hai and the Shantung Peninsula. These lows significantly erode the dominance of the Siberian High ("Asiatic High") pressure system. As a result, cloudiness and precipitation increase during the spring months. Korea is occasionally influenced by the "Yellow Wind" during the spring months. The Yellow Wind occurs when storm winds behind a trough cause dust from the Gobi Desert to become suspended in the air. The dust laden air is subsequently transported over Korea. During a strong yellow wind, visibility can be reduced to less than 1 mile. Spring is also the time for heavy sea fog to form over the coastal areas. The fog forms as the warmer air passes over the cooler Yellow Sea and the East Sea (Sea of Japan). Wind gusts of up to 59 kts have been recorded as well as tornados. The average April temperature in the north is approximately 10 C (50 F) and in the south 12 C (54 F); spring is generally cooler than fall.

Summer Pattern (June-September)

Summer is the rainy season in Korea. During the summer, southern monsoon winds engulf the country, the winds shift to the southwest, and the warm, moisture laden air moving off the oceans clashes with the drier air to the north. These fronts oscillate back and forth across Korea during the summer months. The interior highlands disturb the winds, forcing them into a westerly/southwesterly direction. The majority of the annual precipitation falls between late June and the middle of September, with rains fully developing along the entire peninsula by mid-June. Seoul receives approximately 126 mm (5 in) of precipitation dur-ing the winter (December-March), but in July alone receives approximately 383 mm (14.3 in).

Thunderstorms usually occur about 2 to 5 days per month during this period. Summer precipitation in Korea is as likely to occur at 0200 as at 1400. Humidity is very high and fog will develop whenever a cold air mass confronts this moisture laden air, often forming on cloudless days. The typhoon season occurs from July through September. About once each year, a typhoon will pass very close to or move over Korea, causing heavy showers. Strong winds are usually confined to islands and exposed coastal areas. Although winds might not pose a problem, the associated rainfall can cause significant flash flooding, a very real threat during the rainy season, especially in rough terrain. The mean temperature for Seoul in August is 25.3 C (78 C)

Fall Pattern (October-November)

October is the transition month between the summer rainy season and the cold, dry winter. The predominantly tropical cloudy weather of the summer is replaced by cooler, drier, and less cloudy conditions. The primary weather producers during October are cold frontal systems from the Asian mainland. On the average, one frontal passage per week can be expected during the month. A typical frontal passage is preceded by increasing middle and high cloudiness with light rain. Following the frontal passage, mostly clear skies can be expected for 3 or 4 days. During this clear period it is very likely for fog to form. Fog is especially prevalent in river valleys and in low lying areas.

Winter Pattern (December-March)

The winter in Korea is controlled by the large Siberian High (Asiatic High) pressure system which results in predominantly cold, dry north-westerly winds. About every 4 to 5 days a low-pressure trough will move through Korea, bringing with it cloudiness and light precipitation. The amount of precipitation locally depends mostly on the elevation of the station and the length of time that the air has been over the Yellow Sea. Maximum snowfall occurs over the northwest coast, which is the most exposed to the northwesterly flow, and in the mountain areas. Normally less than 10 percent of the annual precipitation falls during the winter. Frequently the weather is cloudless, clear, and dry, except for the southwestern region of the peninsula. The mean January temperature in Seoul is -4.4 C (24 F)

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Pusan, ROK

Seoul, ROK

Taejon, ROK

Pyongyang, DPRK

Wonsan, DPRK

Yangdok, DPRK

Hyesan, DPRK




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