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CLIMATOLOGY OF CHINA. CLIMATOLOGY OF CHINA. INTRODUCTION GEOGRAPHICAL LOCATION TOPOGRAPHICAL FEATURES AIR MASSES SEASONS OF CHINA PRECIPITATION TEMPERATURE AVIATION WEATHER HAZARDS AIRFIELDS AND ASSOCIATED WEATHER HAZARDS. INTRODUCTION.
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CLIMATOLOGY OF CHINA
CLIMATOLOGY OF CHINA • INTRODUCTION • GEOGRAPHICAL LOCATION • TOPOGRAPHICAL FEATURES • AIR MASSES • SEASONS OF CHINA • PRECIPITATION • TEMPERATURE • AVIATION WEATHER HAZARDS • AIRFIELDS AND ASSOCIATED WEATHER HAZARDS
INTRODUCTION • Height, location and angle of mountains range effectively control the flow of air mass. • The orography and topographical features influences the temperature and precipitation and thus have an impact on climate of china. • The role of mountain ranges as a climate division has to be extended to other elements, especially wind, where they produce local wind circulations systems
GEOGRAPHICAL LOCATION RUSSIA KAZAKSTAN MONGOLIA KYRGYZTAN TAJIKISTAN 96 LAKH SQ KM Qtr of Asia,whole of Europe KOREA YELLOW SEA CHINA NEPAL BHUTAN EAST CHINA SEA TAIWAN BURMA VIETNAM LAOS SOUTH CHINA SEA PHILLIPINES
GEOGRAPHICAL DIVISIONS OF CHINA The Northwest. This region consists of two basins—the Junggar Pendi in the north and the Tarim Basin in the south. The Mongolian Borderlands. Located in north central China, this is a plateau region of mainly sandy, stony, or gravel deserts that grade eastwards into steppe lands with fertile soils.
GEOGRAPHICAL DIVISIONS OF CHINA North West China and Mongolian Borderlands
GEOGRAPHICAL DIVISIONS OF CHINA The Northeast. Comprising all of DongbeiPingyuan east of the Da Hingganing, it incorporates the Manchurian Plains and its bordering uplands. Northeast China
GEOGRAPHICAL DIVISIONS OF CHINA • South China. • This region embraces the Yangzi Gorges and the topographically diverse regions to the south. • The Yangzi Gorges consist of a series • of basins with fertile alluvial soils. • It constitutes a relatively isolated area of hilly terrain.
GEOGRAPHICAL DIVISIONS OF CHINA Northeast China
SEASONS OF CHINA WINTER - DEC - FEB SPRING - MAR – MAY "CRACHIN" - FEB - APR
SEASONS OF CHINA CRACHIN SEASON • Falls in late february, march and early april. • Small anticyclones which sometimes move from the asian continent to the china sea. Here, water temperatures are fairly high and thus the air is warm and moist, unlike the cold and dry continental air. • The collision of maritime and continental air masses leads to the typical "crachin" formation of fog or low Stratus along the coast of the china sea.
WINTER PRESSURE PATTERN 1020 H 1040 1035 1030 1026 1020 1026 1024 1022 1024 1022
PRESSURE PATTERN • In January the asia-pacific region is marked by a well marked high pressure region over Mid-Siberia & Mongolia • A well established low pressure area over the NW pacific ocean. • The continental High is centered around the Baikal Sea and Mongolia, while the centre of the NW-Pacific low lies over the Bering Sea and the Aleutian Islands.
WINTERS : PRESSURE • Since both pressure systems practically lie in the same latitude, a steep pressure gradient occurs which produces strong and persistentNE’ly. They carry dry continental and cold polar air masses over the entire east asian region. • The mean values of sea level pressure in January reach a maximum of 1040 hPa in the centre of the anticyclone and decrease to 1020 hPa only over southern china.
PRESSURE PATTERN • Air masses which mostly affect China during winter are dry and cold and are of polar origin, although they may be warmed and also partly moistened when they move southward. • Cold waves frequently travel from Xinjiang and Mongolia, well up to the southernmost parts of China. • Prevailing winds over most parts of China are from N, NW and NE which results from the well marked anticyclone belt over the region .
UPPER AIR PATTERN The sub-tropical high pressure belt is roughly along 15ºN at 3 km and along 10ºN at 9 km and aloft. As a consequence of the pole ward decrease of temperature, the westerly winds steadily increase in strength up to about 12 km thereafter the speeds decrease slightly At 12 km level, the strongest winds occur in a meandering belt between latitude 25ºN and 35ºN. This core of strongest winds is called the ‘subtropical jet stream’.
UPPER AIR PATTERN Over northern India, it is located between 25ºN & 30ºN whereas over the eastern parts of China, it is between 30ºN and 35ºN. The average wind speed in the jet stream is about 80 knots over North India and 90 knots over eastern parts of China. On individual occasions the maximum wind speed may reach 150-200 Knots over Eastern China. The phenomenon of ‘Clear Air Turbulence’ is often noticed in the vicinity of jet streams.
POLAR SIBERIAN POLARPACIFIC WINTER AIR MASSES
ONSET OF WINTER MONSOON 30 AUG 10 SEP 20 SEP 30 SEP 10 OCT
WINTER SEASON • The cold is very severe between December and February. • The WDs affect the weather over this area during the season and the effect gradually decreases from North to South, unless the disturbance is very active and affects the southern region. • The number of cloudy days increase from clear skies in the month of Nov to 10-15 days as the season advances.
WINTER SEASON Convective clouds (Sc, Cu & Cb) appear in association with active WDs and the activity is considerably lesser towards the South. Precipitation occurs in the form of snowfall and Blizzard and is limited to the hills facing West over Central Tibet. The normal amount of snowfall in the valleys is less than 10 mm/month. The thunderstorm frequency is about 5 per month. Visibility is generally good though fog occurs on 3-5 days in a month.
TEMPERATURE PATTERN January shows an extremely complex and extraordinarily variable pattern of temperature. Temperature rapidly decreases with increasing latitude, i.e. From South to North China. For the same latitude, temperature also decreases with increasing altitude above sea level, i.e. from the eastern lowlands to the western highlands, intra montane basins and mountain ranges.
TEMPERATURE PATTERN • From a global comparison of temperature distribution in January, it is worth noting that in China, the 0° C isotherm is shifted further South • and thus nearer to the equator than elsewhere in the northern hemisphere. • The major part of China experiences a mean temperature below zero in January, while the comparably smaller southern and south eastern sector records positive temperatures. • From a global comparison, China experiences unusually lower winter temperatures
SOUTH - NORTH VARIATION OF TEMPERATURE 40 30 20 JAN 10 JULY YEAR 0 -10 -20 -30 210 203 177 162 126 90 79 61 46 7 1 STATIONS SOUTH - NORTH
SPRING SEASON • Main characteristics of spring weather are: • Rainfall gradually increases. • Weather is variable and most weather systems are migratory. • Frequent extra tropical cyclones occur over NE China.
SPRING SEASON During spring season, the mean pressure at sea level varies from 1007.5 to 1012.5 hPa, without a significant regional variation. The influence of continental high finally disappears by end of May, indicating the end of intrusion of continental air mass over China. The Aleutian low pressure though continues to persist in March, but is seen as a weak system in April and May.
UPPER AIR PATTERN • The main features of the upper winds during this season are generally the same as those during December-January-February except that the wind speeds are lesser. • The mean jet stream which lies between latitudes 30º and 35ºN, has a speed of about 60 knots over the central parts of Asia and 70 knots over east China. • As this season constitutes the transition between Winter and Summer conditions, there is a progressive decrease of the speed of the westerlies from March to May.
DUSTSTORMS • Most favourable areas plains of North China and South Manchuria. • The main season of occurrence is from march to may and July to September. • Most favourable situation is passage of the fronts. • The most likely time of occurrence is noon to evening.
FOG • Advection fog is common in summers, radiation type in winters. • Maximum at night, stays till around 0700 h in the morning. In jan, persists till noon over land areas. • The favourable areas : south china hills and sichuan basin. (186 days per year) • Frequency of <5 days over qinghai-xizang and xinjiang. • Frequency of 5- 25 days per year over coastal regions .
THUNDERSTORMS • Most favorite regions are hainan and luichow peninsula with frequency 90-100 per year during mar-sep. • Frequency 30 Days Over Southern Provinces • Frequency about 5 in the deserts and 20 in the hills.
MEAN HOURLY FREQUENCY OF MIST OVER CHENGDU
AVIATION WEATHER HAZARDS: CHENGDU • Fog, Mist, Haze, Smoke Haze, Rainfall and Thunderstorm. • Fog occurs mainly in the winter season from NOV-JAN. • Mist occurs throughout the year over the airfield on an average of 20 days or more. • Rainfall occurs throughout the year on an average of 10 days or more. • Thunderstorm occurrence is primarily confined to the months from July to September. • This analysis does not bring out any clear weather window, however in summers, afternoons are relatively better.
AVIATION WEATHER HAZARDS: DALI • December, January and February months are generally good weather months in Dali. • Mainly in summer season, the airfield is affected by rain and thunder storm activity. • However, even in summer season early nights and mid nights are generally free from weather hazards.
