CLIMATOLOGY OF CHINA

“ THE GLOBAL VARIATION OF CLIMATE MEETS THE CLIMATE VARIATION IN CHINA ALONE ” KOPPEN (1884)

GEOGRAPHICAL LOCATION CHINA BHUTAN 96 LAKH SQ KM Qtr of Asia,whole of Europe

AIR MASSES OVER CHINA Dry and cold polar air mass by origin Warm and moisture laden by origin TROPICAL PACIFIC EQUATORIAL POLAR PACIFIC POLAR SIBERIAN Warm and moisture laden by origin

SEASONS OF CHINA WINTER - DEC - FEB SPRING - MAR - MAY SUMMER - JUN - AUG AUTUMN - SEP – NOV "MAI-YU" - APR - JUNE "CRACHIN" - FEB - APR

DURATION OF THE SEASONS (MONTHS) REGION / SEASON SPRING SUMMER AUTUMN WINTER NORTHEAST CHINA 2-3 2 5-6 NORTH CHINA 1.5-3 2-4.5 1.5-2 4.5-6 CENTRAL CHINA 3-5 2.5-4.5 SOUTH CHINA 4-6 6-8 -

MONSOONS OVER CHINA According to Chinese meteorologists, the monsoon was defined as an alternation of two kinds of airflows with different properties. Firstly, there are prevailing winds that differ largely in winter and summer. Secondly, since winter and summer monsoons originate in different regions, there are substantial differences in their air-mass properties. Lastly, they are accompanied by various weather phenomena, thus bringing diversity of seasons, such as Rainy, Dry Summer and winter seasons (Zhang Jiacheng 1983)

SUMMER MONSOON ONSET OF SUMMER MONSOON 30 JULY 20 JULY 10 JULY 30 JUNE THE NORTHWARD ADVANCE OF SUMMER MONSOON TAKES PLACE IN ALTERNATING PHASES OF QUICK AND SLOW DEVELOPMENT. 30 JULY THE RETREAT OF MONSOON IN CHINA IS A STRAIGHT FORWARD, RATHER QUICK PROCESS WHICH ONLY LASTS AROUND ONE MONTH (BY LATE OCT). 20 JULY 10 JULY 30 JUNE 20 JUNE 10 JUNE DURING THE LAST 10 DAYS OF MAY, THE MONSOON FRONT STAGNATES IN SOUTHERN CHINA. 01 JUNE 10 MAY 20 MAY

ADVANCE OF MONSOON CURRENT The regions initially influenced by the Summer Monsoon in the beginning of May, are Hainan Island and the southern part of Taiwan Island. It advances to the coast of southern China on May 10, then advances slowly northward. During the last 10 days of May, the Monsoon Front stagnates in southern China, then moves northward rapidly in early June. Arrives in the middle and low reaches of Yangtze in mid-June when the Mei-Yu rains begin. After a stagnation until the first 10-day period in July, advances quickly arriving in northern and north eastern China in late July.

MONSOONS OVER CHINA The Summer Monsoon over China starts half a month earlier and terminates about half a month later so that the total duration of the Summer Monsoon over China is about 1 month longer. In-depth scientific studies (TaoShiyan 1984) have clearly shown that major components for the monsoon in East Asia significantly differ from the monsoon in India.

COMPONENTS OF SUMMER MONSOON CROSS-EQUATORIAL FLOW. ANTI-CYCLONE OVER AUSTRALIA. ITCZ TROPICAL EASTERLY JET SUB-TROPICAL ANTICYCLONE OVER WEST PACIFIC. MAI-YU FRONTAL ZONES. MID-LATITUDE DISTURBANCES.

CHARACTERISTICS OF SUMMER MONSOON IN CASE OF A STRONG SUMMER MONSOON, ABOVE NORMAL RAINFALL IN NORTH & SOUTH CHINA. ONSET AND ADVANCE OF SUMMER MONSOON HAS BEEN FOUND AS EVENTS OF A REMARKABLY GREAT VARIATION OVER TIME. A LARGE INTRA MONSOONAL VARIATION OF RAINFALL ALSO REPRESENTS A CHARACTERISTIC FEATURE OF SUMMER MONSOON IN CHINA. DURATION VARIES FROM FIVE MONTHS IN SOUTH CHINA TO ONE MONTH IN NW CHINA

SEASONAL PRESSURE DISTRIBUTION AT SEA LEVEL SUMMER SEASON

MEAN SEA LEVEL PRESSURE: JULY Weak pressure gradient L

SUMMERS SEASON PRESSURE PATTERN THE PRESSURE FIELD SHOWS A RELATIVELY WEEK PRESSURE GRADIENT. THE MEAN PRESSURE AT SEA LEVEL, OVER THE CONTINENT, DROPS TO 1002 hPa IN THE CENTER OF THE LOW, WHILE IT RISES TO A MAXIMUM OF 1012 HPA OVER N-PACIFIC OCEAN.

SUMMERS SEASON PRESSURE PATTERN OVER MOST PARTS OF CHINA, PRESSURE AT SEA LEVEL, MOSTLY OCCURS AT AN INTERMEDIATE LEVEL BETWEEN 1000 AND 1005 hPa.

UPPER WIND PATTERN SUMMER SEASON

SEASONAL WINDS Prevailing winds reverse their direction from winter to summer. In summer : surface winds mainly from south. The air masses invading china in summer are moist, warm and unstable in nature, the climate effectiveness reduces with increasing distance from coasts/low lands of China sea. Tropical pacific and equatorial air masses.

JULY UPPER WINDS 850 hPa A C C C

SUMMERS : WINDS AT LOWER LEVELS, INDIAN MONSOON TROUGH REPLACES THE WINTERTIME MONGOLIAN COLD HIGH. IN THE MIDDLE TROPOSPHERE SPLITTING OF THE WESTERLIES BY THE TIBETAN PLATEAU AND THE SOUTHERN BRANCH OF WESTERLIES VANISH, WHILE THE SUBTROPICAL HIGH MOVES NORTHWARD AND STRENGTHENS CONSIDERABLE.

JULY UPPER WINDS 500 hPa A A

IN THE UPPER TROPOSPHERE, THE TIBETAN ANTICYCLONE AND UPPER LEVEL EASTERLY JET STREAM PREVAIL AND WESTERLY JET STREAM GREATLY DECREASES.

JULY UPPER WINDS 200 hPa A A

DISTRIBUTION OF MAXIMUM TEMPERATURES 50 40 MONGOLIA 30 20 TAIWAN INDIA HAINAN 100 110 120

MEAN ANNUAL AIR TEMPERATURE DISTRIBUTION K China ca be divided into two parts west and east W K 06 APKC/Class Review Climatology of China

MEAN TEMPERATURES: JULY W W K 06 APKC/Class Review Climatology of China

THE EXTREMES OF TEMPERATURE AREAS REGISTERING MAXIMUM TEMPERATURES MORE THAN 400C : HAINAN PROVINCE NORTH CHINA PLAINS TARIM BASIN HIGHEST RECORDED : 49.60C 13 JULY 75 AT TURPAN. Areas registering max temp > 400C : Highest recorded: 49.60C 13 JULY 75 AT TURPAN. 06 APKC/Class Review Climatology of China

MEAN PRECIPITATION : ANNUAL 50 40 MONGOLIA Two types one due to reversal of airmasses And other due to terrain 30 20 TAIWAN INDIA HAINAN 06 APKC/Class Review Climatology of China 100 110 120

MEAN ANNUAL PRECIPITATION DISTRIBUTION 06 APKC/Class Review Climatology of China

DISTRIBUTION OF MEAN PRECIPITATION IN JULY 06 APKC/Class Review Climatology of China

TRANSIENT DISTURBANCES

TRANSIENT DISTURBANCES Upper tropospheric troughs in westerlies Extra tropical cyclones and anticyclones Typhoons

TROUGHS IN THE WESTERLIES Most of the area stays under westerly regime for majority of time. Troughs and ridges with varying amplitude move across china. Average speed of propagation 10-15o longitude per day. Enhance rainfall in the north and at times to the central parts of china.

TROUGHS IN THE WESTERLIES In summer area north of 40N is located in W’ly regime Influence of Tibetan Plateau, westerlies divided into two stream Northern westerlies and southern westerlies.

MEAN FREQUENCY OF UPPER WESTERLY TROUGHS FOR SELECTED MONTHS (1968-1972) From West From Northwest From Southwest January April July October 12(10-17) 14(11-17) 13 ( 7-16) 15 (11-19) 5 (0-8) 3(1-8) 5 (2-7) 2(1-4) 8 (5-11) 10(6-14) 2 (0- 5)

TYPHOONS

TYPHOONS A tropical cyclone with a wind speed between 17.2 and 32.6 mps in its centre is defined as a typhoon. China’s typhoons account for 36% of all tropical cyclones in the world. Typhoon season is from June – November. Max freq July – October ( monthly frequency 3-5). Associated with strong winds and heavy rainfall in south, east and north china. Accounts for > 50% of annual rainfall in the coastal regions. Do not persist for more than 500 km inland from the coast.

TYPHOON STATISTICS AUG 2.3 6.1 8.4 MONTH DEPRESSION TYPHOON D + TY JUN JAN 0.2 0.5 0.7 FEB 0.4 0.6 MAR 0.1 APR 0.8 MAY 1.1 1.2 JUN 2.0 2.7 JUL 1.4 4.4 5.8 AUG 2.3 6.1 8.4 SEP 1.8 5.3 7.1 OCT 3.8 4.6 NOV 3.1 DEC 1.3 1.7 Total (Year) 8.5 28.8 37.3

PATHS OF TYPHOONS: MAY TO SEPTEMBER

AVIATION WEATHER HAZARDS

THUNDERSTORMS Most favourable regions are Hainan and Luichow peninsula with frequency 90-100 per year during Mar-Sep. Frequency decreases to about 10 northeastwards to Heilungkiang. Frequency 30 days over southern provinces. Frequency about 5 in the deserts and 20 in the hills.

CONCLUSION Although the climate of China is commonly described as a monsoon climate, it is nevertheless often a matter of controversy whether or not China as a whole experiences a monsoon climate, if the term "monsoon" is strictly applied to refer only to a seasonally alternating system of winds associated with a distinct wet and dry season. Non-monsoonal conditions occur in various parts of China such as Xinjiang, central and western part of North Qaidam Basin, western part of North Qinghai-Xizang (Tibetan) Plateau, north part of Inner Mongolia (Helanshan and Yinshan Mountains).

? 06 APKC/Class Review Climatology of China