Editing Geography of Vietnam (section)

==Climate==
{{main|Climate of Vietnam}}
[[File:Koppen-Geiger Map v2 VNM 1991–2020.svg|thumb|300x300px|Vietnam map of Köppen climate classification]]
[[Image:Fires in Burma, Thailand, Laos, and Vietnam.jpg|thumb|Hundreds of active fires burning across the hills and valleys of [[Myanmar]], [[Thailand]], [[Laos]], and Vietnam (labelled with red dots).]]

Vietnam's climate, being located in the tropics and strongly influenced by the [[South China Sea]] has a monsoon-influenced climate typical of that of [[mainland Southeast Asia]].<ref name=vietnamUNEP>{{cite web |url=http://www.unep.org/pdf/dtie/VTN_ASS_REP_CC.pdf |archive-url=https://web.archive.org/web/20110113054646/http://www.roap.unep.org/pub/VTN_ASS_REP_CC.pdf |archive-date=13 January 2011 |title=Viet Nam Assessment Report on Climate Change (VARCC) |publisher=Institute of Strategy and Policy on Natural Resources and Environment |page=31 |access-date=9 November 2018}}</ref>{{rp|25}} In the north, the climate is [[humid subtropical]] and monsoonal and with four distinct seasons (Spring, Summer, Autumn, and Winter) while in the central and south, the climate is [[Tropical monsoon climate|tropical monsoon]] with two seasons (rainy and dry).<ref name=vietnamkhihau>{{cite web |url=http://www.chinhphu.vn/portal/page/portal/chinhphu/NuocCHXHCNVietNam/ThongTinTongHop/dialy |title=MỘT SỐ THÔNG TIN VỀ ĐỊA LÝ VIỆT NAM |publisher=Viet Nam Government Portal |language=vi |access-date=9 November 2018}}</ref><ref name=vietnamiaea2012>{{cite web |archive-url=https://web.archive.org/web/20181109190416/https://www-pub.iaea.org/MTCD/Publications/PDF/CNPP2012_CD/countryprofiles/Vietnam/Vietnam.htm |archive-date=9 November 2018 |url=https://www-pub.iaea.org/MTCD/Publications/PDF/CNPP2012_CD/countryprofiles/Vietnam/Vietnam.htm |title=Vietnam |work=Country Nuclear Power Profiles: 2012 Edition |publisher=International Atomic Energy Agency |access-date=9 November 2018}}</ref><ref name=VNATclimate>{{cite web |archive-url=https://web.archive.org/web/20181109203934/http://www.vietnamtourism.com/en/index.php/about/items/1752 |archive-date=9 November 2018 |url=http://www.vietnamtourism.com/en/index.php/about/items/1752 |title=Climate |publisher=Vietnam National Administration of Tourism |access-date=9 November 2018}}</ref> In addition, [[temperate climate]] exists in mountainous areas, which are found in [[Sa Pa (town)|Sa Pa]] and [[Da Lat]], while a more [[continental climate]] exists in [[Lai Châu province]] and [[Sơn La province]].<ref name=vietnamkhihau/> The diverse topography, wide range of latitudes (Vietnam spans over 15° of latitude), and influences from the South China Sea lead to climatic conditions varying significantly between regions.<ref name=vietnamNC2>{{cite web |archive-url=https://web.archive.org/web/20181109185653/https://unfccc.int/resource/docs/natc/vnmnc02.pdf |archive-date=9 November 2018 |url=https://unfccc.int/resource/docs/natc/vnmnc02.pdf |title=Viet Nam's Second National Communication to the United Nations Framework Convention on Climate Change |publisher=Ministry of Natural Resources and Environment |access-date=9 November 2018}}</ref>{{rp|24}}

Based on geographic and climatic conditions, there are seven different climatic regions in Vietnam:<ref name=vietnamUNEP>{{cite web |url=http://www.unep.org/pdf/dtie/VTN_ASS_REP_CC.pdf |archive-url=https://web.archive.org/web/20110113054646/http://www.roap.unep.org/pub/VTN_ASS_REP_CC.pdf |archive-date=13 January 2011 |title=Viet Nam Assessment Report on Climate Change (VARCC) |publisher=Institute of Strategy and Policy on Natural Resources and Environment |page=31 |access-date=9 November 2018}}</ref>{{rp|26}}<ref name=vietnamFAO>{{cite web |last1=Nguyen |first1=Mui |archive-url=https://web.archive.org/web/20181109202700/https://ees.kuleuven.be/klimos/toolkit/documents/661_Vietnam.pdf |archive-date=9 November 2018 |url=https://ees.kuleuven.be/klimos/toolkit/documents/661_Vietnam.pdf |title=Viet Nam |work=Country Pasture/Forage Resource Profiles |publisher=Food and Agriculture Organization |year=2006 |pages=9–12 |access-date=9 November 2018}}</ref> Northwest, Northeast, North Delta (Red River Delta), North Central (North Central Coast), South Central (South Central Coast), Central Highlands, and the South.<ref name=vietnamUNEP/>{{rp|26}} The South is subdivided into the [[Southeast (Vietnam)|Southeast]] for the southeastern provinces and the [[Mekong Delta]] for the southwestern provinces.<ref name=vietnamFAO/> Generally, these seven different climatic regions are grouped into two main types: The North (includes Northwest, Northeast, North Delta (Red River Delta), North Central (North Central Coast)) which includes all areas north of the Hải Vân Pass and the South (South Central Coast, Central Highlands and the extreme south) which includes all areas south of the Hải Vân Pass.<ref name=vietnamkhihau/><ref name=vietnamiaea2012/><ref name=VNATclimate/><ref name=Ho2011>{{cite journal |author1=Thi-Minh-Ha Ho |author2=Van-Tan Phan |author3=Nhu-Quan Le |author4=Quang-Trung Nguyen |archive-url=https://web.archive.org/web/20181110181926/https://www.int-res.com/articles/cr2012/49/c049p087.pdf |archive-date=10 November 2018 |url=https://www.int-res.com/articles/cr2012/49/c049p087.pdf |title=Extreme climatic events over Vietnam from observational data and RegCM3 projections |journal=Climate Research |volume=49 |pages=87–100 |year=2011 |issue=2 |doi=10.3354/cr01021 |access-date=10 November 2018|doi-access=free }}</ref> These climatic regions are based on time of rainy season and other climatic elements such as insolation, sunshine, temperature, precipitation, and humidity.<ref name=vietnamUNEP/>{{rp|38–39}}

During winter, polar air originating from the Siberian High penetrate deeply into the low latitudes, facilitated by the eastern [[Tibetan Plateau]] that funnels the air southwards in a northeast direction (the cool air is a wind coming from the northeast).<ref name=vietnamUNEP/>{{rp|27}} Many cold fronts can penetrate into Vietnam during winter of which there are three to four occurrences every month in northern Vietnam.<ref name=vietnamUNEP/>{{rp|27}} This leads to cold temperatures where temperatures drop by {{convert|4|to|5|C-change|0}}.<ref name=vietnamUNEP/>{{rp|27}} Cold weather, occasionally extreme cold can persist for a long time, being characterized by a long stretch of cloudless or partly cloudy days in the first half of winter or a long stretch of cloudy and drizzly conditions in the latter half of winter.<ref name=vietnamUNEP/>{{rp|27}} Cold weather occurs more frequently in the north than in the south due to cold fronts penetrate the north more frequently.<ref name=vietnamUNEP/>{{rp|27}}

In summer, the general wind pattern are southwesterly winds in the southern parts of Vietnam and southeasterly winds in northern Vietnam.<ref name=vietnamUNEP/>{{rp|28}} The predominantly [[Block (meteorology)|air blocks]] in Vietnam are the equatorial and tropical blocks that originate from high pressure systems in the Southern Hemisphere, and a maritime tropical block originating from the subtropical high pressure system in the Pacific Ocean (Pacific subtropical high pressure).<ref name=vietnamUNEP/>{{rp|28}} In addition, during summer, Vietnam is influenced by tropical air from the [[Bay of Bengal]] which occurs when a continental low pressure originating from South Asia (South Asian continental low) moves eastwards towards Vietnam, covering almost all of Vietnam and southern China; this causes hot, dry weather in the North Central Coast as westerly winds descend and warm [[adiabatically]] on the eastern slopes of the [[Annamite Range]] (Truong Son Range).<ref name=vietnamUNEP/>{{rp|28}} On average, eleven storms and tropical low pressures develop in the South China sea during summer of which half are [[tropical cyclone]]s that originate from the western Pacific.<ref name=vietnamUNEP/>{{rp|28}} These storms and cyclones then move westwards towards Vietnam.<ref name=vietnamUNEP/>{{rp|28}} On average, Vietnam is affected by six to eight [[typhoons]] or tropical cyclones per year.<ref name=vietnamNC2/>{{rp|25}}

Spring and Fall are transitional seasons.<ref name=vietnamUNEP/>{{rp|27}} The atmospheric circulation in these seasons represent a transition between winter–summer and summer–winter respectively.<ref name=vietnamUNEP/>{{rp|28}}

Mean annual temperatures in the country, based on meteorological data from weather stations range from {{convert|12.8|to|27.7|C|F|0}} in [[Hoang Lien Son]].<ref name=vietnamUNEP/>{{rp|30}}<ref name=vietnamNC2/>{{rp|24}} At the highest altitudes in the Hoang Lien Son range, mean annual temperatures is only {{convert|8|C|F|0}}.<ref name=vietnamUNEP/>{{rp|30}} As temperatures vary by altitude, temperatures decrease by {{convert|0.5|C-change|0}} for every {{convert|100|m|ft|0}} increase in altitude.<ref name=vietnamUNEP/>{{rp|30}} The lowest mean annual temperatures are found in the mountainous areas where the altitude is higher and in northern areas due to their higher latitudes.<ref name=vietnamUNEP/>{{rp|30}} Many mountainous areas in the north have experienced subzero conditions.<ref name=vietnamUNEP/>{{rp|31}} In contrast, temperatures in the Spratly Islands never falls below {{convert|21|C|F|0}}.<ref name=vietnamUNEP/>{{rp|31}} Because Vietnam is strongly influenced by the monsoon, the mean temperatures in Vietnam are lower than other countries located at the same latitude in Asia.<ref name=vietnamkhihau/><ref name=VNATclimate/> The highest temperatures normally occurs in March–May in the south and May–July in the north.<ref name=vietnamUNEP/>{{rp|31}} Temperatures in summer are relatively equal among the northern and southern parts of the country with differences being mostly due to altitude (the decrease in temperature is predominantly due to altitude).<ref name=vietnamUNEP/>{{rp|30}}

Mean annual rainfall in the country ranges from {{convert|700|to|5,000|mm|in|abbr=on}} although most places in Vietnam receive between {{convert|1,400|to|2,400|mm|in|abbr=on}}.<ref name=vietnamUNEP/>{{rp|33}} The majority of rainfall occurs during the rainy season, which is responsible for 80%–90% of the annual precipitation.<ref name=vietnamNC2/>{{rp|24}} Generally, northern parts of the country receive more rainfall than southern parts of the country.<ref name=vietnamUNEP/>{{rp|33}} Drizzle is a weather phenomenon that is characteristic of the weather in winter in the north and north central coast.<ref name=vietnamUNEP/>{{rp|36}} Depending on the region, the onset of the rainy season (defined as when the monthly average precipitation exceeds {{convert|100|mm|in|abbr=on}}) differs.<ref name=vietnamUNEP/>{{rp|35}}