Editing Geography of Nepal (section)

==Climate==
[[File:Köppen climate types of Nepal.svg|thumb|300px|Nepal map of Köppen climate classification zones]]

===Altitudinal belts===
[[Image:Satellite image of Nepal in October 2002.jpg|thumb|right|350px|Satellite image of Nepal in October 2002]]
Nepal's latitude is about the same as that of the United States state of [[Florida]], however with elevations ranging from less than {{convert|100|m|ft|-2|sp=us}} to over {{convert|8000|m|ft|-3|sp=us}} and precipitation from {{convert|160|mm|in|0|sp=us}} to over {{convert|5000|mm|ft|0|sp=us}} the country has eight climate zones from tropical to perpetual snow.<ref>{{Citation
 | title = The Map of Potential Vegetation of Nepal - a forestry/agroecological/biodiversity classification system
 | series = Forest & Landscape Development and Environment Series 2-2005 and CFC-TIS Document Series No.110.
 | year = 2005
 | url = http://curis.ku.dk/ws/files/20497354/de2_001.pdf
 | isbn = 87-7903-210-9
 | access-date = Nov 22, 2013
 | archive-date = 3 December 2013
 | archive-url = https://web.archive.org/web/20131203032538/http://curis.ku.dk/ws/files/20497354/de2_001.pdf
 | url-status = dead
 }}</ref>

The '''[[tropical climate|tropical]] zone''' below {{convert|1000|m|ft|-2|sp=us}} experiences [[frost]] less than once per decade. It can be subdivided into lower tropical (below 300 meters or 1,000&nbsp;ft.) with 18% of the nation's land area) and upper (18% of land area) tropical zones. The best [[mango]]es and well as [[papaya]] and [[banana]] are largely confined to the lower zone. Other fruit such as [[litchee]], [[jackfruit]], [[citrus]] and mangoes of lower quality grow in the upper tropical zone as well. Winter crops include grains and vegetables typically grown in temperate climates. The Outer Terai is virtually all in the lower tropical zone. Inner Terai valleys span both tropical zones. The Sivalik Hills are mostly upper tropical. Tropical climate zones extend far upriver valleys across the Middle Hills and even into the Mountain regions.

The '''[[Subtropics|subtropical]] climate zone''' from {{convert|1000|to|2000|m|ft|-2|sp=us}} occupies 22% of Nepal's land area and is the most prevalent climate of the Middle Hills above river valleys. It experiences frost up to 53 days per year, however, this varies greatly with elevation, proximity to high mountains and terrain either draining or ponding cold air drainage. Crops include [[rice]], [[maize]], [[millet]], [[wheat]], [[potato]], [[Drupe|stone fruits]] and citrus.

The great majority of Nepal's population occupies the tropical and subtropical climate zones. In the Middle Hills, "upper-caste" Hindus are concentrated in tropical valleys which are well suited for rice cultivation while [[Adivasi|Janajati]] ethnic groups mostly live above in the subtropical zone and grow other grains more than rice.

The '''[[Temperate climate]] zone''' from {{convert|2000|to|3000|m|ft|-2|sp=us}} occupies 12% of Nepal's land area and has up to 153 annual days of frost. It is encountered in higher parts of the Middle Hills and throughout much of the Mountain region. Crops include cold-tolerant rice, maize, wheat, [[barley]], potato, [[apple]], [[walnut]], [[peach]], various cole, [[amaranth]]us and [[buckwheat]].

The '''[[Subalpine#Subalpine zone|Subalpine]] zone''' from {{convert|3000|to|4000|m|ft|-2|sp=us}} occupies 9% of Nepal's land area, mainly in the Mountain and Himalayan regions. It has permanent settlements in the Himalaya, but further south it is only seasonally occupied as pasture for sheep, goats, yak and hybrids in warmer months. There are up to 229 annual days of frost here. Crops include barley, potato, [[cabbage]], [[cauliflower]], amaranthus, buckwheat and apple. Medicinal plants are also gathered.

The '''[[Montane ecology#Alpine grasslands and tundra|Alpine]] zone''' from {{convert|4000|to|5000|m|ft|-2|sp=us}} occupies 8% of the country's land area. There are a few permanent settlements above 4,000 meters. There is virtually no plant cultivation although medicinal herbs are gathered. [[Sheep]], [[goat]]s, [[Domestic yak|yaks]] and hybrids are pastured in warmer months.

Above 5,000 meters the climate becomes '''[[Snow line|Nival]]''' and there is no human habitation or even seasonal use.

Arid and semi-arid land in the [[rainshadow]] of high ranges have a '''[[Cold desert#Cold desert climates|Transhimalayan climate]]'''. Population density is very low. Cultivation and husbandry conform to subalpine and alpine patterns but depend on snowmelt and streams for irrigation.

Precipitation generally decreases from east to west with increasing distance from the [[Bay of Bengal]], source of the summer monsoon. Eastern Nepal gets about {{convert|2500|mm|in|-1|abbr=on}} annually; the Kathmandu area about {{convert|1400|mm|in|0|abbr=on}} and western Nepal about {{convert|1000|mm|in|-1|abbr=on}}. This pattern is modified by adiabatic effects as rising air masses cool and drop their moisture content on windward slopes, then warm up as they descend so relative humidity drops. Annual precipitation reaches {{convert|5500|mm|ft|0|abbr=on}} on windward slopes in the [[Annapurna]] Himalaya beyond a relatively low stretch of the [[Lower Himalayan Range]]. In [[Rain shadow|rainshadows]] beyond the high mountains, annual precipitation drops as low as {{convert|160|mm|in|0|abbr=on}}.

===Seasons===
The year is divided into a wet season from June to September—as summer warmth over Inner Asia creates a low-pressure zone that draws in moist air from the Indian Ocean—and a dry season from October to June as cold temperatures in the vast interior create a high-pressure zone causing dry air to flow outward. April and May are months of intense water stress when cumulative effects of the long dry season are exacerbated by temperatures rising over {{convert|40|°C|°F}} in the tropical climate belt. Seasonal drought further intensifies in the [[Siwaliks]] hills consisting of poorly consolidated, coarse, permeable sediments that do not retain water, so hillsides are often covered with drought-tolerant scrub forest. In fact, much of Nepal's native vegetation adapted to withstand drought, but less so at higher elevations where cooler temperatures mean less water stress.

The summer [[Monsoon of South Asia|monsoon]] may be preceded by a buildup of thunderstorm activity that provides water for rice seedbeds. Sustained rain on average arrives in mid-June as rising temperatures over [[Inner Asia]] creates a low-pressure zone that draws in moist air from the Indian Ocean, but this can vary up to a month. Significant failure of monsoon rains historically meant drought and famine while above-normal rains still cause flooding and landslides with losses in human lives, farmland and buildings.

The monsoon also complicates transportation with roads and trails washing out while unpaved roads and airstrips may become unusable and cloud cover reduces safety margins for aviation. Rains diminish in September and generally end by mid-October, ushering in generally cool, clear, and dry weather, as well as the most relaxed and jovial period in Nepal. By this time, the harvest is completed and people are in a festive mood. The two largest and most important Hindu festivals—[[Dashain]] and [[Tihar (festival)|Tihar]] ([[Diwali|Dipawali]])—arrive during this period, about one month apart. The post-monsoon season lasts until about December.

After the post-monsoon comes the winter monsoon, a strong northeasterly flow marked by occasional, short rainfalls in the lowlands and plains and snowfalls in the high-altitude areas. In this season the Himalayas function as a barrier to cold air masses from Inner Asia, so southern Nepal and northern India have warmer winters than would otherwise be the case. April and May are dry and hot, especially below {{convert|1200|m|ft|-3|sp=us}} where afternoon temperatures may exceed {{convert|40|°C|°F}}.