Spatial and Temporal Pattern of Climate in Nepal

The climate of Nepal can't be assigned to any particular type because of variation in altitude, topography, orography ad resulting temperature and precipitation. Th altitudinal range of Nepal varies from 65m to 8848m with the distance of 200km from south to north. Much of the Nepal falls within monsoon region, with regional climate variation largely being a function of elevation. National mean temperature is about 15-degree centigrade and increase from north to south. Average annual rainfall is 1500 mm with rainfall increasing from west to east. The northwest corner has the least rainfall. Urban climatology deals with the modifying of climate due to urbanization. Atmospheric pollution is a major factor modifying urban climate.

Summary

The climate of Nepal can't be assigned to any particular type because of variation in altitude, topography, orography ad resulting temperature and precipitation. Th altitudinal range of Nepal varies from 65m to 8848m with the distance of 200km from south to north. Much of the Nepal falls within monsoon region, with regional climate variation largely being a function of elevation. National mean temperature is about 15-degree centigrade and increase from north to south. Average annual rainfall is 1500 mm with rainfall increasing from west to east. The northwest corner has the least rainfall. Urban climatology deals with the modifying of climate due to urbanization. Atmospheric pollution is a major factor modifying urban climate.

Things to Remember

  • Urban climatology deals with the modifying of climate due to urbanization. Atmospheric pollution is a major factor modifying urban climate.
  • The altitudinal range of Nepal varies from 65m to 8848m with the distance of 200km from south to north. 
  • Average annual rainfall is 1500 mm with rainfall increasing from west to east. The northwest corner has the least rainfall.
  • Urban areas also differ from their area counterparts in surface materials, surface shapes, heat and moisture sources.
  • The concentration of pollutants in the air above a city creates an urban aerosol which decreases the solar insolation, especially at higher latitude and winter seasons. 

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Spatial and Temporal Pattern of Climate in Nepal

Spatial and Temporal Pattern of Climate in Nepal

Spatial and Temporal Pattern of Climate in Nepal

The climate of Nepal can't be assigned to any particular type because of variation in altitude, topography, orography ad resulting temperature and precipitation. Th altitudinal range of Nepal varies from 65m to 8848m with the distance of 200km from south to north. Much of the Nepal falls within monsoon region, with regional climate variation largely being a function of elevation. National mean temperature is about 15-degree centigrade and increase from north to south. Average annual rainfall is 1500 mm with rainfall increasing from west to east. The northwest corner has the least rainfall.

Physiographically, Nepal can be divided into the following highlands units:

1. Terai/siwaliks region (<1500m): The climate of terai and siwaliks is warm subtropical monsoon type. The summer is hot and wet and winter is short and dry. The average annual rainfall ranges from 100cm-250cm and temperature from 10-degree centigrade in winter up to40-degree centigrade in summer.

2. Middle mountain (1500-3000m): The region has a humid mesothermal climate. Discontinuous valleys and elevated plains are found in this region. The region receives the maximum amount of rainfall in the country and average annual precipitation varies from 150-500 cm.

3. High mountain region (3000-3500):This region elevates from 3000m-3500m. Micro thermal climate prevails in this region with cool summer and frosty winter. The average annual precipitation is about 90cm and mostly in the form of snowfall.

4. Himalayan region?(>3500): It forms the northern boundary of a country and elevates from 3500m onward. The climate is a polar type with low rainfall in the form of snowfall and temperature mostly below 0-degree centigrade.

Nepal also includes some regions like Mustang, Manang, Dolpa valleys beyond the Himalayan region. The region is unaffected by the monsoon as it lies on rain shadow part of the monsoon wind. The climate of this region is semi-arid steppe type and average annual precipitation is less than 25 cm.

Climatic Patterns of Nepal

Or

Characteristics Feature of Climate of Nepal

The climatic parameters in this region show a marked variation in temporal scale. The climate of Nepal can be divided into four seasons.

1. Pre-monsoon season (Mar-May):

This season is dominated by dry climate westerly wind. The atmospheric condition is dusty and windy. The precipitation phenomenon is due to a convective phenomenon. The temperature gradually increases from March till May resulting the hotter days with increasing heat amounts. High-temperature results a local convection activity in the range of 39-degree centigrade to 44-degree centigrade. In general, temperature decreases by 6-degree centigrade for each increase in altitude by 1000m.

2. Rainy (monsoon) season (June-sept):

This season is associated with south-easterly monsoon wind. Generally, monsoon arrives over the eastern part on June 10 and within a week, it covers the whole country. When monsoon wind approached, precipitation gets started with high precipitation on the windward side and low precipitation on the leeward side. The precipitation in this season accounts for almost 80% of the total amount of rainfall. The moisture condition of an atmosphere is found to be high and a temperature is found to be low in comparison to a pre-monsoon season. The solar insolation is low during this period because of the cloudiness in the sky.

3. Post monsoon season (Oct-Nov):

This season starts just after the retreat of monsoon (south-easterly wind) and again westerly wind prevails. This season receives very little precipitation. This season is characterized by fine weather with sunny days.

4. Winter season (Dec-Feb):

In the season westerly wind dominates. The wind comes from Siberian high-pressure region and so it is characterized by cold weather. The westerly winds are laden with moisture from Mediterranean and other seas in the southern Europe. This moisture gets precipitated in Nepal in the form of winter precipitation. This phenomenon is termed as western disturbance, causes precipitation in the higher region in the form of snowfall. The southern part of a country is mild but northern part is very cold. Fog formation in the atmospheric reduces the solar insolation.

Urban Climatology

Cities, concentrate people and their activities in small areas, thereby providing an excellent opportunity to examine cultural modification of climate. Urban climatology deals with the modifying of climate due to urbanization. Atmospheric pollution is a major factor modifying urban climate. Urban areas also differ from their area counterparts in surface materials, surface shapes, heat and moisture sources. In fact, these affect radiation, visibility, temperature, wind, humidity, cloudiness, and precipitation.
The concentration of pollutants in the air above a city creates an urban aerosol which decreases the solar insolation, especially at higher latitude and winter seasons. The aerosol is best developed during a condition of stable air.
In spite of the diminished insolation, the center of typical cities constitute a heat island, that has a shape and size related to urban morphology, building and industries and that results from urban heat generation and storage. Temperature normally is highest near the urban center and declines gradually towards the suburban. Owing to the blanketing effect of a pollutant on the radiation budget, diurnal ranges of temperature are less in urban areas than over the countryside. The emission of greenhouse gases (GHGs), exchange of cool air and hot air by the heat engines and the urban albedo factors are responsible for the development of island in the urban area.
The roughness of city surface increases frictional drag and turbulence which causes gustiness and erratic flow of wind. The mean speed wind in the city is lower-flow of wind. The mean wind speed in the city is lower than the surrounding country part.The tendency of air to rise above the threat island is a possible expansion of greater cloudiness over cities may account impact for greater precipitation.
The appropriate average effects of urbanization on climatic elements can be shown by the following the table.
Elements Comparison with rural area
Clouds cover 5-10% greater
Fog, winter 100% more
Fog, summer 30% more
Precipitation 5-10% more
Snowfall 5% less
Relative humidity 2%
Relative humidity in summer 8%
Duration of sunshine 5-15% less
Annual mean temperature 0.5-1 degree centigrade

References:

Miller, Jr. G.T.Living in the Environment. Wadsworth Publication, 2003.

S.C., Santee.Environmental Science. India, New Center: New Center Book Agency (P) Ltd, 2004.

Lesson

Climatology

Subject

Environmental science

Grade

Bachelor of Science

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