The Extent and Affect of the Monsoon's Through Comparing and Contrasting

As alluded to in the two previous posts of this blog, the climate conditions of Bangalore are formed by the cities relative position to the equator and the topographical makeup of the surrounding environment.  These geographical components create the air masses which dictate the climatic conditions of the region and are responsible for the monsoon winds that have such a significant impact throughout the seasons of the city.  So one would assume any pronounced differences in either the latitude of an area or a differing topographical regime would drastically change the climatic conditions affecting an area.  This is indeed usually the case; however the magnitudes of the monsoons that affect the Indian subcontinent tend to neutralize the extremities of these changes. A primary example of this is seen by comparing and contrasting the city of Bangalore, India with that of Kathmandu, Nepal.  The two cities are within 500 meters of each other in terms of elevation, but are found on the opposite ends of the Indian Subcontinent (from the northeast to the southwest), covering a distance of over 1,800 kilometers. With Bangalore residing within the tropic of cancer at 13 ̊ North latitude and Kathmandu within three degrees of the Horse Latitudes of 30 ̊ North, expectations of dramatic temperature and precipitation differentials should be pronounced.  However in this scenario it is not the case.  Kathmandu is unique in that it is positioned on the windward side of the world’s highest mountain range, the Himalayas. As illustrated below the sheltering dynamic surrounding the city along with the  pronounced force of the monsoons, has a dramatic effect on the cities climate. 

Map showing the location of the two cities in relation to each other.

Climate

The graphic above shows a comparison between the average monthly mean, high and low temperatures of the two cities.  The difference is slight in overall temperatures considering all factors, while near identical in the summer months of June, July, and August.  The most pronounced variation can be seen in the average monthly lows during the winter months.



While both cities high precipiation totals from the months of May to October and relativily low totals for the remainder of the year can be attributed to the monsoon winds and associated air masses, Kathmandu recieves vastly more because of the surronding topography.  The city lies on the windward side and at the base of the Himalayas.  This positioning subjects the city to copious amounts of rain from orographic lifting of the warm moist air mass from the Indian Ocean during the rainy season. 

 



Topography

Bangalore: As the above photograph confirms, the city lies on a relatively flat terrain with only slight variations found within the city proper and surrounding region.

Kathmandu: As seen the topography of the city is much more dramatic than that of Bangalore.  Sitting within the foothills of the Himalayas has a significant impact on the climate of the city.  The mountains can be seen faintly towering in the background. 

A map showing the total annual rainfall worldwide. A profound difference can be seen in the amount of precipitation received in southeast Asia when compared to the vast deserts of the Middle East in the Northern African Sahara, all which are approximately at the same latitude. 

SOURCES:

GOOGLE EARTH. (n.d.).

Indian Institute of Science, Centre for Ecological Sciences. (n.d.). Study Area: Bangalore. Retrieved March 07, 2012, from ces.iisc.ernet.in: http://ces.iisc.ernet.in/energy/wetlands/sarea.html

Kaspi, Y., & Schneider, T. (2012). Climate Dynamics of Earth and Other Planets. Retrieved April 01, 2012, from Tapio Schneider: http://www.gps.caltech.edu/~tapio/animations.html

Kathmandu Climate Guide. (n.d.). Retrieved April 16, 2012, from Kathmandu: http://www.climatetemp.info/nepal/

Keller, E. A., & DeVecchio, D. E. (2012). Natural Hazards. Upper Saddle River: Pearson Prentice Hall.

Lutgens, F. K., & Tarbuck, E. J. (2007). The Atmosphere: An introduction to meteorology. Upper Saddle River: Pearson Prentice Hall

Manjaro, C. (2011, October 04). Air Pollution is Stunting India's Monsoon. Retrieved April 02, 2012, from The Watchers: http://thewatchers.adorraeli.com/2011/10/04/air-pollution-is-stunting-indias-monsoon/

McKnight, T. L., & Hess, D. (2008). Physical Geography: A landscape appreciation. Upper Saddle River: Pearson Prentice Hall.

National Oceanic and Atmospheric Admininstration. (n.d.). Bangalore WMO:43295. Retrieved March 07, 2012, from dossier.ogp.noaa.gov: ftp://dossier.ogp.noaa.gov/GCOS/WMO-Normals/RA-II/IN/43295.TXT

NOAA. (n.d.). Climate Prediction Center. Retrieved April 01, 2012, from National Weather Service: http://www.cpc.ncep.noaa.gov/products/people/Kousky/Lectures/lecture-17-seasonal-cycle-monsoons-conv-zones.ppt.

Shreshta, V. P. (2007). A Concise Geography of Nepal: Kathmandu. Mandal Publications.

University of Wisconsin-Madison. (n.d.). Air Masses and Fronts. Retrieved April 01, 2012, from cimss.ssec.wisc.edu: http://cimss.ssec.wisc.edu/wxwise/class/frntmass.html

Ward, A. D., & Trimble, S. W. (2004). Environmental Hydrology. Boca Raton: CRC Press.

The Role of Air Masses and the Intertropical Convergence Zone on Seasonal Climatic Variations

The influence of an air masses is regarded as one of the most fundamental elements of weather and climate regimes, determining an area’s associated temperature and precipitation development.   Defined, an air mass is an exceedingly large mass of air that shares a relatively homogeneous temperature and moisture content at any given altitude, or horizontal direction, that is a part of the mass. Though small variations do exist within these masses, as to be expected, as they usually exceed over 1,500 kilometers. As the mass moves away from its point of origin, the characteristics of that location are transferred to the locations it travels over.  Movements of these masses are driven from pressure differentials from latent heat flux on the surface, for Bangalore this movement coincides with that of the intertropical convergence zone (ITCZ).  Masses are classified under two categories, their relation to the equator, which consists of arctic, polar, tropical, or equatorial; and their topographical surface of their origin, either maritime over large bodies of water, or continental over landmasses. For instance in the case of Bangalore a continental polar (cP) and continental arctic (cA) mass is predominant in the fall and winter, which produces dry conditions, while a maritime equatorial (mE) is dominant in the spring and summer, bringing moister conditions. Though seemingly vastly different, these two masses do hold similarities, like most masses they are formed on relatively flat, uniform surfaces with stagnant surface circulation. The complexity of these topics can be quite extensive, but can be somewhat clarified by examining the following graphics.

The graphic above shows the approximate region of origin for the major air masses of the world. Of these, two have a significant impact on the precipitation characteristics of Bangalore, the continental polar and continental arctic masses originating in Siberia, and the maritime equatorial mass over the Indian Ocean.  These masses traverse in and out of the Indian subcontinent, largely because of three main reasons. First the surface temperature differential shaped by the seasons, followed by the difference in specific heat of water molecules and molecules incorporating the makeup of land surfaces, and finally the influence of the intertropical convergence zone.  

The intertropical convergence zone (ITCZ) is a band that represents the convergence of the NE and SE trade winds, within a close proximity to the equator.  Also referred to as the equatorial low, this band brings high levels of precipitation from the release of latent heat from the persistent warm rising air.  The ITCZ loosely follows the sub-solar point over India, which is representative of the seasonal shift between the wet and dry. As seen above the ITCZ is deep within the the Indian Ocean in January, drawing in the cool dry continental air from the northern Asian continent.  The opposite is true in July, as the land is warmed more rapidly than the water from the ocean, it draws in the humid unstable air, resulting in heavy precipitation. 

The above graphics help demonstrate the typical direction and extent of the ITCZ and how and where it affects Bangalore.

The above map shows the amount of precipitation across the world in the month of January.  As can be seen the India receives minimal amounts during this period. as the dry continental Siberian mass influence the convective and thermal forces above the land.  The temperature however remains relatively mild due to Bangalore's positioning within the tropics.

A vastly different scenario develops in Bangalore soon after the spring equinox when heavy precipitation occurs from the end of April to the beginning of October. As can be seen above the movement of the maritime equatorial mass from the Indian Ocean moves north, inudating the land with some of the highest precipitaion totals on the entire planet.

Another factor that accounts for the amount of precipitation and the movements and development of air masses within the atmosphere in Bangalore, is the Indian Ocean Oscillations. Similar to the movements of El Nino and La Nina oscillations, except to a much lesser extent, depending on the phase rainy or drought conditions can fall upon Bangalore or the Indian sub continent as a whole.

Current Atmospheric Conditions

Bibliography

Indian Institute of Science, Centre for Ecological Sciences. (n.d.). Study Area: Bangalore. Retrieved March 07, 2012, from ces.iisc.ernet.in: http://ces.iisc.ernet.in/energy/wetlands/sarea.html

Kaspi, Y., & Schneider, T. (2012). Climate Dynamics of Earth and Other Planets. Retrieved April 01, 2012, from Tapio Schneider: http://www.gps.caltech.edu/~tapio/animations.html

Keller, E. A., & DeVecchio, D. E. (2012). Natural Hazards. Upper Saddle River: Pearson Prentice Hall.

Lutgens, F. K., & Tarbuck, E. J. (2007). The Atmosphere: An introduction to meteorology. Upper Saddle River: Pearson Prentice Hall.

Manjaro, C. (2011, October 04). Air Pollution is Stunting India's Monsoon. Retrieved April 02, 2012, from The Watchers: http://thewatchers.adorraeli.com/2011/10/04/air-pollution-is-stunting-indias-monsoon/

McKnight, T. L., & Hess, D. (2008). Physical Geography: A landscape appreciation. Upper Saddle River: Pearson Prentice Hall.

National Oceanic and Atmospheric AdmininstrationBangalore WMO:43295. Retrieved March 07, 2012, from dossier.ogp.noaa.gov: ftp://dossier.ogp.noaa.gov/GCOS/WMO-Normals/RA-II/IN/43295.TXT

NOAA. (n.d.). Climate Prediction Center. Retrieved April 01, 2012, from National Weather Service: http://www.cpc.ncep.noaa.gov/products/people/Kousky/Lectures/lecture-17-seasonal-cycle-monsoons-conv-zones.ppt.

Petersen, C. (n.d.). Education: GEEBIT. Retrieved March 07, 2012, from GISS Institute on Climate and Planets: http://icp.giss.nasa.gov/education/geebitt/

University of Wisconsin-Madison. (n.d.). Air Masses and Fronts. Retrieved April 01, 2012, from cimss.ssec.wisc.edu: http://cimss.ssec.wisc.edu/wxwise/class/frntmass.html

Ward, A. D., & Trimble, S. W. (2004). Environmental Hydrology. Boca Raton: CRC Press.