Editing Kolkata (section)

== Geography ==
{{Main|Geography of Kolkata}}
[[File:Earth from Space- Kolkata, India ESA24701909.jpeg|thumb|Kolkata from space captured by Copernicus [[Sentinel-2]].]]
Spread roughly meridionally along the east bank of the [[Hooghly River]], Kolkata sits within the lower [[Ganges Delta]] of eastern India approximately 75&nbsp;km (47&nbsp;mi) west of the international border with Bangladesh; the city's elevation is {{cvt|1.5|-|9|m|ft|0}}.<ref>{{cite web |title=PIA01844: space radar image of Calcutta, West Bengal, India |url=http://photojournal.jpl.nasa.gov/catalog/PIA01844 |publisher=NASA |access-date=15 January 2012 |date=15 April 1999 |url-status=live |archive-url=https://web.archive.org/web/20120114231031/http://photojournal.jpl.nasa.gov/catalog/PIA01844 |archive-date=14 January 2012 }}</ref> Much of the city was originally a wetland that was reclaimed over the decades to accommodate a burgeoning population.<ref>{{cite book |last=Chatterjee |first=S. N. |title=Water Resources, Conservation and Management |year=2008 |publisher=Atlantic Publishers and Distributors |location=New Delhi |isbn=978-81-269-0868-4 |page=33 }}</ref> The remaining undeveloped areas, known as the [[East Kolkata Wetlands]], were designated a "wetland of international importance" by the [[Ramsar Convention]] (1975).<ref>{{Cite journal |last1=Roy Chadhuri |first1=S. |last2=Thakur |first2=A. R. |title=Microbial genetic resource mapping of East Calcutta wetlands |journal=Current Science |volume=91 |issue=2 |date=25 July 2006 |pages=212–17 }}</ref> As with most of the [[Indo-Gangetic Plain]], the soil and water are predominantly [[alluvium|alluvial]] in origin. Kolkata is located over the "Bengal basin", a pericratonic tertiary basin.<ref name="soil characterisation">{{cite conference |url=http://gndec.ac.in/~igs/ldh/conf/2009/articles/T01_03.pdf |title=Characterization of soil over Kolkata municipal area |first1=Diptendra |last1=Das |first2=B. C. |last2=Chattopadhyay |date=19 December 2009 |conference=Indian Geotechnical Conference |conference-url=http://gndec.ac.in/~igs/ldh/conf/2009/ |volume=1 |location=Guntur, India |pages=11–12 |access-date=19 November 2012 |url-status=live |archive-url=https://web.archive.org/web/20131106050646/http://gndec.ac.in/~igs/ldh/conf/2009/articles/T01_03.pdf |archive-date=6 November 2013 }}</ref> Bengal basin comprises three structural units: shelf or platform in the west; central hinge or shelf/slope break; and deep basinal part in the east and southeast. Kolkata is located atop the western part of the hinge zone which is about {{cvt|25|km|mi}} wide at a depth of about {{cvt|45000|m|ft}} below the surface.<ref name="soil characterisation" /> The shelf and hinge zones have many faults, among them some are active. Total thickness of sediment below Kolkata is nearly {{cvt|7500|m|ft}} above the [[Basement (geology)|crystalline basement]]; of these the top {{cvt|350|-|450|m|ft|-1}} is [[Quaternary]], followed by {{cvt|4500|-|5500|m|ft|-1}} of [[Tertiary]] sediments, {{cvt|500|-|700|m|ft|-1}} [[Trap rock|trap]] wash of [[Cretaceous]] trap and {{cvt|600|-|800|m|ft|-1}} [[Permian]]-[[Carboniferous]] [[Gondwana]] rocks.<ref name="soil characterisation" /> The quaternary sediments consist of clay, silt and several grades of sand and gravel. These sediments are sandwiched between two clay beds: the lower one at a depth of {{cvt|250|-|650|m|ft|-1}}; the upper one {{cvt|10|-|40|m|ft|-1}} in thickness.<ref name="Bunting">{{Cite report |last1=Bunting |first1=S. W. |last2=Kundu |first2=N. |last3=Mukherjee |first3=M. |publisher=Institute of Aquaculture, University of Stirling |location=Stirling, UK |url=http://www.dfid.stir.ac.uk/dfid/nrsp/download/sitanal.pdf |title=Situation analysis. Production systems and natural resources use in PU Kolkata |page=3 |access-date=26 April 2006 |url-status=live |archive-url=https://web.archive.org/web/20060505141605/http://www.dfid.stir.ac.uk/dfid/nrsp/download/sitanal.pdf |archive-date=5 May 2006 }}</ref> According to the [[Bureau of Indian Standards]], on a scale ranging from {{nowrap|I to V}} in order of increasing susceptibility to earthquakes, the city lies inside [[Earthquake hazard zoning of India|seismic zone III]].<ref name="hazardprofile">{{cite web |url=http://www.undp.org.in/dmweb/hazardprofile.pdf |title=Hazard profiles of Indian districts |access-date=23 August 2006 |work=National Capacity Building Project in Disaster Management |publisher=[[UNDP]] |archive-url=https://web.archive.org/web/20060519100611/http://www.undp.org.in/dmweb/hazardprofile.pdf |archive-date=19 May 2006 }}</ref>

=== Climate ===
{{Main|Climate of Kolkata}}
Kolkata is subject to a [[tropical savanna climate]] that is designated ''Aw'' under the [[Köppen climate classification]]. According to a [[United Nations Development Programme]] report, its wind and cyclone zone is "very high damage risk".<ref name="hazardprofile" />

{{Kolkata weatherbox}}

==== Temperature ====
The annual mean temperature is {{cvt|26.8|C|F|1}}; monthly mean temperatures are {{cvt|19|-|30|C|F|0}}. Summers (March–June) are hot and humid, with temperatures in the low 30s Celsius; during dry spells, maximum temperatures sometime exceed {{Convert|40|C}} in May and June.<ref name="weatherbase">{{cite web |publisher=Canty and Associates LLC |url=http://www.weatherbase.com/weather/weatherall.php3?s=090824&refer=&units=metric |title=Weatherbase entry for Kolkata |access-date=26 April 2006 |url-status=live |archive-url=https://web.archive.org/web/20110907174739/http://www.weatherbase.com/weather/weatherall.php3?s=090824&refer=&units=metric |archive-date=7 September 2011 }}</ref> Winter lasts for roughly {{frac|2|1|2}} months, with seasonal lows dipping to {{cvt|9|–|11|C|F|0}} in December and January. May is the hottest month, with daily temperatures ranging from {{cvt|27|-|37|C|F|0}}; January, the coldest month, has temperatures varying from {{cvt|12|-|23|C|F|0}}. The highest recorded temperature is {{cvt|43.9|C|F|1}}, and the lowest is {{cvt|5|C|F|0}}.<ref name="weatherbase" /> The winter is mild and very comfortable weather pertains over the city throughout this season. Often, in April–June, the city is struck by heavy rains or dusty squalls that are followed by thunderstorms or hailstorms, bringing cooling relief from the prevailing humidity. These thunderstorms are [[Convection rain|convective]] in nature, and are known locally as ''kal bôishakhi'' ({{lang|bn|কালবৈশাখী}}), or "Nor'westers" in English.<ref name="kalboisakhi">{{cite web |url=http://amsglossary.allenpress.com/glossary/search?id=kal-baisakhi1 |title=kal Baisakhi |access-date=5 September 2006 |work=Glossary of Meteorology |publisher=American Meteorological Society |archive-url=https://web.archive.org/web/20060830065710/http://amsglossary.allenpress.com/glossary/search?id=kal-baisakhi1 |archive-date=30 August 2006 }}</ref>

==== Rainfall ====
Rains brought by the Bay of Bengal branch of the [[Southwest monsoon|south-west summer monsoon]]<ref name="monsoontribune">{{Cite news |last1=Khichar |first1=M. L. |last2=Niwas |first2=R. |date=14 July 2003 |title=Know your monsoon |newspaper=The Tribune |location=Chandigarh, India |url=http://www.tribuneindia.com/2003/20030714/agro.htm#2 |access-date=9 June 2007 |url-status=live |archive-url=https://web.archive.org/web/20070618121810/http://www.tribuneindia.com/2003/20030714/agro.htm#2 |archive-date=18 June 2007 }}</ref> lash Kolkata between June and September, supplying it with most of its annual rainfall of about {{cvt|1850|mm|in|0}}. The highest monthly rainfall total occurs in July and August. In these months often incessant rain for days brings life to a stall for the city dwellers. The city receives 2,107 hours of sunshine per year, with maximum [[Insolation|sunlight exposure]] occurring in April.<ref name="ESS" /> Kolkata has been hit by several cyclones; these include systems occurring in [[1737 Calcutta cyclone|1737]] and [[1864 Calcutta cyclone|1864]] that killed thousands.<ref>{{cite journal |last=Bilham |first=Roger |year=1994 |title=The 1737 Calcutta earthquake and cyclone evaluated |journal=Bulletin of the Seismological Society of America |volume=84 |issue=5 |pages=1650–57 |doi=10.1785/BSSA0840051650 |bibcode=1994BuSSA..84.1650B |s2cid=130396862 |url=http://cires.colorado.edu/~bilham/gif_images/1737Calcutta.pdf |access-date=20 July 2011 |url-status=live |archive-url=https://web.archive.org/web/20110811224058/http://cires.colorado.edu/~bilham/gif_images/1737Calcutta.pdf |archive-date=11 August 2011 }}</ref><ref>{{cite book |title=Report on the Calcutta cyclone of the 5th October 1864 |last1=Gastrell |first1=James Eardley |first2=Henry Francis |last2=Blanford |year=1866 |publisher=O.T. Cutter, Military Orphan Press |location=Calcutta |url=https://archive.org/details/reportoncalcutt00blangoog |access-date=20 July 2011 }}</ref> More recently, [[Cyclone Aila]] in 2009 and [[Cyclone Amphan]] in 2020 caused widespread damage to Kolkata by bringing catastrophic winds and torrential rainfall.

=== Environmental issues ===
{{Main|Environmental issues in Kolkata}}
Pollution is a major concern in Kolkata. {{As of|2008}}, [[sulphur dioxide]] and [[nitrogen dioxide]] annual concentration were within the national ambient air quality standards of India, but respirable [[Particulates|suspended particulate matter]] levels were high, and on an increasing trend for five consecutive years, causing smog and haze.<ref name="ambientairquality">{{cite web |author=Central Pollution Control Board |publisher=Ministry of Environment and Forests, Government of India |url=http://cpcb.nic.in/upload/AnnualReports/AnnualReport_37_ANNUAL_REPORT-08-09.pdf |title=Annual report 2008–2009 |page=40 |access-date=2 February 2012 |archive-url=https://web.archive.org/web/20120426072456/http://cpcb.nic.in/upload/AnnualReports/AnnualReport_37_ANNUAL_REPORT-08-09.pdf |archive-date=26 April 2012 }}</ref><ref>{{cite news |url=http://www.telegraphindia.com/1081030/jsp/calcutta/story_10035984.jsp |title=Smog city chokes & grounds: foul air, moist and smoky |newspaper=The Telegraph |location=Kolkata |date=30 October 2008 |access-date=25 April 2011 |archive-url=https://web.archive.org/web/20110604143452/http://www.telegraphindia.com/1081030/jsp/calcutta/story_10035984.jsp |archive-date=4 June 2011 }}</ref> Severe air pollution in the city has caused a rise in pollution-related respiratory ailments, such as lung cancer.<ref name="BBC51707">{{Cite news |last=Bhaumik |first=Subir |title=Oxygen supplies for India police |url=http://news.bbc.co.uk/2/hi/south_asia/6665803.stm |publisher=BBC |date=17 May 2007 |access-date=23 June 2007 |url-status=live |archive-url=https://web.archive.org/web/20070612072737/http://news.bbc.co.uk/2/hi/south_asia/6665803.stm |archive-date=12 June 2007 }}</ref>