Three months of swinging Celsius

The middle of February is when the chill begins to abate. The middle of May is when the monsoon is longed for. In our towns, district headquarters and cities, that climatic journey of 90 days is one of a steady rise in the reading of the temperature gauge, from the low 20s to the mid 30s.

This large panel of 90 days of daily average temperatures shows, in 57 ways, the effects of the rains that almost every district has experienced during the last two months. For each city, the curved line is the long period ‘normal’ for these 90 days, based on daily averages. Also for each city, the second line which swings above and below the ‘normal’ is the one that describes the changes in its daily average from February to May 2015.

[You can download (1.52MB) a full resolution image of the panel here.]

Where this second line crosses to rise above the normal, the intervening space is red, where it dips below is coloured blue. The patches of red or blue are what tell us about the effects of a lingering winter, or rains that have been called ‘unseasonal’ but which we think signal a shift in the monsoon patterns.

The 90-day temperature chart for Goa, with daily averages nearer the long period normal over the latter half.

Amongst the readings there is to be found some general similarities and also some individual peculiarities. Overall, there are more blue patches than there are red ones, and that describes how most of the cities in this panel have escaped (till this point) the typical heat of April and May. The second noteworthy general finding is that these blue patches occur more frequently in the second half of the 90 days, and so are the result of the rainy spells experienced from March to early May.

Hisar (in Haryana) has remained under the normal temperature line for many more days than above or near it. So have Gorakhpur (Uttar Pradesh), Pendra (Chhattisgarh), Ranchi (Jharkhand), Nagpur (Maharashtra) and Jharsuguda (Odisha).

On the other hand in peninsular and south India, the below ‘normal’ daily average temperature readings are to be found in the latter half of the time period, coinciding with the frequent wet spells. This we can see in Kakinada, Kurnool and Anantapur (Andhra Pradesh), Bangalore, Gadag and Mangalore (Karnataka), Chennai, Cuddalore and Tiruchirapalli (Tamil Nadu) and Thiruvananthapuram (Kerala). [A zip file with the charts for all 57 cities is available here (1.2MB).]

What pattern will the next 30 days worth of temperature readings follow? In four weeks we will update this bird’s eye view of city temperatures, by which time monsoon 2015 should continue to give us more blues than reds. [Temperature time series plots are courtesy the NOAA Center for Weather and Climate Prediction.]

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The cities and their multitudes

The 166 Indian cities in the UN population list. What do the colours mean? Dark blue is for city populations up to 250,000; light blue is 250,000-500,000; pink is 500,000 to 1 million; orange is 1 million to 5 million; red is 5 million and above. The source for the data is ‘World Urbanization Prospects: The 2014 Revision’, from the United Nations, Department of Economic and Social Affairs, Population Division.

Bigger cities growing at a rate faster in the last decade than earlier decades. This is what the image shows us. These are 166 cities of India whose populations in 2014 were 300,000 and above. The jagged swatches of colour that seem to march diagonally across the image describe tiers of population, for the table is arranged according to the populations of these cities in 2015, with the annual series beginning in 1985 and extending (as a forecast) until 2030.

The populations of four cities will cross 0.5 million in 2015: Jalgaon (Maharashtra, whose population will be 506,000 in 2015), Patiala (Punjab, 510,000), Thoothukudi (Tamil Nadu, 514,000) and Imphal (Manipur, 518,000). They will join a group of cities which in 2014 crossed the 0.5 million mark: Gaya (Bihar, 508,000 in 2015), Rajahmundry (Andhra Pradesh, 511,000), Udaipur (Rajasthan, 517,000), Bilaspur (Chhattisgarh, 518,000), Kayamkulam (Kerala, 533,000) and Agartala (Tripura, 550,000).

Just ahead of these are Vellore (Tamil Nadu, whose population in 2015 will be 528,000 and which crossed 0.5 million in 2013), Mathura (Uttar Pradesh, 529,000 and 2014), Tirunelveli (Tamil Nadu, 530,000 and 2011), Sangli (Maharashtra, 545,000 and 2009), Tirupati (Andhra Pradesh, 550,000 and 2013), Ujjain (Madhya Pradesh, 556,000 and 2009), Kurnool (Andhra Pradesh, 567,000 and 2012), Muzaffarnagar (Uttar Pradesh, 587,000 and 2011), Erode (Tamil Nadu, 590,000 and 2010) and Cherthala (Kerala, 593,000 and 2013).

To make this chart I have used the data from ‘World Urbanization Prospects: The 2014 Revision’, from the United Nations, Department of Economic and Social Affairs, Population Division. The 166 cities of India are extracted from the main table, ‘Annual Population of Urban Agglomerations with 300,000 Inhabitants or More in 2014, by Country, 1950-2030’.

This quarter, five Indian cities will cross the million mark

This quarter, that is October to December 2013, a number of India’s cities will cross population landmarks. The 2011 Census fixed the country’s urban population at just over 311 million, a population that had grown over ten years by 31.8% (compared with the rural population growth of 12.3%).

What this means is that India’s cities and towns are adding to their numbers every year and every month at roughly the decadal rate seen for 2001-11. Each urban centre has recorded its own rate of population growth but all together, the rate of growth in the populations of India’s urban settlements has raised the number of Class I towns (those with a population of 100,000 and more) to 490 – the category had 394 in 2001!

So, for the last quarter of 2013, here are the new population marks that will be crossed:
* Tiruppur in Tamil Nadu (1,033,000), Aligarh in Uttar Pradesh (1,002,000), Bareilly in Uttar Pradesh (1,065,000), Mysore in Karnataka (1,047,000) and Guwahati in Assam (1,018,000) will all cross the million mark.

And moreover:
* Muzaffarabad in Uttar Pradesh (527,000), Kurnool in Andhra Pradesh (531,000), Vellore in Tamil Nadu (515,000), Udaipur in Rajasthan (504,000) and Tirunelveli in Tamil Nadu will cross the 0.5 million population mark.
* Nellore in Andhra Pradesh (627,000), Malegaon in Maharashtra (614,000) and Durgapur in West Bengal (610,000) will cross the 0.6 million population mark.
* Puducherry (union territory, 708,000), Guntur in Andhra Pradesh (733,000) and Gorakhpur in Uttar Pradesh (714,000) will cross the 0.7 million population mark.
* Warangal in Andhra Pradesh (826,000) has crossed the 0.8 million population mark. Moradabad in Uttar Pradesh (987,000), Bhubaneshwar in Odisha (967,000) and Jalandhar in Punjab (928,000) will cross the 0.9 million population mark.