Mapping the not-so-normal monsoon: 

Mapping the not-so-normal monsoon: 

Context

• The retreating south-west monsoon for 2017 has turned out to be normal for the second consecutive year. But there are various grey factors attached to the normal monsoon this year.

What is considered normal rainfall?

• Indian Meteorological Department deems a season ‘normal’ if the all-India quantum of rain falls within a 10% range of its long-period average of 887.5 mm.
• India has received a total 841.3 millimetres (mm) of rain in the south-west monsoon season from June 1 to September 30 this year.
• The 2017 monsoon fell short of the number only by 5%. In fact, the cumulative rainfall numbers this year aren’t very different from 2016 when the country recorded 862 mm of rain.

What effect does a good rainfall have on crops?

• In the year 2016-17, India harvested a record crop of cereals (252.7 million tonnes) and managed a quantum jump in its output of both pulses (16.3 million tonnes in 2015 to 22.9 million tonnes in 2016) and oilseeds (25 to 32 million tonnes).
• A good harvesting like that of 2016 – 17 contributed to a significant bump-up in the agriculture sector of the GDP which grew 4.9% in FY17 compared with 0.7% in FY16.
• The spatial and the temporal distribution of rains becomes the main reason behind making and breaking crop prospects. The 2017 monsoon on this score was unusual.

What are the expectation for the year 2017-18?

• Expecting a repetition of the impressive performance from last year is not realistic.
• In 2016, the monsoon started slow, but picked up pace in the latter half of the season. But this year’s monsoon has behaved in exactly the opposite fashion.
• Year 2017 started with excess rains of about 4% and 2% against normal seasonal patterns in June and July, the months of August and September have seen all-India rainfall fall 12-13% short of normal levels.
• Good rains in the months of June and July may have contributed to good sowing and coverage of the kharif crops. But deficit rains in August and September could impact the eventual output by pruning crop yields.
• The rainfall in the last two months of the south-west monsoon prescribe the reservoir storage and soil moisture, setting the tone for the plantation of the winter crops.
• The kharif crop, the rabi season has been equally important to the country’s agricultural prospects in recent years. Rabi output often matches or even exceeds the kharif output.
• Oilseeds are also predominantly winter crops. Therefore, dry spells in the latter half of this monsoon, taken with deficient rains in key rabi growing regions, can make for less than rosy rabi prospects.

Why is weather forecasting important?

• The purpose of a weather forecast is to provide as accurate as possible prediction of what the weather will be like in the near future.
• Weather forecasting is important to most aspects of day to day life, including aviation, boating, other modes of transportation, farming, tourism, sports, etc.
• Weather is a natural phenomenon and it can only be studied using predictions based on regular pattern.
• In absence of accurate weather forecasts there are high chances of damage to life and property. The certainty helps people to be aware of the calamities approaching.
• The more warning people have the better they can prepare and the least likely they are to die due to such natural disasters.
• Pilots need to know the weather to plan their flights, sailors need to know what the weather will be like to plan their activities, and farmers need to know what the weather will be like to help them plan watering, fertilizer and pesticide application, and harvest activities, to name a few.

India Meteorological Department (IMD) AND IT’S FUNCTIONING

• Indian meteorological department also referred to as MET department is an agency of the Ministry of Earth Sciences of the Government of India.
• It is the principal agency responsible for meteorological observations, weather forecasting and seismology.
• It is headquartered at Pune and operates observation centres at various other places.

INDIAN SATELLITES INVOLVED IN WEATHER FORECAST

Weather satellites:

• There are two basic types of weather satellites: those in geostationary orbits and those in polar orbits.
• Geostationary satellites: these satellites orbit very high above the earth at an altitude of 35,800 km and take the same time to orbit the earth as the earth takes to revolve once. From earth, therefore, the satellite appears to stay still always above the same region all the time.
• These satellites give ‘real-time’ images and hence, a series of photographs from these satellites can be displayed in a sequence to show cloud movement.
• Polar orbit satellites: This type of satellite orbits in a path that closely follows the Earth’s meridian lines, passing over the north and south poles once each revolution. These circle at a much lower altitude at about 850 km. This means that they can photograph clouds from a much closer level and provide more detailed information about violent storms and cloud systems.

Uses:

• Radiation measurement from earth surface
• Fishermen can find out valuable information about the temperature of the sea from measurements of these satellites.
• Infrared sensors on satellites can monitor crop conditions, areas of deforestation and regions of drought.
• Satellites can detect volcanic eruptions and the motion of ash clouds.
• Ice-mapping, snow storms in the Arctic and Antarctica and the mountain chains-Monitoring of Global Warming
• Observation of Auroras
• Water and air pollution can be pinpointed
• Oil spills can be detected.

Weather Satellites in India (those in service):

• INSAT system: the Indian National Satellite system was commissioned with the launch of INSAT-1B in 1983 and ushered in a revolution in India’s television, radio and meterological broadcasting. Of the 24 satellites so far launched, 11 are still in operation.
• INSAT-3C
• INSAT-3D
• INSAT-3E
• KALPANA-1
• MEGHA-TROPIQUE

SYSTEMS INTERFERING WITH THE INDIAN MONSOON

El-nino: El-Nino is the warm phase of the El-nino Southern Oscillation or ENSO and is associated with a band of warm water that develops in the central and east-central equatorial Pacific. It is accompanied by high pressure in the western pacific and low pressure in the eastern pacific.

El-nino modoki: It is a coupled ocean-atmosphere phenomenon in the tropical pacific. Conventional El-Nino is associated with strong anomalous warming in the eastern equatorial pacific while El Nino Modoki is associated with strong anomalous warming in the central tropical pacific and cooling in the eastern and western tropical pacific.

Indian ocean dipole: The Indian Ocean Dipole or the Indian nino is an irregular oscillation of the sea-surface temperatures in which the western Indian Ocean becomes alternately warmer and colder than the eastern part of the ocean. Monsoon in India is generally affected by the temperatures between the Bay of Bengal in the east and the Arabian sea in the west.