Monsoon delayed or bad calendar hindering accurate prediction?
Column by Sandhya Jain
At the time of Independence, the Indian Government blindly borrowed the unscientific Gregorian calendar for scientific activities like weather prediction, abandoning the time tested sidereal calendar used in India for centuries.
The following article by Smt. Sandhya Jain is reproduced from Vijayavani.com of which she is the editor. It sheds interesting light on the sorry state of the Met Office which has the crucial task of predicting the annual monsoon. As the author acknowledges she has drawn on the expertise of the eminent mathematician Dr. C.K. Raju, who makes the highly reasonable suggestion that a conference should held to study the soundness and suitability of the calendar used in monsoon prediction and examine various alternatives. What follows is a brief introduction that might help readers to appreciate some of the technical points in the article.
(The title of the article has been changed from the original “The Sawan Calculus” to the one above to suit the style and format of FOLKS. We are grateful to Smt. Jain for granting the permission to reproduce it with editorial comments.)
This year, as happens all too often, the Meteorological Office (of the National Weather Bureau) was way off the mark in predicting the start of monsoon. As usual they claimed the monsoon would be ‘delayed’ only after the monsoon failed to obey their prediction. Many observers have noted, as in the article below, Hindu astronomers using their traditional panchangs (almanacs) seem to predict both the date and the quantum of monsoon rains much more accurately than do their ‘modern’ counterparts sitting in government offices spending public money.
What could be the reason? Do these Jyotish’s have mystical powers of prediction? Hardly. They use a calendar that was designed—using knowledge and experience gained over millennia—to be correlated to the seasons, especially the rainy season as it occurs in India. The Gregorian calendar that the Met Office and the government use was designed in 1582 to correct for the mismatch between the Julian calendar then in vogue and a proper date for Easter to coincide with the date (imagined) in the Council of Nicea in 325 AD. Unlike the Hindu panchangs, which were designed specifically with the Indian seasons in mind, the Gregorian calendar is a total misfit with the seasons. Using it to predict the monsoon is like using a thermometer to measure height.
The Gregorian calendar is a convenient civil calendar used for official activities worldwide. But just as the Sun doesn’t do anything special on a Sunday (a civil holiday), nature including the seasons, do not have to obey the dictates of the Gregorian calendar and they don’t. For example, the summer doesn’t have to begin on the day the school summer holidays begin. This being the case, it is hardly surprising that the beginning of the monsoon frequently disobeys the prediction based on the Gregorian calendar. It is like using the school calendar to predict the summer. (Never mind the fact that weather models are notoriously complex and unsound.)
This means, to predict the seasons, including the rainy season, it is necessary to have a calendar that is correlated with the Earth’s features and the way it interacts with the Sun. Astronomers for example use just such a calendar; it is called the sidereal calendar. It doesn’t obey Pope Gregory’s diktat but is correlated with the motion of the Earth and the Sun relative to the fixed stars. It is a time-keeping system astronomers use to keep track of the direction to point their telescopes to view a given star in the night sky.
Briefly, a sidereal day is a “time scale that is based on the Earth’s rate of rotation measured relative to the fixed stars.” This is the system used by modern astronomers and also the Hindu Jyotishs since time immemorial.
Stars are a useful frame of reference because from a given observation point, a star found at one location in the sky will be found at nearly the same location on another night at the same sidereal time. Hindu astronomy and modern astronomers both take advantage of this phenomenon. (Every amateur astronomer knows how hard it is to pick up an object in the telescope.) If the position of the Earth in its orbit around the Sun is reckoned with respect to the equinox, the point at which the orbit crosses the celestial equator, then its dates can accurately indicate the seasons, that is, they are synchronized with the declination of the Sun. Such a calendar is called a tropical solar calendar.
The problem with such a calendar is that the calendar equinoxes, and hence the seasons also, shift in the course of time due to a phenomenon known as the precession of the equinoxes. The calendar then goes out of phase and has to be corrected. (Equinox is a day on which the day and the night are of equal duration. There are two such days in each tropical year— called the vernal (spring) and the autumnal (fall) equinoxes.) The important point to note is that the Gregorian calendar was not designed taking these phenomena into consideration. It is a purely civilian calendar designed for our convenience. But Nature doesn’t give a damn for our convenience. (NS Rajaram, Contributing Editor, Folks Magazine)
Delayed or miscalculated?
According to the Hindu panchang, the month of sawan which along with bhadon comprises India’s monsoon season, began on July 4; rains drenched this parched city [Delhi] on July 5. Was the monsoon on time, or ‘delayed’ as the Met Office kept lamenting? The Union Ministry of Agriculture was clueless how to reassure farmers who sowed the kharif crop too early. [Sic: The Indian or the Hindu system divides the year into six seasons or ritus. The monsoon overlaps the varsha or the rainy season composed of the months of shravana and bhadrapada. This is so now but was not always due to the precession of the equinoxes. NSR]
Dr. C.K. Raju, who played a key role in building India’s first supercomputer Param and received the Telesio-Galilei Academy of Science’s gold medal for 2010 for discovering and correcting a mistake made by Albert Einstein, says the monsoon was similarly ‘delayed’ in 2003, 2004, 2006, 2009, and 2010. Each time, the rains eventually belied the Met Office’s predictions of drought.
This is because the Gregorian calendar on which the scientific community relies is not suitable for such calculations. [Sic: No, the Met Office, not the ‘scientific community’ which includes astronomers who go by sidereal time. NSR] India must first decide if the monsoon synchronizes with the tropical or sidereal year. The tropical (solar) year is the length of time the sun takes to return to the same position in the cycle of seasons as seen from earth, such as from one vernal equinox to the next. [Sic: Doing this should be easy enough with weather data on record for a hundred years or more. NSR]
It is not wholly synchronous with the earth’s orbit around the sun (sidereal, actual year) due to the precession of the equinoxes, and is around 20 minutes shorter (the difference can accumulate over long periods). Indian astronomy rests on the sidereal year; a better method of timekeeping as the sun’s transit against fixed stars (nakshatras, e.g. Dhruv-tara) is easy to observe and traditionally determined sowing and harvesting activities.
Europe was aware that it lacked the knowledge to precisely calculate the length of either the tropical or sidereal year, which India knew from at least the 3rd century. Hence the Gregorian calendar reform committee headed by Christoph Clavius tried to consult Indian calendrical sources; just prior to the calendar reform of 1582, his student Matteo Ricci was in India, scouting calendrical manuals in Cochin! [Sic: This is interesting if it can be further substantiated. Clavius’s source appears to have been the Prussian Tables of Erasmus Reinhold. Also, Matteo Ricci who was in Goa went to China as a missionary in 1582. His mathematical knowledge is uncertain. NSR]
The Gregorian calendar reform was needed because the Julian calendar fixed the length of the year very crudely as the Romans were weak with fractions; so the calendar slipped roughly one day every 128 years. By 1582 CE, it had slipped about 10 days out of phase in the 1250-odd years since the Council of Nicaea fixed the date of Easter by fixing the date of the vernal equinox on XII calends (21 March). By the end of the 16th century, the vernal equinox fell around 11 March on the Julian calendar. [Sic: This slippage is an astronomical phenomenon; it happens even if the length of the solar year is calculated more exactly. To be precise, modern value for the slippage (precession) is 50.3 seconds of arc per year or 1 degree every 71.6 years. NSR]
The Gregorian reform corrected this anomaly by advancing the calendar by 10 days, and by making every centennial year not a leap year unless divisible by 400 (e.g. 2000). It thus came closer to a more accurate figure for the fractional part of the length of the tropical year. The correction was vital for the practical purpose of fixing latitude from observation of solar altitude at noon, necessary for navigation which was then extremely important for Europe which lagged behind the Indians and Arabs.
Shockingly, after independence, the Indian calendar reform committee adopted the Gregorian calendar and said the seasons depend on the tropical year! Superficially, the tropical year seems supported by astronomical treatises like Surya Siddhanta and PancaSiddhantika, but the passages have been misunderstood. Anyway, even prior to Varahamihıra and the PancaSiddhantika, Aryabhata explicitly advocated the sidereal year; Marxist historians concur that Indian agriculture was linked to the nakshatras.
Modern India has not seriously studied the monsoons, though even today good monsoons drive the economy. Late Meghnad Saha believed heat balance alone mattered in configuring the monsoons; C.K. Raju thinks wind regime is the key, but says major research is necessary to establish a paradigm. The ancients coped by creating over 5000 panchangs, each ‘corrected’ to account for latitude (hence the Kerala monsoon arrives much before rains in Delhi) and longitude. There is a powerful cultural context here– the Indian calendar revolves around the rainy season (varsha) as the year (varsh) relates to rain. It is eternally relevant for agriculture as poor calculations can wreak havoc through mistimed agricultural operations.
Unscientific fraud called ‘scientific temper’
The Nehruvian quest for “scientific temper” led to slavish adoption of the Gregorian calendar for calculating the seasons and monsoon rhythm, though objective analysis shows that every year the monsoon arrives in harmony with the panchang, though ‘scientists’ keep bleating about ‘delays’! Refusing to learn from experience or history, they have ruined farmers and harvests. [Sic: Again the Met Office, not ‘scientists’. The term ‘scientific temper’ is an abomination used by politicians and propagandists to introduce pseudo-science and political superstitions in the guise of science. NSR]
The keynote of the Hindu calendar is the monsoons on which agriculture rests, and not summer or winter which may be relevant in Europe. Monsoons depend upon the wind regime. The global circulation of wind is not decided solely by the position of the sun. Hot air rises at the equator, but does not descend at the poles. Due to the Coriolis force, the earth’s rotation causes air to be deflected and to descend before the Horse-Latitudes (sub-tropical latitudes between 30 and 35 degrees north and south). [Sic: Very good point. It is the highly seasonal monsoon that governs life in India, not summer or winter. NSR]
Thus, the monsoons also depend upon the Coriolis force, which is an inertial force. Since the only possible inertial framework is one fixed relative to the distant stars, the Coriolis force relates to the sidereal motion of the earth, and monsoons relate to the sidereal year. Had monsoons related to the tropical year, the cumulative difference between the tropical and sidereal year would have put the Indian calendar out of phase. This never happened. [Sic: The ancient Hindus knew about the precession and adjusted their calendars accordingly. They also recorded equinox (or solstice) transitions like Mrigashira-Rohini, Rohini-Krittika, etc. NSR]
By forcing farmers to abandon the ancient nakshatra-governed seasons in favour of the tropical year, Nehruvian secularism and scientific temper have compromised our food security. An eerie coincidence that has facilitated the eclipse of agriculture from public consciousness is the virtual disappearance of rural symbols once associated with major political parties – Cow and Calf (Congress); Plough and Kisan (Janata, Lok Dal), while the Sickle of the Communist parties has degenerated into an offensive weapon. This is a telling comment on the growing urban bias in our polity and our distorted understanding of the economy, the adverse effects of which have already come to haunt us. [Sic: The nakshatras (fixed stars) don’t govern the seasons, but may help us better measure them. NSR]
Two decades of liberalization-globalization and thousands of crores of ‘incentives’ later, the service and manufacturing sectors have failed to promote growth or made a dent in employment nation-wide. The economy is gasping for a good monsoon to lift it out of the present morass. Can we at least now trash the liberalization-era myth that there is no link between agriculture and growth?
Comment: There is some polemic towards the end that may not appeal to everyone, but the basic point made— that the Met Office has a poor record when it comes to predicting the monsoon cannot be disputed. It is also a fact that the Calendar Reform Committee acted in haste and without scientific deliberation in adopting the Gregorian calendar for everything. Dr. Raju’s suggestion to examine different calendars against their prediction accuracy is eminently sound and needs to be followed up. It should not be particularly hard to do given the wealth of historical data available in the Met Office archives. NSR