Nityanand Singh

On Climatic Fluctuations and Environmental Changes of the Indo-Gangetic Plains, India

Paralleling the Southern Himalayan Province, the Indo-GangeticPlains region (IGPR) of India (geographical area ∼ 6,00,000 km2) is veryimportant for the food security of South Asia. Due to numerous factors inoperation there is widespread apprehension regarding sustainability offragile ecosystems of the region. Literature provides detailed documentation of environmental changes due to different factors except climatic. The present study is intended to document the instrumental-period fluctuations of important climatic parameters like rainfall amounts (1829–1999), severe rainstorms (1880–1996) and temperature (1876–1997) exclusively for the IGPR. The summer monsoon rainfall over western IGPR shows increasing trend(170 mm/100-yr, significant at 1% level) from 1900 while over central IGPR it shows decreasing trend (5 mm/100-yr, not significant) from 1939 and over eastern IGPR decreasing trend (50 mm/100-yr, not significant) during 1900–1984 and insignificant increasing trend (480 mm/100-yr, not significant) during 1984–1999. Broadly it is inferred that there has been a westward shift in rainfall activities over the IGPR. Analysis suggests westward shift in the occurrence of severe rainstorms also. These spatial changes in rainfall activities are attributed to global warming and associated changes in the Indian summer monsoon circulation and the general atmosphericcirculation. The annual surface air temperature of the IGPR showed rising trend (0.53 ° C/100-yr, significant at 1% level) during 1875–1958 and decreasing trend (–0.93 ° C/100-yr, significant at 5% level) during 1958–1997. The post-1958 period cooling of the IGPR seems to be due to expansion and intensification of agricultural activities and spreading of irrigation network in the region. Lateral shift in the river courses is an environmental hazard of serious concern in the IGPR. In the present study it is suggested that meteorologic factors like strength and direction of low level winds and spatial shift in rainfall/climatic belt also play a significant role along with tectonic disturbances and local sedimentological adjustments in the vagrancy of the river courses over the IGPR.

Instrumental period rainfall series of the Indian region (AD 1813—2005): revised reconstruction, update and analysis

Sontakke and Singh (The Holocene 6, 315—31, 1996) developed instrumental period summer monsoon (June—September total) rainfall series (1813—1995) for six homogeneous zones and all of India using 306 raingauge stations. This reconstruction has been revised and updated. Besides reconstructing backward and updating to 2005 the longest possible summer monsoon rainfall series (1813—2005), post-monsoon (October— December total) and annual rainfall series have also been developed for seven homogeneous zones: North Mountainous India (NMI), Northwest India (NWI), North Central India (NCI), Northeast India (NEI), West Peninsular India (WPI), East Peninsular India (EPI), South Peninsular India (SPI), and the whole country using data from 316 well-spread stations. The different series are reported here. The underlying mechanism of the possible cause of the recent decreasing trend in monsoon rainfall and increasing trend in post-monsoon rainfall is described.

Construction of All-India Summer Monsoon Rainfall Series for the Period 1844–1991

Abstract An all-India summer monsoon rainfall series for the instrumental period of 1844–1991 has been constructed using a progressively increasing station density to 1870, and one that is fixed thereafter at a uniformly distributed 36 stations. The statistical scheme accounts for the increasing variance contributed to the all-India series by the increasing number of stations during the period 1844–1870. An interesting outcome of this study is that a reliable estimate of summer monsoon rainfall over India can he obtained using only 36 observations.

Longest instrumental regional and all-India summer monsoon rainfall series using optimum observations: reconstruction and update

Long period June-to-September total rainfall series are vital for the study of summer monsoon/climatic variability over the Indian region. Owing to high spatial variability in rainfall, the representa tiveness of the summer monsoon rainfall series for the entire country is limited. In order to develop an effective system for monsoon rainfall studies, the country has been divided into six zones, named as North West India (NWI), North Central India (NCI), North East India (NEI), West Peninsular India (WPI), East Peninsular India (EPI) and South Peninsular India (SPI). Fluctuation, empirical orthogonal function (EOF) and cluster analyses of the summer monsoon rainfall of the period AD 1871-1984 of 306 raingauges are carried out for this classifi cation. Updating the different zonal rainfall series on a real-time basis from all the gauges is a difficult task. In the present study, an objective technique is applied to select a subset of gauges whose mean showed the highest correlation with the all-gauges mean series; a total of 116 raingauge stations (19 for NWI, 27 for NCI, 15 for NEI, 18 for WPI, 14 for EPI and 23 for SPI) maintained by the India Meteorological Department (IMD) have been identified for updating the different zonal series. The different zonal series are extended as far as possible backward (prior to AD 1871) by applying an objective technique to the available gauges. The NEI and the EPI series are extended back to 1848, the NWI to 1844, the NCI to 1842, the WPI to 1817 and the SPI to 1813. Though of limited practical value, the all-India series is widely used in studies of long-range monsoon forecasting, teleconnections and large-scale climate dynamics. The all-India monsoon rainfall series from AD 1871 onwards is therefore calculated from the area-weighted mean of the six zones. The series is also extended back to AD 1813 by applying the objective technique on the available gauges. The different recon structed series for the longest instrumental period are reported.

The Wet and Dry Spells across India during 1951–2007

Abstract Characteristics of wet spells (WSs) and intervening dry spells (DSs) are extremely useful for water-related sectors. The information takes on greater significance in the wake of global climate change and climate-change scenario projections. The features of 40 parameters of the rainfall time distribution as well as their extremes have been studied for two wet and dry spells for 19 subregions across India using gridded daily rainfall available on 1° latitude × 1° longitude spatial resolution for the period 1951–2007. In a low-frequency-mode, intra-annual rainfall variation, WS (DS) is identified as a “continuous period with daily rainfall equal to or greater than (less than) daily mean rainfall (DMR) of climatological monsoon period over the area of interest.” The DMR shows significant spatial variation from 2.6 mm day−1 over the extreme southeast peninsula (ESEP) to 20.2 mm day−1 over the southern-central west coast (SCWC). Climatologically, the number of WSs (DSs) decreases from 11 (10) over the ...

On the duration of the rainy season over different parts of India

SummaryApplying a new criterion, based on the average monthly precipitation, the start and the cessation dates of rains over different parts of India have been determined using data from 466 widely-spread stations. The duration of rains or the rainy season is found to vary from nil to the entire year in some parts of the country. Based on the duration of the rainy season and the amount of precipitation six precipitation zones have been demarcated in the country and the utility of this demarcation for practical purposes is discussed. The relationship between the annual precipitation variability and the duration of the rainy season is also discussed.ZusammenfassungUnter Verwendung eines neuen Kriteriums, das auf der mittleren Monatssumme beruht, wurden Beginn und Ende der Regenzeit mit Hilfe der Daten von 466 über dem Land verteilten Stationen für verschiedenen Teile Indiens bestimmt. Die Extreme lagen bei keiner bis zu einer ganzjährigen „Regenzeit“ für einzelne Landesteile. Über Dauer und Niederschlagsmenge der Regenzeit wurden sechs Niederschlagszonen unterschieden. Die Brauchbarkeit dieser Einteilung für praktische Anwendungen sowie die Beziehung zwischen der Schwankung der Niederschlagsmenge und der Dauer der Regenzeit werden besprochen.

Some features of the arid area variations over India: 1871–1984

Spatial variability of the annual rainfall over drier regions of India is studied by examining the variations in the arid areas. A long period (1871–1984) arid area series has been prepared for the entire country, including the two broad subregions of North India and Peninsular India, using annual rainfall data from 306 well distributed stations. Following an objectively determined criterion based on rainfall amount alone, the yearly area under arid conditions is obtained by totalling areas which received annual rainfall totals less than 560 mm. The interannual variability of the arid area series is large and its distribution is highly right-skewed, demonstrating large spatial variations in the annual rainfall over India. Statistical tests do not suggest any significant long-term trend in the arid area series, but persistently low values of the arid area after 1941 are noteworthy. Implications for the study of risk analysis and assessment of drought and desertification processes are discussed.

Spatial variability of aridity oyer northern India

Spatial variability of aridity over northern India (north of 20°N) is studied by examining variations in the arid area. Area with an objectively determined summer monsoon rainfall (June to September total) of less than 500 mm is identified as arid area. The summer monsoon rainfall of 212 rain-gauges from 212 districts of the region for the period 1871–1984 are used in the analysis. An interesting feature of the arid area series is that it shows decreasing trend from beginning of the present century. The summer monsoon rainfall fluctuations over five subjectively divided zones over northern India are examined to understand the association between rainfall and the arid area variations. The rainfall series for northwest India shows a significant increasing trend and that for northeast India a significant decreasing trend from the beginning of this century. Rainfall fluctuations over the remaining zones can be considered intermediate stages of a systematic spatial change in the rainfall pattern. This suggested that the recent decreasing trend in the arid area is due to a westward shift in the monsoon rainfall activities. From correlation analyses it is inferred that perhaps the recent decreasing trend in the arid area and increasing trend in the monsoon rainfall over northwest India are associated with a warming trend of the northern hemisphere.

Mycotic Salpingitis in a Japanese Quail (Coturnix coturnix japonica)

An adult female Japanese quail (Coturnix coturnix japonica) was received for postmortem examination. Necropsy revealed the presence of white to grayish nodules 2-5 mm in diameter on the serosal surface of the oviduct. Aspergillus flavus was isolated from these nodules in pure culture. Histologically, these nodules were medium to large granulomatous lesions in serosa and the muscular wall of the oviduct. The lesions contained a large central necrotic core surrounded by giant cells, macrophages, and mononuclear cells. Similar cells in addition to heterophils also infiltrated the serosa, muscular layer, submucosa, and mucosa to varying degrees. Branched septate hyphae predominantly invaded the central caseous mass and to some extent invaded the surrounding areas of the nodules.

Some features of the periods contributing specified percentages of rainfall to annual total in Kerala, India

SummaryBased on daily rainfall data over a period of 80 years (1901–1980) taken at 75 stations, this paper reports interannual and long term fluctuations of the following parameters of the periods contributing each of 2, 5, 10, 20–90 and 95% rainfall to annual total over each of North Kerala and South Kerala rainfall subregions of India:(i)the starting date,(ii)the ending date,(iii)the length of the rainfall period or duration,(iv)the total rainfall (which is a fixed percentage of the annual total) of the rainfall period, and(v)the rainfall time-distribution characteristic which has been quantified by computing Olivers precipitation concentration index (PCI) using daily rainfall data of the concerned rainfall period. For most of the rainfall periods, the time series of starting and ending dates and length are homogeneous and random, and tend to observe the normal probability distribution. The different PCI series of North Kerala and the annual rainfall series of South Kerala show significantly decreasing trend which are indicative of considerable change in the hydroclimatic environment of Kerala. Possible changes in the southwest monsoon circulation along the west coast of India and excessive deforestation in Kerala which might have caused these rainfall changes are discussed.ZusammenfassungUnter Heranziehung der Tagesniederschlagsdaten von 75 Stationen über einen Zeitraum von 80 Jahren (1901–1980) untersucht vorliegende Studie Langzeitschwankungen folgender Parameter jener Perioden, die für jede der beiden Niederschlagszonen Nord-Kerala und Süd-Kerala 2, 5, 10, 20–90 und 95% zum gesamten Jahresniederschlag beitragen:1.Anfangsdatum,2.Enddatum,3.Dauer der Niederschlagsperiode,4.die Niederschlagssumme der Periode (die einem fixen Prozentsatz des Jahresniederschlags entspricht) und5.die Charakteristik der Niederschlagszeitverteilung, die mittels Olivers Niederschlagskonzentrations-Index (PCI) unter Heranziehung der Tagesniederschlagsdaten der behandelten Niederschlagsperioden quantifiziert wurde. Für die meisten Niederschlagsperioden gilt, daß die Zeitreihen der Anfangs- und Enddaten als auch der Dauer homogen und zufällig verteilt sind und im allgemeinen der Normalverteilung folgen. Die unterschiedlichen PCI-Reihen von Nord-Kerala und der Jahresniederschlagsserien von Süd-Kerala weisen einen deutlich abnehmenden Trend auf, Indikatoren für die bedeutenden Veränderungen des Hydroklimas in Kerala. Die Studie behandelt mögliche Veränderungen der Süd-West-Monsun-Zirkulation entlang der indischen Westküste und die ausgedehnte Entwaldung in Kerala, die diese Niederschlagsveränderungen bewirkt haben könnten.