Some characteristics of very heavy rainfall over Orissa during summer monsoon season

Orissa is one of the most flood prone states of India. The floods in Orissa mostly occur during monsoon season due to very heavy rainfall caused by synoptic scale monsoon disturbances. Hence a study is undertaken to find out the characteristic features of very heavy rainfall (24 hours rainfall ≥125 mm) over Orissa during summer monsoon season (June-September) by analysing 20 years (1980-1999) daily rainfall data of different stations in Orissa. The principal objective of this study is to find out the role of synoptic scale monsoon disturbances in spatial and temporal variability of very heavy rainfall over Orissa. Most of the very heavy rainfall events occur in July and August. The region, extending from central part of coastal Orissa in the southeast towards Sambalpur district in the northwest, experiences higher frequency and higher intensity of very heavy rainfall with less interannual variability. It is due to the fact that most of the causative synoptic disturbances like low pressure systems (LPS) develop over northwest (NW) Bay of Bengal with minimum interannual variation and the monsoon trough extends in west-northwesterly direction from the centre of the system. The very heavy rainfall occurs more frequently with less interannual variability on the western side of Eastern Ghat during all the months and the season except September. It occurs more frequently with less interannual variability on the eastern side of Eastern Ghat during September. The NW Bay followed by Gangetic West Bengal/Orissa is the most favourable region of LPS to cause very heavy rainfall over different parts of Orissa except eastern side of Eastern Ghat. The NW Bay and west central (WC) Bay are equally favourable regions of LPS to cause very heavy rainfall over eastern side of Eastern Ghat. The frequency of very heavy rainfall does not show any significant trend in recent years over Orissa except some places in north-east Orissa which exhibit significant rising trend in all the monsoon months and the season as a whole

Inter-annual variability of summer monsoon rainfall over Orissa (India) in relation to cyclonic disturbances

The summer monsoon rainfall over Orissa, a state on the eastern coast of India, is more significantly related than Indian summer monsoon rainfall (ISMR) to the cyclonic disturbances developing over the Bay of Bengal. Orissa experiences floods and droughts very often due to variation in the characteristics of these disturbances. Hence, an attempt was made to find out the inter-annual variability in the rainfall over Orissa and the frequencies of different categories of cyclonic disturbances affecting Orissa during monsoon season (June-September). For this purpose, different statistical characteristics, such as mean, coefficient of variation, trends and periodicities in the rainfall and the frequencies of different categories of cyclonic disturbances affecting Orissa, were analysed from 100 years (1901-2000) of data. The basic objective of the study was to find out the contribution of inter-annual variability in the frequency of cyclonic disturbances to the inter-annual variability of monsoon rainfall over Orissa. The relationship between summer monsoon rainfall over Orissa and the frequency of cyclonic disturbances affecting Orissa shows temporal variation. The correlation between them has significantly decreased since the 1950s. The variation in their relationship is mainly due to the variation in the frequency of cyclonic disturbances affecting Orissa. The variability of both rainfall and total cyclonic disturbances has been above normal since the 1960s, leading to more floods and droughts over Orissa during recent years. The inter-annual variability of seasonal rainfall over Orissa and the frequency of cyclonic disturbances affecting Orissa during monsoon season show a quasi-biennial oscillation period of 2-2.8 years. There is least impact of El Nino southern oscillation (ENSO) on inter-annual variability of both the seasonal rainfall over Orissa and the frequencies of monsoon depressions/total cyclonic disturbances affecting Orissa

Interannual variability of summer monsoon rainfall over Orissa in relation to tropospheric circulation features

The summer monsoon rainfall over Orissa shows largescale interannual variability due to variation in the characteristics of meteorological parameters like temperature, pressure/geopotential height and wind at surface and in the troposphere. A study was therefore undertaken to find out the characteristic features of surface and upper air meteorological parameters in the troposphere and their relationship with summer monsoon rainfall over Orissa. For this purpose, rainfall data over 31 uniformly distributed stations in Orissa along with the surface meteorological parameters at seven stations and upper air parameters at different standard isobaric levels up to 200 hPa over four stations in Orissa and its neighbourhood during summer monsoon season over a period of 19 years (1980-98) have been considered. The principal objective of this study is to find out the contribution of different meteorological parameters in the spatio-temporal variability of summer monsoon rainfall over Orissa. The interannual variability of rainfall mostly depends on the interannual variation of wind over Orissa and its neighbourhood. Strong northeasterlies over north coastal Orissa along with the southeasterly winds over Gangetic West Bengal and northwesterlies over northwest Orissa, south Orissa and north coastal Andhra Pradesh at the lower and mid-tropospheric levels are favourable for good rainfall over Orissa as a whole. They are also favourable for good rainfall over the western side of the Eastern Ghats and over the central zone, extending from the central part of coastal Orissa to western Orissa. This pattern of wind is also associated with the synoptic disturbances over northwest Bay of Bengal. Hence, the higher/lower number of days of synoptic disturbances over the NW Bay causes excess/deficient rainfall over Orissa. The stronger gradient of mean sea-level pressure and geopotential over the region to the south of the monsoon trough passing through north coastal Orissa at lower and mid-tropospheric level, is favourable for good rainfall over Orissa. Divergence at the upper troposphere (200 hPa) due to a trough in the upper tropospheric westerlies to the right of Visakhapatnam and an east-west ridge to the south of Visakhapatnam and over the NW Bay is favourable for rainfall over Orissa. There is no significant trend in both zonal and meridional winds at the upper troposphere (200 hPa) over the region, supporting insignificant trend in summer monsoon seasonal rainfall over Orissa during 1980-98

Majorana neutrinos with split fermions in extra dimensions

We propose new solutions to the neutrino mass problem in theories with large extra dimensions in a thick wall scenario. It has recently been argued that our 3-brane could be a thick wall at the boundary of the bulk. The gauge bosons and the Higgs scalars have an almost flat profile on this wall, while fermions could have localized profile with left-handed and right-handed components displaced with respect to each other. We point out that with split fermions it is possible to generate Majorana neutrino masses contributing to the neutrinoless double beta decay. The almost degenerate neutrinos can also come out naturally in this case. Unlike other models of neutrino masses in extra dimensions there are no bulk fields in this scenario.Comment: 12 pages, 1 figure, revise

Spatio-temporal variability of summer monsoon rainfall over Orissa in relation to low pressure systems

The summer monsoon rainfall over Orissa occurs mostly due to low pressure systems (LPS) developing over the Bay of Bengal and moving along the monsoon trough. A study is hence undertaken to find out characteristic features of the relationship between LPS over different regions and rain-fall over Orissa during the summer monsoon season (June-September). For this purpose, rainfall and rainy days over 31 selected stations in Orissa and LPS days over Orissa and adjoining land and sea regions during different monsoon months and the season as a whole over a period of 20 years (1980-1999) are analysed. The principal objective of this study is to find out the role of LPS on spatial and temporal variability of summer monsoon rainfall over Orissa. The rainfall has been significantly less than normal over most parts of Orissa except the eastern side of Eastern Ghats during July and hence during the season as a whole due to a significantly less number of LPS days over northwest Bay in July over the period of 1980-1999. The seasonal rainfall shows higher interannual variation (increase in coefficient of variation by about 5%) during 1980-1999 than that during 1901-1990 over most parts of Orissa except northeast Orissa. Most parts of Orissa, especially the region extending from central part of coastal Orissa to western Orissa (central zone) and western side of the Eastern Ghats get more seasonal monsoon rainfall with the development and persistence of LPS over northwest Bay and their subsequent movement and persistence over Orissa. The north Orissa adjoining central zone also gets more seasonal rainfall with development and persistence of LPS over northwest Bay. While the seasonal rainfall over the western side of the Eastern Ghats is adversely affected due to increase in LPS days over west central Bay, Jharkhand and Bangladesh, that over the eastern side of the Eastern Ghats is adversely affected due to increase in LPS days over all the regions to the north of Orissa. There are significant decreasing trends in rainfall and number of rainy days over some parts of southwest Orissa during June and decreasing trends in rainy days over some parts of north interior Orissa and central part of coastal Orissa during July over the period of 1980-1999

Some characteristics of low pressure systems and summer monsoon rainfall over Orissa

The present study was undertaken to find out characteristic features like frequency, intensity, movement, region of formation, days of occurrence, etc. of synoptic disturbances such as low, depression, cyclonic storm, etc. forming over Orissa and neighbouring sea and land regions during summer monsoon season (June- September). The study is based on the data of 20 years (1980-1999). The principal objective of this study was to understand the contribution of the low pressure systems (LPS) including low, depression and cyclonic storm to interannual variability of summer monsoon rainfall over Orissa. Most of the LPS develop over northwest (NW) Bay of Bengal and move towards east Madhya Pradesh across Gangetic West Bangal (GWB) during June, July and across Orissa during August and September. The rainfall over Orissa is more related with the frequency of LPS days over Orissa and adjoining land/sea regions than with the frequencies of LPS, cyclonic disturbances (CD) and CD days over those regions. The seasonal monsoon rainfall over Orissa is significantly higher with higher frequency of LPS days over NW Bay and Orissa. It is less with higher frequency of LPS days over Jharkhand followed by west central Bay off north coastal Andhra Pradesh and Bangladesh. The frequencies of monsoon low days are higher over NW Bay and Orissa thus compensating the adverse impact of reduced CD and CD days on rainfall over Orissa in recent years. The monthly and seasonal monsoon rainfall over Orissa show no significant trends in recent years. It may be due to insignificant trends in those LPS days which are significantly correlated with rainfall over Orissa

Spatial variability of daily rainfall over Orissa, India, during the southwest summer monsoon season

Southwest summer monsoon rainfall over Orissa, a state of eastern India, shows characteristic spatial and temporal variability, due to the interaction of basic westerly flow with orography and the synoptic-scale monsoon disturbances developing over the northern Bay of Bengal and moving west-northwestwards along the monsoon trough. The aim of this study is to find out the main features of the spatial variability of daily monsoon rainfall over Orissa and associated synoptic systems. Empirical orthogonal function (EOF) analysis is a good tool to filter out the main components from any noise, and this was applied to daily monsoon rainfall (June-September) data of 31 uniformly distributed stations over a period of 20 years (1980-1999). The association of synoptic systems with significant EOFs has been confirmed by analysing daily synoptic systems over Orissa and its neighbourhood during the same period. The first three EOFs in S-mode may be attributed to good monsoon rainfall in association with low-pressure systems/cyclonic circulation (LPSC), like lows, depressions, cyclonic storms and cyclonic circulation extending up to the mid-tropospheric level over the northwest (NW) Bay/NW and the adjoining northeast (NE) Bay, over Gangetic West Bengal (GWB) and over Orissa/NW and the adjoining west central (WC) Bay. The fourth and fifth EOFs may be attributed to a weak monsoon condition being associated only with a monsoon trough without any embedded system and LPSC over the NE and the adjoining NW Bay respectively. Based on rotation of significant EOFs in T-mode, which gives better regionalization, Orissa consists of five homogeneous regions of daily monsoon rainfall: (i) eastern Orissa, (ii) western Orissa, (iii) northwest Orissa, (iv) north Orissa and (v) northeast Orissa. Eastern Orissa gets higher rainfall than the other regions, due to LPSC over NW Bay/NW and the adjoining NE Bay, western Orissa rainfall is due to LPSC over Orissa/NW and the adjoining WC Bay; likewise, northwest Orissa rainfall is due to LPSC over GWB, north Orissa rainfall is due to LPSC over the NE and the adjoining NW Bay, and northeast Orissa rainfall is due only to a monsoon trough without any significant embedded system over Orissa and adjoining land/sea areas

Masses of Fermions in Supersymmetric Models

We consider the mass generation for the usual quarks and leptons in some supersymmetric models. The masses of the top, the bottom, the charm, the tau and the muon are given at the tree level. All the other quarks and the electron get their masses at the one loop level in the Minimal Supersymmetric Standard Model (MSSM) and in two Supersymmetric Left-Right Models, one model uses triplets (SUSYLRT) to break $SU(2)_{R}$-symmetry and the other use doublets(SUSYLRD).Comment: 24 pages, 2 figures and 3 table

Leptogenesis with Left-Right domain walls

The presence of domain walls separating regions of unbroken $SU(2)_L$ and $SU(2)_R$ is shown to provide necessary conditions for leptogenesis which converts later to the observed Baryon aymmetry. The strength of lepton number violation is related to the majorana neutrino mass and hence related to current bounds on light neutrino masses. Thus the observed neutrino masses and the Baryon asymmetry can be used to constrain the scale of Left-Right symmetry breaking.Comment: References added, To appear in Praman