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1
KUMAR, J. RAJENDRA, and S. K. DASH. "Inter-annual and intra-seasonal variation of some characteristics of monsoon disturbances formed over the Bay." MAUSAM 50, no. 1 (December 17, 2021): 55–62. http://dx.doi.org/10.54302/mausam.v50i1.1804.
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The characteristics of monsoon disturbances during drought and flood years for the period 1971-96 are studied to find out their inter-annual variations. Variations of some of the characteristics of monsoon disturbances formed over Bay during 1979-88, with respect to different monsoon conditions such as strong, weak and break monsoons, are also studied. The results show that monsoon disturbance days are higher during flood years than during drought years. Drought years are associated with higher chances of low pressure areas to intensity into depressions, less westward movement, more horizontal extent, intense pressure departure from normal in comparison with flood years. However, more monsoon disturbances tilt significantly during flood years. The rainfall associated with these disturbances is highly variable and does not depend on the density, horizontal and vertical extent of the individual system. More number of lows intensify into depressions during strong monsoon conditions compared to those of weak monsoon conditions. Lows and depressions during strong monsoons have more westward movement and longer life period. Generally, very few lows form during break monsoon and none of them intensify into depression. Hence, the presence of mid-tropospheric heating during strong and weak monsoons is essential for the formation of depression. Synoptic systems which abate break monsoon condition and re-establish normal monsoon are also discussed.
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KUMAR, J. RAJENDRA, V. THAPLIYAL, and S. K. DASH. "Decadal and epochal variation of frequency and duration of monsoon disturbances and their secular relationship with rainfall over India." MAUSAM 55, no. 3 (January 19, 2022): 397–408. http://dx.doi.org/10.54302/mausam.v55i3.1171.
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Decadal and epochal variation of frequency and duration of monsoon disturbances like low pressure areas (lows), depressions and Cyclonic Storms (CS) over Indian region are studied by using 110 years (1890-1999) data. No linearly decreasing/increasing trend is observed during 110 years period in any of their frequencies. However, epochal linearly decreasing/increasing trends are noticed in decadal frequencies or duration of different monsoon disturbances. Decadal frequencies of depressions, CS and depressions are decreasing from 1970-79, till recently ended decade of 1990-99. During recent decade, less than half of the total number of depressions and CS are formed compared with 1970-79. On the other hand, total number of lows are increasing significantly from 1960-69 to recent decade, when more than double the number of lows of 1960-69 are formed.
Since Indian Summer Monsoon Rainfall (ISMR) also shows interdecadal variation of below normal and above normal phases, variation of frequencies of different monsoon disturbances and their total durations are also examined in similar time scale to understand their relationship with interdecadal variation of ISMR. Stability and secular nature of these relationships are also examined based on their decadal and 10-year moving Correlation Coefficients (CC) for the period 1890-1999. Relationship of decadal anomaly of their frequencies with interdecadal variation of ISMR shows that number of depressions and CS, are higher than the normal during the above normal ISMR decades and less during the below normal decades of ISMR. Reverse is true for the number of lows. The decadal and 10-years moving CC between ISMR and frequencies of different monsoon disturbances and total monsoon disturbance days clearly show epochal variation of their relationship in interdecadal time scale with ISMR. Hence present study shows that secular variation of CC not only exists between ISMR and its various regional and global parameters used in long range forecast of ISMR but also between ISMR and its main synoptic features e.g., monsoon disturbances.
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BHADRAM, C. V. V. "A synoptic study of active and weak southwest monsoon over Andhra Pradesh." MAUSAM 54, no. 2 (April 1, 2003): 385–92. http://dx.doi.org/10.54302/mausam.v54i2.1523.
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An attempt has been made in this study to identify the synoptic systems that cause active or vigorous monsoon conditions over the three meteorological sub-divisions of Andhra Pradesh using the data for the years 1986 to 2000. Despite significant decrease in the frequency of formation of monsoon depressions in recent years, monsoon performance is noticed to be very good. Monsoon lows and upper air cyclonic-circulations (cycirs) found to be the chief synoptic systems which activate the monsoon over the state. Typical cases of these synoptic situations are discussed.
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JENAMANI, RAJENDRA KUMAR, and S. K. DASH. "A study on the role of synoptic and semi-permanent features of Indian summer monsoon on it’s rainfall variations during different phases of El-Nino." MAUSAM 56, no. 4 (January 20, 2022): 825–40. http://dx.doi.org/10.54302/mausam.v56i4.1038.
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Characteristics of different synoptic and semi-permanent features of Indian Summer Monsoon Rainfall (ISMR), such as monsoon disturbances (lows and depressions), monsoon trough and Tibetan anticyclone and duration of monsoon, are studied individually for different phases of El-Nino during the period 1960-98 to understand why during some El-Nino single events, ISMR was deficient while during other years, ISMR was on the positive side of normal or normal. This study examines cases of El-Nino double events with deficient and near deficient ISMR in one of the two years and in both the years respectively. The cases of deficient ISMR without any El-Nino are also discussed. Emphasis has been given on the effects of the synoptic and semi-permanent features on spatial variations of ISMR.
Results show that characteristics of synoptic and semi-permanent features were important for ISMR and these were responsible for producing normal or above normal ISMR during some years in spite of El-Nino such as 1997. Also in the absence of El-Nino, ISMR was deficient because of less number of days of monsoon trough, lows and depressions, and weak Tibetan anticyclone. The reverse happened during flood years when there was no La-Nina. Statistical analysis indicates very high correlation coefficients (CCs) of these synoptic and semi-permanent features with ISMR than those of SST of Nino-3 region. India received highest monsoon rainfall during 1961 because total number of days of intense monsoon disturbances and monsoon trough and the total duration of monsoon over India during the year was the highest. This study shows that monsoon disturbances and monsoon trough are the most important components of synoptic and semi-permanent features, which affected spatial variation of ISMR in 1965 and 1966 with deficient rainfall and in 1961 and 1994 with excess rainfall over a large part of India.
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RAJAMANI, S. "Energetics of the monsoon circulation over south Asia :Part -I Diabatic heating and the generation of available potential energy." MAUSAM 36, no. 1 (April 5, 2022): 7–12. http://dx.doi.org/10.54302/mausam.v36i1.1573.
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Considering the monsoon circulation as the mean zonal flow with standing or stationary eddies (monsoon trough etc) and the transient eddies (monsoon depressions, lows etc) supermposed on it, diabatic heating and generation of available potential energy over south Asia have been computed for the typical monsoon month of July 1963, based on the computations of vertical velocity from omega-equation, and thermodynamic energy equation.
Regions of upward vertical velocity are found to be areas of good rainfall. Rate of monthly mean diabatic heating in the troposphere is of the order of 0.5 deg. C and is. higher at 500 and 300 mb levels than at lower levels. Positive generation of both zonal and standing eddy available potential energy is inferred.
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Haertel, Patrick, and William R. Boos. "Global association of the Madden-Julian Oscillation with monsoon lows and depressions." Geophysical Research Letters 44, no. 15 (August 14, 2017): 8065–74. http://dx.doi.org/10.1002/2017gl073625.
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Koteswaram, P. "Upper level 'Lows' in low latitudes in the Indian Area during SW Monsoon season and 'Breaks' in the monsoon." MAUSAM 1, no. 2 (February 9, 2022): 162–64. http://dx.doi.org/10.54302/mausam.v1i2.4559.
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MUKHERJEE, AK, and G. NATARAJAN. "Westward moving sea level low pressure systems in the south Bay of Bengal during southwest monsoon." MAUSAM 19, no. 3 (May 5, 2022): 285–88. http://dx.doi.org/10.54302/mausam.v19i3.5325.
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The movement of low pressure systems from the east, across south Bay of Bengal and south Indian Peninsula, during July and August, when the southwest monsoon has established itself over India has been studied for a 20-year period from 1946 to 1965, Only well marked systems, which could be delineated on the sea level synoptic chart, are reported In the present paper, The characteristics of these systems and its relation with other systems breaks in southwest monsoon etc are discussed.
The effect of migratory lows on rainfall has been studied for Madras State, Kerala and coastal Mysore, While Madras gets good rain with scattered heavy to very heavy falls, the rainfall over the West Coast particularly in the northern parts, is comparatively less marked.
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Yanase, Wataru, Hiroshi Niino, Shun-ichi I. Watanabe, Kevin Hodges, Matthias Zahn, Thomas Spengler, and Irina A. Gurvich. "Climatology of Polar Lows over the Sea of Japan Using the JRA-55 Reanalysis." Journal of Climate 29, no. 2 (January 7, 2016): 419–37. http://dx.doi.org/10.1175/jcli-d-15-0291.1.
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Abstract Polar lows are intense meso-α-scale cyclones that develop over the oceans poleward of the main baroclinic zone. A number of previous studies have reported polar low formation over the Sea of Japan within the East Asian winter monsoon. To understand the climatology of polar lows over the Sea of Japan, a tracking algorithm for polar lows is applied to the recent JRA-55 reanalysis. The polar low tracking is applied to 36 cold seasons (October–March) from October 1979 to March 2015. The polar lows over the Sea of Japan reach their maximum intensity on the southeastern side of the midline between the Japanese islands and the Asian continent. Consistent with previous case studies, composite analysis demonstrates that the polar low development is associated with the enhanced northerly flow on the western side of a synoptic-scale extratropical cyclone, with the cold trough in the midtroposphere and with increased heat fluxes from the sea surface. Furthermore, the present climatological study has revealed two dominant directions of motion of the polar lows: southward and eastward. Southward-moving polar lows are steered by a strong northerly flow in the lower troposphere, which is enhanced on the western side of synoptic-scale extratropical cyclones, while the eastward-moving polar lows occur within a planetary-scale westerly flow in the midlatitudes. Thus, the direction of polar low motion reflects the difference in planetary- and synoptic-scale conditions.
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MOHAPATRA, M. "Relative contribution of synoptic systems to monsoon rainfall over Orissa." MAUSAM 58, no. 1 (November 26, 2021): 17–32. http://dx.doi.org/10.54302/mausam.v58i1.1125.
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ABSTRACT. The low/depression over northwest (NW) Bay of Bengal is the largest contributor to seasonal monsoon rainfall over all stations in Orissa and Orissa as a whole. The Low Pressure Systems (LPS) and cyclonic circulation (cycir) extending upto 500 hPa level over NW Bay of Bengal alone contribute about 22% to the seasonal monsoon rainfall through about 12 days. The monsoon trough without any significant embedded systems over Orissa and adjoining regions contributes about 28% to seasonal rainfall through about 55 days. All types of LPS including low, depression and cyclonic storm yield maximum rainfall in their left forward (southwest) sectors. The maximum rainfall belt lies more southward due to a depression compared to that due to a low. The spatial distribution of rainfall due to cycir is less systematic. The interaction due to Eastern Ghat plays a significant role in spatial distribution of rainfall over western and eastern sides of the Eastern Ghat due to monsoon lows and depressions over Orissa and adjoining Bay and land regions. The orographic interaction due to Eastern Ghat with the cycirs over Orissa and adjoining Bay and land regions is significantly less leading to no significant difference in spatial distribution of rainfall over eastern and western sides of the Eastern Ghat.
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Douglas, Arthur V., and Phillip J. Englehart. "A Climatological Perspective of Transient Synoptic Features during NAME 2004." Journal of Climate 20, no. 9 (May 1, 2007): 1947–54. http://dx.doi.org/10.1175/jcli4095.1.
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Abstract This note provides a first look at a recently developed long-term climatology of transient synoptic features in northern Mexico. Key features investigated include inverted troughs, cutoff lows, cold fronts, and open troughs (westerly short waves). This 35-yr analysis of transient systems crossing northern Mexico (1967–2001) was developed to help place the summer climatology of the 2004 North American Monsoon Experiment (NAME) into a broader perspective. Inverted troughs are found to be the most commonly occurring transient synoptic feature during the monsoon with a mean frequency of occurrence of 55 days per summer season (June–September). Inverted troughs are found to contribute from 20% to 25% of the average summer rainfall observed in northern Mexico. Rainfall doubles during inverted trough days compared to days without transient systems being present. In 2004 the monsoon season was greatly shortened due to a poorly developed subtropical high. Compared to long-term means, inverted troughs contributed less rainfall to the region in 2004 and this was, in part, associated with the shortened monsoon season. In contrast, frontal penetration into the region was almost double the 35-yr mean. These climatologies are designed to provide NAME researchers with benchmarks to assess model performance relative to how these models handle these systems and their associated rainfall. The work presented is a small portion of a much larger study that aims to determine the impact of all of these rain-bearing transient systems on the monsoon in northern Mexico.
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JADHAV, S. K., and A. A. MUNOT. "Statistical study of the low pressure systems during summer monsoon season over the Indian region." MAUSAM 55, no. 1 (January 19, 2022): 15–30. http://dx.doi.org/10.54302/mausam.v55i1.853.
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The occurrence of a closed low pressure area due to low, depression or cyclonic storm is termed as Low Pressure System (LPS). LPS plays an important role in the distribution of rainfall during the southwest monsoon season. Lows produce widespread rainfall as compared to depressions and cyclonic storms which yield concentrated rainfall over a smaller area. The distribution of rainfall depends upon the track and life span of LPS. Most of the LPS formed over the Bay of Bengal travel in northwest direction strengthening the rainfall activities over the large parts of the country. In this study, the LPS formed during the monsoon season, June to September for the period 1891-2000 over the region covering India, Pakistan, Bangladesh, Bay of Bengal and Arabian Sea are taken into account. The duration of LPS is also studied in terms of LPS Days during the monsoon season. The statistical analysis of LPS and LPS Days is carried out for the monsoon months and for the monsoon season as a whole, for the period 1891-2000. It is seen that the frequency of LPS during any of the monsoon months does not exceed six but three LPS in a month are more common. Total number of LPS during the monsoon season ranges from 9 to 18. In June and July maximum total duration of LPS lies between 10-14 LPS Days while in August and September, it is between 15-19 LPS Days. August is the month having maximum number of LPS and LPS Days. The frequency analysis shows that monthly and seasonal LPS and LPS Days are normally distributed. It is also observed that even though season's total number of LPS has no significant increase or decrease, the LPS Days have significantly increased during the decades, 1971-80 and 1981-90.
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JOSHI, P. C., B. SIMON, and P. K. THAPLIYAL. "Satellite estimated water vapour in relation to Asian monsoon Circulation." MAUSAM 52, no. 1 (December 29, 2021): 109–16. http://dx.doi.org/10.54302/mausam.v52i1.1681.
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Water vapour plays a crucial role in various exchange and transport processes in the atmosphere and its knowledge in the tropics is extremely important for input to various global circulation models. The vast oceans of earth's surface provide a large source of moisture and continuously modify the thermodynamics of the atmosphere through latent heat flux and condensational heating. In the tropics, especially in the Indian ocean the water vapour is highly heterogeneousin nature, and is one of the parameters which is responsible for cloud formation, associated with tropical systems like monsoon flows, depression, cyclones etc. The present paper reviews the various information’s available from deferent geostationary and polar orbiting satellites about water vapour affecting the southwest monsoon region around the Indian Ocean and Indian subcontinent.
The temperature and moisture data from TIROS operational vertical sounder (TOVS) and INSAT-2E water vapour channel are examined to study water vapour distribution. Their usefulness in characterizing the Asian south-west (SW) monsoon circulation is focused. The Western Indian ocean showed an increase in mid-tropospheric moisture (700-500hPa) over about 8 to 10 days prior to the onset over Kerala coast. NOAA/TOVS layer tmperature and humidity is used to extrapolate the humidity profile at standard pressure levels. It is also used to compute latent and sensible heat flux. Total integrated water vapour from SSM/I is also used for estimating latent heat fluxes and for the diagnostics of NWP models. Recently, INSAT-2E water vapour channel was used to monitor the monsoon circiulation features. The new WV channel brought out clearly the feeding of various air masses, especially water vapour associated with monsoon onset and monsoon lows.
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Khan, Saifullah, and Mahmood Ul Hasan. "Evapotranspiration Distribution and Variation of Pakistan (1931-2015)." Annals of Valahia University of Targoviste, Geographical Series 17, no. 2 (October 1, 2017): 184–97. http://dx.doi.org/10.1515/avutgs-2017-0017.
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AbstractEvapotranspiration is the main element of aridity and desertification and to balance the natural hydrological processes. Pakistan has a high degree of evapotranspiration, as it is in subtropical belt, with long sunshine duration and low cloudiness in summers. June is the warmest month, when the evapotranspiration exceeds 7mm (0.28inches), whereas, January is the coldest month, when evapotranspiration of the country falls to 1mm (0.04inches). The maximum evapotranspiration has been recorded at the southern latitudes of the country (Hyderabad and Jacobabad), while it decreases towards northwest (mountainous region) and Gilgit-Baltistan (Astore and Skardu). This variation in evapotranspiration is due to fluctuation in temperature, precipitation, sunshine duration, wind speed, relative humidity, physical relief and latitudinal as well as altitudinal extend of the country. The average evapotranspiration of Pakistan is 4.5mm with an increase of 1.0mm during 1931-2015. In winter and summer season, the lower Indus basin, has recorded high evapotranspiration as compared to the northern mountainous region. The average evapotranspiration of Pakistan during winter season is 2.7mm, while in summer it is 6.3mm. This variation is due to the variation in the length of day and night, humidity, precipitation, surface pressure, wind speed, and topography of the land. During cold season the average evapotranspiration of the country is 13.7mm, pre-monsoon season 17.1mm, monsoon season 15.8mm and post monsoon season 8mm. Obviously, the highest evapotranspiration of Pakistan has recorded during pre-monsoon season with extreme temperature, scarce precipitation, long sunshine duration, lowest relative humidity, low pressure, and calm winds and chilly condition. Furthermore, during cold (0.1mm), pre-monsoon (3.5mm), and monsoon season (2.2mm) the evapotranspiration shows an increase, where as it reveals a negative deviation of -5.6mm in post monsoon season due to increase in the precipitation from reversible monsoon lows at the southern latitudes of the country. Generally, the evapotranspiration of Pakistan increases from northwest to southeast and a main agent of delimitation of the arid region of the country. The main factors that cause variation in the evapotranspiration of the country from south towards north are temperature, precipitation, sunshine duration, relative humidity, surface pressure, wind speed, fogs, cloudiness, topography, latitudinal and altitudinal extend of the country that required further research.
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Davidson, Noel E. "Vorticity Budget for AMEX. Part II: Simulations of Monsoon Onset, Midtropospheric Lows, and Tropical Cyclone Behavior." Monthly Weather Review 123, no. 6 (June 1995): 1636–59. http://dx.doi.org/10.1175/1520-0493(1995)123<1636:vbfapi>2.0.co;2.
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Molinari, John, and David Vollaro. "Development of a One-Month-Long, Westward-Propagating Subtropical Low in Boreal Summer." Monthly Weather Review 146, no. 1 (January 1, 2018): 231–42. http://dx.doi.org/10.1175/mwr-d-17-0127.1.
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Abstract A strong MJO event produced an upper-tropospheric jet streak in northeast Asia and repeated wave breaking in the jet exit region along 150°E during July 1988. A midlatitude low moved equatorward and intensified in the presence of bandpass-filtered (15–100 day) Q vector forcing for upward motion associated with the wave breaking. This forced ascent helped to moisten the atmosphere enough to increase the column water vapor to above 55 mm. This value was sufficiently large to support a self-sustaining low even after the upper forcing weakened. The horizontal scale of the Q vector forcing was about 1500 km, consistent with the scale of most favorable convective response to quasigeostrophic forcing in the subtropics described by Nie and Sobel. The low lasted one month as it moved southwestward, then westward, while remaining north of 20°N. Maximum precipitation along the track of the low exceeded 700 mm, with an anomaly more than 400 mm. A climatology of long-lasting lows was carried out for the monsoon gyre cases studied previously. During El Niño, long-lasting lows often began near the equator in the central Pacific, and were likely to have a mixed Rossby–gravity wave or equatorial Rossby wave structure. It is speculated that the quasi-biweekly mode, the submonthly oscillation, the 20–25-day mode, and the Pacific–Japan pattern are each variations on this kind of event. During La Niña, long-lasting lows that originated in midlatitudes were more common. It is argued that these lows from midlatitudes represent a unique disturbance type in boreal summer.
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Hunt, Kieran M. R., Andrew G. Turner, and Len C. Shaffrey. "Extreme Daily Rainfall in Pakistan and North India: Scale Interactions, Mechanisms, and Precursors." Monthly Weather Review 146, no. 4 (April 2018): 1005–22. http://dx.doi.org/10.1175/mwr-d-17-0258.1.
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While much of India is used to heavy precipitation and frequent low pressure systems during the summer monsoon, toward the northwest and into Pakistan, such events are uncommon. Here, as much as a third of the annual rainfall is delivered sporadically during the winter monsoon by western disturbances. Such events of sparse but heavy precipitation in this region of typically mountainous valleys in the north and desert in the south can be catastrophic, as in the case of the Pakistan floods of July 2010. In this study, extreme precipitation events (EPEs) in a box approximately covering this region (25°–38°N, 65°–78°E) are identified using the APHRODITE gauge-based precipitation product. The role of the large-scale circulation in causing EPEs is investigated: it is found that, during winter, it often coexists with an upper-tropospheric Rossby wave train that has prominent anomalous southerlies over the region of interest. These winter EPEs are also found to be strongly collocated with incident western disturbances whereas those occurring during the summer are found to have a less direct relationship. Conversely, summer EPEs are found to have a strong relationship with tropical lows. A detailed Lagrangian method is used to explore possible sources of moisture for such events and suggests that, in winter, the moisture is mostly drawn from the Arabian Sea, whereas during the summer, it comes from along the African coast and the Indian monsoon trough region.
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SAHA, KSHUDIRAM, and SURANJANA SAHA. "On the monsoons of South America Part 2 : Interaction with extratropical disturbances and formation of tropical depressions and upper-tropospheric cyclonic vortices." MAUSAM 55, no. 2 (January 19, 2022): 237–56. http://dx.doi.org/10.54302/mausam.v55i2.1080.
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The paper reveals a stationary wave structure of the heat low circulation over South America during the southern summer and discusses how the stationary wave may interact with eastward-propagating extratropical disturbances of the two hemispheres. The interactions appear to explain several observed features of the continent’s weather and climate. In particular, they appear to lead to formation of westward-propagating tropical disturbances, such as monsoon lows and depressions and upper-tropospheric cyclonic vortices. The origin, structure, development and movement of these disturbances are discussed. The paper also looks into the nature and structure of the South Atlantic Convergence Zone (SACZ) and discusses its interaction with the extratropical disturbances of the southern hemisphere.
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Krishnamurthy, V., and J. Shukla. "Intraseasonal and Seasonally Persisting Patterns of Indian Monsoon Rainfall." Journal of Climate 20, no. 1 (January 1, 2007): 3–20. http://dx.doi.org/10.1175/jcli3981.1.
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Abstract The space–time structure of the active and break periods of the Indian monsoon has been studied using 70-yr-long high-resolution gridded daily rainfall data over India. The analysis of lagged composites of rainfall anomalies based on an objective categorization of active and break phases shows that the active (break) cycle, with an average life of 16 days, starts with positive (negative) rainfall anomalies over the Western Ghats and eastern part of central India and intensifies and expands to a region covering central India and parts of north India during the peak phase, while negative (positive) anomalies cover the sub-Himalayan region and southeast India. During the final stage of the active (break) period, the positive (negative) rainfall anomalies move toward the foothills of the Himalayas while peninsular India is covered with opposite sign anomalies. The number of days on which lows and depressions are present in the region during active and break periods is consistent with the rainfall analysis. The number of depressions during the active phase is about 7 times that during the break phase. Using multichannel singular spectrum analysis of the daily rainfall anomalies, the seasonal monsoon rainfall is found to consist of two dominant intraseasonal oscillations with periods of 45 and 20 days and three seasonally persisting components. The 45- and 20-day oscillations are manifestations of the active and break periods but contribute very little to the seasonal mean rainfall. The seasonally persisting components with anomalies of the same sign, and covering all of India, have a very high interannual correlation with the total seasonal mean rainfall. These results support a conceptual model of the interannual variability of the monsoon rainfall consisting of seasonal mean components and a statistical average of the intraseasonal variations. The success in the prediction of seasonal mean rainfall depends on the relative strengths of the seasonally persisting components and intraseasonal oscillations.
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Hatsuzuka, Daisuke, and Hatsuki Fujinami. "Effects of the South Asian Monsoon Intraseasonal Modes on Genesis of Low Pressure Systems over Bangladesh." Journal of Climate 30, no. 7 (April 2017): 2481–99. http://dx.doi.org/10.1175/jcli-d-16-0360.1.
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The quasi-biweekly oscillation (QBW) is a dominant intraseasonal mode in summer rainfall over Bangladesh. Active phases of the QBW are often accompanied by low pressure systems (LPSs) such as vortex-type lows. This study investigated the effects of two intraseasonal modes, the QBW and the boreal summer intraseasonal oscillation (BSISO), on the genesis of LPSs over Bangladesh during 29 summer monsoon seasons. Daily lag composites of convection and low-level atmospheric circulation were constructed for active-phase cases with LPSs (LPS case) and without LPSs (non-LPS case) based on rainfall in the QBW over Bangladesh. In the QBW mode, a westward propagation of an anticyclonic anomaly from the western Pacific to the Bay of Bengal (BoB) is common in both cases. However, the anticyclonic center in the LPS case is located slightly to the east of that in the non-LPS case, which results in stronger cyclonic vorticity over and around Bangladesh. In contrast, the BSISO mode shows an opposite phase between the two cases: a cyclonic (anticyclonic) anomaly propagating northward from the equator to the BoB in the LPS case (non-LPS case). In the LPS case, the cyclonic anomaly in the BSISO mode enhances the westerly (easterly) flow over the BoB (Bangladesh) in the active phase, resulting in the enhancement of cyclonic vorticity over the northern BoB and Bangladesh, in cooperation with the QBW mode. These results suggest that both the QBW and BSISO modes have significant influence on the environmental conditions for LPS genesis over Bangladesh.
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Grimm, Alice M., and C. J. C. Reason. "Intraseasonal Teleconnections between South America and South Africa." Journal of Climate 28, no. 23 (December 1, 2015): 9489–97. http://dx.doi.org/10.1175/jcli-d-15-0116.1.
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Abstract Teleconnection of climate anomalies between various parts of the tropics and extratropics is a well-established feature of the climate system. Building on previous work showing that a teleconnection exists between the South American monsoon system and interannual summer rainfall variability over southern Africa, this study considers intraseasonal variability over these landmasses. It is shown that strong teleconnections exist between South African daily rainfall and that over various areas of South America, with the latter leading by 4–5 days, for both winter and summer, involving regions with strong rainfall in these seasons. During the summer, the mechanisms involve both a modulation of the local Walker cell as well as extratropical Rossby wave trains. For winter, the latter mechanism is more important. While in summer tropical convective anomalies over South America play an important role, in winter the subtropics become more important. In both cases, these modulations lead to regional changes in circulation over southern Africa that are favorable for the dominant synoptic rainfall-producing weather systems such as cutoff lows and tropical extratropical cloud bands.
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Zhang, Kun, Feifei Wang, Ningquan Weng, Xiaoqing Wu, Xuebin Li, and Tao Luo. "Optical Turbulence Characteristics in the Upper Troposphere–Lower Stratosphere over the Lhasa within the Asian Summer Monsoon Anticyclone." Remote Sensing 14, no. 16 (August 21, 2022): 4104. http://dx.doi.org/10.3390/rs14164104.
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The high elevation, complex topography, and unique atmospheric circulations of the Tibetan Plateau (TP) make its optical turbulence characteristics different from those in low-elevation regions. In this study, the characteristics of the atmospheric refractive index structure constant (Cn2) profiles in the Lhasa area at different strength states of the Asian summer monsoon anticyclone (ASMA) are analyzed based on precious in situ sounding data measured over the Lhasa in August 2018. Cn2 in the upper troposphere–lower stratosphere fluctuates significantly within a few days during the ASMA, particularly in the upper troposphere. The effect of the ASMA on Cn2 varies among the upper troposphere, tropopause, and lower stratosphere. The stronger and closer the ASMA is to Lhasa, the more pronounced is the “upper highs and lower lows” pressure field structure, which is beneficial for decreasing the potential temperature lapse rate. The decrease in static stability is an important condition for developing optical turbulence, elevating the tropopause height, and reducing the tropopause temperature. However, if strong high-pressure activity occurs at the lower pressure layer, such as at 500 hPa, an “upper highs and lower highs” pressure field structure forms over the Lhasa, increasing the potential temperature lapse rate and suppressing the convective intensity. Being almost unaffected by low-level atmospheric high-pressure activities, the ASMA, as the main influencing factor, mainly inhibits Cn2 in the tropopause and lower stratosphere. The variations of turbulence intensity in UTLS caused by ASMA activities also have a great influence on astronomical parameters, which will have certain guiding significance for astronomical site testing and observations.
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Chen, Tsing-Chang. "Characteristics of Summer Stationary Waves in the Northern Hemisphere." Journal of Climate 23, no. 17 (September 1, 2010): 4489–507. http://dx.doi.org/10.1175/2010jcli3149.1.
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Abstract Summer stationary waves in the Northern Hemisphere are separated by a midlatitude transition zone into the subtropical monsoon regime with a vertical phase reversal and the subarctic regime with a vertically uniform structure. The dynamics and maintenance mechanism of the subtropical stationary waves have been investigated in the context of monsoon circulation. Depicted in terms of streamfunction with 40-yr ECMWF Re-Analysis (ERA-40), the dynamic characteristics of stationary waves in the transition zone and the subarctic region are thus the focus of this study. The dynamics and maintenance mechanism of these waves were explored with the streamfunction budget and the velocity potential maintenance equations. Stationary waves across the transition region consist of anticyclonic shear zones over the North Pacific and North Atlantic and a cyclonic shear zone in east Eurasia. These transition elements are linked to subtropical oceanic anticyclones and continental thermal lows. At high latitudes, a three-wave structure emerges with a weak central Eurasian trough aligned with two deep oceanic troughs. A longitudinal phase change occurs across the transition zone, but the direction of the east–west circulation associated with the transitional anticyclonic (cyclonic) zone is the same as that of the subtropical trough (high). This phase change is caused by the dynamics transition from the Sverdrup regime to the Rossby regime because of the increasing importance of relative vorticity advection. At high latitudes, relative vorticity advection becomes the dominant dynamic process in the upper atmosphere, but is negligible in the lower troposphere. This subarctic dynamic regime results in the vertically uniform structure of stationary waves. These waves are maintained by in situ diabatic heating (cooling) ahead of three subarctic troughs (ridges). Thus, the structure of the east–west circulation of subarctic stationary waves is opposite to that of subtropical stationary waves. These findings not only disclose more detailed structure and dynamics of summer stationary waves, but also provide a more complete basis to validate summer climate simulations and to search for the cause of interannual variation in summer climate.
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Dixon, Ross D., Anne Sophie Daloz, Daniel J. Vimont, and Michela Biasutti. "Saharan Heat Low Biases in CMIP5 Models." Journal of Climate 30, no. 8 (April 2017): 2867–84. http://dx.doi.org/10.1175/jcli-d-16-0134.1.
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Representing the West African monsoon (WAM) is a major challenge in climate modeling because of the complex interaction between local and large-scale mechanisms. This study focuses on the representation of a key aspect of West African climate, namely the Saharan heat low (SHL), in 22 global climate models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) multimodel dataset. Comparison of the CMIP5 simulations with reanalyses shows large biases in the strength and location of the mean SHL. CMIP5 models tend to develop weaker climatological heat lows than the reanalyses and place them too far southwest. Models that place the climatological heat low farther to the north produce more mean precipitation across the Sahel, while models that place the heat low farther to the east produce stronger African easterly wave (AEW) activity. These mean-state biases are seen in model ensembles with both coupled and fixed sea surface temperatures (SSTs). The importance of SSTs on West African climate variability is well documented, but this research suggests SSTs are secondary to atmospheric biases for understanding the climatological SHL bias. SHL biases are correlated across the models to local radiative terms, large-scale tropical precipitation, and large-scale pressure and wind across the Atlantic, suggesting that local mechanisms that control the SHL may be connected to climate model biases at a much larger scale.
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Berry, Gareth, Michael J. Reeder, and Christian Jakob. "Physical Mechanisms Regulating Summertime Rainfall over Northwestern Australia." Journal of Climate 24, no. 14 (July 15, 2011): 3705–17. http://dx.doi.org/10.1175/2011jcli3943.1.
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Abstract Summertime (December–February) rainfall over northwestern Australia has increased significantly since the middle of the twentieth century. As a prerequisite to understanding the observed trend, this investigation examines the broad characteristics of rainfall and identifies the physical mechanisms by which rainfall in the region is initiated. This is achieved using a combination of in situ, spaceborne, and numerical reanalysis datasets. Hourly pluviograph data and the Tropical Rainfall Measuring Mission (TRMM)-3B42 dataset show distinctly different diurnal cycles of rainfall in different geographical subregions; near the coast, rainfall rates peak in the midafternoon, whereas inland (near the maximum rainfall trend) the rainfall rate is largest overnight. These data also indicate that most of the summertime rain falls in events lasting 2–5 days. Analysis of the ECMWF Re-Analysis (ERA-Interim) demonstrates that convergence into the continental heat low controls the diurnal cycle of rainfall but cannot explain the synoptic variability. Composites of wet and dry conditions from ERA-Interim expose synoptic-scale differences in the environmental flow. Prior to rain falling in the interior of northwestern Australia, there is a distinct shift in the origins of low-level air parcels, such that air with high convective available potential energy is advected from the tropical maritime regions, rather than from over the continent. Preliminary analysis suggests that these flow changes may be linked to transient synoptic disturbances such as midlatitude cyclones and monsoon lows. Rather than reflecting a large-scale change in the ocean state, these results imply that the observed increase in rainfall may be linked more closely to changes in the synoptic weather systems.
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Quadir, Dewan Abdul, Towhida Rashid, Shammi Akhter, and MN Ahasan. "Investigation of Meteorological Conditions Favourable for Formation of Thunderstorm Occurred Over Bangladesh Through Simulation by WRF-ARW Model." Dhaka University Journal of Science 68, no. 1 (January 30, 2020): 71–77. http://dx.doi.org/10.3329/dujs.v68i1.54599.
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Investigation of meteorological conditions favorable for formation of pre-monsoon thunderstorm over Bangladesh has been conducted by simulating a selected thunderstorm case using ARW dynamic core of WRF model (WRF-ARW). A multi-cell thunderstorm formed on 30-03-2018 over the northwestern tip of Bangladesh and adjacent territories of India and moved south-southeast wards with its highest development at 09:30 UTC was selected for this study. The chosen case of thunderstorm has 3 distinct cells of which 2 cells have the width of over 100 km each and the third one located in the eastern Bangladesh and had the width of 50 km. A WRF ARW model has been applied to examine the atmospheic characteristics favorabe for genesis of selected case run in a double nested domain of resolution of 9x9 km2 in the outer domain and 3 3 km2in the inner domain. The analysis of the geopotential height field of 925 hPa level generated by WRF model at different hours of 31 March 2018 clearly indicates favourable condition with pockets of micro lows and their progression towards central to southeastern Bangladesh. The strong winds blowing from Bay of Bengal along an anticyclone over the Bay brings sufficient moisture to the north. The southerly winds meet the easterly and also westerly winds providing strong low level convergence which favors the convective activities forming cumulus cells. The orography of foothills may also enhance the convections. The wind in the upper tropospheric winds attains jet speed over these areas. The distribution of divergence and vorticity in the 925 hPa level shows the evolution of system. The distribution of precipitation shows that the spatial patterns were well captured. Vertical velocity has been plotted along the vertical-horizontal plane oriented in the east-west direction across a high rainfall cell. This shows that the highest development of narrow vertical cell extends up to 100 hPa level. Following the temporal evolution of the system, it is seen that the highest development delayed by around 2 hours. Some mitigation strategies in respect of thunderstorms and associated lighting are also discussed.
Dhaka Univ. J. Sci. 68(1): 71-77, 2020 (January)
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Minobe, Shoshiro, Akinori Sako, and Makoto Nakamura. "Interannual to Interdecadal Variability in the Japan Sea Based on a New Gridded Upper Water Temperature Dataset." Journal of Physical Oceanography 34, no. 11 (November 1, 2004): 2382–97. http://dx.doi.org/10.1175/jpo2627.1.
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Abstract A new gridded water temperature dataset of upper 400-m depths (0, 50, 100, 200, 300, and 400 m) for the Japan Sea (or East Sea) is produced by using an optimal interpolation technique from 1930 to 1996, based on oceanographic observations collected in the World Ocean Database 1998. The temperature data are analyzed by a complex empirical orthogonal function (CEOF) with six levels combined using the data for a period from 1957 to 1996, during which most of gridded data are available. Before calculating the CEOFs, low-pass or high-pass filters (cutoff period at 7 yr) are applied to separate interannual and decadal temperature changes, respectively. One interannual and two decadal CEOF modes are identified. The interannual first CEOF mode is characterized by the energetic variability around and south of the subpolar front in the western Japan Sea, accompanied by northward and northeastward phase propagations emanating from the Tsushima Strait. The decadal first CEOF mode exhibits a broad structure prevailing over the whole Japan Sea, but large amplitudes are trapped by the subpolar front, with 60°–90° phase lags between the northeastern and southwestern Japan Sea. The decadal second CEOF mode has a localized structure with strong correlations in the Yamato Basin. The relation between the atmosphere and ocean is analyzed by a correlation analysis of wintertime sea level pressures (SLPs) onto the temporal coefficients of the CEOF modes. The interannual first CEOF mode is accompanied by the SLP anomalies over the western North Pacific Ocean with steep SLP gradients over the Japan Sea, suggesting that this mode is forced by local wind anomalies associated with the SLP changes over the western North Pacific. The decadal first CEOF mode is likely to be caused by changes of the east Asian winter monsoon due to the SLP variability of the northern part of the Siberian high, which is closely associated with the decadal fluctuations of the Arctic Oscillation and the North Atlantic Oscillation. The second decadal CEOF mode is accompanied by high SLP correlations over the central North Pacific associated with strength changes of Aleutian lows, suggestive of remote forcing from the central North Pacific.
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Tan, Liangcheng, Yanzhen Li, and Wenxia Han. "A Paleoclimate Prognosis of the Future Asian Summer Monsoon Variability." Atmosphere 12, no. 11 (October 23, 2021): 1391. http://dx.doi.org/10.3390/atmos12111391.
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In recent years, more and more record-breaking extreme weather/climate events have been reported from the Asian monsoon region, which have caused tremendous loss of property and lives. In this paper, we analyzed the Asian summer monsoon (ASM) variability during the Holocene and evaluated future climate extremes in monsoonal China from a paleoclimatic view. We found a significant regime transition to more chaotic fluctuations, with enhanced decadal variability of the ASM since 6.6 ka BP. We suggested the gradual intensification of ENSO was responsible for enhancing the ASM variability since the late mid-Holocene. If the observed relationship of monsoon mean intensity, ENSO and decadal variability of the ASM in the past 11.2 ka continue to exist, enhanced decadal variability of ASM in the future warming world will be expected. As a result, the intensification of daily precipitation extremes, superimposed on enhanced decadal variability of ASM, might make the record-breaking extremes more frequent in the future, increasing the risk of climate-related disasters in China.
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S. N. PANDEY, R. BHATLA, MANOJ K. SRIVASTAVA, and R. K. MALL. "Floods and hazardous heavy rainfall in India: Comparison between local versus oceanic impact." Journal of Agrometeorology 12, no. 1 (June 1, 2010): 40–43. http://dx.doi.org/10.54386/jam.v12i1.1265.
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India, leading to heavy rainfall. Such heavy rainfall result in floods for wider region of northern India, and, which, finally, causes loss of agriculture, human and animal’s life, outbreak of diseases/ epidemics, and thus affecting national economy. An attempt has therefore, been made to analyze the disastrous events that occurred in the summer monsoon months over different states in India for the period 1981-2000. The analyses included the raining event which were active, but, caused due to- or without the monsoonal-systems that were formed in north Indian Ocean. Results showed that West Bengal was the mostly affected state during monsoon season, where both, local as well as monsoonal systems were equally responsible for heavy rainfall/ flood events. The local atmospheric phenomenon affected highly to Uttar Pradesh, West Bengal, Gujarat, and Maharashtra, whereas for systems that were associated with the north Indian Ocean and Bay of Bengal, the states of West Bengal and Orissa were the mostly affected states. From the study, it may be concluded that all the heavy rainfall related disastrous weather events formed over different states in India was not only due to systems developed over Oceans, rather, local atmospheric phenomena had equally important contributor of similar affects, particularly for northern and western India.
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Gupta, Raj, DK Benbi, and IP Abrol. "Indian Agriculture needs a Strategic Shift for Improving Fertilizer Response and Overcome Sluggish Foodgrain Production." Journal of Agronomy Research 4, no. 3 (December 25, 2021): 1–16. http://dx.doi.org/10.14302/issn.2639-3166.jar-21-4018.
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In India, loss of fertility through soil erosion is primarily a summer monsoons mediated phenomenon. Reversing the land degradation processes contribute to water availability, soil fertility maintenance, adapting to climate change and overall food security. Whereas kharif (monsoon/rainy season crop) foodgrain production largely depends on summer monsoons, the rabi season (post-rainy season/winter crop) rainfall is too little to exert a direct influence. In spite of larger acreage under kharif foodgrain crops, total fertiliser consumption during kharif and rabi seasons is comparable. Negative rainfall anomalies (deficit) adversely affected total fertiliser consumption and their use efficiency. Despite significant differences in fertiliser application rates, the response to applied fertiliser nutrients is almost similar in the two seasons. This implies that nutrient use efficiency (NUE) has a ‘manageable’ and an ‘unmanageable’ component wherein 4R practices are difficult to implement under unfavourable kharif weather conditions. Partial factor productivity of fertilizer nutrients (PFPF) has continuously declined over decades mainly because of depletion of soil organic carbon, imbalanced use of nutrients and inability to maintain soil moisture supplies. These observations plus yield-gap analysis permitted us to conclude that past trends of declining NUE can only be reversed through a shift either in sustainable land management practices or enhancing the genetic yield potential/ biomass of crop cultivars or by combining both and making kharif crop planting independent of monsoons rains through direct dry seeding.
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Rao, B. V. Mohana, A. Mani, B. Sarojini Devi, S. Vishnuvardhan, and Ch Sujani Rao. "Spatial and Temporal Variations of Land Use and Land Cover In Kadiri Watershed Using Rs & Gis Techniques." International Journal of Plant & Soil Science 35, no. 15 (June 8, 2023): 23–31. http://dx.doi.org/10.9734/ijpss/2023/v35i153069.
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The change detection and land use and land cover (LULC) maps are more important powerful forces behind numerous ecological systems and fallow land. It is widely known that land use/land cover (LULC) changes significantly alter watershed hydrology and sediment yields. The impact, especially on erosion and sedimentation, is likely to be exacerbated in regions dominated by high rainfall patterns such as monsoons. RS & GIS technologies are very useful to determine the LULC changes. Present research area Kadiri Watershed of Anantapur district of Andhra Pradesh, India, drains an area about 240 km2 including 15 villages. The average annual rainfall in this area varies between 600mm to 700mm in which 60%, 35% and 5% of total rainfall occurs in South-West (S-W),North-East (N-E) and in Summer seasons respectively. The current research focuses on demarcating the spatiotemporal LULC changes. These effects directly affect the ecosystem, land resources, cropping pattern and agriculture. LULC assessment and surveillance are essential for long-term planning and sustainable use of natural resources. The LULC maps were prepared for the study area using Landsat-5, Senthinel 2 images pertaining to pre-monsoon and post-monsoon seasons of 2013, 2017 and 2021. Variations in the extents of agriculture, plantations, scrubs, water bodies, open lands, and built-up areas were noted during these years in the pre-monsoon season, and they ranged from 22 to 35 and 43%, 2 to 3 and 5%, 22 to 28%, 1 to 4%, 52 to 29 and 15%, as well as 1 to 5%, respectively. Similar fluctuations were seen in the post-monsoon season, where they ranged from 29 to 40 and 47%, 3 to 7%, 33 to 30%, 2 to 4%, 32 to 20 and 7%, as well as 1 to 5%. Kadiri watershed, an agriculturally dominant area, has seen an increase in cultivated land due to the conversion of fallow land and open scrub into cropland as a result of good rainfall received during the south-west monsoon during in assessment years and implementation of watershed development activities. These findings highlight the potential impacts of LULC changes in a monsoon-dominated watershed and may contribute to the development of successful LULC-based watershed management strategies for prevention of flooding and sediment loss.
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Sadhwani, Kashish, T. I. Eldho, Manoj K. Jha, and Subhankar Karmakar. "Effects of Dynamic Land Use/Land Cover Change on Flow and Sediment Yield in a Monsoon-Dominated Tropical Watershed." Water 14, no. 22 (November 14, 2022): 3666. http://dx.doi.org/10.3390/w14223666.
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It is widely known that land use/land cover (LULC) changes significantly alter watershed hydrology and sediment yields. The impact, especially on erosion and sedimentation, is likely to be exacerbated in regions dominated by high rainfall patterns such as monsoons. This study analyzed the hydrological responses of LULC changes in terms of streamflow (SF) and sediment yield (SY) in a monsoon-dominated tropical watershed, the Periyar River Watershed (PRW) in Kerala, India. This watershed drains an area of 4793 km2 characterized by an average monsoon rainfall of 2900 mm from June to November. The watershed hydrology and sediment dynamics were simulated using the Soil and Water Assessment Tool (SWAT) model for the impact assessment at the watershed outlet and the sub-watershed level. Historical LULC data were analyzed for 1988, 1992, 2002, and 2016 using the maximum likelihood method, and future LULC changes were projected for 2030, 2050, 2075, and 2100 using the Markov chain–cellular automata technique. Between 1988 and 2016, the urban area increased by 4.13 percent, while plantation and forest coverage decreased by 1.5 percent. At this rate, by 2100, the urban area is expected to grow by 16.45% while plantations and forest area will shrink by 13.7% compared to 1988. The effects of these changes on SF and SY were found to be minimal at the watershed outlet; however, at the spatial scale of sub-watersheds, the changes varied up to 70% for surface runoff and 200% for SY. These findings highlight the potential impacts of LULC changes in a monsoon-dominated watershed and may contribute to the development of successful LULC-based watershed management strategies for prevention of flooding and sediment loss.
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Mahata, Khadak Singh, Maheswar Rupakheti, Arnico Kumar Panday, Piyush Bhardwaj, Manish Naja, Ashish Singh, Andrea Mues, et al. "Observation and analysis of spatiotemporal characteristics of surface ozone and carbon monoxide at multiple sites in the Kathmandu Valley, Nepal." Atmospheric Chemistry and Physics 18, no. 19 (October 5, 2018): 14113–32. http://dx.doi.org/10.5194/acp-18-14113-2018.
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Abstract. Residents of the Kathmandu Valley experience severe particulate and gaseous air pollution throughout most of the year, even during much of the rainy season. The knowledge base for understanding the air pollution in the Kathmandu Valley was previously very limited but is improving rapidly due to several field measurement studies conducted in the last few years. Thus far, most analyses of observations in the Kathmandu Valley have been limited to short periods of time at single locations. This study extends the past studies by examining the spatial and temporal characteristics of two important gaseous air pollutants (CO and O3) based on simultaneous observations over a longer period at five locations within the valley and on its rim, including a supersite (at Bode in the valley center, 1345 m above sea level) and four satellite sites: Paknajol (1380 m a.s.l.) in the Kathmandu city center; Bhimdhunga (1522 m a.s.l.), a mountain pass on the valley's western rim; Nagarkot (1901 m a.s.l.), another mountain pass on the eastern rim; and Naikhandi (1233 m a.s.l.), near the valley's only river outlet. CO and O3 mixing ratios were monitored from January to July 2013, along with other gases and aerosol particles by instruments deployed at the Bode supersite during the international air pollution measurement campaign SusKat-ABC (Sustainable Atmosphere for the Kathmandu Valley – endorsed by the Atmospheric Brown Clouds program of UNEP). The monitoring of O3 at Bode, Paknajol and Nagarkot as well as the CO monitoring at Bode were extended until March 2014 to investigate their variability over a complete annual cycle. Higher CO mixing ratios were found at Bode than at the outskirt sites (Bhimdhunga, Naikhandi and Nagarkot), and all sites except Nagarkot showed distinct diurnal cycles of CO mixing ratio, with morning peaks and daytime lows. Seasonally, CO was higher during premonsoon (March–May) season and winter (December–February) season than during monsoon season (June–September) and postmonsoon (October–November) season. This is primarily due to the emissions from brick industries, which are only operational during this period (January–April), as well as increased domestic heating during winter, and regional forest fires and agro-residue burning during the premonsoon season. It was lower during the monsoon due to rainfall, which reduces open burning activities within the valley and in the surrounding regions and thus reduces sources of CO. The meteorology of the valley also played a key role in determining the CO mixing ratios. The wind is calm and easterly in the shallow mixing layer, with a mixing layer height (MLH) of about 250 m, during the night and early morning. The MLH slowly increases after sunrise and decreases in the afternoon. As a result, the westerly wind becomes active and reduces the mixing ratio during the daytime. Furthermore, there was evidence of an increase in the O3 mixing ratios in the Kathmandu Valley as a result of emissions in the Indo-Gangetic Plain (IGP) region, particularly from biomass burning including agro-residue burning. A top-down estimate of the CO emission flux was made by using the CO mixing ratio and mixing layer height measured at Bode. The estimated annual CO flux at Bode was 4.9 µg m−2 s−1, which is 2–14 times higher than that in widely used emission inventory databases (EDGAR HTAP, REAS and INTEX-B). This difference in CO flux between Bode and other emission databases likely arises from large uncertainties in both the top-down and bottom-up approaches to estimating the emission flux. The O3 mixing ratio was found to be highest during the premonsoon season at all sites, while the timing of the seasonal minimum varied across the sites. The daily maximum 8 h average O3 exceeded the WHO recommended guideline of 50 ppb on more days at the hilltop station of Nagarkot (159 out of 357 days) than at the urban valley bottom sites of Paknajol (132 out of 354 days) and Bode (102 out of 353 days), presumably due to the influence of free-tropospheric air at the high-altitude site (as also indicated by Putero et al., 2015, for the Paknajol site in the Kathmandu Valley) as well as to titration of O3 by fresh NOx emissions near the urban sites. More than 78 % of the exceedance days were during the premonsoon period at all sites. The high O3 mixing ratio observed during the premonsoon period is of a concern for human health and ecosystems, including agroecosystems in the Kathmandu Valley and surrounding regions.
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RAGHAVENDRA, V. K. "Trends and periodicities of rainfall in sub-divisions of Maharashtra State." MAUSAM 25, no. 2 (February 7, 2022): 197–210. http://dx.doi.org/10.54302/mausam.v25i2.5194.
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The Maharashtra State of India is divided into four meteorological sub-divisions, viz., Konkan, Madhya Maharashtra, Marathwada and Vidarbha. Of these, Madhya Maharashtra and Marathwada are prone to droughts. The principal rainy season is the monsoon season of June to September when over 80 per cent of the annual rainfall is received. The coefficient of variation is about 20 per cent for the annual and monsoon rainfall except in Marathwada where it is 25 per cent. The annual and monsoon rainfalls follow the normal distribution for their yearly frequencies. In this region the annual and the monsoon rainfall series are highly correlated. In the loss drought prone sub-division of Konkan, the annual and monsoon rainfalls show a 100 year cycle. In all the sub-divisions the successive years' rainfalls are not dependent. The trend as revealed by fitting of orthogonal polynomials is shown as a quadratic curve for the annual and monsoon rainfalls of Konkan and Madhya, Maharashtra, the sub-divisions on either side of the Western Ghats. The low pass filter and Mann-Kendall test against randomness confirmed the trend in Konkan rainfall. The power spectral analysis of the data indicates the existence of long term trend for monsoon rainfall of Konkan, 60 year cycle for the annual rainfall of Konkan and Madhya Maharashtra, 30.year cycle for the annual and monsoon rainfall or Vidarbha, 20-year cycle for the monsoon rainfall of Marathwada, 15-year cycle for the monsoon rainfall of Madhya Maharashtra, 7.5-year cycle for the annual and monsoon rainfall of Marathwada.
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P. Hemasankari, D. Prema, Kaladaran, and Vasanth Kripa. "Seasonal variations of hydrographic parameters off the Chennai coast, India." Ecology, Environment and Conservation 29, no. 01 (2023): 374–80. http://dx.doi.org/10.53550/eec.2023.v29i01.056.
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The environment plays a major role in determining the abundance of fishes in a particular region and it helps to predict the probable fishing zone. This environment variables includes temperature, salinity, pH, TSS, DO (Dissolved Oxygen), chlorophyll a, b and c, primary productivity, gross and net, nutrients, phosphate, nitrate and ammonia. These parameters were estimated using standard procedures. These parameters in a particular fishing zone varies from season to season. This seasonal variations of these parameters and its relationship with each other are studied in Ennore, (Lattitude, 80°19’31"E, and Longitude, 13°14’51"N). an industrially polluted area along Chennai coast. Factor analysis is done to remove the redundant highly correlated variables from the data, replacing the entire data with uncorrelated variables. During the post monsoon season, the 4 components extracted by factor analysis indicates that the nutrient, nitrate, chlorophyll b, TSS and dissolved oxygen are important variables deciding the photosynthetic activity, in summer season, 3 components were extracted and the variables that decide photosynthetic activity includes nutrient nitrate, temperature and nutrient ammonia. In pre-monsoon season, 5 components were extracted by factor analysis and the deciding variables include pH, chlorophyll, c, chlorophyll a, chlorophyll b and salinity. In monsoon season, 3 components were extracted and the deciding variables include TSS, DO and temperature for the photosynthetic activity to take place. The eigen values worked out in all the 4 seasons are above 1 and are reliable. The eigen value is highest in the post monsoon component tested, 4.39 and the least eigen value, 1.05 is in the pre monsoon season. Pre monsoon season among all seasons shows highest percentage of cumulative variance. In the post monsoon season, the variables N-Nitrate, chlorophyll b, TSS and DO in the components 1, 2, 3 & 4 decide the growth of phytoplankton with 12% loss of information. In the summer season, the variables, N-Nit, temp., and N-amm., in the components 1, 2 and 3 are the deciding factors for the growth of phytoplankton with 26% loss of information. In the post monsoon season, the variables, pH, chlorophyll c, chlorophyll a, chlorophyll b and salinity in the components, 1, 2, 3, 4 and 5 respectively decides the phytoplankton growth with 11% loss of information. In the monsoon season, the variables, TSS, DO and salinity in the components 1, 2 and 3 decide the growth of phytoplankton with 22% loss of information. These variables are representative of all original 11 variables and the components are not linearly correlated with each other. The size of the data from 11 variables can be reduced to three components by using factor analysis with the principal components extraction.
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M. J. S. Bowman, D., and J. C. Z. Woinarski. "Biogeography of Australian monsoon rainforest mammals: implications for the conservation of rainforest mammals." Pacific Conservation Biology 1, no. 2 (1994): 98. http://dx.doi.org/10.1071/pc940098.
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Monsoon rainforests form an archipelago of small habitat fragments throughout the wet-dry tropics of northern Australia. According to the definition of Winter (1988) the current monsoon rainforest mammal assemblage contains only one rainforest specialist mammal species (restricted to Cape York Peninsula), and is dominated by eutherian habitat generalists (murids and bats) that mostly occur in surrounding savannah habitats. The mammal assemblages in monsoon rainforests across northern Australia (Cape York Peninsula, Northern Territory and the Kimberley) are essentially regional subsets of the local savannah and mangrove mammal assemblages, and consequently share only a limited number of species in common (most of which are bats). The lack of rainforest specialists in northwestern Australia is thought to be due to: (i) the lack of large tracts (> 1 000 ha) of monsoon rainforest habitat; (ii) the possible substantial contraction of these habitats in the past; and (iii) the limited extent of gallery rainforests, such rainforests being important habitats for rainforest mammals in South American savannahs. Unfortunately it is not possible to identify the threshold of habitat area required to maintain populations of monsoon rainforest specialist mammal species because of an impoverished fossil record pertaining to the past spatial distribution of monsoon rainforests. The implications of the lack of a specialist mammal fauna in Australian monsoon rainforests for the future of heavily fragmented tropical rainforests elsewhere in the world is briefly discussed. It is concluded that the analogy of habitat fragments to true islands is weak, that rainforest plant species are less vulnerable to local extinction than mammals, that the loss of mammal rainforest specialists may not result in a dramatic loss of plant species, and that corridors of rainforest may be critical for maintenance of rainforest mammal assemblages in areas currently subject to forest clearance.
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Hyvärinen, A. P., T. Raatikainen, D. Brus, M. Komppula, T. S. Panwar, R. K. Hooda, V. P. Sharma, and H. Lihavainen. "Effect of the summer monsoon on aerosols at two measurement stations in Northern India – Part 1: PM and BC concentrations." Atmospheric Chemistry and Physics Discussions 11, no. 1 (January 19, 2011): 1715–48. http://dx.doi.org/10.5194/acpd-11-1715-2011.
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Abstract. Particulate matter (PM) and black carbon (BC) concentrations were measured at two locations in Northern India during 2006–2010. The first measurement station is a background site in Mukteshwar, about 350 km northeast of New Delhi, in the foothills of the Indian Himalayas. The second measurement site was located in Gual Pahari, about 25 km south of New Delhi. Here we focused on resolving the effects of the Indian summer monsoon on the particulate matter and black carbon concentrations at the two stations. The average monsoon time concentrations were decreased by 55–70% compared to the pre-monsoon average concentrations at both stations, having a linear relationship with the total local rainfall during the monsoon season. In Mukteshwar during the monsoon, the 24 h PM2.5 concentrations were always below the Indian National Air Quality Standard of 60 μgm−3. In Gual Pahari, 13% of days exceeded this level during the monsoon season. However, the 24 h guideline of 25 μgm−3 given by the World Health Organization was more difficult to meet. In addition to loss processes, aerosol concentrations during the early monsoon were found to be affected by primary emissions, most likely dust event from the Thar Desert. This resulted in elevated fractions of the coarse mode, PM2.5−10 at both stations. In Mukteshwar, additional dust contribution came from the arid regions on the southern slopes of Himalayas. We also determined the characteristic transition times between the pre-monsoon, monsoon and post-monsoon. The onset and withdrawal transitions occurred faster in Mukteshwar than in Gual Pahari, both being typically less than 10 days. Transition periods in Gual Pahari took between 17 and 31 days. The shorter transition times in Mukteshwar were probably related to the more intense rains due to the mountain location.
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Tara, J., and Monika Sharma. "Life history of Papilio Polytes Romulus (Lepidoptera: Papilionidae) on Murraya Koenigii (Curry leaf), an economically important medicinal plant in Jammu." Journal of Non-Timber Forest Products 17, no. 2 (June 1, 2010): 173–78. http://dx.doi.org/10.54207/bsmps2000-2010-o6509h.
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Papilio polytes romulus has been recorded as a serious pest of Murraya koenigii (L.) Spreng. in Jammu region of J.&K. State during the survey conducted from March 2008 to February 2009. Caterpillars cause tremendous loss by defoliating young and tender leaves of host plant. The pest occurs throughout the year. A comparative analysis of its luife history during pre-monsoon and post-monsoon periods was conducted under laboratory conditions which indicated that it takes an average of 27.0+0.86 days and 32.93+0.14 days for the completion of one generation i.e. egg to adult during pre-monsoon and post-monsoon periods respectively. Observations on the mean developmental period of various life stages during pre-monsoon period such as incubation, total larval period, pupal period, adult longevity was recorded as 3.2+ 0.27 days, 13.87+1.47 days, 9.4+0.57days, 6.4+0.54 days respectively. However, during post-monsoon period these stages viz. incubation, total larval period, pupal period, adult longevity was found to last for an average of 4.12+0.25 days, 18.18+1.50 days, 10.33+0.51 days, 7.2+0.50 days respectively. Feeding behaviour, extent and mode of damage caused to Murraya koenigii by caterpillars of Papilio polytes romulus was also recorded.
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Hyvärinen, A. P., T. Raatikainen, D. Brus, M. Komppula, T. S. Panwar, R. K. Hooda, V. P. Sharma, and H. Lihavainen. "Effect of the summer monsoon on aerosols at two measurement stations in Northern India – Part 1: PM and BC concentrations." Atmospheric Chemistry and Physics 11, no. 16 (August 15, 2011): 8271–82. http://dx.doi.org/10.5194/acp-11-8271-2011.
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Abstract. Particulate matter (PM) and equivalent black carbon (BCe) concentrations were measured at two locations in northern India during 2006–2010. The first measurement station was a background site in Mukteshwar, about 350 km northeast of New Delhi, in the foothills of the Indian Himalayas. The second measurement site was located in Gual Pahari, about 25 km south of New Delhi. Here we focused on resolving the effects of the Indian summer monsoon on the particulate matter and equivalent black carbon concentrations at two stations. The average monsoon time concentrations were decreased by 55–70 % compared to the pre-monsoon average concentrations at both stations, decreasing as a function of the total local rainfall during the monsoon season. In Mukteshwar during the monsoon, the 24 h PM2.5 concentrations were nearly always below the Indian National Air Quality Standard of 60 μg m−3. In Gual Pahari, 13 % of days exceeded this level during the monsoon season. However, the 24 h guideline of 25 μg m−3 given by the World Health Organization was more difficult to meet. In addition to loss processes, aerosol concentrations during the early monsoon were found to be affected by primary emissions, most likely from dust events from the Thar Desert. This resulted in elevated fractions of the coarse mode, PM2.5–10 at both stations. In Mukteshwar, additional dust contribution came from east of the station, from the Himalayan region. We also determined the characteristic transition times between the pre-monsoon, monsoon and post-monsoon. The onset and withdrawal transitions occurred faster in Mukteshwar than in Gual Pahari, both being typically less than 10 days. Transition periods in Gual Pahari took between 17 and 31 days. The shorter transition times in Mukteshwar were probably related to the more intense rains due to the mountain location, and the fact that the station was most of the time in the free troposphere.
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Zhang, Taotao, Tao Wang, Gerhard Krinner, Xiaoyi Wang, Thomas Gasser, Shushi Peng, Shilon Piao, and Tandong Yao. "The weakening relationship between Eurasian spring snow cover and Indian summer monsoon rainfall." Science Advances 5, no. 3 (March 2019): eaau8932. http://dx.doi.org/10.1126/sciadv.aau8932.
Full textAbstract:
Substantial progress has been made in understanding how Eurasian snow cover variabilities affect the Indian summer monsoon, but the snow-monsoon relationship in a warming atmosphere remains controversial. Using long-term observational snow and rainfall data (1967–2015), we identified that the widely recognized inverse relationship of central Eurasian spring snow cover with the Indian summer monsoon rainfall has disappeared since 1990. The apparent loss of this negative correlation is mainly due to the central Eurasian spring snow cover no longer regulating the summer mid-tropospheric temperature over the Iranian Plateau and surroundings, and hence the land-ocean thermal contrast after 1990. A reduced lagged snow-hydrological effect, resulting from a warming-induced decline in spring snow cover, constitutes the possible mechanism for the breakdown of the snow-air temperature connection after 1990. Our results suggest that, in a changing climate, Eurasian spring snow cover may not be a faithful predictor of the Indian summer monsoon rainfall.
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Parasnis, S., Mary Selvam, Ramachandra Murty, and Ramana Murty. "Dynamic Responses Warm of Monsoon Clouds Salt Seeding." Journal of Weather Modification 14, no. 1 (October 17, 2012): 36–37. http://dx.doi.org/10.54782/jwm.v14i1.65.
Full textAbstract:
High resolution temperature measurements during single-level air- craft penetrations through warm monsoon clouds before and after salt seeding had a significant wave-length of about 2 km. The slope of the spectra relating to not-seeded traverses followed a -5/3 power law. The slope of the spectra relating to seeded traverses increased when liquid water content increased and rain formed. The temperature spectra of the seeded traverses showed a net energy gain in the larger wave-lengths ( >540 m) and a net energy loss in the shorter wavelengths. The net-energy gain could be due to condensation of water vapor on the salt parti- cles, the net energy loss to the decrease in the small scale turbulence resulting from the invigoration of the updraft. These features could be manifestations of the alteration of the dynamics of the cloud through salt seeding.
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Iqbal, A. Muhammed, Kattany Vidyasagaran, and Narayan Ganesh. "Host specificity of some wood decaying-fungi in moist deciduous forests of Kerala, India." Journal of Threatened Taxa 9, no. 4 (April 26, 2017): 10096. http://dx.doi.org/10.11609/jott.3168.9.4.10096-10101.
Full textAbstract:
The low diversity tropical forest is dominated by host specialized wood decaying fungi (Hymenochaetales, Polyporales) with narrow host range. To understand whether or not wood decaying fungi in a highly diverse tropical moist deciduous forest have any kind of host specialization, sporophores of 22 species of wood decaying fungi were recorded on 17 tree species in three seasons viz., pre monsoon, monsoon and post monsoon from the moist deciduous forests of Peechi-Vazhani Wildlife Sanctuary, Kerala, India. Only two of the 22 species with three or more records showed signs of host specialization. In the case of other fungi, the number of host tree species increased with increasing number of occupied or colonized logs. The findings support the assumption that most of the wood decaying fungi have broad host ranges in highly diverse forest types in the tropics.
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Tripathy, Biplab, and Tanmoy Mondal. "Socioeconomic Challenges faced by Basin’s People in India." Think India 22, no. 2 (October 31, 2019): 296–304. http://dx.doi.org/10.26643/think-india.v22i2.8730.
Full textAbstract:
India is a subcontinent, there huge no of people lived in river basin area. In India there more or less 80% of people directly or indirectly depend on River. Ganga, Brahamputra in North and North East and Mahanadi, Govabori, Krishna, Kaveri, Narmoda, Tapti, Mahi in South are the major river basin in India. There each year due to flood and high tide lots of people are suffered in river basin region in India. These problems destroy the socio economic peace and hope of the people in river basin. There peoples are continuously suffered by lots of difficulties in sort or in long term basis. Few basin regions are always in high alert at the time of monsoon seasons. Sometime due to over migration from basin area, it becomes empty and creates an ultimate loss of resources in India and causes a dis-balance situation in this area.
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GODBOLE, RV, and RR KELKAR. "Net Terrestrial Radiative Heat Fluxes over India during Monsoon." MAUSAM 20, no. 1 (April 30, 2022): 1–10. http://dx.doi.org/10.54302/mausam.v20i1.5421.
Full textAbstract:
Infrared radiative heat flux and instantaneous rate of temperature change have been computed for Indian, subcontinent for monsoon season by making use of the numerical method developed for the purpose. The effects of water Vapour alone have been considered. It is found that the radiative beat loss near the surface is minimum over the Western Ghats. Over northeast and northwest India, the radiative heat loss is relatively high. Also, the radiative cooling integrated from the surface upto 300 mb indicates a large cooling over northeast and northwest India (>loC per day) and relatively small cooling over the southern Peninsula ( <0.25°C per day). Analysis of the day to day values of net flux and temperature suggest no cause-and-effect relationship. However, a good correspondence has been noticed between net flux, temperature and total moisture content as far as surface level is concerned. The day to day values of net flux at higher levels follow very closely to those at the surface.
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Pratihary, A. K., S. W. A. Naqvi, G. Narvenkar, S. Kurian, H. Naik, R. Naik, and B. R. Manjunatha. "Benthic mineralization and nutrient exchange over the inner continental shelf of western India." Biogeosciences 11, no. 10 (May 27, 2014): 2771–91. http://dx.doi.org/10.5194/bg-11-2771-2014.
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Abstract. The western Indian continental shelf is one of the most productive coastal systems of the world ocean. This system experiences extreme changes in its oxygen regime, being normoxic from November to May and suboxic (denitrifying)/anoxic from June to October, owing to the biogeochemical response to cyclical monsoonal influence. In order to understand the impact of the seasonally varying oxygen regime on benthic mineralization, nutrient exchange and, in turn, on the shelf ecosystem, we carried out the first ever intact-core incubations during two contrasting seasons – spring intermonsoon and fall intermonsoon (late southwest monsoon) at a 28 m-deep fixed site on the inner shelf off Goa, dominated by fine-grained cohesive sediments. The results showed that incomplete sediment oxygen consumption (SOC) occurred during April as opposed to the complete SOC and subsequent sulfide flux observed in the fall intermonsoon incubations. The sediments acted as a perennial net source of DIN (dissolved inorganic nitrogen i.e. NO3− + NO2− + NH4+), PO43− and SiO44− to the overlying water column. The efflux of DIN increased from 1.4 to 3.74 mmol m−2 d−1 from April to October, of which NH4+ flux comprised 59–100%. During the oxic regime, ∼75% of diffusing NH4+ appeared to be nitrified (2.55 mmol m−2 d−1), of which ∼77% remained coupled to benthic denitrification. Consequently, 58% of NH4+ flux was lost in active coupled nitrification–denitrification, resulting in substantial N loss (1.98 mmol m−2 d−1) in the sediments. The continental shelf sediments switched over from being a NO3− source during the oxic regime to a NO3− sink during the anoxic regime. During suboxia, benthic denitrification that is fed by NO3- from the overlying water caused N loss at the rate of 1.04 mmol m−2 d−1. Nitrogen loss continued even under sulfidic conditions during October, possibly through the chemolithoautotrophic denitrification, at a potential rate of 3.21 mmol m−2 d−1. Phosphate flux increased more than 4-fold during October as compared to April, due to reductive dissolution of Fe- and Mn oxides. The SiO44− flux increased during October apparently due to the higher availability of siliceous ooze from diatom blooms commonly occurring in the monsoon season. Slow oxidation of organic carbon (Corg) under anoxia, lower temperature and reduced benthic faunal activity appeared to decrease benthic mineralization by 25% as suggested by the drop in the Corg oxidation rate from 63.8 mmol C m−2 d−1 in April to 47.8 mmol C m−2 d−1 in October. This indicated a higher preservation of Corg during the late southwest monsoon. Sediment porosity, Corg content and nutrients did not show significant variations from April to October. Porewaters were found to be enriched with NH4+, PO43− and SiO44− but depleted in NO3− and NO2− in these organic-rich sediments. Significant DIN, PO43− and SiO44− effluxes indicate the potential of benthic input in meeting nutrient demand of the phytoplankton community in this seasonally N-limited shelf system.
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Hou, Congyu, Zhifeng Yang, and Wei Ouyang. "Surface Runoff and Diffuse Nitrogen Loss Dynamics in a Mixed Land Use Watershed with a Subtropical Monsoon Climate." Processes 11, no. 7 (June 25, 2023): 1910. http://dx.doi.org/10.3390/pr11071910.
Full textAbstract:
The surface hydrology and diffuse pollution loading is hypothesized based on the unique characteristics under different rainfall types in watersheds with a subtropical monsoon climate. This study evaluated the effects of different rainfall event intensity on surface runoff and diffuse nitrogen loss in a subtropical watershed located in the latitude range between 22.5° north and 25° north in southern China by adapting the hydrological model SWAT (Soil and Water Assessment Tool). The rainfall events were classified into four categories including light rainfall (LR), moderate rainfall (MR), intense rainfall (IR), and extreme rainfall (ER). Our results showed that the ER events had the lowest occurrences of 7 days per year, but they contributed the most to total surface runoff (54.29%) and TN losses (57.63%) in the subtropical watershed researched. Although forests and pastures had a better effect on reducing diffuse pollution, their surface runoff and nitrogen loss were still proved to be serious under ER events. As for the nitrogen loss form, water-soluble nitrogen oxides nitrogen (ON-N) loss was the dominant form of total nitrogen (TN) loss, which accounted for 90% of the total loss in the simulated watershed in the subtropical monsoon climate region. Under LR events, however, nitrate nitrogen (NO3-N) accounted for 74.54% and 55.59% of TN losses from paddy fields and dry lands, respectively. The effects of antecedent soil water content (ASW) on surface runoff and TN loss were higher under ER events. The surface runoff and TN loss in the high-ASW condition were 1.17–3.86 times and 1.34–1.76 times higher, respectively, than in the low-ASW condition. These findings highlighted the important influence of ER events on diffuse pollution and have significant implications for controlling diffuse pollution under different rainfall types. This conclusion proved that extra attention and efforts are required in handling non-point-source pollution in subtropical monsoon watersheds than the watersheds in cooler regions because the natural systems including forest and pastures are no longer effective enough in controlling surface runoff and TN loss during ER.
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Supriya Surachita and Sharat Kumar Palita. "Freshwater fish diversity in hill streams of Saberi River in Eastern Ghats of Odisha, India." Journal of Threatened Taxa 14, no. 4 (April 26, 2022): 20828–39. http://dx.doi.org/10.11609/jott.7341.14.4.20828-20839.
Full textAbstract:
Freshwater fish diversity of the hill streams of Saberi River (a major tributary of the Godavari River system) in Koraput district in Eastern Ghats of southern Odisha was studied from September 2017 to August 2019. Sites for the present study were located between Gupteswar Proposed Reserve Forest (PRF) of Odisha on the eastern side, and Kanger Valley National Park of Chhattisgarh on the western side. A total of 36 species of freshwater fish belonging to 24 genera, 13 families and six orders were recorded from the study sites, of which two species are exotic. Family Cyprinidae dominated with 14 species. Species richness and diversity is greater during the pre-monsoon months followed by post-monsoon and monsoon months respectively. The physico-chemical parameters of water in the study sites during all seasons are within prescribed limits for fish culture. Among the four major types of fish habitats identified in the study sites (riffles, runs, pools and logs), pools were the most preferred, and logs the least preferred habitat for the fishes. Habitat analysis indicated that deep pools and runs are the primary habitats contributing to the maximum species diversity, and therefore, protection of these particular habitats is recommended for conservation and management of ichthyodiversity.
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Supriya Surachita and Sharat Kumar Palita. "Freshwater fish diversity in hill streams of Saberi River in Eastern Ghats of Odisha, India." Journal of Threatened Taxa 14, no. 4 (April 26, 2022): 20828–39. http://dx.doi.org/10.11609/jott.7341.14.4.20828-20839.
Full textAbstract:
Freshwater fish diversity of the hill streams of Saberi River (a major tributary of the Godavari River system) in Koraput district in Eastern Ghats of southern Odisha was studied from September 2017 to August 2019. Sites for the present study were located between Gupteswar Proposed Reserve Forest (PRF) of Odisha on the eastern side, and Kanger Valley National Park of Chhattisgarh on the western side. A total of 36 species of freshwater fish belonging to 24 genera, 13 families and six orders were recorded from the study sites, of which two species are exotic. Family Cyprinidae dominated with 14 species. Species richness and diversity is greater during the pre-monsoon months followed by post-monsoon and monsoon months respectively. The physico-chemical parameters of water in the study sites during all seasons are within prescribed limits for fish culture. Among the four major types of fish habitats identified in the study sites (riffles, runs, pools and logs), pools were the most preferred, and logs the least preferred habitat for the fishes. Habitat analysis indicated that deep pools and runs are the primary habitats contributing to the maximum species diversity, and therefore, protection of these particular habitats is recommended for conservation and management of ichthyodiversity.
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Chowdhury, Soumyajit, and Rahi Soren. "Butterfly (Lepidoptera: Rhopalocera) Fauna of East Calcutta Wetlands, West Bengal, India." Check List 7, no. 6 (December 1, 2011): 700. http://dx.doi.org/10.15560/10960.
Full textAbstract:
East Calcutta Wetlands (ECW), lying east of the city of Kolkata (formerly Calcutta), West Bengal in India, demonstrates the usage of city sewage for traditional practices of fisheries and agriculture. As a Ramsar Site, the wetland demands exploration of its bioresources for better understanding and management of the ecosystem operating therein. Butterflies (Lepidoptera: Rhopalocera) being potent pollinators and ecological indicators, are examined in the present study. The diversity study, conducted for two consecutive years (Jan. 2007-Nov. 2009) in all the three seasons (pre-monsoon, monsoon and post-monsoon), revealed seventy-four species. As butterflies depend on preferred host and nectar plants during their larval and adult stages respectively, the lack of these sources in some parts of ECW indicate degraded habitats with low species richness. Ongoing unplanned anthropogenic activities like habitat modifications (conversion of wetlands to agricultural lands) are resulting in the loss of wetland biodiversity and hence ecosystem integrity in ECW.
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Huang, Shihming, and Leo Oey. "Malay Archipelago Forest Loss to Cash Crops and Urban Expansion Contributes to Weaken the Asian Summer Monsoon: An Atmospheric Modeling Study." Journal of Climate 32, no. 11 (May 9, 2019): 3189–205. http://dx.doi.org/10.1175/jcli-d-18-0467.1.
Full textAbstract:
Abstract In the Malay Archipelago (Indonesia and Malaysia), forest is lost on large scales to cash-crop plantation (oil palm, rubber, and acacia, including fallow lands) and urban expansion. Deforestation changes land surface properties and fluxes, thereby modifying wind and rainfall. Despite the expansive land-cover change over a climatically sensitive region of the tropics, the resulting impact on the Asian summer monsoon has not been studied. Here we study the atmospheric response caused by the island surface change due to deforestation into cash-crop plantations and urban expansion. Using a large ensemble of atmospheric model experiments with observed and idealized land-cover-change specifications, we show that the deforestation warms the Malay Archipelago, caused by an increase in soil warming due to decreased evapotranspirative cooling. The island warming agrees well with in situ and satellite observations; it causes moisture to converge from the surrounding seas into Sumatra and Malaya, and updrafts, rainfall, and cyclonic circulations to spread northwestward into southern India and the Arabian Sea, as well as a drying anticyclonic circulation over the Indo-Gangetic plains, Indochina, and the South China Sea, weakening the Asian summer monsoon. The modeled monsoon weakening agrees well with, and tends to enhance, the observed long-term trend, suggesting the potential for continued weakening with protracted cash-crop plantation and urban expansion.